Clinical evaluation of two new unshielded and shielded silicon diode detectors in external photon beam radiation therapy: SunSILICON and SunSILICON P

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BACKGROUND: Advanced external photon beam radiotherapy requires dosimetry detectors with high spatial resolution and minimal perturbation effects. Silicon diode detectors are widely used due to their high sensitivity and small sensitive volumes, but fluence perturbation effects and energy dependence can affect performance and depend on detector construction. Shielded and unshielded configurations are used to address these challenges, but their clinical performance and limitations require systematic evaluation. PURPOSE: This study aims to evaluate the clinical performance of two newly developed silicon diode detectors-SunSILICON (unshielded) and SunSILICON P (shielded)-for relative dosimetry in external photon beam radiotherapy. The detectors' response behaviors are compared to established detectors across the full clinical range of field sizes and beam energies, focusing on percentage depth dose (PDD) and lateral beam profile measurements. METHODS: Co unit, using various types of motorized water phantoms. Comparative measurements were performed with ionization chambers, as well as other silicon and diamond detectors. Over 600 scans were analyzed, and gamma analysis was applied to assess agreement using 0.5%/0.5 mm for PDDs and 1%/1 mm for lateral beam profiles. Angular dependence, detector sensitivity and the effective point of measurement (EPOM) were determined in solid phantoms. RESULTS: SunSILICON and SunSILICON P demonstrated excellent agreement with established detectors within their specified field size ranges. Gamma passing rates exceeded 99% for most comparisons, with minor deviations in large fields or at field size limits. The shielded SunSILICON P showed reduced energy dependence in large fields compared to the unshielded version, while SunSILICON showed superior performance in small fields. Both detectors exhibited minimal angular dependence (<1% for clinically relevant angles) and negligible intra-type variation. The measured EPOMs matched calculated values within uncertainty. The combination of both detectors enables comprehensive coverage of clinical dosimetry needs. CONCLUSIONS: SunSILICON and SunSILICON P provide reliable, high-resolution dosimetry for external photon beam radiotherapy across a broad range of clinical scenarios. Their performance is comparable to or exceeds that of established silicon and diamond detectors, with the shielded version particularly suited for larger fields due to its reduced energy dependence. Together, these detectors offer a robust solution for clinical relative dosimetry.

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