A miniature "scintillator-fiberoptic-PMT" detector system for the dosimetry of small fields in stereotactic radiosurgery

Linear accelerator-based stereotactic radiosurgery is an important modality in the management of localized intracranial abnormalities and often is the only option for treatment of certain lesions. The quantification of the absorbed radiation doses delivered for this modality has been a challenge due to the small size of the treatment fields (typically 5-30 mm collimated fields) and the type of detectors presently available. This paper presents comparative dose measurements performed using a miniature (1.6 × 10^-3 cm³) plastic scintillator detector to the commonly used detectors for the dosimetry of small photon fields used for stereotactic radio-surgery. The spatial resolution of the plastic scintillator detector was compared to that of a p-type Si diode and a 0.1-cm³ ionization chamber. Small field dosimetry parameters (beam profiles, percent depth doses, and dose output factors) using the scintillation detector, the 0.1-cm³ ionization chamber, the p-type Si diode, and radiographic film are presented. This comparative study shows that designing a miniature scintillator detector system is feasible and when compared to other benchmark detectors is an appropriate detector for the dosimetry of small stereotactic radiosurgery photon fields.