Radiation quality of photons in small and large receptors--a microdosimetric analysis

The quality of different photon radiations in small and largereceptors is assessed in terms of microdosimetry. Monte Carlosimulations are performed for the electrons released by photons.To represent the case of a small receptor, only electrons releasedby the non-degraded incident photons are tracked. For a largereceptor, all electrons released in the complete degradationprocess are followed. Dose averaged values, y_D, of the linealenergy are derived from the simulated tracks for monoenergeticphotons from 10 keV to 2 MeV. In microdosimetry, the dose meanlineal energy is the major parameter of radiation quality. Theresults demonstrate distinct differences in radiation qualitybetween high-energy gamma rays and conventional X rays thatare present not just in small cell samples but also in largereceptors, such as the human body. The values of y_D suggestthat, for both small and large receptors, conventional X raysshould be about twice as effective as gamma rays from ⁶⁰Co.