Current Status of Dosimetry Tools for Clinical Proton Beams

Abstract

The use of proton beams is increasing in radiation therapy due to the physical characteristics of the Bragg curve, offering dosimetric advantages over conventional radiation. However, dosimetric measurements are necessary for safe and accurate irradiation with clinical proton beams. The accuracy of dosimetry should be considered in terms of the required dose at the target volume, which in general, requires standard uncertainty levels of 3%–5%. Reference dosimetry should thus be done with uncertainties well below those levels, typically better than 1%, by using cylindrical ionization chambers. By contrast, for non-reference measurements, the use of other dosimeters should be considered provided that the energy and linear energy transfer (LET) dependence of the detector response has been checked against the ionization chambers. The response of films, silicon diodes, and other available solid-state detectors exhibits strong energy or LET dependence, and their use is limited to conditions with nearly constant LET. This review is described current dosimetric tools and methods for use with proton beams in routine clinical practice.