Palaniappan Senthil Manikandan, Sanjay Sudhakar Supe, Manickam Ravikumar and Sathiyan Saminathan
The purpose of the study was to analyze the effects of the number of intensity levels on treatment planning outcome of static IMRT method with dynamic IMRT method and also to investigate the integral dose to non-target tissues in both the methods. The IMRT planning was carried out using Eclipse treatment planning system with millennium 120 multileaf collimator (Varian Clinac- 2100 DHX). Five cases each of head and neck, cervix and esophagus cancer were selected for this study. For each case, planning was carried out using both delivery methods. Further for the static IMRT, different numbers of intensity levels ranging from 5 to 20 were studied. The optimization values were kept common for both the techniques and only the leaf motion calculation was varied. The parameters associated with the Dose volume histograms were examined for a more quantitative comparison. The integral doses (0.5 Gy to 30 Gy) of Non-target tissues were also calculated for both techniques. Analyses were performed using a t test to determine difference in any of the parameters examined. For three sites studied, there were no significant changes observed between static IMRT (above 10 intensity levels) and dynamic IMRT method. However there were significant differences observed with 5 intensity level static IMRT plans compared to dynamic IMRT plans. There were no significant changes observed in normal tissue dose values between static IMRT plans and dynamic IMRT plans. The total number of monitor unit was more for dynamic IMRT plans compared to static IMRT plans for all three sites. The integral doses from 0.5 Gy to 30 Gy were analyzed and no significant changes were observed between static IMRT and dynamic IMRT plans
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