Dosimeters and Devices for IMRT QA

This chapter discusses the history, rationale, tools, and methods for the quality assurance (QA) of intensity-modulated radiation therapy (IMRT) plans and the machines that deliver them. The chapter first introduces the reader to IMRT and the relevant QA literature. The chapter next describes the metrics used to evaluate IMRT plans when comparing a dose distribution calculated by a treatment planning system to a dose distribution measured by a QA device. The chapter then describes the individual dosimeters and devices use for such measurement, including point detectors, radiographic and radiochromic film, detector arrays, electronic portal imaging device (EPID)-based analysis, log file analysis, transmission detectors, and 3D dosimeters. The chapter closes with a discussion of the periodic QA needed for machines that deliver IMRT plans. Acceptance testing and commissioning are described as well the specific test used for daily, monthly, and annual QA. The equipment used for these tests is also introduced.