In vivo dosimetry for gynaecological brachytherapy using a novel position sensitive radiation detector: feasibility...

Area of Science:

• Medical Physics
• Radiotherapy
• Dosimetry

Background:

• Gynecological radiotherapy with high dose rate (HDR) brachytherapy involves complex treatment planning and dose constraints.
• Accurate dose verification to the target and organs at risk, such as the bladder, is crucial.
• In vivo dosimetry, while valuable, has been limited by detector motion relative to the radiation source.

Purpose of the Study:

• To introduce and assess a novel dosimetry method using a position-sensitive radiation detector for in vivo dosimetry in HDR brachytherapy.
• To evaluate the feasibility of the RADPOS system for verifying dose delivery and detecting potential treatment deviations.

Main Methods:

• A prototype RADPOS system, integrating a MOSFET dosimeter with a position sensor in a magnetic field, was investigated.
• Positioning accuracy was quantified using a PMMA phantom, and MOSFET energy dependence was assessed.
• Sensitivity and uncertainty analyses were performed to determine action levels for organ motion and source mispositioning.

Main Results:

• The RADPOS system demonstrated positioning accuracy within 1 mm, meeting in vivo dosimetry requirements.
• It can detect 2 mm of bladder motion with a 5% false positive rate and a 9% dose error action level.
• Detecting source position errors below 5 mm and 10% dose error was challenging with a single detector, suggesting the need for multiple MOSFETs.

Conclusions:

• The RADPOS system enables accurate positioning of radiation dosimeters relative to the applicator in HDR brachytherapy.
• This dosimetry procedure allows for real-time monitoring of delivered dose and detection of issues like organ motion or source mispositioning.
• Further clinical investigation is recommended to validate the system's utility in patient care.