Optimizing MR-linac motion phantom for treatment plan verification

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Radiation Therapy (RT) has rapidly evolved to accurately and precisely target tumors while sparing normal tissue. Quality control (QC) testing is used to detect process failures which could result in errors in radiation delivery. Phantoms are test tools that allow medical physicists to characterize machine performance and verify radiation therapy plans. The latest innovation in radiation delivery machines, the MR-Linac, requires new phantoms and QC methods tailored to its increased complexity. One of the main advantages of the MR-Linac is the excellent soft tissue contrast, which is better suited for adaptive RT. For disease sites where complex motion is present, this adaptive RT can only be realized with 4D MRI imaging and associated 4D treatment planning methods. The objective of this project is for the Sunnybrook MR-linac medical physics group to partner with the Modus QA team to optimize and commercialize two accessories for the MRI4D motion phantom. One accessory is a dosimetry insert, which has multiple Optically Stimulated Luminescence Dosimeters (OSLDs) for measurement of the dose distribution around a tumour model. The second accessory is a deformable motion insert, which uses reciprocating pistons to compress a foam tissue/tumor model to generate complex 4D deformation and hysteresis. A detailed evaluation of each prototype as well as recommendations on QA methodology will be developed using the Sunnybrook MR-Linac. This project will benefit the long term clinical needs of cancer patients by developing a QC process for MR-Linac motion management. Additionally, this project will support the growth of an Ontario-based company.