Table of contents

Preface

The 18th Asia-Oceania Congress of Medical Physics (AOCMP) in conjunction with the 16th South-East Asia Congress of Medical Physics (SEACOMP) was held in Kuala Lumpur from 11 to 14 November 2018. The annual event is aimed to gather medical physics communities in the Asia-Oceania region for the sharing of knowledge, expertise, scientific discussions, cultural exchange and updates of medical physics activities. Besides, the event is a platform for the establishments of regional education, training and professional developments in medical physics and for the advancement in status and standard of practice of the medical physics profession in the region. The theme for this congress is "A Sustainable Future for Medical Physics". This is the second time the congress is held in Malaysia. The first AOCMP organised in Malaysia was in year 2004.

300 abstracts from 28 countries were accepted for the congress, 151 were oral contributions and 149 were posters. The congress also had many invited lectures by international and local experts. The congress was divided into three main themes; imaging, therapy and others (including radiobiology and radiation protection).

83 papers are included in this proceedings volume organised into the three main themes (1) imaging: CT dose optimisation & image quality, non-ionising imaging, nuclear medicine imaging, radiography, mammography and tomosynthesis; (2) therapy: radiotherapy dose verification, radiotherapy image guidance & motion management, quality assurance & commissioning, treatment planning, particle therapy, brachytherapy; and (3) others: medical physics education, radiation detector, radiation protection & safety, radiobiology & biophysics.

All articles published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Each article was peer-reviewed by at least two reviewers from the scientific committee and appointed reviewers based on their field of expertise. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Many thanks to all invited speakers, oral presenters and poster presenters for their participation and to the Organising Committee members for all their hard work in making the congress happen. Thanks to all authors who submitted the manuscript of the work presented at the congress to be included in the volume. The Scientific Committee members and reviewers are also thanked for reviewing the submitted manuscripts and improve the scientific quality of this proceedings. Finally, thanks to all who attended the congress and the sponsors for their financial support.

Editors, Proceedings of AOCMP SEACOMP 2018

Hafiz M Zin. Universiti Sains Malaysia

Ahmad Nazlim Yusoff, Universiti Kebangsaan Malaysia Ahmad Taufek Abdul Rahman, Universiti Teknologi MARA Kwan Hoong Ng, Universiti Malaya

Scientific Committee and Reviewers

Ahmad Nazlim Yusoff

Ahmad Taufek Abdul Rahman

Aini Ismafairus Abd Hamid

Freddy Haryanto

Hafiz Mohd Zin

Hairil Rashmizal Abdul Razak

Hwee Shin Soh

Jeannie Hsiu Ding Wong

Mahbubunnabi Tamal

Marianie Musarudin

Mohd Fahmi Mohd Yusof

Mohd Syahir Mansor

Mohd Zahri Abdul Aziz

Muhammad Bakhsh

Muhammad Khalis Abdul Karim Muhammad Shahrun Nizam B.A Daman Huri Aik Hao Ng

Kwan Hoong Ng

Noor Diyana Osman

Noorazrul Yahya

Noramaliza Mohd Noor

Norhanna Sohaimi

Norhayati Mohd Zain

Nur Hartini Mohd Taib

Rafidah Zainon

Rozilawati Ahmad

Sofina Tamam

Suffian Mohamad Tajudin

Suhairul Hashim

Supriyanto Pawiro

Susie Lau

Li Kuo Tan

Ngie Min Ung

Wan Nordiana Rahman

Wei Loong Jong

Chai Hong Yeong

Yessie Widya Sari

List of Organisers, Supportted by and Sponsors are available in this PDF

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

We validated the tail replacement technique in the modulation transfer function (MTF) calculation of CT images using edges of homogeneous and non-homogeneous phantom using an automated method. The algorithm for the automated MTF calculation consists of several steps. The upper edge of the phantom was detected from its axial image and pixel values was taken to create an edge spread function (ESF). The left tail of the ESF was flipped horizontally to replace the right tail. Differentiating the ESF produced a line spread function (LSF) which was Fourier transformed to produce the MTF. To validate the result for the non-homogeneous phantom was compared with that for a homogeneous phantom. Results showed that in the homogeneous module, the MTF curve generated without tail replacement corresponded to its shape in use. However for the non-homogeneous module, the MTF obtained without tail replacement differed considerably from its shape in use. The 50% value of MTF (MTF-50) without tail replacement was 0.44 cycles/mm compared to 0.33 cycles/mm in use. Using the tail replacement, the MTFs in the homogeneous and non-homogeneous modules were comparable, with MTF-50 values of 0.33 cycles/mm for both. In summary, the MTF cannot be conventionally measured from the edge of the non-homogeneous module, but it can be resolved using the tail replacement technique on the ESF curve.

During production of F-18 in a medical cyclotron, high energy protons and secondary neutrons hit the highly reactive components of the target assembly resulting to activation products. In determining the presence of activation products and quantifying their respective activities, high resolution gamma spectroscopy using high purity germanium (HPGe) was used. From the results of the spectroscopy analysis, the doses were estimated using two methods: calculation method and MCNPX simulations. For the gamma spectroscopy analysis, the sample was prepared using aqua regia and was sent to PNRI. The analysis was done using GEM Series HPGe Coaxial Detector System. The results of the gamma spectroscopy showed the presence of ⁵⁶Co, ⁵⁷Co, ⁵⁸Co, and ⁵⁴Mn after a cooling period of eighty (80) days. For the MCNP simulations, the Havar® window foil was simulated as an isotropic disc source and a soft - tissue mimicking box detector was used and positioned at 100 cm from the center of the simulated window foil. *F8 tally was used to estimate the effective dose arising from a single activation product homogeneously distributed in the window foil and was done under the assumption that no other radiation sources were present in the simulation. Using calculation method, the effective dose estimates of ⁵⁶Co, ⁵⁷Co, ⁵⁸Co, and ⁵⁴Mn were found to be of minimal values during replacement of ¹⁸O vial at one meter. Moreover, it was found out that the highest contributors of dose during replacement of an ¹⁸O vial and maintenance of cyclotron are ⁵⁶Co and ⁵⁸Co. After a period of one year, the guiding activation products become ⁵⁷Co and ⁵⁴Mn due to their long half - lives. Furthermore, the annual dose estimates of these activation products were found to not exceed the annual dose limits for the whole body and for the extremities. As for disposal and storage, a period of four years will allow the Havar® window foil to reach the exemption levels set by PNRI.

The aim was to compare the WEKA and SVM-light software based on support vector machine (SVM) algorithm using features from brain T1-weighted MRI for differentiating AD patients and normal elderly subjects. The FreeSurfer software was used to extract cerebral volumes and thicknesses from T1-weighted brain MRI (100 AD patients and 100 normal elderly subjects). Seven structures were selected based on literature reviews consisting of hippocampus and amygdala volume, entorhinal cortex thickness of both hemispheres, and total gray matter volume. Relative volume of hippocampus, amygdala, and total gray matter were normalized by total intracranial volume (TIV). Fifteen combinations of seven structures were applied as input features to WEKA and SVM-light. The receiver operating characteristic (ROC) analysis and area under the curve (AUC) were used to evaluate the classification performance. The combination of hippocampus relative volume and entorhinal cortex thickness provided the highest classification performance and the AUC values were 0.913 and 0.918 for WEKA and SVM-light, respectively. There was no statistically difference of the AUC values (p-value > 0.05) between two software using the same input features. In conclusion, there was no statistically difference between the use of WEKA and SVM-light software for differentiating AD patients and normal elderly subjects.

The aim of this study was to evaluate the application of monoenergetic (ME) extrapolation technique of dual-energy computed tomography (DECT) for metal artefact reduction using phantom study. This study involved phantom study with a customized phantom consisting different types of metal implant such as titanium and stainless steel. The phantom was scanned using a single-source DECT scanner (SOMATOM Definition AS+, Siemens Healthcare, Germany) with dual-energy mode of 140/80 kV spectrum. The commercially available post-processing software (Syngo DE, Siemens) was applied to generate ME image datasets with different extrapolated energies ranged from 55 to 160 keV. The reduction of artefacts was measured qualitatively and quantitatively using region of interests (ROIs) statistical analysis. The results show 60% of metal streak regions were reduced significantly at higher extrapolated energy which is 160 keV. Quantitative analysis also resulted in lower HU readings within the region of artefact for 160 keV. However, higher extrapolated energy resulted in higher noise and lower signal-to-noise (SNR) value. ME images at 160 keV appear noisier while ME images at 64, 70 and 80 keV appear smoother. Metal artefacts induced by both metal implants were reduced significantly using DECT ME extrapolation and diagnostic quality of CT images also improved. It can be achieved by using higher ME of DECT. However, image noise is higher, and SNR is reduced with higher ME extrapolated energy.

The relationship between resting effective connectivity (EC) among default mode network (DMN) regions and auditory working memory (AWM) performance is still poorly understood. In this work, resting-state functional magnetic resonance imaging (rsfMRI) was used to determine the optimum connectivity model between posterior cingulate cortex (PCC) and medial prefrontal cortex (mPFC) in 40 healthy male volunteers. in low and normal working memory groups of subjects. Correlation between EC with AWM performance and AWM-capacity was also studied. The participants were divided into two groups which are normal and low AWM-capacity groups based on Malay Version Auditory Verbal Learning Test. The AWM performance was assessed using a word-based backward recall task. Both assessments were conducted outside the MRI scanner. The participants were scanned using a 3-T MRI system and the data were analyzed using statistical parametric mapping (SPM12) and spectral Dynamic Causal Modelling (spDCM). Results revealed that PCC and mPFC were significantly interconnected in both groups. Group analyses showed that the connection between PCC and mPFC exhibits an anti-correlated network. The results also indicated that the AWM performance and AWM-capacity were not associated with EC. These findings suggest that EC at rest between the two regions may not significantly influence cognitive abilities important for this AWM task.

Whole body flourine-18-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) is part of the standard management of oncologic diagnosis and staging. However, there is a growing concern over the radiation exposure of patient undergoing PET/CT due to higher radiation dose compared to other imaging modalities. The aim of this study is to estimate the effective dose received by 104 patients that undergone a whole body ¹⁸F-FDG PET/CT at the University of Malaya Medical Centre (UMMC). The effective dose from CT were calculated using two methods, namely, dose length product (DLP) method as recommended by International Commission on Radiological Protection (ICRP) Publication 102 and size specific dose estimates (SSDE) method as recommended by American Association of Physicist in Medicine, AAPM Report No. 204. Meanwhile, for PET dosimetry, the effective dose resulting from the radiopharmaceutical injection was estimated by means of the model proposed by ICRP Publication 106. The average effective dose for a whole body ¹⁸FFDG PET/CT examination was found to be 14.82 ± 3.2 mSv for DLP method and 9.47 ± 1.5 mSv for SSDE method. DLP method shows over estimated effective dose because average malaysian population is smaller than reference Perspex phantom which is 32 cm diameter. From this study, estimates lifetime attribute risk (LAR) based on BEIR VII report is only 0.09% for SSDE method compare to DLP method which is 0.14%.

The objective of this research was to obtain the optimal automatic exposure control (AEC) settings for CT thorax examinations for obese paediatric patients. This was to ensure lower radiation dose for this special cohort while maintaining diagnostic image quality. A layer of fat tissue equivalent material was used to wrap around the torso of a paediatric phantom to simulate an obese patient. Optically stimulated luminescence dosimeters (OSLDs) were inserted at different positions within the thorax region. Three sets of CT images were acquired at DoseRight Indices (DRI) of 13, 15 and 17. The CT images were used for qualitative and quantitative assessments. The contrast to noise ratio (CNR) of images with DRI of 13 (211.08 ± 21.35) were significantly lower than CNR of images with DRI of 15 (231.67 ± 20.35) and 17 (245.10 ± 25.44; p < 0.01). For signal to noise ratio (SNR), there were significant differences among images with all DRI settings (p < 0.01). The mean absorbed dose received by the phantom at DRI of 13, 15 and 17 were 1.07 ± 0.05 mSv, 1.16 ± 0.07 mSv and 1.75 ± 0.08 mSv, respectively. In this study, DRI of 15 was determined as the optimal setting for obese paediatric patients for the age group of 5 to 14 years old. We have demonstrated that there is scope to reduce radiation dose to obese paediatric patients in CT thorax examinations while still maintaining diagnostic quality images.

