RESUMO

Intensity modulated radiation therapy (IMRT) is a technology intensive treatment modality involving the delivery of highly conformal dose distributions to patients. IMRT is becoming a standard of care for many disease sites and approximately 30%-60% of cancer patients in the United States receive IMRT treatments. Given the complexity of the IMRT treatment planning and delivery processes, a number of AAPM reports and guidance documents addressed the technical aspects of IMRT, including the need for comprehensive acceptance testing, commissioning, and QA programs for IMRT planning and delivery equipment. The implementation of these verification programs is essential to ensure the accuracy of IMRT delivery. Despite the critical role of patient-specific IMRT verification QA to ensure the safe delivery of IMRT treatments to patients as planned, there is little systematic guidance on the type of methodologies, tools, and acceptable tolerance levels that are needed in clinical practice. Furthermore, there are limited discussion on the pros and cons of the different delivery methods for QA measurements, and no recommendations on how to assess the clinical relevance of failed IMRT plans. LEARNING OBJECTIVES: 1. To discuss commonly employed IMRT measurement methods and discuss the pros and cons of each method. 2. To review methodologies for absolute dose verification (single small-volume, 1D, 2D methods), and review dose-difference, DTA, and Gamma analysis techniques including the variability of vendors implementation 3. To review IMRT QA passing rates for given tolerances and action levels, and discuss the clinical relevance of failed IMRT QA.