Comparative Study of Fast Superposition, Superposition Algorithm in Intensity Modulated Radiotherapy Techniques for Prostate Cancer

Abstract

This study aims to compare the dosimetric coverage of the Planning Target Volume (PTV) and the dose to main organs at risk (OARs) between two different algorithms fast superposition (FSUP), superposition (SUP) using intensity-modulated radiotherapy (IMRT) techniques for prostate cancer. Ten patients with prostate cancer were selected for this study. For each patient, IMRT plans were created with 6 MV photon beam quality using CMS XiO treatment planning system. The delivery of IMRT was carried out using the step and shoot techniques. The dose coverage for each patient was designated to an ICRU report 62 reference point in the PTV, medium coverage of the planned target volume to be 95% of the prescribed dose while the maximum dose in the target volume to be not greater than 107% of the prescribed dose. A hypofractionated prescription dose of 70 Gy/28# at 2.5 Gy per fraction was used. Besides we compared the number of MUs and OARs dose to D15%, D25%, D35%, D50% on both algorithm planning sets. For target, this evaluation was made with comparing the conformity index (CI) and homogeneity index (HI). In our study, the results show the OARs got less dose from the SUP algorithm compared to FSUP algorithms. Statistically not significant difference was observed in V107% of PTV, MU/CC, conformity Index (p = 0.057, p = 0.215, p = 0.370) and 95% PTV Volume received prescription dose from both Plans. But Homogeneity Index for both algorithms was statistically significant (p = 0.000, p = 0.001). For prostate cancer, the superposition algorithm showed better results in the IMRT plan compared to the fast superposition algorithm.