SU‐E‐T‐382: Investigation of the Characteristics of the OCTAVIUS Detector 1000 SRS for Verification of the Small Field Size IMRT and SRS Beams

Purpose: The aim for the study was to investigate characteristics of the OCTAVIUS Detector 1000 SRS for verification of the small field size IMRT and SRS beams. Methods: Several different treatments sites have been chosen. High modulation steep gradient small field size beams were delivered in two different setup settings. In the first setup virtual water phantom has been placed on the detector and irradiated. In the same setup EDR film has been irradiated. Measured data has been analyzed. In the second setup detector has been placed in the PTW Octavius phantom and irradiated. In the same setup EDR film and PTW 729 have been irradiated. Measured data has been analyzed. Results: In the first setup detector has been irradiated with virtual water phantom and measured Result showed excellent agreement with the film measurements. Along the compared profiles, absolute dose measured was in ±1 % of the film measurements in the high dose region and ±3 % in low dose region. Measured results showed also very good agreement in region of high gradients. Second set of measurements showed excellent agreement with the film measurements in high dose region with absolute dose difference within ±1% and ±3% in low dose region. Agreement with PTW 729 was in ±3 % in high and low dose region along the compared profiles. Region of high gradient showed better agreement with the film than with PTW 729 due to the inferior detector resolution. Conclusion: Broad range of measurements performed in the investigation showed that OCTAVIUS Detector 1000 SRS is a dosimetrically accurate and sensitive device and it can be used for clinical verification of the highly modulated small field size beams used in the IMRT and SRS treatments.