National University Hospital of Singapore experience: intensity modulated radiotherapy commissioning based on task group 119, a report from AAPM

3D conformal was the standard of care for radiotherapy before intensity modulated radiotherapy (IMRT) started in the late 1990s. Since then, usage of IMRT has been growing rapidly. IMRT involves an inverse planning approach with complex MLC movement and multiple gantry angles. In 2008, the Radiological Physics Center (RPC) irradiated 250 head and neck phantoms and found that 28% failed to meet either 7% dose accuracy in low gradient region or 4 mm DTA in high gradient, or both. This experience suggested that many clinics did not commission their IMRT system adequately. In 2009, Task Group 119 (TG-119) of AAPM produced a set of quantitative confidence limits as baseline expectation values for IMRT commissioning. These confidence limits (CL) were based on collective data from 9 facilities that had passed the RPC credentialing tests for IMRT. Any facility that wants to use these benchmarks should perform the planning, measurement and analysis as suggested by TG-119