Toward Magnetic Resonance Only Treatment Planning: Distortion Mitigation And Image-Guided Radiation Therapy Validation

TOWARD MAGNETIC RESONANCE ONLY TREATMENT PLANNING: DISTORTIONMITIGATION AND IMAGE-GUIDED RADIATION THERAPY VALIDATIONbyRYAN GLEN PRICEAugust 2016Advisor: Dr. Carri K. Glide-Hurst Major: Medical PhysicsDegree: Doctor of PhilosophyWhile MR-only treatment planning has shown promise, there are still severalwell-known challenges that are currently limiting widespread clinical implementation.Firstly, MR images are affected by both patient-induced and system-level geometricdistortions that can significantly degrade treatment planning accuracy. . In addition, the availability of comprehensive distortion analysis software is currently limited. Also whilemany groups have been working toward a synthetic CT solution, further study is neededon the implementation of synCTs as the reference datasets for linac-based image-guided radiation therapy (IGRT) to help determine their robustness in an MR-onlyworkflow.A 36×43×2 cm phantom with 255 known landmarks (~1 mm) was scanned using 1.0T high-field open MR-SIM at isocenter in the transverse, sagittal, and coronalaxes, and a 465x350x168mm 3D phantom was scanned by stepping in the superior-inferior direction in 3 overlapping positions to achieve a total 465x350x400mm sampledFOV yielding >13,800 landmarks(3D Gradient-Echo, TE/TR/α = 5.54 ms/30 ms/28°,voxel size =1×1×2mm). A binary template (reference) was generated from a phantom