The gauss-newton algorithm is applied to reconstruct a two-dimensional image of Electrical Impedance Tomography (EIT) using python program. The study aimed to determine the characteristics of body tissues either conductive or resistive properties through the tissue structure which is displayed in the form of images so we can distinguish between one tissue and another. In this study, it was a fabricated hardware system, phantom, and software system. The EIT technique is performed by injecting a low constant electrical current of 1 mA at 50 kHz frequency on a pair of electrodes on 16 copper electrodes (Cu) surrounding a phantom filled with ground meat as conductor of electricity, flat bone, and cord bone of chicken as anomalies. The principle of the neighboring method achieved voltage measurements from the other electrode pair. The measurement data is processed with the python program using gauss-newton algorithm to obtain a reconstructed image of the tissue structure. The characteristics of body tissue can be identified from the color distribution, position, shape, and size of the object in the reconstructed image so it can distinguish between one tissue and another. The original analysis of body tissue either conductive or resistive properties could be reconstructed by two-dimensional electrical impedance tomography conjunction with the gauss-newton algorithm.

Electrical Impedance Tomography (EIT) is a non-invasive medical imaging technique which estimates the electrical impedance distribution within some tissue. The study aimed to assess the performance of the EIT system in a thorax imaging by analysis of sensitivity distribution. Sensitivity distribution was visualized using COMSOL Multiphysics simulation in a human thorax represented as an elliptic cylinder phantom consisting of homogeneous and inhomogeneous medium with varying different dimensions of 16 electrode EIT system. Current density distribution was collected for sensitivity analysis using the neighboring method. The sensitivity distribution at each position in the phantom is different. It is caused by the interaction of current density from transmitter and receiver terminal. The different varying parameter of the system can also influence sensitivity distribution. The sensitivity of inhomogeneous phantom is very non-uniformly distributed. The performance of systems was assessed by analysis of the change of sensitivity with the change of electrode dimensions in the homogeneous and inhomogeneous medium.

Platinum nanodendrites (PtNDs) are high-Z nanomaterials (Z=78) that possess a promising potential to be introduced as a novel contrast agent in diagnostic radiology. The objective of this study is to investigate the performance of PtNDs as contrast agent in computed tomography in term of CT number and CNR. PtNDs of different sizes (29, 36, 42, 52 nm) were prepared into final concentration of 1.0 mM in 3 mL syringes. CT scans were performed on PtND samples, distilled water and iodinated contrast agent arranged in phantom. The scans of each samples were conducted at 0.6 mm slice thickness and 80 kVp setting. CT number and contrast to noise ratio (CNR) were measured and calculated. The attenuation property of PtNDs shows size dependent characteristics, as the smallest PtNDs tested (29 nm) shows the lowest CT number (3.73 ± 0.37), followed by 36 nm PtNDs (21.23 ± 0.77), 42 nm (62.77 ± 2.08) and 52 nm (89.33 ± 4.60). CNR quantification reveals that there are no significant different of CNR values for PtNDs of size 29 nm, 36 nm, and 42 nm (around 24.67 ± 0.25), while 52 nm PtNDs sees drop of CNR (20.14 ± 0.57). Compared to iodinated contrast agent, 42 and 52 nm PtNDs show higher CT number, with slightly reduced CNR. This preliminary study suggests that PtNDs have the potential to be applied as contrast agents for CT imaging. The study also demonstrates that the performance of nanomaterial based contrast agent and x-ray attenuation properties are dependent on nanoparticles size and further study is required to elucidate multiparameter involved.

MRI is an important diagnostic imaging tool as it provides excellent soft tissue contrast resolution. Artefact in MRI is an undesirable appearance in the image that affect the image quality and may hinder true diagnosis of the pathological events. Gold in bulk form does not cause any artefact in MRI as it is diamagnetic whereas in its nanoscale version, it was proven to pose magnetic properties. Previous studies also shown that some personal care products (PCPs) produce artefact in MR images due to the presence of metallic compounds in the PCP. Hence, this study was conducted to investigate the effect of PCP with gold nanoparticles (AuNPs) on brain MRI images. The study was conducted using 1.5 Tesla MRI system where moisturiser and compact powder with AuNPs were tested. The products were applied onto the micropore tape attached to the MRI water phantom. The phantom was placed in an RF coil at the isocentre of the MRI bore and scanned using T1-weighted fast-spin-echo (FSE), T2-weighted FSE and fluid attenuated inversion recovery (FLAIR) sequences. The images were evaluated using Visual Grading Analysis (VGA) checklist by two radiologists. Based on the VGA score, brain MRI images in moisturiser group were all scored '1' which indicate minimal artefact with only loss of fine details seen. Whereas, brain MRI images of compact powder group were all scored '0' which indicate no artefact seen. Therefore, it can be concluded that PCP with AuNPs produce little to no artefact on brain MRI images, thus, there will be no need for the patient who wears PCP with AuNPs to clean their face prior to brain MRI examination.

The aim of this study is to evaluate effective dose received by participants from Lung Cancer Screening program in Institut Kanser Negara (IKN), Putrajaya. This retrospective study was performed between April 2016 - December 2016 where all scanning acquisition protocols and dose information from forty (40) participants were recorded and investigated. The screening process involves two types of imaging technique, the Dual Energy Subtraction (DES) Chest Xray and Low-Dose Computed Tomography (LDCT) imaging technique. Participant's effective dose (ED) from DES and MSCT were analysed by using PCXMC (Version 2.0, Finland) and CT-EXPO (Version 2.3, Germany) software, respectively. It was observed that the mean ( ± SD) value for DES (at 60 kV), DES (at 120 kV) and MSCT examinations were 0.006 ± 0.005 mSv, 0.018 ± 0.005 mSv and 1.558 ± 0.129 mSv, respectively. In a whole, the total cumulative ED values for participants were ranged from 1.376 mSv to 1.986 mSv. It was summarized that both optimized techniques were useful for screening needs and the ED value from this study were lower when compared to other established reference.

⁹⁰Y has internal pair production which enables the imaging of this isotope with positron emission tomography (PET). The acquisition time is a crucial factor which strongly influence the image quality due to very small decay branch of this isotope. Hence, the aim of this study was to evaluate the impact of acquisition time on image quality and visibility of ⁹⁰Y PET. A NEMA IEC body phantom with set of fillable spheres were filled with ⁹⁰Y to generate a hot lesion to background ratio of 8:1. PET image was acquired by Philips Gemini TF PET/CT scanner with acquisition time per bed varied from 15, 30, 60 and 120 minutes. Image quality was assessed by percentage hot contrast (HC), image noise (CV), signal-to-noise (SNR) ratio and visibility (VS). From a result, hot spheres and their edges were more defined as acquisition time increased. Additionally, SNR and visibility were increased with acquisition time and sphere size as expected but percentage hot contrast was decreased. Thus, this can be explained by the growing of noise at shorter acquisition times and smaller spheres. In conclusion, ⁹⁰Y PET imaging was feasible but the imaging protocol should be carefully considered particularly in small object.

This study investigated the suitability of nanoDot optically stimulated luminescence (OSL) dosimeters for entrance surface dose (ESD) measurements in common X-ray diagnostics. OSL dosimetry system supplied by Landauer Inc, (Glenwood, IL, USA) consisting of nanoDot OSL dosimeters and microStar reader were used. ESDs were measured with nanoDots placed on whole-body anthropomorphic phantom (for direct measurements) and in free air without backscatter material (for indirect measurements) in accordance with the IAEA Technical Report Series No. 457. Measurements were carried out in five X-ray projections including AP abdomen, AP chest, PA chest, AP thoracic spine and AP skull. The mean ESD for each projection was evaluated from multiple measurements with three different field sizes. Mean ESDs (direct measurements) for AP abdomen, AP chest, PA chest, AP thoracic spine and AP skull were 4.3 mGy, 0.7 mGy, 0.3 mGy, 6.8 mGy and 2.8 mGy respectively. While in the case of indirect measurements, the corresponding mean ESD values were 4.8 mGy, 0.7 mGy, 0.2 mGy, 7.2 mGy and 3.7 mGy respectively. The results were found to be within IAEA and European Commission (EC) diagnostic reference levels (DRLs) range. The percentage difference of the ESDs measured by direct and indirect methods in all projections were between 0 to 40%. It was affirmed that nanoDot OSL dosimeter is a good candidate for ESD measurement in common radiographic examinations, while taking into account the effect of energy dependence.

The Kidney stones in the urinary tract area formed due to many factors. Most medical cases, this disease was diagnosed after the order of millimeters or centimeters. The purpose of this study was to characterize standard polystyrene solutions with light scattering techniques as a calibration tool that will be used to characterize urine crystals. The first stage begins with a literature review and optical settings. The second stage, the arrangement, and components of the tool were validated by measuring the aperture width based on the experiment and measuring the most appropriate cuvette to be used in the sample. The third stage, polystyrene was dissolved with 10 ml of tetrahydrofuran and measured by variations in molecular weight and concentration of polystyrene. The molecular weight of polystyrene was 4000, 90000, 200000, 400000 and 900000 grams/mol. The results showed the width of the gap according to the experiment was 0.05 mm. The cuvette which has a diffraction width value similar to the measurement without cuvette (Blank) measured from the central beam axis to dark 1 was a cuvette diameter of 27 mm. The results of the polystyrene solution showed a diffraction width change in the polystyrene solution for each molecular weight and concentration change. The higher the molecular weight and concentration, the smaller the diffraction width.

The signal-to-noise ratio (SNR) is an important measure of the quality of computed tomography (CT) images. In this study, a new clustering method is proposed to calculate the SNR ratio of CT image. Multi- Objective Simulated Annealing clustering is used for the comparison based on segmentation parameters such as SNR ratio. Two samples are used in this study as phantom materials, namely, Rhizophora Spp. binderless and araldite resin particleboard, with dimension of 20 cm x 20 cm. For each scanned datum, ImageJ software is utilised as the combination method to analyse CT images. Results shows that the automatic clustering algorithm improves the SNR results of the sample images. In addition, the SNR value of images using MOSA clustering is higher than that of normal CT images.

This study was to establish various conversion factors and its impact on the quantitative accuracy of an absolute activity in phantom between 2 variant clinical SPECT/CT system from the same vendors in different centre. Multiple series of uniform phantom scans were performed with 370 MBq filled activity in the uniform phantom using different isotropic voxel sizes (64 × 64 × 64, 128 × 128 × 128, and 256 × 256 × 256). For activity validation purpose, single anthropomorphic phantom scan with different activities ratios for different organs (0:0:1:10, lung: spine: background: liver), matrix sizes and iterations were performed. Various conversion factor (in cps/Bq or Bq/cps) estimated from various matrix sizes (CF₆₄, CF_128, and CF₂₅₆) were applied to generate the activity concentration of distribution in SPECT/CT images. The measured activities for background and liver were then compared to an absolute activity distribution and reported as a percentage difference, while for lung and spine region were reported as activity relative errors percentage. The identical methods were replicated in the other system and the differences between the system were evaluated. Both systems produced an identical trend of CF curves over the different iterations number and voxel sizes. Both systems were capable to estimate the activity distribution within 10% and 15% of error for the liver and background respectively using 256 × 256 × 256 voxel sizes. Furthermore, the relative error percentage was within 10 to 15% of error. Different variant of SPECT/CT system from the same vendor could be able to estimate an accurate activity distribution in phantom according to an identical procedure of CF establishment.

This work was aimed to assess the detectability of microcalcifications as a function of tube voltage in 2D mammography using an in-house developed Channelized Hotelling Observer (CHO). The images of a 3D structured phantom, containing acrylic beads of different diameters in water and inserted signals (microcalcifications, spiculated and non-spiculated mass models) were assessed. Images had been acquired on a Siemens Mammomat Inspiration system at 5 different tube voltage levels (28-32 kVp) under AEC setting. The detectability of microcalcifications was analyzed in terms of percentage correctly detected signals (PC) as well as diameter threshold (d_tr), using the CHO and human observers. Two Laguerre-Gauss and 8 Gabor channels were included in the two-layers CHO. The model and human observer results were retrieved from a 4-alternative forced choice (4-AFC) study. At 28 kVp and 32 kVp, the diameter thresholds d_tr of microcalcifications together with their 95% confidence intervals (CI95) were 0.114 [0.110-0.118] mm and 0.119 [0.116-0.122] mm for the CHO, and 0.110 [0.093-0.127] mm and 0.123 [0.111-0.134] mm for the human observers. The Pearson correlation (r) between the PC values of model and human observer was more than 0.934. The in-house developed CHO and the human observer scores correlated very well for the application on 2D digital mammography acquired with different tube voltages. The overlapping range of CI95 of the d_tr for the tested kVp shows that the tube voltage setting does not significantly affect the detectability of microcalcifications neither by the CHO nor by the human observers.

