A Custom 3D Printed Film Jig for Robust Autoradiography of the GYN Ring Applicator
Abstract
Purpose
Verification of source dwell positions in HDR ring applicators is critical due to variability introduced by source wire slack. Conventional autoradiographic film methods are often limited by setup uncertainties—such as manual stem marking—and typically require external irradiation for geometric reference. We developed a 3D-printed film jig to improve robustness, reproducibility, and clinical efficiency of source position verification for Varian GYN ring applicators.
Methods
A custom jig was designed and fabricated using a Bambu X1C FDM 3D printer (PLA/PETG) to secure the ring applicator and radiochromic film in a fixed, well-defined geometry. The design ensures stable film contact and precise rotational alignment without requiring external kV or electron beam imaging. Reproducibility and sensitivity to setup variation were assessed through multiple autoradiographic measurements acquired across repeated setups.
Results
The jig eliminated common uncertainties associated with manual marking, significantly reducing setup time and complexity. Measurements across five trials demonstrated a positional uncertainty of 0.51 mm for 8 out of 9 dwells, supporting the reliability of the setup. However, dwell #2 showed a 1.45 mm error, which is likely machine-inherent. Film-to-film variability (0.62 mm including dwell #2) was higher than observer-to-observer variability (0.36 mm, n=3). The jig enabled straightforward verification without additional reference irradiation procedures.
Conclusion
This 3D-printed jig provides a practical, low-cost, and robust solution for routine HDR GYN ring applicator QA. By improving reproducibility and simplifying workflows, this approach supports vendor-recommended verification while reducing clinical burden. It is well-suited for both commissioning and routine quality assurance.