WE-A-T-6E-01: Tools for IMRT QA

Abstract

The intensity Modulated Radiation therapy (IMRT) is an advanced form of three-dimensional conformal radiation therapy (3-D CRT) that not only uses 3-D imaging and treatment delivery, but allows for varying radiation beam intensities to produce much more conformal dose distributions than those possible with conventional 3-D CRT. The complex nature of IMRT planning and delivery impose new requirements for quality assurance (QA) process. A comprehensive QA for IMRT must address the issues involving the verification of pre-treatment, patient-specific, delivery and post-treatment. A complete set of tools, including detectors and phantoms, and techniques are necessary to accomplish the new QA tasks. Some of the detectors used for IMRT QA include films, TLDs, EPIDs, ion chambers and gel dosimeters. Each of them has distinct characteristics and limitations. Several phantoms are also available to accomplish the verification measurements, including cylindrical or a stack of solid water. Tools also have been developed for the dosimetric analysis of the measurements and calculations. Some of these tools include isodose overlay, dose difference histograms, distance-to-agreement and gamma evaluation. This presentation will review the QA tools and techniques that are currently in use for all aspects of IMRT process. Educational Objectives: 1. To identify the QA tasks involving IMRT 2. To identify the requirements for the QA tools 3. To describe the QA tools for all aspects of IMRT process 4. To explain the limitations of the QA tools 5. To compare the IMRT QA tools and techniques