Lack of backscatter factor measurements in HDR applications with MOSkins

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• Intraoperative brachytherapy (IOBT) HDR applicators are used clinically.
• Conventional TG-43 dose calculations may overestimate dose due to lack of backscatter material above applicators.
• Accurate dose verification is critical for effective cancer treatment.

Purpose of the Study:

• To measure backscatter correction factors for IOBT HDR brachytherapy applicators.
• To evaluate the dosimetric characteristics of MOSFET devices for IOBT measurements.
• To compare experimental measurements with Monte Carlo simulations.

Main Methods:

• Utilized Centre for Medical Radiation Physics (CMRP) MOSFET devices for dose measurements.
• Employed HDR Ir-192 source, kilovoltage treatment unit, and high-energy linac for dosimetric characterization.
• Assessed MOSFET reproducibility, stability, linearity, and angular/energy response.

Main Results:

• IOBT applicators without backscatter material reduced delivered dose by an average of 10%.
• MOSFET angular response variability was the largest contributor to measurement uncertainty.
• Experimental results showed good agreement with published Monte Carlo data.

Conclusions:

• MOSFET detectors are suitable for high dose gradient measurements in IOBT.
• Absence of backscatter material significantly impacts IOBT dose delivery.
• Accounting for detector dosimetric characteristics is essential for accurate uncertainty estimation in IOBT.