Purpose: The High-Dose-Rate (HDR) vaginal cylinder treatment is typically designed using the initial CT, while the subsequent implants are verified using rudimentary methods (i.e., visual inspection, ruler measurements, etc.) and/or X-ray imaging. We are proposing the use of a 3D-printed individualized template that could provide simple and reproducible vaginal cylinder insertion.
Material and methods: Six patients were included in the study with prescriptions of 6 Gy/fraction for 2 to 5 fractions (total 27 treatments). The first 1 to 2 treatments were delivered without the template and the rest with the CT-based 3D-printed templates. Cone beam CTs (CBCTs) were acquired to verify the cylinder placement for all treatments. D2cc of the bladder and rectum are recorded on both planning CT and the following on-treatment CBCTs.
Results: By using the templates, the tip position variation on average (±1 SD) reduced from 0.8±0.5 cm to 0.6±0.4 cm, and angular difference decreased from 5.3±3.5° to 4.7±2.4°. The pitch and yaw deviation are reduced from 0.9 ± 5.8° and 0.4±2.9° to 0.0±3.9° and -0.2±3.0°, respectively. The deviation of D2cc to bladder from the plan reduced from 6±4% to 5±3%, and rectum from 5±2% to 4±4%.
Conclusion: The 3D-printed patient-specific cylinder templates could potentially improve the geometrical reproducibility of cylinder treatments at no cost of additional imaging. The D2cc for the bladder and rectum are determined by the treatment length rather than their respective volumes.
Keywords: 3D print; Brachytherapy; D2cc; HDR; Vaginal cylinder.
Copyright © 2021 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.