Recording gamma images using a hand held small field of view (SFOV) hybrid gamma camera requires a few minutes to complete an acquisition. Operator motion during image acquisition may deteriorate image quality and hence affect diagnostic accuracy. The purpose of this study was to assess the magnitude of movement caused by the operator when holding a camera weighing approximately 1kg. Six participants were invited to take part and each was provided with a full explanation of the study. A SFOV hybrid gamma camera was used to acquire gamma images of a radioactive point source containing approximately 15 MBq of ^99mTc-pertechnetate placed at source-to-collimator distance (SCD) of 7 cm. Each participant was requested to hold the camera for 3 minutes at their convenience during image acquisition in a clinical setting. A control image was acquired with the camera head mounted on a fixed articulated arm. The scintigraphic images obtained were post-processed and saved as DICOM images prior to assessment using bespoke software (MOCO) to determine the magnitude of motion by tracking the centre of mass (COM) of the hot spot. From this study the centre of mass (COM) was found to move away from the initial point by 4.34 ± 2.43 mm and 7.18 ± 3.34 mm in x and y directions respectively. Subjective assessment of the images acquired with the camera held by an operator showed blurring of details when compared to the control image. The mean COM displacement for the first 30 seconds of the image acquisition was less than 5 mm; however it exceeded 5 mm after one minute of acquisition. This study suggests that the image acquisition time of the SFOV gamma camera should preferably be within a minute when the camera is hand held during use.

We aimed to validate Monte Carlo (MC) simulation models against measurements and evaluate the effect of object size on axial absorbed dose distributions during abdominal computed tomography (CT) acquisitions based on MC simulations. A medium-sized abdominal phantom, with holes to insert a pencil ionization chamber, was acquired using a 192-slice dual-source CT scanner at a tube voltage of 120 kVp and a displayed volume CT dose index of 5.0 mGy. Absorbed doses were measured using the pencil ionization chamber and an electrometer, and normalized absorbed doses to center were calculated for all measurement locations. The Particle and Heavy Ion Transport code System version 3.02 was used to simulate normalized absorbed doses of 19 locations through small-, medium-, and large-sized abdominal phantom models with a tube voltage of 120 kVp. In the measurement and MC simulation, the normalized absorbed dose to center in the medium-sized abdominal phantom was 1.48 ± 0.28 and 1.62 ± 0.35, respectively. Higher normalized doses were observed at peripheral regions when the phantom size was larger.

The purpose of this study was to obtain information on optimum exposure parameter combination on simulated thorax and abdomen examinations using Direct-Digital Radiography (DR) and Computed Radiography (CR) systems. An in-house phantom dedicated for quick QC was utilized as an image quality quantification tool in term of contrast. The optimization was performed on Philips Essenta DR, CR Fuji Profect CS, and CR Agfa 10-X. Exposures were performed using corresponding clinical setting with combinations of kVp, mAs, filters, and a variation of simulated patient thicknesses. The Figure of Merit (FOM) was employed as optimization parameter, calculated as ratio of squared Signal Difference to Noise Ratio (SDNR) and surface dose for every measurement. The image quality was evaluated using Modulation Transfer Function (MTF) and Contrast Consistency (CV). Based on FOM, MTF, and CV calculations, acquisitions optimization for thorax examination using DR was obtained on 55-63 kVp, 5-8 mAs, with additional filter 1 mm Al + 0.1 mm Cu. For abdomen examination, the optimized results were 81-102 kVp, 8-12.5 mAs, with additional filters 1 mm Al+0.1 mm Cu and 1 mm Al+0.2 mm Cu. On the other hand, the optimized results using CR on thorax examination were on the range of 55-63 kV, 4-8 mAs, also with the same additional filters with DR. The results of optimization of abdomen examination were on the range of 85-102 kV, 8-20 mAs, and again with the same additional filters. This gave information that different receptors used on the same x-ray unit produced almost similar optimization conditions.

Music has an important role in our life nowadays. Music can affect emotions and brain activity that can be measured through brain waves as electrical signals produced by neurons to carry sensory and cognitive information. In this study, brain waves for 10-12 normal male-non musician undergraduate students under three kinds of treatment are read using wireless electroencephalography (EEG) with 14 channels. For the first treatment, EEGs data are recorded when the subjects are in relax condition, i.e. rest and listening music. For the second treatment, subjects were stimulated with music in two loudness levels and for the last treatment subjects were stimulated with two different tempos of a song. From all subjects of this work, it was obtained that the right brain hemisphere is more active when listening music (significance level of 0.02). The average power spectra slightly increase with increasing music loudness (significance level of 0.35-0.45). Changes in musical tempo cause a decrease of the power spectra of alpha and beta bands (significance level of 0.25-0.30).

This study was aimed to obtain optimum parameter combination in simulated cranial, thorax, and abdominal examinations using computed radiography (CR) and direct digital radiography (DDR) systems. Optimization was performed using in-house phantom with contrast objects on Siemens Luminos Agile Max DDR and Siemens Axiom Luminos TF CR. Paediatric patients were separated into four age groups; 0-1 year (group A), 1-5 years (group B), 5-10 years (group C), and 10-15 years (group D). Slab phantoms with different total thickness were used to simulate patients belonging to each age group for different anatomical region (cranial, thorax, and abdomen). Optimization were performed in three steps; first kVp, followed by mAs, and then additional filter optimization. All the steps of optimization were performed based on FOM (figure of merit) values calculated as ratio of squared SDNR (signal difference to noise ratio) and entrance surface dose with the highest FOM representing the optimum condition. The results of this optimization were evaluated based on the highest FOM generated from each exposure. For both CR and DDR, optimum parameters (i.e. highest FOM) are different for each age group and anatomical region. Even with different X-Ray units, the CR device had slightly similar optimized parameters.

In this study, two CR receptors (Agfa CR-85X and Agfa CR-10X) and two DDR receptors (Brivo DR-F and Essenta) were characterized in terms of detector sensitivity and image quality. An in-house phantom was specially designed to accommodate image quality assessment for quick QC and is tested as a purpose of this study. The reference quantitative aspect that were used to characterize the imaging units are the correlation between Pixel Value and image receptor dose, whereas evaluation of image quality based on the modules on the in-house phantom uses new proposed metrics (coefficient of linearity, CL, and coefficient of variance, CV). Each system's unique Pixel Value-dose characteristics are also expressed in the results of the in-house phantom's metrics (i.e. CL and CV). In addition, the constancy of measured modulation transfer function suggests potential use for system quality judgment. As all characterizations (Pixel Value-dose characteristics, MTF, and new metrics) indicated on unique result for each systems, the study implies that the designed in-house phantom as well as its proposed metric can be promising to be used to characterize digital radiography systems during quick QC.

Urinary stones are commonly differentiated into four types; calcium, struvite, cystine, and uric acid. While two of them, cysteine and struvite, could not be distinguished easily, in fact, they need a different kind of treatments. Significantly, the purpose of this study was to classify of urinary stones based on edge detection using a semi-automatic threshold. Five urinary stones were scanned using eight sources voltage. The source voltage was 65, 75, ..., 115 KV. The consistent parameters were set at; 0.2⁰ rotation, 13.89 µm resolution, and 1 mm aluminum. The reconstructed images were quantified in CT Analyser 1.16.4.1. The region of interest (ROI) was a circle with a diameter of 275 pixels as well as the semi-automatic threshold were drawn on the reconstructed image. Based on the Hounsfield unit (HU) analysis, there were three groups of urinary stone on source voltage of 85 KV. The first group (struvite) has consisted of stone number 1 (461.42) and 3 (489.05). The second group (cystine) has consisted of stone number 2 (55.08) and 5 (-233.41). The third group was stone number 4 (634.18). The edge detection using semi-automatic threshold can classify five urinary stones into three types; struvite, cystine, and the other group.

Currently, state-of-the-art SPECT/CT with 3D reconstruction allows for quantitative data that can be represented as standardized uptake value (SUV). However, there are a number of factors that affect the value. The goal of this study was to investigate the factors affecting SUV of ^99mTc-MDP bone SPECT/CT. A NEMA phantom with ^99mTc-MDP background activity concentration of 18 kBq/ml and tumor to background ratio of 4:1 were studied. The data were acquired based on clinical bone SPECT/CT imaging protocol and OS-EM algorithm with compensation for attenuation, scatter and resolution recovery was applied using 10 subsets and varying iterative numbers from 1 to 5. SUVs (SUV_mean and SUV_max) were measured for each sphere using Q.Metrix software. Moreover, three cut-off frequencies of Butterworth filter including 0.35, 0.48 and 0.65 cycle/cm with order of 10 were investigated at 20 iterative updates. The percentage of difference of both SUVs for each sphere was calculated. Both SUVs tended to increase when the iterative update of the OS-EM and cut-off frequency of Butterworth filter were increased. Measurement of SUVs from SPECT/CT is feasible. However, the iterative update, cut-off frequency and sphere size can affect both SUVs.

The purpose of this study was aimed to evaluate the symmetrical effect of pitch factor to SNR (Signal to Noise Ratio) in thorax phantom CT images. Thorax CT phantom was designed to contain cork and cylindrical objects with several sizes located symmetrically respect to Y-axis. Phantom size is 20 cm diameter, 22 cm length, and the objects simulated vessels filled with contrast medium (diameter A: 2mm, B: 1.7 mm, C: 1 mm, respectively). The distance between two objects: A: 6 cm, B: 8 cm, and C: 12 cm. Image acquisitions were performed:130 kVp, tube rotation 0.6s, 70 mAs, and pitch values were 0.5, 0.8, 1.0, 1.5, 1.8 and 2.0. CT images represented by 9 axial images with a slice thickness of 5 mm. The difference of SNRs (Δ): a value of ΔA, in general high at initial slice and fall significantly up to the third slice and then followed by a nearly constant value. ΔB at initial slice trend decreased with increasing slice images. ΔC at all pitch initially shown zero value and increase to maximum up to second slice (not more than 20 units) and tend to constant after at sixth slice. Effect of all pitch values on symmetrical object images was influenced by the distance between two corresponding objects and slice order. Generally at the initial slice, the SNR difference between two corresponding objects (Δ) relatively high compared with the following order slice. Therefore, in clinical practice, it is recommended to give additional FOV at least 1.5 cm at the initial slice interest.

The purpose of this study was to evaluate the degree of contrast enhancement and image quality of computed tomography (CT) thorax examination using different contrast administration protocols. Data was retrospectively collected from 140 patients from two centres; 70 patients (Group A) from Advanced Medical and Dental Institute (IPPT), Universiti Sains Malaysia [19 males, 51 females; mean age ± standard deviation (SD) 53.6 ± 11.2 years; mean weight ± SD 54.04 ± 13.77 kg] using automatic bolus tracking (ABT) with weight-based contrast volume (WBV) administration, and 70 patients (Group B) from Hospital Pulau Pinang (HPP), Ministry of Health Malaysia [24 males, 46 females; mean age ± SD 54.5 ± 13.2 years] using fixed time-delay (FTD) with fixed contrast volume (FV) technique. The degree of enhancement was quantified by measuring Hounsfield unit (HU) values in different arteries and veins, and rated on a 5-point scale (1 = very poor, 5 = excellent) for qualitative assessment. The mean enhancement values in Group B were found to be higher than those in Group A (P < 0.001). There was no statistically significant difference between mean qualitative scores on a 5-point scale in both groups (P = 0.185). A weak correlation was seen between HU values with administered contrast volume (r = 0.1152). Overall, FTD with FV protocol was found to have higher degree of contrast enhancement for routine CT thorax examination. The qualitative assessment showed no significant difference between both protocols although higher mean grading in CT image quality was given by assessors for ABT with WBV technique.

