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Abstract #2906

Evaluation of 4D-T2w MRI methods for lung radiotherapy treatment planning with application to an MR-linac

Joshua N Freedman1,2, David J Collins1,2, Christopher M Rank3, Hannah Bainbridge1, Simeon Nill1, Marc Kachelrie├č3, Martin O Leach1,2, Uwe Oelfke1, and Andreas Wetscherek1

1Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom, 2CR-UK Cancer Imaging Centre, The Institute of Cancer Research, London, United Kingdom, 3Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Due to enhanced soft-tissue contrast, 4D-T2w MRI could improve lung tumour target delineation in radiotherapy compared with 4D-CT; reducing planning margins and dose to healthy tissue for treatments on an MR-linac. We have developed a method for generating 4D-T2w MRI, where 3D-T2w MRI is warped using motion vector fields; calculated by image-registration between respiratory phases of 4D-T1w MRI (the MVFP method). Here, 4D-T2w MRI calculated with MVFP and with amplitude-binning of continuously acquired 2D-T2w MRI, are compared. 4D-T2w MRI from the MVFP method exhibited higher image quality and geometrical fidelity than the 2D-binning scheme, but displayed possible motion under-estimation.

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