MOSFET dosimetry with high spatial resolution in intense synchrotron-generated x-ray microbeams

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Microbeam Radiation Therapy (MRT) utilizes precisely shaped x-ray microbeams for targeted irradiation.
• Accurate dose assessment with microscopic spatial resolution is crucial for MRT efficacy and safety.
• Metal-oxide-semiconductor field-effect transistor (MOSFET) detectors offer the necessary narrow sensitive element for microbeam dosimetry.

Purpose of the Study:

• To assess absorbed doses using MOSFET detectors in targets irradiated by synchrotron-generated x-ray microbeams.
• To measure dose distributions and calculate peak-to-valley dose ratios (PVDRs) using different multislit collimators (MSCs).
• To compare experimental measurements with Monte Carlo (MC) simulations for absorbed dose distribution.

Main Methods:

• Utilized MOSFET detectors to measure dose distributions from x-ray microbeam arrays in a tissue-equivalent phantom.
• Employed two different multislit collimators (MSCs) to shape the x-ray microbeams.
• Performed Monte Carlo (MC) simulations to model absorbed dose distribution and compared with experimental data.

Main Results:

• MC simulations overestimated PVDRs by up to a factor of 3 compared to measurements for microbeam heights below 1 mm.
• Discrepancies between measured and simulated PVDRs decreased to <50% for larger microbeam arrays (25 microm x 1 cm).
• Closer agreement between measured and simulated PVDRs was observed for the Tecomet MSC compared to the Archer MSC.

Conclusions:

• Discrepancies between MC simulations and MOSFET measurements in PVDRs are significant, particularly for smaller microbeam dimensions.
• The energy-dependent response of MOSFET detectors is a key factor contributing to the observed discrepancies.
• Accurate dosimetry and careful validation of simulation models are essential for advancing microbeam radiation therapy research and application.