A multileaf collimator phantom for the quality assurance of radiation therapy planning systems and CT simulators.

摘要

PURPOSE: The evolution of three-dimensional conformal radiation treatment has led to the use of multileaf collimators (MLCs) in intensity-modulated radiation therapy (IMRT) and other treatment techniques to increase the conformity of the dose distribution. A new quality assurance (QA) phantom has been designed to check the handling of MLC settings in treatment planning and delivery. METHODS AND MATERIALS: The phantom consists of a Perspex block with stepped edges that can be rotated in all planes. The design allows for the assessment of several MLC and micro-MLC types from various manufacturers, and is therefore applicable to most radiation therapy institutions employing MLCs. The phantom is computed tomography (CT) scanned as is a patient, and QA assessments can be made of field edge display for a variety of shapes and orientations on both radiation treatment planning systems (RTPS) and computed tomography simulators. RESULTS: The dimensions of the phantom were verified to be physically correct withinan uncertainty range of 0-0.7 mm. Errors in leaf position larger than 1 mm were easily identified by multiple observers. CONCLUSIONS: The MLC geometry phantom is a useful tool in the QA of radiation therapy with application to RTPS, CT simulators, and virtual simulation packages with MLC display capabilities.