Abstract
The purpose is to devise a patient‐specific quality assurance procedure for RapidArc radiotherapy using the MapCHECK detector array. We use our existing MapCHECK system and a Solid Water phantom with an embedded ion chamber to develop a quality assurance procedure for RapidArc treatment after commissioning. The ion chamber used to measure the absolute dose is surrounded by 6 cm layers of solid water on the anterior and posterior sides. Partial arcs derived from the treatment planning system were used with MapCHECK to determine the actual shape of the dose and correct for the angular dependence. The ion chamber measurements were within 1% of the absolute doses predicted by the Eclipse treatment system. When using a partial arc from 60° to 300° on the MapCHECK array (gamma index <1: 3%, 3 mm, 10% threshold), we obtain a 97.52% average passing rate. A combination of ion chamber phantoms, partial arcs and the MapCHECK system can be used for quality assurance of RapidArc therapies.PACS number: 3.6.96.0
Highlights
As a supplement to tomotherapy, Yu(1) suggested intensity-modulated arc therapy (IMAT)
We recorded the central axis dose through MapCHECK for all 17 patients
We compare the absolute doses determined from the treatment planning system (TPS) to doses measured in our ion chamber phantom
Summary
As a supplement to tomotherapy, Yu(1) suggested intensity-modulated arc therapy (IMAT). Over the years, increasing computer power and the creation of new planning systems, such as the analytical anisotropic algorithm (AAA), have made a new generation of fast radiation therapies possible. Volumetric modulated arc therapy (VMAT), delivers radiation continuously while the gantry of the linear accelerator rotates through one or more arcs. Several parameters are involved in this process: the aperture shape and orientation of the multileaf collimator (MLC), the gantry rotation speed and the dose rate. VMAT requires the linear accelerator controller to establish a real-time relationship between these parameters. This synchronization is a daunting task, but necessary for efficient delivery. The difficulties associated with VMAT require a specific means of quality assurance for its patients
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