Accuracy of an in vivo dosimetry-based source tracking method for afterloading brachytherapy - A phantom study

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• High dose rate (HDR) prostate brachytherapy (BT) requires precise delivery of radiation.
• In vivo dosimetry (IVD) offers real-time dose monitoring during treatment.
• Source tracking (ST) using IVD can potentially improve treatment accuracy.

Purpose of the Study:

• To evaluate the accuracy of an IVD-based ST method for HDR prostate BT.
• To determine the impact of detector placement on ST accuracy.

Main Methods:

• Source tracking (ST) was performed needle-by-needle using a least-squares fit.
• Accuracy was assessed in a phantom using five reproduced HDR prostate BT geometries.
• An Al2O3:C radioluminescence detector within a BT needle measured dose rate at 20 Hz.

Main Results:

• ST was applicable in all needles across nine irradiations.
• Mean accuracy was submillimeter (-0.01 ± 0.38 mm radial, 0.30 ± 0.38 mm longitudinal) when the detector was centrally located.
• Accuracy decreased when the detector was positioned inferior to the most inferior active dwell positions, especially in the prostate apex region.

Conclusions:

• IVD-based ST is adequately accurate for clinical HDR prostate BT.
• Submillimeter accuracy is maintained if the IVD detector is superior to active dwell positions.
• Detector placement relative to the prostate apex significantly influences ST accuracy.