Microdosimetric considerations in the use of the boron neutron capture reaction in radiation therapy

Abstract

This thesis attempts to further the understanding of the dosimetric and microdosimetric aspects of the boron neutron capture reaction (BNCR) in two distinct radiation therapy modalities, the conventional BNCT and boron neutron capture enhanced fast neutron therapy (BNCEFNT). The absorbed dose in these two modalities consists of contributions from gamma rays, neutrons and the neutron capture reactions in tissue including the BNCR. The use of low pressure tissue equivalent proportional counters for the dual purpose of dosimetry and microdosimetry of the complex radiation fields used in BNCT and BNCEFNT has been thoroughly investigated. Commercially obtained, paired 1/2″ Rossi type LET counters (with and without boron‐10 in the A‐150 TEP wall) were used in this work. The counters were dose calibrated by positioning the proton edge in the measured spectra at a lineal energy of 150 keV/micrometer. Using this paired counter technique, the gamma, neutron and BNCR dose components in different radiation fields were resolved. Experimental results indicate that this technique is well suited for the dosimetry of BNCT and BNCEFNT fields. The uncertainties in these dose measurements are smaller than, or comparable to those achieved using conventional techniques. The microdosimetric spectra measured by the proportional counters have been found to be useful for evaluating the quality of these radiation fields.