Vibratory (e.g., piezoelectric) devices can stimulate cortical responses from the somatosensory area during functional magnetic resonance imaging. Twelve healthy, right-handed subjects (7 males and 5 females) were scanned with a 3.0 T magnetic resonance imaging scanner and stimulated at 30-240 Hz using a piezoelectric vibrator attached to the subjects' index fingers. The functional images were analysed to determine the brain activation region by performing random effects analyses at the group level. One-way analysis of variance was used to measure changes in frequency on brain activity. The activated regions were identified with WFU PickAtlas software, and the images were thresholded at Puncorrected < 0.001 for multiple comparisons. The average effect of frequency revealed significant activations in the right insula and right middle frontal gyrus; the corresponding region in the somatosensory area may act as a top-down control signal to improve sensory targets. Results revealed significant differences between frequencies; 90 Hz > 120 Hz activated right inferior parietal gyrus, 120 Hz > 150 Hz activated right cerebellum, and 60 Hz > 90 Hz activated right supramarginal gyrus and bilateral inferior frontal gyrus pars triangularis. Findings indicated the role of secondary somatosensory areas and the cerebellum in performing higher-order functions and discriminating various frequencies during vibratory stimulation. Increasing the patient sample size and testing higher frequencies in future experiments will contribute to furthering brain mapping of somatosensory areas.

Inspection of imaging SPECT system performance was controlled by Quality Control (QC) regularly. Tomographic imaging parameters in QC, i.e. homogeneity, contrast, and spatial resolution should be tested. These results make it reliable whether the SPECT system will be used. The modular Jaszczak phantom was used for that purpose, as it offers the investigation to all three parameters with a single measurement. Compared to the contrast and spatial resolution, an objective identification of possible ring artifact in the homogeneity is challenging. Artifact simulation of SPECT images which have been generated by disturbance of 4 × 4 cm² copper sheet located on surface LEHR collimator have been conducted to study the detectability of ring artifact. Uniformity section of Jaszczak phantom which filled with ^99mTc was used for acquisition. The confirmed ring artifact was analyzed by Edge Detection and Circle Hough Transform provided by imageJ, and students t-test statistically. From the evaluation by edge detection and circle Hough transform, the present of ring artifact only detected in artifact SPECT images using 1.00, 0.75, and 0.50 mm copper sheet thickness, while in t-test method all copper sheet thickness (including 0.25 mm) detect ring artifact in images.

This research was aimed to develop an in-house phantom for quality control (QC) of image quality in PET/CT imaging. Wax and rice powder were mixed to produce tissue-equivalent materials characterized by Hounsfield Unit (HU). The in-house phantom was two circular cylinders with 20 cm in diameter and 10 cm in length which consists of six symmetric vessel pairs with varied diameters of 4.20, 6.20, 8.30, 9.80, 16.30, and 19.00 mm. Each measurement was performed using radioactivity concentrations of ¹⁸F-FDG with variation from 1 to 17 µCi/mL Images were displayed with the pixel size of 4 × 4 mm². Image quality was evaluated in terms of conversion factor between full-width-half-maximum (FWHM) and actual diameter, and a pixel value for local uniformity of each object. Two types of phantoms have been designed which were liver-equivalent material (LEM) and muscle-equivalent material (MEM). HU and electron densities were (74.17 ± 1.48) HU and 3.396 × 10²³ electron/m³ for LEM, while (20.27 ± 0.33) HU and 3.461 × 10²³ electron/m³ for MEM, respectively. The conversion factor was initially high at 2.240 ± 0.07 for diameter 4.20 mm, falls to 0.99 ± 0.003 for diameter 9.80 mm, slowly decrease up to 0.82 ± 0.01 at diameter 16.30 mm, and then nearly constant at 0.82 with increasing diameter for both phantoms. The in-house phantom could be used to analyse the image quality performance of PET imaging with a tissue-specific material. The phantom design including the development of tissue-surrogate materials, size, and geometrical considerations of the features will be beneficial for innovating QC tools.

The purpose of this study is to investigate the feasibility of double low-dose (low radiation and low contrast medium doses) computed tomography pulmonary angiography (CTPA) in the diagnosis of pulmonary embolism. This retrospective study involved analysis of 59 patients undergoing 64- and 128-slice CTPA examinations which were scanned with a pitch of 0.9 and 100 and 120 kVp, respectively, while flash mode of CTPA was done with a pitch of 3.2 and 120 kVp. There were no significant differences in image quality assessment between the low kVp and standard kVp or high-pitch CTPA protocols (p=0.181-0.186). The mean effective dose for the 100 kVp protocol was significantly lower than that for the120 kVp and the flash mode protocols (p < 0.001). The contrast medium was between 35-45 ml for the 100 and 120 kVp protocols, and 20-30 ml for the 120 kVp flash mode protocol. Double low-dose CT pulmonary angiography is feasible for detection of pulmonary embolism with acquisition of diagnostic images.

The purpose was to determine conversion factors (CF) of SPECT hot images respect to the original size of hot objects in the bone medium. In house phantom has been made in the form of a cubical acrylic (37cm x 15cm x 15cm) provided with cylindrical channel filled with bovine bone powder with the diameter (1.5; 3.5; 5.4; 7.4 cm). As hot objects, a mixture of bone powder and ^99mTc source with various activity and diameter were embedded in filled bone channels. Image acquisitions were carried using Intevo Symbia E Siemens SPECT/CT and LEHR collimator, with surface collimator distance 9.6 cm. There were 6 different in activities and diameter of hot objects in each channel. Conversion factor (CF) was defined as the ratio between FWHM of hot object image profile and the original hot object size. CF value for each diameter channel was varied with the activity and size of the object diameter. The source activities used were 0.1-0.2 mCi and the observed object diameters were 7-12 mm. For hot object size less than resolution stated in SPECT specifications (4 mm), CF values were in the range 1.7-3.4 for 1.5 cm and 3.5 cm channel diameter. For hot objects diameter, 7.5-12 mm, CF value was mostly independent of channel diameters, with the value of (1.1 ± 0.2). This preliminary study informs that CF values of SPECT hot images independent with the size of the host bone medium. Whereas for object diameter ≤ 7.5 mm very relatively higher and influenced by the size of the host bone medium.

Quality control in nuclear medicine imaging is very imprortant which regularly carried out before running exam. The most important in QC is to evaluate QC parameter on SPECT images. Phantoms can be useful for evaluate QC parameters. The phantom was designed to quick QC SPECT system. Hot image from in-house hot phantom and cold image from Jaszczak phantom were used in this study with increasing activity concentration in in-house and Jaszczak phantom. This research is aimed to compare measurement results QC parameters of local uniformity and contrast on SPECT image generated with in-house and Jaszczak phantom. Measurement results from in-house hot phantom showed that lowest activity (0.99 MBq/mL) generated hardly visualized hot image for small diameter object (4.2 and 5.6 mm), and starting to be visible for 8.6 mm object with contrast value of 46.44. The same trend occurred to cold images generated by Jaszczak phantom, at lowest activity (0.068 MBq/mL) the ROI 8.6 mm on diameter object of 15.9 mm give rise to nearly the same contrast of that in hot image. No significant difference was found between local uniformity measured with in-house hot phantom and Jaszczak phantom. In-house hot phantom was robust and can be used as quick QC tool for SPECT system.

Brainwave is widely used as an indicator of brain activity and can be detected by electroencephalography (EEG). The development of EEG device has become more advanced along with the invention of low-cost tiny electronic modules and wireless technology. This research aimed to develop a low-cost wireless modular device for brainwave acquisition based on Arduino microcontroller. The system was designed into sensor block for brainwave receiver and conditioning, and mainboard block for data processing. Dry-active electrode was developed as the sensor, followed by preamplifier module which was also installed at the sensor block. Active filter and DRL circuits were developed on the mainboard part. Arduino UNO was used as the main processor of the device. The developed modules were then evaluated using signal generator to examine the module characteristics and consistency. As the result, the preamplifier module was detected to reach 40.34 dB on gain ability. The cutoff frequency on the active filter module was calculated on 31 Hz. Furthermore, Arduino UNO was identified to have a consistency on input and output voltage.

The aim of this study was to develop software for dual-tracer subtraction parathyroid SPECT using Tc-99m pertechnetate and Tc-99m MIBI. The software was developed using MATLAB and designed into 3 main steps: image registration, image normalization, and subtraction SPECT. Image registration was performed for all transaxial, coronal and sagittal planes with option to manually adjust slice-by-slice. For normalization, a region of interest (ROI) was manually drawn around the thyroid gland for all transaxial slices of pertechnetate SPECT and the thyroid contours were automatically copied to the MIBI SPECT. A normalization factor was then calculated and used to normalize the pertechnetate SPECT. Finally, MIBI SPECT was subtracted from pertechnetate SPECT to generate subtraction SPECT images. Retrospective data from patients were used to evaluate the software. The abnormal findings on subtraction SPECT were confirmed with the surgical pathologic report used as the gold standard. A total of 10 abnormal glands were surgically removed of which 8 were identified by the subtraction SPECT. These findings corresponded to the pathologic results that confirmed 2 adenomas and 6 hyperplastic glands. However, 2 hyperplastic glands were missed due to their small size. This software is user-friendly, efficient and can be used for dual-tracer subtraction parathyroid SPECT.

The radiation beam from a linear accelerator originates from the acceleration of the electrons in the accelerating structure. As the gantry rotates together with the accelerating structure, it is at different orientations with respect to the magnetic field of Earth. The deviations in the path of the electron beam due to the changes in the magnetic fields are corrected by steering coils surrounding the accelerating structure. In the present investigation, all deviations in photon and electron beam parameters of a high energy linear accelerator with gantry rotation are checked. The central axis dose is measured using a parallel-plate ionization chamber placed in the fabricated phantom via parallel-plate chamber holder. To measure the beam flatness and symmetry, a dosimetric plate designed to hold a radiosensitive film is used. The evaluation performed using the fabricated phantom confirms the accuracy of the dose delivered to patients at various gantry angles.

Proton therapy system (Sumitomo Heavy Industries, Ltd.) in Sapporo Teishinkai Hospital consists of a cyclotron, a rotating gantry and a multi-purpose nozzle. This nozzle can irradiate both wobbler beam and line scanning beam. Performance of line scanning was evaluated in this study. The authors investigated for items related to the beam delivery. Dose linearity was investigated with a water phantom and a large parallel plate chamber with several dose rates. For evaluation of irradiation time precision, a solid water phantom and the large parallel plate chamber were used. Furthermore, several spot patterns were measured by Scintillator/CCD camera system for the estimation of beam position. Dose linearity is found with less than 1.8 % error with varying conditions. Regarding irradiation time, error is also confirmed with less than about 1.4 % in this measurement. Beam position accuracy and beam size constancy is also precise enough to be used in clinical use. In conclusion, it is found that results in this study are good enough for treatment.

Current post-RFA (radiofrequency ablation) evaluation of unresectable liver tumours relies on visual inspection of non-enhancing tissues on the contrasted CT (computed tomography) images. This research investigated the correlation between CT number shift (dHU) and tissue temperature change (dT) during real-time CT-guided RFA of ex-vivo bovine livers. The study aimed to develop a non-invasive CT thermometry method to guide clinicians in assessing ablation outcome. 10 liver samples were individually ablated for 12 minutes using a RFA electrode, powered by an impedance-controlled RF generator (Cool-tipTM, Metronic, USA) and subsequently cooled for 15 minutes. An optical fiber inscribed with 4 equally spaced Fiber Bragg Gratings (FBG) was inserted sideward through the liver to measure 4 temperature points at the grating positions. CT scans were performed at interval of 3 minutes from 0 to 27 minute. CT numbers at the grating positions were manually extracted, and dHU and dT were computed and plotted to investigate the relationship. From the results, CT number decreased as temperature increased during RFA, and vice versa. A negative linear relationship (y = -0.66x + 1.23, R² = 0.925) between dHU and dT was observed. The thermal sensitivity was determined as -0.66 ± 0.03 HU/˚C. The strong correlation between dHU and dT during RFA could be used to estimate tissue temperature based on the CT number measured during real time CT-guided RFA. This approach would help the interventionalists in determining the ablation outcome hence improving treatment efficacy.

