抄録
A dosimetry study using an anthropomorphic head phantom (Radiosurgery Verification Phantom (RSVP)) and a micro ionization chamber for stereotactic radiosurgery was performed. To study the characteristics of the micro ionization chamber, tissue maximum ratios (TMRs), off-axis ratios (OARs) and output factors were measured and compared, using a Si semiconductor detector and the film method. The directional difference in sensitivity and the effect of the polarity of the micro io nization chamber were measured. According to the results obtained, the measured values and the values obtained through calculation were in agreement within 6.3%. The difference was due to the larger size of the micro io nization chamber as compared to the other method. Therefore we applied a correction for this size effect and obtained better agreement within 2%. On the basis of the results of the present study we were able to confirm the overall accuracy and establish a means of quality assurance (QA) for stereotactic radiosurgery.
