A retrospective analysis to determine if the timing of H&D curve production has a clinically significant effect on the percent difference in agreement of isodose delivery for film-based IMRT QA

Abstract

The current practice of film-based intensity-modulated radiation therapy (IMRT) quality assurance (QA) involves exposing the QA phantom and subsequently exposing a series of small fields to produce an H&D curve. Both of these procedures currently are completed on the same day. To avoid the need to produce several H&D curves, our current practice is to accumulate at least 10 IMRT cases to perform the QA deliveries concurrently, thereby requiring that we only expose a single film to provide an H&D curve to be utilized for all 10 cases. Our current standard requires that the IMRT QA be completed prior to the first treatment delivery. This standard precludes the facilitation of the possible accumulation of IMRT cases, thereby mandating that we expose many more films for H&D curves. This project will investigate the possibility of applying H&D curves exposed on different days than the IMRT QA. We will determine the percent difference between IMRT QA isodose agreement with planned isodose delivery, given that the H&D curve was performed concurrently VS. the IMRT QA isodose agreement with planned isodose delivery with several different H&D curves taken on random dates. This analysis will be performed using the RIT software. The goal of the project is to determine if the timing of H&D curve production has a clinically significant effect on the percent difference in agreement of isodose delivery for IMRT QA. We will not be recommending the parameters that will define clinical significance but rather report the effect for individual discernment.