This study compares methods of addressing the dose perturbation occurred in planning and delivery stage of spinal adjuvant Stereotactic Body Radiotherapy (SBRT) caused by the presence of titanium implants. Dose prediction by TPS was conducted while the CT number of titanium was (a) default, calculated by AAA algorithm ("No Overridden"); (b) relative electron density, mass density matched, calculated by AAA algorithm ("AAA"); (c) relative electron density, mass density matched, calculated by AXB algorithm ("AXB"). In (i) phantom study, dose predictions were compared with measurement conducted with 2 mm, 6 mm and 10 mm thickness of titanium alloy Grade 5 (Ti6Al4V) using field sizes of 1 × 1 cm², 2 × 2 cm², and 4 × 4 cm². In (ii) planning study, retrospective dose predictions on patient plans were carried out to evaluate the impact on clinical outcome. The mean discrepancies (%) between measurement and "No Overridden", "AAA", "AXB" at tissue - titanium interface (titanium - tissue interface) were respectively -16.86 (10.93), -14.05 (11.24), 0.71 (1.54) for 2 mm and 6 mm thickness of titanium; and -18.42 (11.20), -18.29 (11.04), -10.14 (0.01) for 10 mm thickness of titanium, respectively. The patient study results by "AXB" yielded a significant deficit in tumour volume coverage at prescribed dose compared to "AAA" and "No Overridden" by 5.23 % and 9.06 %, respectively. "No Overridden" and "AAA" can potentially generate acceptable prediction in specific scenarios where the depth of target remains approximately unchanged while the gantry rotates. The AXB algorithm is recommended to be used in routine practice involving titanium implants.

The purpose of this study is to investigate the broad 4.438 MeV ¹²C photo-peak found in the Geant4 simulated prompt gamma spectrum from proton beam collision on a thin carbon target. The broad 4.438 MeV ¹²C peak has been reported in previous work using the AFRODITE clover detector performing an absolute comparison of measured and simulated prompt gamma production for a carbon target in the proton therapeutic range. The simulated prompt gamma spectrum was obtained for a 95 MeV proton beam collision on the carbon target by counting the emitted prompt gammas over a 4ˇ solid angle using a Geant4(v10.01.p3) cross-section code with the suggested physics list for inelastic scattering in the proton therapeutic range (binary cascade model). This result was compared to prompt gamma spectra from other Geant4 inelastic scattering physics models. First, the default inelastic cross-section data set (Geisha) was compared to the Tripathi data set, producing basically identical spectra, indicating that the cross-section data set has no bearing on the binary cascade inelastic scatter model. Second, comparisons of the precompound model using an exciton number of 1 and the Geisha cross-section data set provides a 4.438 MeV photo peak that is closer to the experimental result. The precompound model with an exciton number of 1 and the default (Geisha) cross-section data set significantly narrowed the 4.438 MeV photo peak, giving the peak that most closely resembled measured data.

Intensity Modulated Radiation Therapy (IMRT) is a complex form of radiation delivery for the treatment of malignant tumours and other diseases. In IMRT treatment planning, quantitative assessment is crucial to measure and improve the plan quality and treatment delivery. The search for simple and universal quantitative metrics to assess IMRT treatment plan quality has been identified as important, but as yet not entirely successful. The aim of this study was to assess the IMRT treatment plan quality from the perspective of planning conformity. Conformity index (CI) was adopted to quantify the plan conformity. Virtual phantoms were developed for the initial conformity assessment, in order to form a basis for treatment plan inter-comparisons amongst the different IMRT techniques. A series of multi organs at risk (OARs) phantoms was developed to simulate the planning target volume (PTV) and OARs for different configurations. Conformity assessments were undertaken on all the IMRT plans generated using the virtual phantoms. This study has demonstrated the successful development of virtual phantoms to assess objectively and systematically the IMRT treatment plan conformity.

Yttrium-90 (⁹⁰Y) has been widely used in therapeutic nuclear medicine including in the selective internal radiation therapy with ⁹⁰Y-microsphere. In the procedure ⁹⁰Y source is protected within the radiation shielding apparatus made of perspex. However, bremsstrahlung radiation may be generated when ⁹⁰Y interacts with matter. The aim of this study was to evaluate bremsstrahlung radiation produced from radiation shielding apparatus using a scintillation detector and Monte Carlo simulation. The ⁹⁰Y source in glass vial was placed in the radiation shielding apparatus. Bremsstrahlung measurement and spectrum were performed and recorded using thallium-doped sodium iodide (NaI(Tl)) scintillation detector. Counting time and distance between the detector and apparatus were varied to obtain the optimal condition for bremsstrahlung measurement. Monte Carlo N-Particle (MCNP) 5 was used to simulate bremsstrahlung radiation with the same geometry used in the measurement. For experimental measurement results, the optimal distance and counting time were 10 cm and 120 s, respectively. Although the result of bremsstrahlung spectrum from the detector and simulation exhibited similar trend, markedly greater count rate was observed in simulations than in detector measurements. In conclusion, ⁹⁰Y bremsstrahlung can be produced from radiation protection apparatus and this can be evaluated by either measurement or simulation.

This research aimed to investigate the dosimetric change in target and organs at risk during prostate cancer treatment. Target and critical organs positions in prostate cancer were based on daily CBCT. A total of 220 daily CBCT form five patients who were treated with VMAT technique for 79.2 Gy prescribed dose in 44 fractions were selected. The CTV, PTV, bladder and rectum volumes were manually contoured on daily CBCT images after registered with planning CT. The original plan was transferred and recalculated on daily CBCT images. The DVHs were selected to analyze the dosimetric results. In the result, the percent volume difference at V_95% of CTV and PTV were 1.5% ± 3.7% and -6.5% ± 5.0%, respectively. The average volume difference of all V_70Gy, V_65Gy and V_60Gy of daily CBCT and planning CT images showed -21.9% ± 22.6 % and 2.1% ± 51.0% for bladder and rectum, respectively. In conclusion, the dosimetric comparison between using daily cone beam CT and planning CT in VMAT technique for prostate cancer therapy is not significantly different for CTV, in contrast dosimetric difference of the PTV, bladder and rectum are significantly changed.

On-site audits in brachytherapy are performed for all HDR units after commissioning in the Czech Republic. Air-kerma strength, source positioning accuracy, dose calculation accuracy by treatment planning system, and reconstruction algorithm in terms of geometry accuracy are verified. Results obtained in 2003 – 2018 for 24 audited HDR brachytherapy sources are described in the paper. Weak points in HDR brachytherapy process are emphasized. The audited centres often failed in good knowledge of applicators, especially of needles with different blind tip lengths.

Six different phantoms (2x CIRS, 1x Agmeco, 1x QUASAR, 1x Gammex, 1x CatPhan) and Varian formulas were used to evaluate their suitability for CT numbers to relative electron density (RED) calibration in the treatment planning system at two centres using two CT scanners. The variability in calibration curve and the influence to dose calculation in the TPS were estimated for 6 MV and 18 MV. The presence of scattering material around inhomogeneities and influence of CT spectra (90 kV, 120 kV, 140 kV) were evaluated. All phantoms were found convenient for calibration except CatPhan where large deviations were observed for dense bone. Phantoms without scatter material around inhomogeneities should be used with caution. Varian formula slightly overestimates calibration curve in the region of 200 - 300 HU. The tolerance level of 10% suggested for RED during commissioning is reasonable as it can cause change in dose of 3% and 1.5% for 6 MV and 18 MV respectively as a very conservative estimate. Calibration curves should be acquired for all scanning protocols with different CT spectra.

The important task of radiotherapy is to make sure that the radiation dose to the target tumour is accurate as prescribed and the dose to the organ at risk is minimized. Therefore, the aim of this study is to compare and evaluate the efficiency of the dose calculation algorithms: namely convolution, superposition, and fast superposition which installed in Treatment Planning System (TPS) (CMS XiO, USA). In this study, we modified protocols described in IAEATecdoc-1583, where four typical treatment techniques such as single field, multiple field, wedge field, and multi-leaf collimated (MLC) field were analysed from the system. The measurement data for calculated dose and measured dose were taken from thorax CIRS anthropomorphic phantom. The assessment of algorithms was done by comparing the point dose calculated with the measured dose. The study shows that the superposition algorithm produced relative error less than ± 3% which passed 100% of all reference points, whilst the convolution algorithm and fast superposition presented relative error more than ± 3% which passed 82% and 91% of reference points, respectively. In conclusion, the evaluation of radiotherapy treatment plan shall take into account the type of dose calculation algorithm model in order to optimize radiotherapy treatment and ensure the radiation safety to the patient.

This study aimed to evaluate the absorbed doses received by the organs at risk (OARs) following Iridium-192 (¹⁹²Ir) high dose rate (HDR) brachytherapy of the left breast. The MIRD5 adult female anthropomorphic phantom, readily available in the Geant4 Monte Carlo package was used. However, the left breast was modified from 195 to 145 cm³, to represent a breast following lumpectomy. Left breast was chosen due to its higher cancer occurrence than the right breast. The HDR sources were constructed with an outer cylindrical dimension of 4.5 mm (length) × 0.9 mm (diameter). Various influencing parameters were studied, i.e. catheter arrangement (single versus dual plane), source inter-dwell distances (5 versus 10 mm), and different radionuclides, i.e. Cobalt-60 (⁶⁰Co) and ¹⁹²Ir, by delivering a total treatment dose of 32 Gy to the left breast. Absorbed doses to the OARs (e.g. left lung, heart, right breast, spleen, etc.) were then evaluated. A maximum left lung dose of 1.5 Gy was recorded, while doses to the other OARs were all below 1 Gy. The treatment using dual plane catheter arrangement contributed to a slightly higher dose to the OARs, despite equal dose to the breast. There was no dose difference between different inter-dwell distances used in this study. ⁶⁰Co resulted in a slightly higher left lung dose than that of ¹⁹²Ir, while the results were the opposite for the other OARs. HDR brachytherapy allows high dose to be delivered to the breast within a short period of time, with minimal absorbed doses to the OARs.

This study aimed to evaluate the absorbed doses received by the organs at risk (OARs) following prostate treatment with permanent Iodine-125 (¹²⁵I) brachytherapy seeds. In order to simulate an enlarged abnormal prostate due to malignancy, the MIRD5 adult male anthropomorphic phantom (readily available in the Geant4 Monte Carlo package) was modified by increasing the prostate volume to 35 cm³. The permanent seeds were constructed with an outer cylindrical dimension of 4.5 mm (length) × 0.8 mm (diameter). The effects of various activity per seed (0.5, 0.6 and 0.8 mCi), number of seeds (62, 78, 94 and 110 seeds) and radionuclides, i.e. Palladium-103 (¹⁰³Pd), ¹²⁵I and Cesium-131 (¹³¹Cs), towards the absorbed dose to the OARs (i.e. rectum, urinary bladder and both testicles) were investigated. In this study, prostate dose of up to 237 Gy was simulated, which resulted in 11 Gy dose to rectum, 7 Gy to urinary bladder and 4 Gy to each testicle. The doses were considered as reasonable, given the low dose rate nature of the treatment, allowing tissue repair for the OARs. Optimal seeds arrangement was found to consist of 78 or fewer seeds, as it resulted in the lowest dose to the OARs. For similar prostate dose, ¹⁰³Pd resulted in the lowest dose to the OARs, followed by ¹²⁵I and ¹³¹Cs. Permanent seed brachytherapy allows high dose to be delivered to the prostate, while ensuring minimal dose to the OARs.

This study was to evaluate the image quality and radiation dose of kV-CBCT when varying mAs and reconstruction filter. The radiation dosimetry (CBDI_w) and quality control of kV-CBCT image were done. Routine protocols in head, thorax, and pelvis protocols were performed as a reference image. Then the images were acquired with varied mAs, the other parameters were fixed. Each technique was reconstructed with different filter. The image quality in terms of low contrast and high contrast resolution including CBDI_w were compared. The result found that the variation of mAs with auto filter affected low contrast resolution, but slightly effect high contrast resolution. When mAs increased, low contrast detectability increased. Decreasing one step of mAs (16.67%) kept in acceptable image quality and reduced about 15% of CBDI_w. The smooth filter improved the low contrast resolution, but it decreased the high contrast resolution. While the sharp or ultra-sharp filter improved the high contrast resolution. In conclusion, the changing of mAs affects the low contrast resolution and CBDI_W. While the reconstruction filter changed the both of low and high contrast resolution, but no effect to CBDI_w. To optimize the image quality and radiation dose of routine protocols, mAs can reduce one step-down.

