Development and evaluation of a multi-detector semiconductor dosimetry system for source tracking and 3D dose reconstruction in high dose rate brachytherapy.

BACKGROUND

High-dose rate brachytherapy (HDR BT) has a steep dose gradient that helps sparing surrounding organs, at the same time allowing to irradiate the target organ with more dose. However, the limited fraction count and sharp dose fall-off require high positional accuracy, which currently cannot be verified during HDR BT treatment.

PURPOSE: To address the risk of inaccuracies in low-fraction HDR BT, a semiconductor-based in vivo dosimetry (IVD) system for real-time dose monitoring was developed.

METHODS

The dosimetry system consists of three needles, each containing three 0.7 ×0.7× 0.7 mm semiconductor detectors linked to a preprocessing amplifying module and computer. Accuracy was assessed via detector response, signal stability, source localization using multilateration, and a comparison of the reconstructed volumetric dose distribution from our IVD system with treatment planning systems' (TPS) data.

RESULTS

The IVD system successfully tracked source position and reconstructed 3D dose distributions. Comparison with TPS at standard resolution (2.5 ×2.5× 1.25 mm) showed strong agreement, with 13 Gy isodose surface overlap ranging from 92.3% to 93.8%. At higher resolution (0.5 ×0.5× 0.625 mm), overlap improved to 94.9%. Dose-volume histogram (DVH) analysis of the prostate ROI confirmed close overlap, with mean dose (19.82 Gy vs. 20.03 Gy) and D95 (12.48 Gy vs. 12.93 Gy) matching the TPS values.

CONCLUSION

This IVD system enables accurate source localization and dose verification in HDR BT. High agreement with TPS across volumetric and DVH metrics demonstrates its potential as a real-time quality assurance tool, enhancing the safety and precision of brachytherapy.