Commissioning of a 1.5T Elekta Unity MR‐linac: A single institution experience
| Autor: | Sridhar Yaddanapudi, Amanda Boczkowski, Daniel E. Hyer, Jeffrey E. Snyder, Joel St-Aubin, Stephen A. Graves, David Dunkerley |
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| Rok vydání: | 2020 |
| Předmět: |
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Image quality Linear particle accelerator Imaging phantom MRI‐Linac 030218 nuclear medicine & medical imaging 03 medical and health sciences Medical Imaging 0302 clinical medicine Humans commissioning Radiology Nuclear Medicine and imaging IMRT Single institution Radiation treatment planning Instrumentation unity Physics Radiation Phantoms Imaging business.industry Radiotherapy Planning Computer-Assisted Isocenter Magnetic Resonance Imaging Multileaf collimator adaptive radiotherapy 030220 oncology & carcinogenesis Radiotherapy Intensity-Modulated Particle Accelerators Nuclear medicine business |
| Zdroj: | Journal of Applied Clinical Medical Physics |
| ISSN: | 1526-9914 |
| DOI: | 10.1002/acm2.12902 |
| Popis: | MR image‐guided radiotherapy has the potential to improve patient care, but integration of an MRI scanner with a linear accelerator adds complexity to the commissioning process. This work describes a single institution experience of commissioning an Elekta Unity MR‐linac, including mechanical testing, MRI scanner commissioning, and dosimetric validation. Mechanical testing included multileaf collimator (MLC) positional accuracy, measurement of radiation isocenter diameter, and MR‐to‐MV coincidence. Key MRI tests included magnetic field homogeneity, geometric accuracy, image quality, and the accuracy of navigator‐triggered imaging for motion management. Dosimetric validation consisted of comparison between measured and calculated PDDs and profiles, IMRT measurements, and end‐to‐end testing. Multileaf collimator positional accuracy was within 1.0 mm, the measured radiation isocenter walkout was 0.20 mm, and the coincidence between MR and MV isocenter was 1.06 mm, which is accounted for in the treatment planning system (TPS). For a 350‐mm‐diameter spherical volume, the peak‐to‐peak deviation of the magnetic field homogeneity was 4.44 ppm and the geometric distortion was 0.8 mm. All image quality metrics were within ACR recommendations. Navigator‐triggered images showed a maximum deviation of 0.42, 0.75, and 3.0 mm in the target centroid location compared to the stationary target for a 20 mm motion at 10, 15, and 20 breaths per minute, respectively. TPS‐calculated PDDs and profiles showed excellent agreement with measurement. The gamma passing rate for IMRT plans was 98.4 ± 1.1% (3%/ 2 mm) and end‐to‐end testing of adapted plans showed agreement within 0.4% between ion‐chamber measurement and TPS calculation. All credentialing criteria were satisfied in an independent end‐to‐end test using an IROC MRgRT phantom. |
| Databáze: | OpenAIRE |
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