The Effect of Modulation Complexity Score (MCS) on the IMRT Treatment Planning Delivery Accuracy

Intensity modulated radiation therapy (IMRT) is an effective treatment planning technique for various types of tumors such as head and neck (H&N) or pelvis. A complexity algorithm was invented to predict the deliverability and the accuracy for IMRT plans called the Modulation Complexity Score ranging from 0 to 1. The %GP is a metric depends on %DD /DTA to find the variation between the calculated dose from TPS and the measured dose from the phantom during the QA. This study is trying to assess the correlation between the MCS and planning verification outcome. Thirty-four patients treated with step and shoot IMRT technique for anatomical sites: H&N and pelvis. The planning process performed using Monaco 5.1 TPS then exported to Elekta Synergy linear accelerator. The phantom is used for the QA procedure is Octavius 4D-1500 with Verisoft 7.1 software analysis to evaluate the gamma passing rate for commonly used criteria 3%/3 mm at a 5% threshold. The MCS calculated using MATLAB 2019a. It results that the H&N plans are significantly more complex than the pelvis once with p-value 0.0192. The analysis shows a weak correlation between the MCS and MU for both treated sites. The complex H&N plans give a good value for %GP. Also, simpler pelvis plans obtain better global %GP results. Thus, modulation Complexity score can give a simple indication for pretreatment verifications of the IMRT plans for H&N and pelvis sites.