Community hospital experience commissioning a new MR-based HDR program
Jessica M. Fagerstrom,1,2 Jeffrey Marotta,2 Justin Cantley1,2
1Northwest Medical Physics Center, Lynnwood, WA; 2Kaiser Permanente, Seattle, WA
AAPM/COMP Annual Scientific Meeting, Virtual (2020).
Purpose: A community hospital developed an MRI-based high dose rate (HDR) brachytherapy program. The program launched treating locally advanced cervical and non-operable endometrial cancer, intending to add other sites in the future. To initiate the program, physics acceptance testing and commissioning were performed.
Methods: A Varian Bravos afterloader was purchased for use with BrachyVision treatment planning system (TPS), and Varian and third-party applicators. TPS validation of the TG-43 algorithm was completed by following the vendor-provided installation product acceptance procedures, and by comparing published values to calculated points and volumes. Secondary dose check software was reviewed following similar procedures. Interrupt testing determined an internal policy for minimum planned dwell time.
The facility’s MR safety team reviewed all applicators and approved their use. Inventory and visual inspection were completed, and autoradiographs were acquired of all applicators. Radiographs were acquired including marker wires indicating source positions. A length assessment device was used to establish channel lengths. Vendor-provided digital solid models were validated for solid applicators, where applicable. Sterilization procedures were established with central processing.
Applicators were set in all-plastic containers filled with agar gel doped with copper sulfate using food-grade agar powder, distilled water, and CuSO4 solution, with applicators held in place using custom-cut foam blocks. The phantoms were scanned in both MRI and CT using the sequences intended for patient procedures.
Results: Recommendations for applicator use were made based on commissioning measurements. Varian MR-compatible vaginal segmented cylinders, rigid guide tubes, mould probes, and a cervix probe set; and third-party vaginal guides, plastic needles, and polymer tandems were commissioned and approved for clinical use.
Conclusion: Acceptance testing and commissioning for an MR-based HDR program was completed in a community hospital setting. AAPM Task Groups Reports 236, 284, and 303, all currently under development, will offer future guidance on this process.