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Commissioning and Implementation of Magnetic Resonance Imaging Systems for Pediatric Radiation Therapy Planning

C Hua

C Hua*, J Uh , MJ Krasin , JT Lucas Jr, CL Tinkle , TE Merchant, St. Jude Children's Research Hospital, Memphis, TN


WE-RAM2-GePD-JT-3 (Wednesday, August 2, 2017) 10:00 AM - 10:30 AM Room: Joint Imaging-Therapy ePoster Theater

Purpose: We commissioned two dedicated magnetic resonance imaging (MRI) systems in a radiation oncology department and report on adaptations and implementations of MRI for radiotherapy (RT) treatment planning in the pediatric population.

Methods: After installation of two wide-bore MRI systems for RT planning, the system performance and image quality of the standard head coils and coils in RT configurations were measured with ACR, vendor-provided, and in-house phantoms. Patient setup, coil placements, and scan protocols were developed for various anatomic sites in children and include 3D acquisition for high-resolution multiplanar reformation incorporating fat suppression and respiratory motion-compensation techniques.

Results: The system geometric distortion was ≤ 1 mm and <2mm over a 32-cm and 40-cm diameter spherical volume, respectively. For a patient with the body width of 20, 30, and 40cm and positioned centered inside the magnet bore, the longitudinal extent with ≤1 mm system distortion was measured to be at least 42, 30, and 16 cm, respectively, for the 3T system and 33, 27, and 19 cm for the 1.5T system. The combination of flexible loop coils and posterior coils in RT configurations performed similarly to standard head coils in image quality except for the image-intensity uniformity, which was 11-14% lower, and low contrast detectability, worse for 1.5T with RT coils. In spite of inferior uniformity on phantom images, it was not visually apparent on patients. Pediatric-specific scan protocols and comprehensive QA will be presented.

Conclusion: Using the posterior coil beneath the flat table top in conjunction with the flexible loop coils or the “hanging” anterior coil allows patients to maintain their treatment positions for imaging. With optimized imaging protocols and high geometric accuracy, MRI of pediatric patients in treatment positions can be performed with image quality that approaches that of diagnostic scans and is suitable for treatment planning.

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