Development of an end-to-end testing protocol for image-guided brachytherapy (IGBT) for cervical cancer using a 3D-printed phantom

Purpose As image-guided brachytherapy (IGBT) continues to expand in the Philippines, the need for comprehensive quality assurance (QA) protocols that evaluate the entire clinical workflow becomes increasingly important. However, no standardized end-to-end (E2E) testing framework currently exists for cervical IGBT in the country. Therefore, this study developed a practical and adaptable E2E testing protocol for CT-based cervical IGBT at UP-PGH using an in-house 3D-printed pelvic phantom. Methods A modular pelvic phantom was fabricated using fused deposition modeling (FDM) with polylactic acid (PLA+) filament, incorporating simplified organ structures representing the uterus, high-risk clinical target volume (HR-CTV), vagina, bladder, rectum, and small bowel. Infill density was optimized based on measured CT number and relative electron density (RED). Two PTW 31010 Semiflex chambers were positioned at the reference points for simultaneous dose measurements. The E2E protocol followed the complete CT-IGBT clinical workflow, including applicator insertion, CT imaging, target and OAR contouring, applicator reconstruction, treatment planning, and dose delivery. Two plans were generated, with a 7 Gy dose prescribed to the HR-CTV and Point A. Results At 90% infill density, the phantom achieved near-water equivalence, with a mean CT number of -2.99 ± 10.65 HU and a RED of 1.001. The difference between TPS-calculated and chamber-measured doses was 4.60% and 5.65% for the HR-CTV plan and the Point A plan, respectively. The good agreement between measured and TPS-calculated doses supports the use of the phantom as a functional tool for IGBT E2E testing. Conclusion The developed E2E protocol, implemented using a cost-effective 3D-printed phantom, provides a practical and reproducible framework for assessing the integrity of the CT-IGBT workflow. The protocol complements existing device-level QA checks and supports the standardization of CT-IGBT practice in the Philippines. Future work should include film dosimetry and multi-institutional measurements to establish a national confidence level.