THE USE OF RADIOCHROMIC FILM IN TREATMENT VERIFICATION OF DYNAMIC STEREOTAXIC RADIOSURGERY

Standard silver-based films are usually too sensitive to be used as di rect indicators of dose in dynamic radiosurgery because of optical sat uration. This paper describes the use of a new radiochromic film to me asure 6-MV radiosurgery doses and dose distributions in a head phantom . Dose calibration of the radiochromic film was performed in the range of 2.3-50.2 Gy using light of 632- and 530-nm wavelengths. Radiosurge ry dose distributions were measured using the radiochromic film in a h ead phantom undergoing the same treatment as a patient, and were compa red with the planned distributions. For an example case (nominal 2.0-c m-diam cone), film measurement verified the calculated dose distributi on in one plane. The simple measurement technique described led to exp erimental uncertainties of +/- 0.1 cm for the 90% and 50% isodose line s, +/- 0.3 cm for the 20% line, and +/- 0.5 cm for the 10% line. Isoce nter dose was measured with an uncertainty of +/- 3%. Refinements to t he technique should allow more precise measurements. It is concluded t hat the radiochromic film, with some limitations, is a convenient and useful tool for dynamic radiosurgery quality assurance.