Dosimetric Evaluation of Various 3D-Printed Materials for Patient-Specific Vaginal Brachytherapy Applicators
Abstract
Purpose
Commercial cylindrical applicators used for vaginal brachytherapy may not always ensure sufficient contact with the vaginal mucosa, particularly in patients with reduced tissue compliance, leading to air gaps and dose uncertainty. To address these limitations, patient-specific 3D-printed applicators have been proposed. Although their dosimetric performance can be influenced by the printing material, prior studies have primarily focused on PLA and ABS. Therefore, this study evaluated the dosimetric performance of various 3D-printing materials using a clinical brachytherapy source.
Methods
Cylindrical applicators (diameter: 35 mm, length: 100 mm) were 3D-printed using six filaments (ASA, ABS, HIPS, PLA-CF, PLA, and PETG) with 100% infill. CT images (0.6 mm slice thickness) were acquired for treatment planning and density analysis. CT-based brachytherapy plans were generated using Oncentra treatment planning system (TPS) to deliver a uniform dose to the applicator surface. Point doses were measured using thermoluminescent dosimeters (TLD) placed on applicators fabricated from each material. Additionally, Monte Carlo (MC) simulations were performed for each filament material under the same setup to assess material-dependent dose differences using water as a reference.
Results
The mean measured CT numbers were -56.84, -87.06, -92.12, 62.21, 136.33, and 66.75 HU for ASA, ABS, HIPS, PLA-CF, PLA, and PETG, respectively, with comparable standard deviations across materials (21.37–28.01 HU). Measured doses for ASA, ABS, and HIPS were comparable to calculated doses (0.1-1.1%), whereas PLA, PLA-CF, and PETG exhibited dose deviations ranging from -7.1% to -3.7%. These differences may be attributable to TLD-related measurement uncertainties. MC simulations for all materials were comparable to the water-based dose (absolute differences <1%).
Conclusion
ASA, ABS, and HIPS are recommended due to their water-like dosimetric characteristics. In addition, PLA may be a suitable option for vaginal applicators requiring direct mucosal contact, given its biocompatibility and the small dose differences observed in both measurement and MC simulations.