ESTRO 2022 - Abstract Book

S1326

Abstract book

ESTRO 2022

Results The result of the study shows: (i) Plan quality values both algorithms achieved similar results and no significant differences were observed; (ii) Closely similar results of dynamic range MU/deg is achieved across all dose rates with both gantry speed modulation and the values range from 2.244±0.38 and 2.027±0.35 (iii) Total mean Monitor Units (MU) for PO maximum is 14 % higher than the PRO; (iv) Reduced total beam on time is a major benefit of high DR and GS compare to constant DR and GS; (v) DR has higher priority over GS modulation and compensation mechanism adjustment between both algorithms are different for higher DRs. (vi) Pretreatment quality assurance in gamma evaluation (1 % & 1 mm) using Portal dose and ArcCheck analysis shows a maximum difference of 15 % in slow GS compare to max. GS. For both PO and PRO (vii) Trajectory log files maximum deviations observed for gantry positions, MU and DR results for PO and PRO were -0.1 deg, -0.03, 88.17 MU/min and -0.12 deg, -0.03, 83.84 MU/min respectively. Conclusion These results show that new PO algorithm is either clinically beneficial or neutral in terms of plan quality and efficiency in comparison to PRO. The parameters GS and DR in optimization engine might be undeviating for those variables and capable of generating plans unaided from the limits chosen. The pattern of DR variation between adjacent Control Points in PO was significantly different than PRO. 1 Meherbai Tata Memorial Hospital, Department of Radiation Oncology, Jamshedpur, India; 2 Meherbai Tata Memorial Hospital, Radiation Oncology, Jamshedpur, India; 3 Tata Main Hospital, Department of Radiation Oncology, Jamshedpur, India Purpose or Objective The aim of this study is to analyze and verify characterization of two different algorithms using Simultaneous integrated boost (SIB) in Head and Neck plans. Materials and Methods In our study 15 patients were selected, who received radiation therapy by using Eclipse VMAT Progressive Resolution Optimizer algorithm 15.1. The same cases were re-optimized using a PO algorithm 15.6.A total of 30 treatment plans (15 PRO-VMAT plans and 15 Photon Optimizer-VMAT plans) were produced in the present study. All plans were created using double full arcs, keeping the identical constraints, cost functions and optimization time. Plan evaluation was done using PTV parameters (D98%, D95%, D50%, D2% mean dose and V105%), Homogeneity index (HI), Conformity index (CI), MU per degree with control points (CP), OAR doses and gamma verification (Portal dose and ArcCHECK) values were evaluated. Treatment was delivered in Varian Truebeam 2.5, energy 6 MV with Millennium 120 MLC. Results The PTV coverage (D95%) for PRO and PO were 98.69 Gy ± 0.83, 98.80 Gy ± 0.94, HI were 0.093 ± 0.022 and 0.086 ± 0.020, CI were 0.987 ± 0.008 and 0.988 ± 0.009. Monitor units (MU) for PRO and PO were 647.47 ± 137.88, 655.17 ± 138.36. The Portal dose results were (3%,3mm (%) & 1%,1mm (%)) for PO and PRO 100 ± 0.06, 95.1 ± 1.37 and 100 ± 0.05, 95.2 ± 1.32. For ArcCHECK 99.95 ± 0.12, 94.67 ± 3.01 and 99.95 ± 0.07, 93.55 ± 3.86 respectively. OAR’s dose results are given below table 1 PO-1545 Comparison of PRO and PO algorithms in Rapid arc (VMAT) delivery for Head and Neck SIB treatments V. SUNDARAM 1 , G. Rao 2 , M. Nandi 1 , V.P. Reddy 1 , N. pokhala 1 , K. Mondal 1 , A. Prakash 3 , M. Bhattacharjee 1