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Quality Assurance of Truebeam Multi-Leaf Collimator Using a MLC QA Phantom

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J Zhang

J Zhang1*, D Hong2 , J Lu1 , (1) Cancer Hospital of Shantou University Medical College, Shantou, Guangdong, (2) The First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong


SU-E-T-646 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose:To perform a routine quality assurance procedure for Truebeam multi-leaf collimator (MLC) using MLC QA phantom, verify the stability and reliability of MLC during the treatment.

Methods:MLC QA phantom is a specialized phantom for MLC quality assurance (QA), and contains five radio-opaque spheres that are embedded in an "L" shape. The phantom was placed isocentrically on the Truebeam treatment couch for the tests. A quality assurance plan was setted up in the Eclipse v10.0, the fields that need to be delivered in order to acquire the necessary images, the MLC shapes can then be obtained by the images. The images acquired by the electronic portal imaging device (EPID), and imported into the PIPSpro software for the analysis. The tests were delivered twelve weeks (once a week) to verify consistency of the delivery, and the images are acquired in the same manner each time.

Results:For the Leaf position test, the average position error was 0.23mm±0.02mm (range: 0.18mm~0.25mm). The Leaf width was measured at the isocenter, the average error was 0.06mm±0.02mm (range: 0.02mm~0.08mm) for the Leaf width test. Multi-Port test showed the dynamic leaf shift error, the average error was 0.28mm±0.03mm (range: 0.2mm~0.35mm). For the leaf transmission test, the average inter-leaf leakage value was 1.0%±0.17% (range: 0.8%~1.3%) and the average inter-bank leakage value was 32.6%±2.1% (range: 30.2%~36.1%).

Conclusion:By the test of 12 weeks, the MLC system of the Truebeam is running in a good condition and the MLC system can be steadily and reliably carried out during the treatment. The MLC QA phantom is a useful test tool for the MLC QA.

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