Suitability of various radiation detectors in accelerator based radiosurgery dosimetry

In linear accelerator based radiosurgery/radiotherapy, small circular x-ray beams are used for treating small targets stereotactically. The dosimetry of such small radiation fields needs small size detectors conventionally not available in a radiotherapy department. In the present work, we measured various beam parameters, namely, PDD, beam profiles and output factors for collimators ranging from 12.5 mm to 40 mm diameter with four detectors, two of which are normally available in any radiotherapy centre having a linear accelerator. We find that for field diameters smaller than 20 mm, there is a definite requirement of specially small detectors, such as a microion chamber (0.01 cc) or a 2.5 mm diode. (author)