Development of a 3D-Printed Deformable Prostate Insert for a Novel Pelvic End-To-End (PETE) Phantom to Benchmark Adaptive Radiation Therapy

Purpose: Magnetic resonance image-guided radiation therapy (MRgRT) utilizes MR-imaging\u27s powerful soft tissue contrast for high precision RT and facilitates on-line adaptive radiation therapy (ART). However, multimodality MR-compatible phantoms with accurate anatomy are currently limited. This work aims to design a deformable prostate insert compatible with a pelvic end-to-end (PETE) phantom for benchmarking MR-guided ART. Methods: Device specifications were acquired by evaluating a physicist-specified user needs profile which outlined necessary insert qualities that will be arranged to interact with silicone balloons simulating the bladder and rectum at varied filling conditions. Design specifications were ranked 1-5 which were applied as a weight to the overall importance of the parameter as determined using a Pugh matrix, which was used to evaluate materials according to their strengths while weighting against a base of 0 (scored -2 to + 2). A cost analysis and production timeline was completed. To determine an accurate anatomical model for the prostate insert, prostate volumes segmented from T2-weighted MRIs for 11 prostate cancer patients were evaluated. Results: MR-compatibility, deformability, and accurate anatomical representation were most important based on weighted scoring. Deformability was assessed by choosing a Shore A classification limit, defining durability and flexibility, with A indicative of softness grading to be between 60A-90A. The average prostate contour volume over 11 patients was 77.2 ± 19.4 mm3 and a representative patient\u27s prostate was selected for 3D printing. Segmented DICOM data was converted to STL for 3D rendering/printing. Soft PLA-flex filament (score = 21) ranked highest and was selected for 3D-printing. Device production was estimated at $40 (250 m roll of soft PLA-flex filament). Conclusion: Design requirements were concluded for development of an anthropomorphic deformable prostate insert compatible with the PETE phantom