Purpose In order to improve segmentation accuracy in head and neck cancer (HNC) radiotherapy treatment planning for the 1.5T MR-Linac, 3D fat-suppressed T2-weighted MRI sequences were developed and optimized. Methods After initial testing of fat suppression techniques, SPectral Attenuated Inversion Recovery (SPAIR) was chosen as the fat suppression technique. Five candidate SPAIR sequences and a non-suppressed T2-weighted sequence were acquired on five HNC patients on the Unity MR-Linac. The primary tumor, metastatic lymph nodes, parotid glands, and pterygoid muscles were delineated by five segmentors. A robust image quality analysis platform was developed to objectively score the SPAIR sequences based on a combination of qualitative and quantitative metrics. Results Sequences were analyzed for signal-to-noise (SNR), contrast-to-noise (CNR) compared to fat and muscle, conspicuity, pairwise distance metrics, segmentor assessment, and MR physicist assessment. From this analysis, the non-suppressed sequence was inferior to each of the SPAIR sequences for the primary tumor, lymph nodes, and parotid glands, but was superior for the pterygoid muscles. Two SPAIR sequences consistently received the highest scores among the analysis categories and are recommended for use to Unity MR-Linac users for HNC radiotherapy treatment planning. Conclusions Two deliverables resulted from this study. First, an optimized 3D fat-suppressed T2-weighted sequence was developed that can be disseminated to Unity MR-Linac users. Second, a robust image quality analysis process pathway, used to objectively score the various SPAIR sequences, was developed and can be customized and generalized to any image quality optimization. Improved segmentation accuracy with the proposed SPAIR sequence can potentially lead to improved treatment outcomes and reduced toxicity by maximizing target coverage and minimizing organ-at-risk exposure.

M.A.D. is an employee of Philips Healthcare. J.C. is an employee of Elekta AB. C.D.F. has received direct industry grant support, speaking honoraria, and travel funding from Elekta AB. The other authors have no conflicts of interest to disclose.

This effort is supported by core resources from the MD Anderson Cancer Center Support Grant (CCSG) Radiation Oncology-Cancer Imaging Program (ROCIP) under Core P30CA016672-44 (A. Koong, PI). T.C.S. is supported by The University of Texas Health Science Center at Houston Center for Clinical and Translational Sciences TL1 Program (TL1TR003169). K.A.W. is supported by the Dr. John J. Kopchick Fellowship through The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, the American Legion Auxiliary Fellowship in Cancer Research, and an NIH/National Institute for Dental and Craniofacial Research (NIDCR) F31 fellowship (1 F31DE031502-01). B.A.M. receives research support from an NIH NIDCR (F31DE029093) Award and the Dr. John J. Kopchick Fellowship through The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences. R.H. and A.S.R.M. are supported by a NIH NIDCR Award (R01DE025248) M.A.D., S.M., M.A.N., S.A., A.S.R.M., C.D.F. received/receives funding and salary support during the period of study execution directly related to this effort from: NIDCR Academic Industrial Partnership Grant (R01DE028290). A.S.R.M. and C.D.F. received funding and salary support during the period of study execution directly related to this effort from: NCI Early Phase Clinical Trials in Imaging and Image-Guided Interventions Program (1R01CA218148). C.D.F. received/receives funding and salary support during the period of study execution directly unrelated to this effort from: the National Institutes of Health (NIH) NIBIB Research Education Programs for Residents and Clinical Fellows Grant (R25EB025787-01); an NCI institutional training award (T32CA261856); an NIH/NCI Cancer Center Support Grant (CCSG) Pilot Research Program Award from the UT MD Anderson CCSG Radiation Oncology and Cancer Imaging Program Seed Grant (P30CA016672); and an NSF Division of Civil, Mechanical, and Manufacturing Innovation (CMMI) grant (NSF 1933369). CDF has received direct industry grant support, honoraria, and travel funding from Elekta AB unrelated to this project. Direct infrastructure support is provided to CDF by the multidisciplinary the Radiation Oncology/Cancer Imaging Program (P30CA016672-44) of the MD Anderson Cancer Center Support Grant (P30CA016672) and the MD Anderson Program in Image-guided Cancer Therapy.

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