Microdosimetry at the nanometre level with different techniques

Abstract

Microdosimetry provides the capability to measure probabilistic distributions of lineal energy in micrometer or sub-micrometer-sized volumes. The shape of these distributions is dependent on the size of the sensitive volume used for scoring, meant to approximate that of the relevant biological target. Recognizing that biological damage and its repair processes occur at different length scales, initiated by damages at the DNA level, single-event distributions can be measured with proportional counters in simulated sites as small as about 30 nm, but hardly below. However, direct measurement of dose-mean lineal energy can be achieved in even smaller site sizes, down to a few nm, using integrated current measurements with an ionization chamber and applying the variance-covariance technique. In this study, we investigate the agreement between dose-mean lineal energy values calculated from single-event distributions and those measured using the variance-covariance technique in photon radiation fields.