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Clinical Workflow for MR-Only Simulation and Planning in Prostate Cancer Patients Undergoing External Beam Radiotherapy (EBRT)

N Tyagi

N Tyagi1*, S Fontenla2 , M Zelefsky3 , M Chong-ton4 , K Ostergren5 , N Shah6 , L Warner7 , M Kadbi8 , J Mechalakos9 , M Hunt10 , (1) Memorial Sloan-Kettering Cancer Center, New York, NY, (2) Memorial Sloan-Kettering Cancer Centre, New York, NY, (3) Memorial Sloan-Kettering Cancer Center, New York, New York, (4) Memorial Sloan-Kettering Cancer Center, New York, NY, (5) MIM Softwrae, Cleaveland, OH, (6) Memorial Sloan-Kettering Cancer Center, New York, NY, (7) Philips Healthcare, Cleveland, OH, (8) Philips Healthcare, Cleveland, OH, (9) Memorial Sloan-Kettering Cancer Center, New York, NY, (10) Memorial Sloan-Kettering Cancer Center, New York, NY


TU-C2-GePD-J(B)-4 (Tuesday, August 1, 2017) 10:00 AM - 10:30 AM Room: Joint Imaging-Therapy ePoster Lounge - B

Purpose: To describe the experience of implementing MR-only simulation and planning workflow in the clinic.

Methods: Forty-eight prostate cancer patients from June-Dec 2016 receiving EBRT were scheduled to undergo MR-only simulation. MR images were acquired for contouring (2D T2w axial, coronal, sagittal), synthetic-CT generation (3D fast-field echo (FFE)-based) and fiducial identification (3D balanced FFE-based). Synthetic-CT was generated using a tissue classification-based commercial software called MRCAT (MR for Calculating Attenuation) on a 3T Philips scanner. A daily external laser QA (< 2mm) and biweekly geometric fidelity QA (< 2mm within 50 cm LR and 30 cm AP) was setup at the MR scanner. MR-only simulation initiates with a half-hour mold appointment in the CT room and a half-hour simulation appointment in the MR. Current CT+MR simulation process was modified to accommodate MR-only simulation workflow. Use of multiple MR images for contouring necessitated an automated step-by-step process for image registration and contouring for which a MIMᵀᴹ workflow was created. Patient treatment setup was achieved by matching MRCAT DRRs with orthogonal KV radiographs and MRCAT CT/MR with CBCTs matched on fiducial/bones.

Results: Forty-two patients successfully underwent MR-only simulation and met all of our institutional dosimetric objectives. The remaining six patients either had a hip prosthesis or their large body sizes fell outside of the geometric fidelity QA criteria and were not candidates for MR-only simulation. The automated MIM workflow successfully streamlined the registration and contouring process. The contouring on MR was much easier, quicker, and more accurate compared with combined CT+MR images because the temporal variation in normal structure was minimal. 2D and 3D treatment setup localization based on bones/fiducials using MRCAT reference image was successfully achieved for all cases.

Conclusion: MR-only simulation and planning with equivalent or superior target delineation, planning and treatment setup localization accuracy is feasible in a clinical setting.

Funding Support, Disclosures, and Conflict of Interest: MRCAT package was provided by Philips Healthcare under a master research agreement

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