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Abstract #1872

Cartesian spirals: An alternative to radial imaging for 4D-MRI in MR-guided radiotherapy

Bastien Lecoeur1,2, Prashant Nair1, Rosalyne Westley3, Li Feng4, Uwe Oelfke1, Wayne Luk2, and Andreas Wetscherek1
1Joint Department of Physics, The Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, Sutton, United Kingdom, 2Computing, Imperial College London, London, United Kingdom, 3The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom, 4Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States

Synopsis

Keywords: Image Reconstruction, Pancreas

Motivation: 4D-MRI could improve online MR-guided radiotherapy treatments on the MR-Linac, but long reconstruction times hinder clinical implementation.

Goal(s): To reconstruct and evaluate respiratory-correlated and time-resolved 4D-MRIs from different acquisitions.

Approach: We reconstructed 4D-MRIs using the XD-GRASP and GRASP-Pro algorithms from a clinical protocol (stack-of-stars) and a new Cartesian spiral sequence. We compared the reconstructions regarding diaphragm motion.

Results: Respiratory-resolved 4D-MRIs were reconstructed under 4 minutes from current acquisitions. Time-resolved 4D-MRIs from clinical acquisitions showed significant artefacts limiting the achievable temporal resolution which can be overcome by using a different acquisition.

Impact: Respiratory-correlated 4D-MRIs reconstruction times were compatible with online radiotherapy constraints for pancreatic cancer patients on the MR-Linac. Reaching high temporal resolutions in reconstructing time-resolved 4D-MRIs is not currently possible from the current clinical protocol.

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Keywords