Commissioning measurements on an Elekta Unity MR-Linac

Physical and Engineering Sciences in Medicine - Tập 45 Số 2 - Trang 457-473 - 2022
Marcus Powers1, John Baines1, Robert K. Crane1, Chantelle Fisher1, S. M. Gibson1, Linda Marsh1, Bronwyn Oar1, Ariadne Shoobridge2, Emily Simpson‐Page3, Marchant Van der Walt1, Glenn de Vine1
1Townsville Cancer Centre, Townsville Hospital and Health Service, Townsville, QLD, Australia
2College of Science and Engineering, James Cook University, Townsville, QLD, Australia
3Cancer Care Services, Royal Brisbane and Women’s Hospital, Herston Qld, Australia

Tóm tắt

AbstractMagnetic resonance-guided radiotherapy technology is relatively new and commissioning publications, quality assurance (QA) protocols and commercial products are limited. This work provides guidance for implementation measurements that may be performed on the Elekta Unity MR-Linac (Elekta, Stockholm, Sweden). Adaptations of vendor supplied phantoms facilitated determination of gantry angle accuracy and linac isocentre, whereas in-house developed phantoms were used for end-to-end testing and anterior coil attenuation measurements. Third-party devices were used for measuring beam quality, reference dosimetry and during treatment plan commissioning; however, due to several challenges, variations on standard techniques were required. Gantry angle accuracy was within 0.1°, confirmed with pixel intensity profiles, and MV isocentre diameter was < 0.5 mm. Anterior coil attenuation was approximately 0.6%. Beam quality as determined by TPR20,10 was 0.705 ± 0.001, in agreement with treatment planning system (TPS) calculations, and gamma comparison against the TPS for a 22.0 × 22.0 cm2 field was above 95.0% (2.0%, 2.0 mm). Machine output was 1.000 ± 0.002 Gy per 100 MU, depth 5.0 cm. During treatment plan commissioning, sub-standard results indicated issues with machine behaviour. Once rectified, gamma comparisons were above 95.0% (2.0%, 2.0 mm). Centres which may not have access to specialized equipment can use in-house developed phantoms, or adapt those supplied by the vendor, to perform commissioning work and confirm operation of the MRL within published tolerances. The plan QA techniques used in this work can highlight issues with machine behaviour when appropriate gamma criteria are set.

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Physical and Engineering Sciences in Medicine

Tập 45 Số 2

457-473

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