Evaluation of some dosimetric properties of a dedicated plane parallel ionization chamber for radiotherapy electron beams

Abstract

Ionization chambers are the reference detectors for electron beam dosimetry. In this paper a dedicated radiotherapy plane parallel ionization chamber manufactured with low cost materials is presented for dosimetry in electron beams. The ionization chamber tested has a sensitive volume of 0.4 cm³, and the collecting electrode and the guard ring were painted with a homogeneous mixture of nail polish and graphite. The dedicated ionization chamber presented linearity of the response with the absorbed dose in the range of 0.5 Gy to 8.0 Gy, an increase of the response with the field size increasing, an angular dependence within ±5°, as recommended by international standards, and a polarity effect of 0.78% with the field size. From the results obtained, it is possible to conclude that the plane parallel ionization chamber tested in this work presents potential use for electron beam dosimetry in clinical routine.