The publishers of Physics in Medicine and Biology (PMB) in association with the journal owners, the Institute of Physics and Engineering in Medicine (IPEM), jointly award an annual prize for the 'best' paper published in PMB during the previous year.

The procedure for deciding the winner has been made as thorough and comprehensive as possible, and the winner may therefore be duly proud. We started off with a shortlist of the 10 research papers published in 2007 which were rated the best based on the referees' quality assessments. Following the submission of a short (1 page maximum) 'case for winning' document by each of the shortlisted authors, an 'IPEM college' of 45 jurors of the status of Fellows of the Institute of Physics and Engineering in Medicine assessed and rated these 10 papers in order to choose a winner. A clear winner emerged—a paper that was, moreover, given the maximum score by one of the original referees, who stated that 'this is the most exciting and potentially important paper I have seen in a long long time'. We have much pleasure in advising readers that the 2007 Roberts Prize is awarded to the group from Sydney and Perth, Australia, for their paper on bystander effects:

Cellular response to modulated radiation fields
E Claridge Mackonis, N Suchowerska, M Zhang, M Ebert, D R McKenzie and M Jackson
2007 Phys. Med. Biol. 52 5469–82

Of course all the shortlisted papers were of great merit, and in this editorial we briefly summarise them all (in the order in which they were published). All those shortlisted will hopefully be happy to be in that position.

The first article on the shortlist is a paper on elastic modulus imaging by Barbone and Oberai (2007). In this work the authors present relatively simple and elegant solutions for inverse problems that attempt to reconstruct the elastic modulus distribution from measured displacement distributions, based on the full (vector) elasticity equations. The exact solutions developed here should be of great interest to those working in the field of elastography, and may lead to the development of real-time imaging tools.

In their paper on electric fields induced in the human body by magnetic resonance imaging (MRI) field gradients, Bencsik et al (2007) describe the results of numerical calculations of the electric field and current density induced in an anatomically realistic body model due to MRI gradient coils. The authors have obtained realistic electric field maps for the first time which should prove to be very useful in helping to predict the most likely sites of peripheral nerve stimulation, and also in the design of new gradient systems for MRI.

The paper by Lazebnik et al (2007) reports the results of a large-scale experimental study of the dielectric properties of normal breast tissue in the radiofrequency (RF) and microwave (MW) frequency ranges. These properties are of great importance in the field of breast cancer detection and hyperthermia treatment by means of RF/MW electromagnetic fields. The large scale of the study (involving tissue obtained from 93 patients) makes this a very reliable study on breast tissue electromagnetic properties on which much future work is likely to rely.

In their paper on computer models of the human body for use in evaluating radiation organ dose, Lee et al (2007) describe the construction of hybrid computational phantoms of a female and a male newborn patient from an existing individual voxel phantom. This paper shows how the non-uniform rational B-spline (NURBS) modelling tool can be used to improve the anatomy of voxel phantoms, especially in regions of the body where medical imaging does not provide enough information for exact organ design, bringing voxel phantoms another step closer to perfectly representing human anatomy.

The next paper (the winner) is on cellular response to modulated radiation fields by Claridge Mackonis et al (2007). Unusually, this work considers the bystander effect—the effect on a cell when a neighbouring cell receives a radiation dose—in radiotherapy situations (rather than in low dose situations). It shows that the type of bystander effect depends on the dose distribution and lays the foundations for improved mathematical radiobiological models. These models could be used in future work to tailor treatment plans that will improve the outcomes for radiotherapy patients.

The paper by Kamath et al (2007) is about fast and efficient field-splitting algorithms for the treatment of tumours which are too large to be covered by a single intensity-modulated radiation-therapy (IMRT) treatment field. The authors have devised an algorithm that shows how to divide IMRT fields most efficiently. The field-splitting solutions generated by their equations are designed to make the best use of dose delivered by the treatment beam. The algorithmic techniques and methods could also be used to develop optimal algorithms for fields other than radiotherapy.

