Adaptation of Unified Dosimetry Index (UDI) and Critical Organ Scoring Index (COSI) for Target and Organ at Risk (OAR) in Prostate IMRT Technique

The aim of the study is to formulate a dosimetry index that can be used for Quality assessment of IMRT treatment plans of prostate site. To compare different radiotherapy plans different indices are utilized. The present study will attempt to combine all the indices into one unified quality index which can define the quality of a treatment plan and serve as a quality indicator of treatment plan developed among similar and different modalities. This quality index will incorporate homogeneity index, conformity index, dose gradient and coverage index resulting in a direct comparison to an ideal plan. We developed another index in this study related to sparing of organs i.e. UDI (OARs) that incorporate the doses of OARs to compare which plan is optimum in terms of target coverage and OARs sparing. In comparison to this UDI (OARs) another work was done to analyze the dosimetry of overall plan including target coverage and organ at risk sparing i.e. critical organ scoring index (COSI). To validate UDI (Target), UDI (OARs) and COSI, 22 patients were studied which were planned on IMRT. We also define the ranking of the plan according to their target coverage and organ sparing quantities as ‘Excellent’, ‘Good’, ‘Average’ or ‘Poor’ plan. UDI index for the target and organ at risk is found to be a useful tool to quantify a treatment plan quality when volumes with different dose prescription are treated. Keywords: Treatment planning system, Conformity index, Homogeneity index, Dose coverage, Dose gradient, Critical organs DOI : 10.7176/CMR/12-1-04 Publication date: January 31 st 2020