Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

Publication date: Available online 25 May 2018
Source:Radiotherapy and Oncology
Author(s): Ning Wen, Joshua Kim, Anthony Doemer, Carri Glide-Hurst, Indrin J. Chetty, Chang Liu, Eric Laugeman, Ilma Xhaferllari, Akila Kumarasiri, James Victoria, Maria Bellon, Steve Kalkanis, M. Salim Siddiqui, Benjamin Movsas
IntroductionThe purpose of this study was to investigate the systematic localization accuracy, treatment planning capability, and delivery accuracy of an integrated magnetic resonance imaging guided Linear Accelerator (MR-Linac) platform for stereotactic radiosurgery.Materials and methodsThe phantom for the end-to-end test comprises three different compartments: a rectangular MR/CT target phantom, a Winston–Lutz cube, and a rectangular MR/CT isocenter phantom. Hidden target tests were performed at gantry angles of 0, 90, 180, and 270 degrees to quantify the systematic accuracy. Five patient plans with a total of eleven lesions were used to evaluate the dosimetric accuracy. Single-isocenter IMRT treatment plans using 10–15 coplanar beams were generated to treat the multiple metastases.ResultsThe end-to-end localization accuracy of the system was 1.0 ± 0.1 mm. The conformity index, homogeneity index and gradient index of the plans were 1.26 ± 0.22, 1.22 ± 0.10, and 5.38 ± 1.44, respectively. The average absolute point dose difference between measured and calculated dose was 1.64 ± 1.90%, and the mean percentage of points passing the 3%/1 mm gamma criteria was 96.87%.ConclusionsOur experience demonstrates that excellent plan quality and delivery accuracy was achievable on the MR-Linac for treating multiple brain metastases with a single isocenter.



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