Journal of applied clinical medical physics · 2025
High spatial resolution dosimetry for radiation oncology with "MagicPlates," a new 976-pixel monolithic silicon detector.
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Filipev Ilia, Alnaghy Saree, Carolan Martin, Paino Jason, Petasecca Marco, Cutajar Dean, Poder Joel, Davies Justin B, Oborn Bradley M, Hardcastle Nicholas, Guatelli Susanna, Lerch Michael, Kron Tomas, Rosenfeld Anatoly
Аннотация
PURPOSE: We introduce the next generation of "MagicPlate" 2D monolithic pixelated semiconductor detectors - MagicPlate-976 (MP976). It features a larger array area, higher spatial resolution, and does not require external triggering. We perform a comprehensive characterization for small-field steep-dose-gradient dosimetry applications in radiation therapy focusing on x-ray beams used in stereotactic treatments.
METHODS: The MP976, developed by the Centre for Medical Radiation Physics, consists of 976 ion-implanted diodes on a thin n-type epitaxial silicon substrate with a total array area of 58 × 58 mm2. The central region has "small" diodes with an area of 0.2 × 0.2 mm2 and 1 mm pitch and the peripheral region has "large" diodes with an area of 0.6 × 0.6 mm2 and 2 mm pitch. The detector was primed with 10 kGy (Co-60) and tested using a Varian TrueBeam linear accelerator for sensitivity change and dose linearity, and variations in response due to dose-per-pulse and beam incidence angle. Output factors, depth dose, and beam profiles were measured and compared with reference data.
RESULTS: After the 10 kGy, the sensitivity declined by (74 ± 5)% for "large" diodes and by (78 ± 7)% for the "small" ones, the dose-per-pulse (DPP) dependence was in the range of commercially available diodes, however, a difference in the DPP dependence between the "large" and "small" diodes of (8.4 ± 0.2)% was found in the studied DPP range from 0.131-1.111 mGy/pulse. The minimum angular response was at 90° for 6 MV and 100° for 10 MV flattened beams (76% and 82%, respectively). The output factors and depth dose response showed agreement with the reference within 3.1% and 1%, respectively. Deviation in small field 80%/20% penumbra measurements was within 0.5 mm for 6 MV FF and 0.3 mm for 10 MV FFF. Full width at half maximum (FWHM) for the beam profiles agreed within 0.5 mm for both beam qualities.
CONCLUSION: The new MagicPlate-976 detector system is shown to be suitable for dosimetry in small fields and steep dose gradients. It provides 1 mm spatial resolution in the central region and 2 mm on the periphery and has no dependence on the field size. The system's high spatial and temporal resolution opens new opportunities for trigger-less, film-less, and time-resolved verification and error identification for complex stereotactic treatment plans.
METHODS: The MP976, developed by the Centre for Medical Radiation Physics, consists of 976 ion-implanted diodes on a thin n-type epitaxial silicon substrate with a total array area of 58 × 58 mm2. The central region has "small" diodes with an area of 0.2 × 0.2 mm2 and 1 mm pitch and the peripheral region has "large" diodes with an area of 0.6 × 0.6 mm2 and 2 mm pitch. The detector was primed with 10 kGy (Co-60) and tested using a Varian TrueBeam linear accelerator for sensitivity change and dose linearity, and variations in response due to dose-per-pulse and beam incidence angle. Output factors, depth dose, and beam profiles were measured and compared with reference data.
RESULTS: After the 10 kGy, the sensitivity declined by (74 ± 5)% for "large" diodes and by (78 ± 7)% for the "small" ones, the dose-per-pulse (DPP) dependence was in the range of commercially available diodes, however, a difference in the DPP dependence between the "large" and "small" diodes of (8.4 ± 0.2)% was found in the studied DPP range from 0.131-1.111 mGy/pulse. The minimum angular response was at 90° for 6 MV and 100° for 10 MV flattened beams (76% and 82%, respectively). The output factors and depth dose response showed agreement with the reference within 3.1% and 1%, respectively. Deviation in small field 80%/20% penumbra measurements was within 0.5 mm for 6 MV FF and 0.3 mm for 10 MV FFF. Full width at half maximum (FWHM) for the beam profiles agreed within 0.5 mm for both beam qualities.
CONCLUSION: The new MagicPlate-976 detector system is shown to be suitable for dosimetry in small fields and steep dose gradients. It provides 1 mm spatial resolution in the central region and 2 mm on the periphery and has no dependence on the field size. The system's high spatial and temporal resolution opens new opportunities for trigger-less, film-less, and time-resolved verification and error identification for complex stereotactic treatment plans.