3D source tracking and error detection in HDR using two independent scintillator dosimetry systems

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• High-dose-rate (HDR) brachytherapy requires precise localization of the radioactive source for accurate dose delivery.
• Current methods for in vivo dosimetry and source tracking have limitations in real-time 3D reconstruction.

Purpose of the Study:

• To develop and evaluate a method for three-dimensional (3D) source position reconstruction in HDR brachytherapy.
• To combine measurements from two independent in vivo detector systems for enhanced accuracy.

Main Methods:

• Time-resolved dosimetry was performed in a water phantom simulating HDR brachytherapy using a $$ Ir source.
• Two detector systems were employed: a multi-plastic scintillator detector (mPSD) and a single inorganic crystal detector (CsI:Tl - ISD).
• Source coordinates (x, y, z) were derived from the intersection of detector measurements, simulating prostate brachytherapy plans.

Main Results:

• The combined detector system achieved 100% dwell position reconstruction with 1σ uncertainty, and 73-96% with 2σ uncertainty.
• Source position agreement was within 3 mm up to 50 mm distance.
• Detector placement within the prostate volume significantly reduced measurement deviations.
• Errors of 1-2 mm were detectable with high true detection probability (>80%) within 50 mm.

Conclusions:

• Combining two detector responses enables absolute 3D source coordinate determination.
• The integrated multi-plastic scintillator detector and inorganic crystal detector system offers a promising solution for real-time 3D source tracking in HDR brachytherapy.