ESTRO 2024 - Abstract Book

S3570

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

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Digital Poster

Comparative study of various homogeneity indices in SIB-VMAT planning for head and neck tumors.

Sreejesh M, Gopishankar Natanasabapathi, Ahitagni Biswas, Manivannan P, Rajendran M, Dhanabalan Rajasekaran, Vellaiyan Subramani, Daya Nand Sharma

All India Institute of Medical Sciences, Radiation Oncology, New Delhi, India

Purpose/Objective:

The goal of this study is to evaluate various homogeneity indices for SIB planning technique in VMAT delivery for Head and Neck tumors.

Material/Methods:

Ten patients with head and neck (HN) tumors were planned with simultaneous integrated boost (SIB) technique in Monaco TPS system (Version 5.11) for volumetric modulated arc therapy (VMAT) delivery. Three PTV’s named as PTVT (target volume including boost volume), PTVB (boost or high-risk volume), PTV (T-B) target volume excluding boost volume were delineated on the patient CT image acquired for planning. Various organ at risk (OAR), were delineated as well. Dose objectives and constraints were assigned to achieve desired dose coverage for the PTVs and set dose limits to OARs. A two-stage planning optimization method was applied to accomplish the planning goals in the TPS. Established homogeneity indices (HIs) such as D5/D95, Dmax/Dmin, (D1–D98)/Dp, D5–D95/Dp, Dmax/Dp, (D2 − D98)/D50 & (D2 − D98)/Dp were evaluated. Additionally, a newly introduced chair heterogeneity index (CHI) was used in this study to investigate its potential in evaluating the dose. Dose coverage of the target kept within +7% and −5% of the prescribed dose were chosen. CHI is defined by the equation: (VRx VDl)/(VDm-Dh) in which VRx, VDl, VDm and VDh were four distinguished points selected from the cumulative dose volume histogram curve (cDVH) of the target. Dl, Dm and Dh represent reference low dose, medium dose and high dose values selected from cDVH of the target. Statistical analysis was performed using R statistical software (v4. 1.2; R Core Team 2021).

Results: