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An optimized calibration method for surface measurements with MOSFETs in shaped-beam radiosurgery
A Sors1, E Cassol2, I Latorzeff3
1Inserm, Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Centre de Radiochirurgie Stéréotaxique, Biophysique Médicale - CHU Rangueil, av. J. Poulhès - TSA 50032, 31059 Toulouse Cedex 9, France.
Metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters are suitable for surface dosimetry in radiosurgery. Optimized calibration methods enable accurate dose verification for small, shaped beams down to 18x18 mm²
Area of Science:
- Medical Physics
- Radiation Oncology
- Dosimetry
Background:
- Metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters are crucial for radiotherapy dose verification.
- Their application in radiosurgery, particularly for small fields, remains underexplored.
Purpose of the Study:
- To propose and optimize a calibration method for MOSFET dosimeters in 6 MV shaped-beam radiosurgery.
- To assess MOSFET suitability for surface measurements in field sizes as small as 18 × 18 mm².
Main Methods:
- Investigated parameters: recovery time, batch uniformity, and build-up cap attenuation.
- Determined sensitivity coefficients (SC) using experimental and inverse square law (ISL) models.
- Validated measurements on a head phantom with irregular fields.
Main Results:
- Optimal calibration achieved with a 5-minute inter-measurement time lapse.
- ISL model reduced calibration measurements for multiple field-SSD combinations.
- MOSFETs showed suitability for surface dosimetry in shaped-beam radiosurgery down to 18 × 18 mm².
Conclusions:
- MOSFET dosimeters are effective for surface dosimetry in shaped-beam radiosurgery.
- Optimized calibration methods, including ISL, enhance accuracy and efficiency.
- The study validates MOSFET use for small field sizes in radiosurgery applications.