Bolus is widely used to protect and reduce irradiation in organ at risk in the process of radiotherapy. Generally, the bolus was made from polymer material due to had property is similar or equivalent to tissue. This study aimed to determine the density, transmission factor, effective mass attenuation coefficient on bolus with radiation of photons and electrons. The bolus material (B) was used Propylene Glycol (PG), Silicon Rubber (SR) and Aluminium Powder (Al), and had four types of bolus namely B - PG 24%, B - PG 24%; SR 8%, B - PG 24%; SR 8%; Al 0,5%, and B - PG 24%; SR 8%; Al 1,5% with dimensions of 11 × 11 cm and thickness of 1 and 1.5 cm. The bolus density is evaluated through the mass of each volume. The measured data revealed that all of the boluses have density values which are similar to tissue or water and air in the range from 0,864 - 1,202 g/cm³. For dosimetry testing, the bolus is irradiated using Linear Accelerator with 6 and 10 MV for photon source and 6 and 12 MeV for an electron source. The results showed that B - PG 24%; SR 8%; Al 1.5% for dosimetry testing both 6 and 10 MV photons obtained properties that resemble soft tissue. Meanwhile, for both dosimetry testing of 12 MeV electrons, the B - PG 24%; SR 8% with addition silicone rubber and aluminum have nature closest to soft tissue. All of the boluses that have been fabricated have properties similar to soft tissue for photon therapy whereas the addition of more aluminum making a bolus has features as a shield on the process of radiotherapy.

Fluoroscopy-guided interventional (FGI) tends to involve long-term procedures that increase the fluoroscopy time and the dose area product (DAP). Therefore, radiation protection is a major concern for interventional radiology staff. This study signifies the occupational and the radiation doses for interventional radiology staff, in particular, non-physician in order to clarify the current dose level for radiographers and nurses. The occupational doses were compared among interventional radiology staff in Institut Kanser Negara (IKN), Putrajaya, Malaysia where 230 patients underwent FGI procedures were observed in one-year. The occupational doses of interventional radiologist (IR), medical officer (MO), radiographer and nurse were recorded using two optically stimulated luminescence dosimeter (OSLD), one worn over and one under their protective aprons. The occupational dose (effective dose) indicated that the IR, MO, radiographer and nurse with double OSLDs were 9.82, 7.91, 6.42 and 6.02 mSv, respectively. The effective dose of IR, MO, radiographer and nurse were 7.63, 7.91, 6.42, 5.66 mSv, respectively using a single OSLD. It has shown a statistically significant difference in the effective dose of double worn OSLDs and one OSLD of (p < 0.05) for interventional radiology staff. In both methods, IR > MO > radiographer > nurse was the highest effective dose in the interventional radiology staff. However, the occupational dose of single OSLD was found to be lower than double OSLDs. It is highly recommended that interventional radiology staff to use double OSLDs during the FGI procedures in order to determine the occupational dose accurately.

The study presents application of an in-house software program to calculate image quality parameters of kV cone-beam CT (CBCT) system in radiotherapy. The parameters include uniformity, noise, contrast-to-noise ratio, CT number linearity, spatial resolution and geometric distortion as recommended in AAPM TG142 and TG179 quality assurance (QA) programme for image quality performance of kV CBCT. The computer algorithm packaged in the software program is developed using MATLAB (MathWorks, Natick, MA). The algorithm was optimised for two CT image quality phantoms, Catphan 600 (The Phantom Laboratory, Salem, NY) and CIRS 062QA (CIRS, Norfolk, VA). The phantoms were scanned with XVI CBCT system (Elekta AB, Stockholm, Sweden) using an optimised CT imaging protocol. The algorithm measures the image quality metrices from the corresponding image quality test patterns in the reconstructed CT images. The algorithm provides image quality parameters from both phantoms quantitatively. The software program allows the results to be exported and recorded in MS Excel for monitoring the performance trend of the image quality parameters. The software reduces measurement uncertainties from qualitative human observation of the test patterns.

The multileaf collimator (MLC) performance is critical during intensity modulated radiotherapy (IMRT) delivery. Picket fence test is typically performed by acquiring images of MLC gaps using film or electronic portal imaging device (EPID) to assess the MLC positional accuracy as part of a comprehensive weekly quality assurance (QA) programme. This study aims to investigate the accuracy of MLC position of Agility MLCs (Elekta, Stockholm, Sweden) using linac log data. The positions of MLCs were tracked during picket fence test using Elekta's propriety optical tracking system on the linac head. The data were recorded at four cardinal gantry angles over six weeks. The fluence from the picket fence was constructed using the tracked MLC positions and compared with the fluence obtained from EPID. The fluence of the picket fence pattern constructed from the tracking data of MLC position showed that the measured range of gap size error within -0.3 mm to 0.8 mm. The average MLC positional error tracked was 0.07 mm ± 0.14 mm (mean ± 1 SD). Gap size measured from tracking data was within the range of the results obtained from EPID. Tracking the MLC position using the optical tracking system provide a more accurate test method for routine QA of the MLC performance. Over the period of investigation, it was found that the MLC performance was within the tolerance of ± 1 mm recommended by AAPM TG142.

The influence on target motion resulted from the respiratory process, the pitch and modulation factor presented in Tomotherapy. This study was aimed to investigate the effect of motion management using CT-images obtained from the fusion process between the static and dynamic scanning mode on the CIRS Thorax Phantom. The images were created using axial and helical modes which amplitudes were varied from 10 mm, 15 mm, and 20 mm. Then, the organ structures were planned using TomoPlan TPS with the variation of pitch ranging from 0.25 to 0.5, and the modulation factor (MF) in the range 2 to 3. Furthermore, evaluation of radiotherapy planning was performed using dose parameters on target, the organ at risk, homogeneity index (HI), and mean leaf open time (LOT). Target volume for static mode was 3.53 cc, whereas target volume has changed to 10.9 cc, 10.3 cc, 16.1 cc for axial and 6.6 cc, 8.5 cc, 14.9 cc for helical scanning. The HI value obtained was less than 0.07 and lower HI was resulted for a larger MF. It means that the higher modulation factor values will provide a uniform dose distribution to the target and lower dose to the OAR. The greater value of pitch gave the greater mean LOT. The optimum parameters were at the pitch of 0.5 and MF of 3 based on the evaluation of mean LOT and HI. Axial scanning mode provides a larger target volume compared to a helical scanning mode. Therefore, the increment of the target volume in delineating organ should be considered.

Flattening filter free linear accelerator (FFF LINAC) has been installed in Indonesia. To ensure the accuracy of FFF irradiation, we evaluate the characteristic of FFF in regular and small fields. We employed the Monte Carlo (MC) simulation of FFF LINAC 6 MV as a standard reference in this study. Then, we compared the calculation of FFF beam at central and lateral axis to the measurement and TPS at 10 × 10, 1 × 1, 2 × 2, 3 × 3, 4 × 4 cm² field sizes. Output factor (OF) and beam quality such that TPR_20,10 and penumbra of FFF LINAC were evaluated. TPR_20,10(S) for 10 × 10 cm² was 0.01 differ between MC and measurement whereas it varied from 0.588 to 0.703 for small fields. Dose difference of lateral axis was agreed within 3% except for the penumbra region. Output factor of small fields measurement indicated that field size of 1 × 1 cm² had a large discrepancy to MC according to this works. The TPR_20,10(10) of MC, TPS, and measurement was not a significant difference, while the OF was tending to a large deviation in 1 × 1 cm². The results showed that our FFF LINAC could be used for small field until 2 × 2 cm².

This study aimed to investigate the Multi Leaf Collimator (MLC) quality assurance (QA) and fluence monitor unit (MU) reconstruction based on log files of Varian Linear Accelerator. The graphical user interface (GUI) was developed using MATLAB to analyze the Log files. The MLC QA was analyzed using the error root mean square (RMS) of leaf parameters. Meanwhile, the fluence MU were reconstructed based on the information of leaf position, jaw position, and fractional MU for each 50 ms. The gamma index evaluation between actual and expected fluence MU was calculated to analyze the segment potential error caused by the MLC position. The average of mean error RMS leaves for Bank A and Bank B are 0.213 ± 0.098 mm and 0.207 ± 0.073 mm, whereas the average of maximum error RMS leaves for Bank A and Bank B are 0.491 ± 0.056 mm and 0.48 ± 0.061 mm, respectively. The mean gamma index results of 2%, 2mm and 3%, 3mm criteria between actual and expected fluence MU for the composite beam for all case are 98.2 ± 1.0% and 99.4 ± 0.3%, respectively. The error of MLC based on the log file analysis is within the tolerance level. The results showed that parameters irradiation such as MLC position, jaw position and fractional MU proper with planning.

The purpose of this study is to determine the correction factor of the composite field (k_pcsr,msr) of Tomotherapy for head and neck cases and to investigate the influence parameters of the pcsr field. This study employed Exradin A1SL and A 16 as the investigated chambers, and EBT3 as the reference dosimeter. The pcsr fields were created based on cylindrical water solid phantom. The results of this study show that the k_pcsr,msr values for both detectors increased with increasing field width (jaw), decreasing complexity level, and increasing pitch value. The yielded results indicate several factors affecting the k_pcsr,msr values: target homogeneity, volume averaging effect, thread effect, and the difference of general recombination at the different field width. These results represent that k_pcsr,msr is specific and depends on the parameters of the composite field. The k_pcsr,msr values for head and neck cases vary from 0.978-1.028. This variation implies that the determination of pcsr field should be according to the parameters used in clinical conditions. Due to the different position of the chamber and the film, the target should have excellent dose homogeneity to avoid the different response of the detectors.

Non-coplanar VMAT spares critical organs with short delivery time while maintaining PTV coverage. Due to the growth patterns of pituitary adenoma, the beam angle selection step was simplified by finding the optimal couch angles and number of arcs. The 2 clinical cases with difference PTV sizes were selected to study the results of dose distribution between coplanar and non-coplanar techniques. Later, couch angles were varied from 30° to 90° and 270° to 330° with a 15° interval. The numbers of arcs were varied from 3 to 4 arcs. Then, the selected protocol was applied to 5 pituitary adenoma patients. It was found that 90° and 270° couch angle showed the highest scores. However, these beams passed directly through the body, so the second couch angles of 75° and 285° were selected instead. For number of arcs optimization, 3-arc plan and 4-arc plan demonstrated a similar score. However, the 3-arc plan illustrated an obviously shorter treatment time. After the selection was proven to the 5 patients, there were 4 patients who passed the criteria, while 1 patient did not pass the hippocampal planning criteria. In conclusion, the suggested couch angles were 75° and 285°. The optimal number of arcs for pituitary adenoma was 3 arcs.

The objective of this study was to evaluate the Delta 4 system for lung VMAT technique. The standard fields and VMAT plans were generated into the homogeneous and heterogeneous phantoms and were evaluated using 2%/2 mm criterion to validate the Delta 4 system. For retrospective study, five lung VMAT plans were evaluated using 2%/2 mm criterion. The point dose was measured to ensure the accuracy of beam delivery. Moreover, the 1.0 mm MLC position error was introduced into the VMAT plan of homogeneous phantom and was evaluated using 2%/2 mm and 1%/1 mm criteria to evaluate the small error detection. The range of percentage gamma passing rate for standard fields and VMAT in both phantoms was 94.6% to 99.8%. For five retrospective lung VMAT plans, the range of percentage gamma passing rate was 96.6% to 99.5%. The point dose differences were within ± 3%. For 1.0 mm MLC position error, the percentage gamma passing rate for 2%/2 mm and 1%/1 mm were 99.1% and 83.6%, respectively. In conclusion, the Delta 4 system can be used in patient specific QA for lung VMAT cases using 2%/2 mm criterion. The error magnitude 1.0 mm can be detected by 1%/1 mm criterion.

This study aims to evaluate the factors influencing electron dose calculation in Eclipse electron Monte Carlo (eMC) on virtual phantoms. Each parameter of accuracy, calculation grid size, random number generator seed, number of particle histories, smoothing method and smoothing level in Eclipse eMC was varied while other parameters were fixed in default value. Gamma analysis was used to evaluate dose distribution accuracy. The reference dose distributions were set as the best option values. The 1% accuracy, 1 mm calculation grid size, 2100000000 random generator seed number, 0 number of particle histories, 3D Gaussian smoothing method and strong smoothing level with 2%/2mm criteria were defined as the best option values. The 6 and 18 MeV energy, the sizes of 6x6 cm² and 10x10 cm² applicator were used. The overall results showed the gamma passing rate higher than 90% except when higher accuracy than 2%, 5 mm calculation grid size, no smoothing/low smoothing level and changed the number of particle histories other than 0 were applied. This study shows that the accuracy, calculation grid size, smoothing method, smoothing level and number of particle histories parameters are significantly impact to dose distribution and the first two factors are also affect to calculation time.

