A COMPARISON OF DOSIMETRY TECHNIQUES IN STEREOTAXIC RADIOSURGERY

Accurate dosimetry of small-field photon beams used in stereotactic ra diosurgery (SRS) can be made difficult because of the presence of late ral electronic disequilibrium and steep dose gradients. In the publish ed literature, data acquisition for radiosurgery is mainly based on di ode and film dosimetry, and sometimes on small ionization chamber or t hermolominescence dosimetry. These techniques generally do not provide the required precision because of their energy dependence and/or poor resolution. In this work PTW diamond detectors and Monte Carlo (EGS4) techniques have been added to the above tools to measure and calculat e SRS treatment planning requirements. The validity of the EGS4 genera ted data has been confirmed by comparing results to those obtained wit h an ionization chamber, where the held size is large enough for elect ronic equilibrium to be established at the central axis. Using EGS4 ca lculations, the beam characteristics under the experimental conditions have also been quantified. It was shown that diamond detectors are po tentially ideal for SRS and yield more accurate results than the above traditional modes of dosimetry.