Publication

Abstract : This study assessed a high-resolution ionisation chamber-based PTW 1600SRS detector array (array) for beam profile analysis and patient-specific quality assurance (PSQA) in CyberKnife (CK) stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). The goal was to determine its suitability for small fields and non-isocentric delivery, which is unique to robotic platforms. Detector performance was examined for dose linearity, reproducibility, beam profiles, output factors, dose-rate dependence, and verification of the Iris collimator field size. Results were benchmarked against diode-based commissioning data. Clinical applicability was tested by retrospectively verifying 20 intracranial SRS and 20 extracranial SBRT plans using gamma analysis with criteria ranging from 3%/3 mm to 1%/1 mm, as well as 4%/1 mm. The detector showed strong dose linearity (R2 = 0.999) and stable reproducibility. Beam profiles matched commissioning values within 0.5 mm, and output factors agreed within 2% for most collimators, with a maximum deviation of 3% at 5 mm. Dose-rate variation remained within 2.5% across relevant SADs. Iris collimator field sizes were consistent with reference measurements. Clinical validation achieved high passing rates, all with tolerance limit of > 95%. It enables accurate beam characterization and reliable PSQA in CK treatments. This work provides the first combined evaluation of beam analysis and clinical validation for this detector on a robotic radiosurgery system, supporting its routine use in small-field quality assurance.