This study aimed to evaluate ion recombination correction for ionization chamber in flattening filter free (FFF) photon beams and compare it to the flattened (with-flattening-filter) photon beams. The evaluation of ion recombination correction factor was performed for FC65-G, SNC600c, and CC13 ionization chambers. The measurements of three ionization chambers were performed using the water phantom and the Varian Trilogy linac with FFF capability. The ion recombination correction factor values for the three ionization chambers were obtained from the calculation using the simple two-voltage method and Jaffe plot curve fitting. The ion recombination correction factor value obtained from all three ionization chambers were higher for unflattened (FFF) photon beams than the flattened (WFF) photon beams with discrepancy less than 3%. The ion recombination correction value obtained from the linear Jaffe plot curve fitting had the highest discrepancy at about 7.67% when compared to the two-voltage method. On the contrary, the ion recombination correction value obtained from the Jaffe plot with quadratic and exponential quadratic curve fitting had discrepancies less than 2% when compared to the two-voltage method.

This study evaluated the effect of small systematic errors, such as those from a multileaf collimator (MLC), on the quality of intensity modulated radiotherapy (IMRT) treatment plan delivery. Two IMRT quality assurance (QA) verification techniques, field-by-field (FBF) and singe-gantry-angle composite (SGAC), were performed to evaluate both original and modified plans using a 2D ion chamber array detector. The dose distributions measured by the array detector for both FBF and SGAC were compared with the dose distribution calculated by the treatment planning system (TPS). FBF was found to be more sensitive than SGAC at detecting small systematic errors such as the opening and closing of the MLC's segments, which were evaluated with respect to a gamma-index of 3%/3 mm and 2%/2 mm. The systematic errors involved in closing the segments of the anterior field by 2 mm and 3 mm showed a significant difference compared with the original field (unmodified): 83.1 ± 1.7% and 42.9 ± 1.9% gamma-index passing rates, respectively, for FBF. For SGAC, the magnitude of closing the MLC by 2 mm remained unnoticed and resulted in a 95.1 ± 2.61% gamma-index passing rate. Opening the MLC by 2 mm gave a false negative, but more than 5% of the rectum received 75 Gy, which exceeded the tolerance radiation dose recommended by the Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC).

Small field dosimetry which related to the use of Flattening Filter Free (FFF) beams is a great challenge because of the perturbation effects caused by the size of the detector's active volume or detector's materials. This phenomenon encourages researchers to do a further study about detector response. In this study, scatter and primary radiation from 6 MV FFF photon beams were studied to evaluate the detector response in small fields for a better understanding of the contribution of every phenomenon. Ion chamber and Gafchromic films were used in three measurement configurations representing open field measurement and approximations of both primary and scatter part of the beam, described as follows: (i) detectors positioned under steel block, exposing the detectors only to scatter part of radiation field, (ii) detectors positioned inside mini phantom, approximating the detector response to primary radiation with minimum scatter, (iii) detectors positioned in the standard open field, which was the superposition of the primary and scatter radiation. The results show that detector responses were heavily depended on its design (i.e. active volume) especially in small beams. The detector response in the open field could be reproduced from the blocked and primary beam set-up with a discrepancy ranging from 1.0% to 36%. Moreover, the volume averaging and other phenomenon affecting the detector response could be observed in the blocked beam.

This study aimed to make in-house dynamic thorax phantom that simulate translational and rotational direction mimicking NSCLC target movement. In addition,this study also investigate dosimetric effect of target movement for several translational amplitude. This work used in-house dynamic thorax phantom based on CIRS Dynamic Thorax Phantom model 008A. This phantom simulated translation in superior-inferior direction, rotational in the anterior-posterior and left-right lateral plane to mimic human respiratory motion. It was designed and controlled by linear actuator motor, servo motor, Adafruit motor shield L293D and Arduino UNO R3. It was implemented to evaluate point dose of 3D-CRT, IMRT, VMAT technique and for 5 mm; 10 mm; 15 mm translational motion amplitude 90° rotational target motion amplitude. The GafChromic EBT 3 film was used as a dosimeter for point dose measurement. This in-house dynamic thorax phantom can mimicking NSCLC target movement for translational amplitude 5 ± 1 mm; 10 ± 1 mm; 15 ± 1 mm and rotational amplitude 90° ± 3°. The average dose deviation of target dose (centre and peripheral) of TPS dose planning and target motion measurement on 3DCRT with 5 mm, 10 mm and 15 mm were 3.2%, 3.1%, and 1.8% respectively, and dose deviation on IMRT were 3.9%, 2.5%, and 2.8%, while dose deviation on VMAT treatment were 4.2%, 4.6%, and 6.1% respectively. The preliminary result supported the previous work by Mukhlisin. Furthermore, rotational movement of phantom contributed in average of 1.5% compare to translational movement only.

A biocompatible and biodegradable radioactive samarium-153 (¹⁵³Sm)-labelled Poly-(L-lactic acid) (PLLA) microspheres was developed for hepatic radioembolization. Samarium acetylacetonate was encapsulated in PLLA microspheres using oil-in-water solvent evaporation method. Physicochemical characterization of the microspheres were analysed using Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray spectroscopy and particle size analyser. The prepared microspheres were irradiated in a nuclear reactor with a neutron flux of 1.49 × 10¹² n.cm-2.s^-1, converting ¹⁵²Sm to ¹⁵³Sm (E_max = 807.6 keV, half-life = 46.3 h). Gamma spectroscopy was carried out to determine the presence of radionuclide impurities while the in-vitro radiolabelling efficiency was performed to analyse the retention of ¹⁵³Sm on the microspheres. The Sm-labelled PLLA microspheres was found spherical with the diameters within 20-60 μm, as indicated by the scanning electron microscopy and particle size distribution results. Gamma spectrometry suggested that no long half-life radioimpurities present after neutron activation. The ¹⁵³Sm-labelled PLLA microspheres has achieved a nominal activity of 5.9 GBq.g^-1 after 6 h neutron activation. The formulation showed more than 97% radiolabelling efficiency in saline and human blood plasma over 550 h. The ¹⁵³Sm-labelled PLLA microspheres are potentially useful for hepatic radioembolization due to their biodegradability, favourable radiation characteristics and excellent radiolabelling efficiency. The preparation of the formulation does not involve ionizing radiation and hence reduces the costs of production.

Advancement of CT technology has increased the frequency of CT scanning in diagnosis. However, the concern on dose increment that related to radiation-associated health risk from CT also improved. The aim of this study was to establish an institutional diagnostic reference level (DRL) for computed tomography (CT) imaging associated with multiple or combined anatomical regions and compared with other international DRLs. CT dose data of 705 subjects were collected retrospectively from January 2015 until December 2017 at AMDI, USM, Malaysia. The most common CT examination of combined anatomical regions were neck-thorax-abdomen-pelvis (NTAP), thorax-abdomen (TA), thorax-abdomen-pelvis (TAP), and abdomen-pelvis (AP). CT dose data such as CTDI_vol, CTDI_w and dose-length product (DLP) were collected including contrast, non-contrast, single-phasic, and multiphasic examinations. The 50th and 75th percentile of dose distribution were calculated and compared with other established DRLs. TAP CT was the most frequently performed examination at AMDI (73%). The local dose values of multiphasic and non-contrast examinations were higher compared to single phasic and contrast study. The results show a weak correlation between different CT sequences and DRLs for AP examination. Local dose values reported for all CT examinations were below any international DRLs except for CT TAP (multiphasic) study. The institutional DRL for combined anatomical regions was established using the third quartile values of dose distribution and is categorized based on CT sequences.

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) has been the focus in medical imaging as MRI contrast agents. SPIONs demonstrate intriguing properties that not only advantageous in diagnostic imaging but also for therapeutic application. In this study, the radiosensitization characteristic of SPIONs in electron beam radiotherapy and brachytherapy were investigated. This study was conducted in-vitro using HeLa cells with SPIONs (15 nm) concentration of 1, 2 and 3 mMol/L. Irradiations were done at doses ranging from 0 to 10 Gy using electron beams of energy 6 and 12 MeV as well as 0.38 MeV ¹⁹²Ir brachytherapy source. Cell survivals were determined from clonogenic assay. Radiosensitization characterization was performed by analyzing the sensitization enhancement ratio (SER) expolated from the survival curves. The results show SPIONs induce radiosensitization effects in electron beams especially at lower energy with SER value obtained up to 1.5. The radiosensitization is more prominent for brachytherapy with SER value around 2. Concentrations of SPIONs also play important roles in which higher SPIONs concentration are more likely to increase radiosensitization effects. In conclusion, radiosensitization are dependent on radiation energy and concentration of the SPIONs. Further characterization of the radiosensitization induced by SPIONs may enable clinical translation of SPIONs as radiosensitizer in radiotherapy.

This paper aims to assess the dose-response characteristics of delaminated GAFCHROMIC™ EBT3 films for radiotherapy beams. Delaminated EBT3 films were produced by peeling off the top polyester substrate of original EBT3 using surgical precision forceps. The films were irradiated to 500 cGy with photon beams of 6 MV and 10 MV, while proton and ¹⁹²Ir exposures were conducted at nominal energies of 150 MeV and 0.38 MeV respectively. Digitisations were made using a flatbed scanner in Red-channel for optimum sensitivity. Analyses of data fitting, reading reproducibility, film integrity and energy dependency were then implemented for comparison with original EBT3 films. Results of R² in each curve suggested that the selected non-linear function appropriately fits the data with low reduced chi-square. However, the delaminated films experience integrity degradation of up to 13% due to active layer distress, affecting the reading reproducibility with values extending to 1.0%. Plus, the mean relative response ratio of energy dependency for delaminated EBT3 in photon irradiations was observed at 0.97, which is inferior to their original counterpart. In summary, the delaminated EBT3 yields comparable dose-response behaviour despite integrity deterioration. It is important to factor film delamination uncertainties into existing uncertainty budget as it is instrumental in reading dose-response deviations. Accurate evaluation together with reliable fabrication processes could make delaminated EBT3 attractive in specific applications including α-particles dosimetry and ultraviolet radiation monitoring.

Stereotactic radiotherapy treatments use high doses of radiation delivered in relatively few fractions compared with conventional radiotherapy. Specialist planning, immobilization and image guidance techniques are needed to achieve accurate treatment. Because doses are high and fractions few, the consequences of treatment errors are more severe than for conventional therapy. A credentialing program for staff and equipment is one strategy that can be used to reduce risk. The Icon Group runs a network of 20 radiotherapy centres in Australia. There has been a rapid growth of stereotactic treatments at Icon. In order to reduce the risks of introducing stereotactic therapy, an in-house credentialing and endorsement program was developed. A multi-disciplinary working group comprising medical physicists, radiation oncologists and radiation therapists was established to develop endorsement policies and procedures. Elements considered included the purchase, commissioning and quality assurance of equipment, the establishment and documentation of safe work practices and staff competency assessment. The endorsement program is in the process of being implemented across the Icon network.

Several clinical situations call for the use of radiobiological principles as powerful clinical tools. The aim of this project is to examine the effect of radiotherapy dose intensity on local tumour control for non-small cell lung cancer (NSCLC) using the biological effective dose (BED) concept. A two-year tumour control probability (TCP) model was developed based on the linear-quadratic cell concept combined with Poisson statistics. The two-year local control outcome was analysed for the radiotherapy dose using the BEDs. The BED calculations and the TCP model were fitted to a series of NSCLC patients drawn from the literature. The investigation is based on the two-year local tumour control rate for stage I-II NSCLC for a dose fractionation size that varied from 1.5-20 Gy per fraction delivered via three radiotherapy treatments: 3D-conformal radiation therapy (3D-CRT), continuous hyperfractionated accelerated radiotherapy (CHART) and stereotactic ablative body radiotherapy (SABR). The BED values of 2,280 patients were computed and analysed as a function of local tumour control. To quantitatively assess the correlation between the BED and local tumour control, a residuals analysis and linear regression were performed. Higher radiotherapy doses were associated with improved local tumour control and survival rates for NSCLC, as suggested by the coefficient of the correlation R² statistical test: 0.83 for the 3D-CRT and 0.91 for the SABR treatment.

