Performance and Operation of a New Magnetic Resonance Simulator for Radiation Therapy
C Hua*, J Uh, S Brady, M Krasin, T Merchant, St. Jude Childrens Research Hospital, Memphis, TNSU-E-J-174 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: To characterize system performance and describe clinical operation of a new magnetic resonance simulator for radiation therapy.
Methods: Radiofrequency receiver coils consist of standard diagnostic and special coils for radiation therapy, including a flat indexed body coil and an immobilization device-compatible head coil under development. The system performance of a 1.5 Tesla magnetic resonance (MR) simulator, SciMedix SM160, was characterized based on the acceptance testing and quality assurance procedures for MR imaging (MRI) described in the AAPM report No. 100, the MRI accreditation quality control manual of the American College of Radiology (ACR), and tests adapted from quality assurance programs for computed-tomography simulators.
Results: All test results of image quality met ACR acceptance criteria. B0 inhomogeneity measured over 45 cm diameter sphere was 8.8 ppm peak to peak. The B0 drift rate measured over 10 consecutive days after acceptance testing was 0.22 ppm/day. The maximum signal intensity was demonstrated with 90 degree spin nutation, indicating the transmitter gain was properly calibrated. Luminance non-uniformity of the display monitor was 6%. TG18-QC test patterns were resolved on the monitor. We have established routine quality assurance tests and facility safety checklists. Imaging protocols tailored to our unique patient population and tumor locations were built.
Conclusion: The evaluated MR simulator demonstrated satisfactory system performance and suitable clinical image quality of anatomical imaging sequences. The patient couch is being redesigned to meet radiotherapy requirements of high positional accuracy. We have begun to utilize this system clinically for tumor and normal tissue delineation in treatment planning and for monitoring tumor volume change during the radiation therapy course.