Purpose: Total scatter factor is one of the most important parameters in commissioning for stereotactic radiosurgery. We compared total scatter factors which were measured by various detectors. Methods: We attached circular collimators (7.5mm, 10.0mm, 12.5mm, 15.0mm, 17.5mm, 20.0mm, 25.0mm and 30mm diameters at isocenter) for stereotactic radiosurgery (BrainLAB) to Varian Clinac 21EX and irradiated 400MU of 10MV (600MU/min) to the detectors at 3cm depth in the water or water equivalent phantom. Total scatter factor was measured by PinPoint 3D chamber (PTW31016), diode detectors (Edge detector (Sun Nuclear), SFD (iba)) and GAFCHROMIC Film EBT2 (ISP). Data were analyzed using MATLAB (MathWorks). Results: We obtained total scatter factors of 0.74 (Edge detector), 0.71 (SFD), 0.67(EBT2), 0.62 (PinPoint 3D Chamber) in 7.5mm diameter collimator. These scatter factors were normalized by largest collimator (30mm) reading of each detector. For the decision of total scatter factors, we normalized these values by 15mm diameter collimator, and averaged diode detectors and EBT2 less than 15mm. We adopted PinPoint 3D chamber's data for 15mm and over. Conclusions: To obtain total scatter factor precisely, we need to take a measurement with various detectors and evaluate the results carefully. As the next step, we are preparing for Monte Carlo simulation to compare with measured data.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging