A Survey on IMRT QA Analysis

Abstract

Purpose: IMRT QA systems have become standard tools in modern clinical medical physics departments. However, methods of IMRT QA analysis vary from institution to institution, as formalized industry standards and/or recommendations from professional societies have yet to be defined. Understanding where we are today is an important step towards: a) improving the effectiveness of IMRT QA and 2) developing standards. Therefore, we conducted an IMRT QA survey. Methods: An online survey polled institutions (one survey per institution) on a collection of questions about methods of IMRT QA. The topics were general to IMRT QA analysis methods common to all IMRT QA systems; none of the questions were vendor/product-specific. Results: 1) A significant fraction of institutions (32.8%) reported using the single gantry angle, composite (SGAC) method for their IMRT QA analysis instead of analyzing field-by-field; 2) The majority of institutions perform absolute dose comparisons rather than relative dose comparisons; 3) The 3% criterion is most used for the percent difference analysis, and the 3 mm criterion for DTA analysis, with the most prevalent standard for acceptance testing being the combined [(3%)/(3 mm DTA)] criteria; and 4) A significant percentage of institutions report not yet having standard benchmarks for acceptance testing (26.6%, 35.3%, and 67.6% of respondents had not yet established standard acceptance criteria for prostate, head/neck, and breast IMRT, respectively). Conclusions: This survey helps us understand how institutions perform IMRT QA analysis today. This understanding will help us move towards more standardized acceptance testing from institution to institution. Before we define standards, it would be useful to connect the conventional planar QA analyses to their resulting impact on the overall plan, using clinically relevant metrics (such as estimated deviations in the DVH).