This study investigates the use of electron spin resonance (ESR) signals from human fingernails for retrospective dosimetry as part of radiation disaster response, focusing on the variabilities of individual responses to radiation. Samples of fingernails were collected from 7 adult donors (Asian type) and irradiated to 35 Gy and 70 Gy of gamma-rays from a Cs-137 source at a dose rate of 0.857 Gy/min. All irradiated fingernails were measured for 39 days with an X-band ESR spectrometer and stored in darkness inside the vacuum desiccator (30% humidity, 20°C) in between measurements at all times. All samples were harvested using one specific nail cutter and given no other special treatments. It was observed that the measured radiation-induced signals faded on about 10-12% after 1 day of exposure. Though the signal intensities showed a significant difference among the donors, stronger linearities in the dose responses were observed in the samples of younger donors. From the results obtained in this study, it is expected that fingernails would be a useful tool for retrospective dosimetry in case of an unexpected radiological accident or medical treatment error associated with exposure in therapeutic dose range, as far as the individual-based calibration curves were available. Further investigations will be made to clarify the reason for the different responses by using the fingernail samples taken from a greater number of donors of different ages and lifestyles.

This study evaluates the correlation and cycle of public interest in radiation worldwide with radiation-related incidents between countries using Google Trends from 2008 to 2018. Google trends was employed to normalise traffic data on a scale of 0 to 100, and were presented as monthly relative search volume (RSV) using radiation, radioactive, nuclear medicine and x-ray as a search term. A remarkable peak was identified in March 2011 during the Fukushima Daiichi nuclear disaster. In conclusion, public interest towards radiation is correlated with radiation-related incidents or events.

Established in 2002, this long running MSc in Medical Physics program was awarded CAMPEP accreditation in 2015, thus being one out of only two CAMPEP approved graduate programs outside North America. The program is a full-time, one-year taught master course delivered by a close university–hospital collaboration. This paper will give an outline of the current program structure and will identify challenges likely affecting the areas of teaching, research and course administration. Strategies to address these challenges will be discussed. Since the accreditation, the number of students enrolled in the program increased from 8 in 2015/16 and 16 in 2016/17 to 21 in 2017/18 and 25 in 2018/19. The number of non-EU students in these cohorts was 2, 5, 4, and 9 respectively. Non-EU students predominantly originate from North America and Saudi-Arabia. The total number of applicants averages at approximately 55 per year. A further increase in student intake has been advocated but might impact negatively on the quality of the clinical training which forms a vital part of the program. Students are given access to clinical systems for laboratory exercises as well as for pursuing research projects, thus gaining some clinical experience which will increase their employability. However, local clinical access has to be limited. In order to mitigate the situation, the program cooperates with medical physics departments nationwide and internationally. Curricular challenges arising from clinical implementations of ever-evolving technologies and from a rapidly changing medical physics landscape in general will be expanded on.

Picocell antennas are used to improve wireless communication coverage inside an area. More picocell antennas are being used to cover small areas, thus, increasing the radiofrequency radiation (RFR) levels in an indoor environment. One method in estimating the radiofrequency radiation is by using spatial interpolation techniques. This study assessed the robustness of a localized deterministic spatial interpolation method compared to its global interpolation counterpart used in generating a radiofrequency radiation map. This was investigated to speed up the data analysis by taking a smaller number of samples. An omnidirectional picocell antenna located in an office lobby area was chosen. The NARDA Selective Radiation Meter SRM-3000^TM with tri-axis antenna was used to check the central frequency and average power density emitted by the antenna. A radiofrequency map was generated using a small sample size in a grid pattern. The local Shepard interpolation method with a radius of influence of 100 cm and a power factor of 1 gives a result with a mean absolute difference lower than the global interpolation method. Thus, error contribution in RFR map generation can be minimized by considering a smaller region of samples in the interpolation.

Fluoridated hydroxyapatite (FHA) occur in teeth and form the basis for application as a biomaterial. This work aims to synthesize and analyze the characteristic of FHA nano-powder with different degrees of fluoridation via microwave irradiation method. FHA nano-powder with a chemical formula of Ca₁₀(PO₄)₆(OH_2-x)F_x (where degrees of fluoridation, x values were selected equal to 0.7 and 1.3) were synthesized using a mixture of calcium hydroxide, diammonium hydrogen phosphate, and ammonium fluoride solutions by utilizing microwave with the variation of irradiation power. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy analysis techniques were utilized in order to evaluate the characteristic of synthesized FHA nano-powder. The XRD and FTIR results confirmed highly crystalline FHA powder with the carbonate peaks in the IR spectrum. Using a Scherrer formula, the average crystallite size was found to be 30 nm. The SEM and EDX results indicated various element composition and several morphologies with the lattice parameter increased along with irradiation power. FHA nano-powder could be synthesized via microwave irradiation method. The results from different kind of analysis illustrated that synthesized FHA nano-powder could fulfill the requirement of ASTM F1185-88 for used as biomaterial.

Magnesium-Hydroxyapatite (MgHA) is synthesized by substituting magnesium (Mg) into hydroxyapatite (HA). The study's aim was to synthesize MgHA nano-powder via microwave irradiation and determine the effects of the microwave irradiation's power and irradiation time variation on the synthesis of the MgHA crystal. The synthesis of MgHA was done by titrating solutions of diammonium hydrogen phosphate and magnesium hydroxide into a solution of calcium hydroxide. The microwave irradiation was done with variations of irradiation power and time. The phase composition, functional groups, morphology, particle size, and the element composition of the MgHA powder was evaluated using the following characterization method; XRD, FTIR, and SEM-EDX. The XRD patterns show that lattice parameters a and c, crystallinity index, and crystallite size of MgHA decreases as the irradiation time increases. The FTIR results show that a stretching mode is caused by the bonding of Mg²⁺ and the hydroxyl group. The SEM and EDX results shows that the substitution of Mg²⁺ causes the particles to agglomerate and the Ca/P value of MgHA was determined to be lesser than 1.67, showing that some Ca²⁺ was released from the apatite. The results show that higher irradiation power and longer irradiation time is more effective in MgHA synthesis.

Carbonated hydroxyapatite (CHA) is a bone implant material that has good solubility and resorption. In this study, CHA was synthesized and characterized using microwave–assisted precipitation method under different irradiation power and time. CHA powder was synthesized starting from calcium hydroxide, diammonium hydrogen phosphate, and calcium hydroxide. Chemical and physical analyses, XRD, FTIR, SEM, and EDX, were applied to investigate the composition, crystallinity, crystallite size and morphology of CHA powder. XRD patterns showed that CHAs had low characteristic peaks that indicating poor crystallinity. According to the crystallinity index, 450 W 30 minutes CHA with CI = 35.3% and SF = 2.908 was chosen as the best result because it was the closest result to the bone crystallinity reference. The crystallite size for all CHA samples reached 19.386 – 24.019 nm, were almost similar to the crystallite size for bone. FTIR and EDX affirmed that CHA bond existed. The carbonated hydroxyapatite was formed B type CHA with some additional A and AB type. CHA crystal was formed of nanorod particle. Hence the physical and chemical analyses suggest that CHA powder can be obtained using a microwave-assisted precipitation method with good results

Hydroxyapatite (HA) is a calcium phosphate with a chemical bond of Ca₁₀(PO₄)₆(OH)₂, which is similar to the inorganic substance contained in human bones. Thus makes HA convenient for further development as a biomaterial. The aim of this work is to understand the effect of variation in microwave power and time in synthesizing HA. HA was synthesized by a mixture of calcium hydroxide and di-ammonium hydrogen phosphate, maintaining the molar ratio between calcium and phosphate of 1.67. The sample was irradiated by microwave irradiation at different powers and time duration. The properties of all samples were investigated by x-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM-EDX). The mass of HA samples showed a quite significant change while the crystallite size of the samples reached 34.99 nm. The FTIR results showed some carbonate peaks. It is proved that the change in irradiation power and time affects the properties of the synthesized HA. The synthesized HA powders showed a similar structure to hydroxyapatite in hexagonal P63/m space group a=b=9.418 and c=6.887.

Chitosan is a natural polysaccharide which has bioresorbable, biocompatible, and non-toxic properties. The combination between chitosan and hydroxyapatite will form a nanocomposite which improves its mechanical properties and can be applied as a bone implant material. The aim of this work was synthesis and characterization of composite hydroxyapatite-chitosan through in situ way utilized by microwave irradiation with time variation. A composite which was formed by hydroxyapatite and 2% chitosan solution through in situ way were irradiated by 270-watt power for 20-60 minutes with an interval of 10 minutes. The XRD results showed peak hydroxyapatite and chitosan. Meanwhile, the highest crystallite size was found in 50 minutes composite with value 20.87 nm. The FTIR spectroscopy identified the functional group of hydroxyapatite and chitosan (NH). Increase in irradiation time caused reduction of chitosan-based on the existence of NH composition. Highest mass was present at time 20 minutes which means the reduction of mass also occurred with increasing irradiation time. The SEM and EDX results indicated the hydroxyapatite has filled chitosan matrix. The presence of NH cluster proved that microwave irradiation method can be used to synthesize nanocomposites hydroxyapatite and chitosan. Increase in irradiation time caused a reduction of chitosan existence and its mass.

The research on the developments of thermoluminescence (TL) material in nano- and microstructure are increasing in recent years. There are many new techniques developed for preparing TL material that aim to improve and investigate the structure, morphology, and TL characteristics. In this study, the TL characteristics of CaSO₄ doped with Dysprosium (Dy) were being observed. CaSO₄:Dy was performed by co-precipitation method with 0.1 mol% Dy concentration. The obtained sample was irradiated with Cs-137 for gamma source and Sr-90 for beta source with doses of 5, 10, 15, 20 and 25 mGy. After irradiation, the structure, morphology, and TL response were observed by using XRD, SEM, and TLD Reader Harshaw 3500. XRD results showed that the average crystallite size for CaSO₄:Dy were 58 nm. But, the presence of dysprosium could not be clearly observed from XRD results. The characterization results from SEM for CaSO₄:Dy had shape resembling needle-like crystal. The TL response of CaSO₄:Dy was compared from beta and gamma radiation source. TL responses for Cs-137 source were 26.56, 34.09, 51.85, 75.97, and 86.29 nC for 5, 10, 15, 20, and 25 mGy, respectively. Sr-90 source with the same dose obtained TL responses as follows: 35.67, 68.60, 100.87, 121.69, and 179.85 nC. The shapes of the glow curves were almost identical, but these curves had different intensities. The TL response from β-ray source obtained a higher intensity than from γ-ray source because the beta source is a particle with mass so that it will have more interaction than gamma source in TLD material.

The formation of composite of collagen and hydroxyapatite (HA) was investigated by ex-situ precipitation method. Synthesis of HA was carried out by precipitation of Ca(OH)₂ 1 M and (NH₄)₂.HPO₄ 0.6 M with the molar ratio of Ca/P 1.67, the mixture was exposed to microwave irradiation (450 W) for 45 min. Subsequently, the result was sintered to produce the powders of HA. Verification of HA powders was performed using X-Ray Diffraction (XRD). Chicken collagen was prepared in our laboratory (Physics Department, Universitas Indonesia). Composite was synthesized by ex-situ precipitation method with a mass fraction of collagen and HA was 2:1. The mixture was stirring continuously for 2 h and aged for 20 h at room temperature. The precipitate was dried by freeze-drying method. The composite result was examined by Scanning Electron Microscopy (SEM). XRD pattern of sintered powder shown as HA crystal. The unit cell of HA crystals was evaluated by High Score Plus Program (a=b=9.425 and c=6.884) with the accuracy 98.175% for a and b lattice and 98.406% for c lattice. The collagen had been verified by SDS PAGE as type 1 collagen and the micrograph illustrated the presence of micropores. Based on SEM examination, the composite revealed that HA had been deposited onto collagen and filled part of void space of collagen. The preliminary study will be beneficial for leading the formation of composites of collagen-HA as biomaterials.

Mechanism of red blood cell (RBC) collision is still an interesting subject to study due to its importance in understanding how to count number of RBCs, e.g. in a blood test, for detecting, diagnosing, and monitoring the progression of blood disorders. In this work RBC system is simplified into a two-dimensional system and head-on one-dimensional collision is chosen for testing the system. Deformation on each cells during collision are observed.