Evaluation of dose distribution using gafchromic EBT film

Dose evaluation for small field such as stereotactic radiosurgery was performed using Gafchromic EBT film. Every film which irradiated 6 MV photon beam was scanned and obtained the optical density (OD) by flat bed scanner after 24 hours of irradiation. This study compared dose from diode in water and Gafchromic EBT film in acrylic phantom to verify the reliability of the film, and to evaluate the SRS in clinical dose distributions from calculation and measurement in the region of virtual target in humanoid and cylindrical phantoms were compared. The Gafchromic EBT film was found to be linear up to 9 Gy. The Dmax for 6 MV was measured at 1.5 cm from the surface by both of diode and the film. As the depth is deeper, the error was measured within 2 ∼ 3% at 10 ∼ 20 cm depth. Comparing between distribution from calculation and measurement, we found that there is 5% error at 90% isodose line. We found that given dose could be measured accurately by using the phantoms. It was feasible to use the Gafchromic EBT film in quality assurance of SRS