Dosimetry study using an anthropomorphic head phantom for stereotactic radiosurgery

Abstract

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-ionization 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-ionization 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.