In their paper on the new magnetic imaging technique known as magnetic particle imaging (MPI), Weizenecker et al (2007) present the first detailed analysis with respect to image quality, sensitivity and resolution. In this technique, iron-oxide-based ferromagnetic nanoparticles are used as tracer agents, which are detected by their non-linear response on an oscillating magnetic field. The paper provides physical models for benchmarking MPI, showing what can be achieved without the need for complex experimental setups.

The next paper is about a novel x-ray phase contrast imaging technique by Olivo and Speller (2007). The authors use coded apertures to measure phase-contrast enhanced radiographs. A numerical model of a one-dimensional version of the imaging system is investigated, to understand the various physical factors that can degrade image quality. This is a simple, elegant idea used to obtain phase-contrast imaging using a conventional x-ray source, and opens up the possibility of transferring a new, highly sensitive x-ray imaging technique into clinical practice.

In their paper on whole-body radiation dosimetry modelling, Xu et al (2007) present a newly-developed set of realistic body models representing a pregnant woman and her foetus that can be used to evaluate radiation exposure during pregnancies. They differ from existing pregnant models by utilizing the boundary representation methodology (polygonal meshes and NURBS) instead of relying on solid geometry modelling. These new models could lead to better planning of radiation imaging and radiation treatment for pregnant women.

Finally, the paper by Holden et al (2007) is about the potential effects of the TASER electrical incapacitation device on the heart. The authors model the current flow in the human heart and estimate the peak current density following injection of TASER currents into the precordial surface of a digital mannequin. By then applying the TASER waveforms to a real biological test system (spontaneously beating, isolated guinea pig hearts), they conclude that, assuming that the guinea pig findings scale up to the human heart, the discharge from a TASER is unlikely to influence cardiac rhythm by direct electrical action on the human heart.

Steve Webb
Editor

Simon Harris
Publisher

Barbone P E and Oberai A A 2007 Elastic modulus imaging: some exact solutions of the compressible elastography inverse problem Phys. Med. Biol. 52 1577–93

M Bencsik, R Bowtell and R Bowley 2007 Electric fields induced in the human body by time-varying magnetic field gradients in MRI: numerical calculations and correlation analysis Phys. Med. Biol. 52 2337–53

Claridge Mackonis E, Suchowerska N, Zhang M, Ebert M, McKenzie D R and Jackson M 2007 Cellular response to modulated radiation fields Phys. Med. Biol.
52 5469–82

Holden S J, Sheridan R D, Coffey T J, Scaramuzza R A and Diamantopoulos P 2007 Electromagnetic modelling of current flow in the heart from TASER devices and the risk of cardiac dysrhythmias Phys. Med. Biol. 52 7193–209

Kamath S, Sahni S, Li J, Ranka S and Palta J 2007 Generalized field-splitting algorithms for optimal IMRT delivery efficiency Phys. Med. Biol. 52 5483–96

Lazebnik M et al 2007 A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries Phys. Med. Biol. 52 2637–56

Lee C, Lodwick D, Hasenauer D, Williams J L, Lee C and Bolch W E 2007 Hybrid computational phantoms of the male and female newborn patient: NURBS-based whole-body models Phys. Med. Biol. 52 3309–33

Olivo A and Speller R 2007 Modelling of a novel x-ray phase contrast imaging technique based on coded apertures Phys. Med. Biol. 52 6555–73

Weizenecker J, Borgert J and Gleich B 2007 A simulation study on the resolution and sensitivity of magnetic particle imaging Phys. Med. Biol. 52 6363–74

Xu X G, Taranenko V, Zhang J and Shi C 2007 A boundary-representation method for designing whole-body radiation dosimetry models: pregnant females at the ends of three gestational periods—RPI-P3, -P6 and -P9 Phys. Med. Biol. 52 7023–44