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E.R. Bartels, D. Harder, The Microdosimetric Regularities of Nanometre Regions, Radiation Protection Dosimetry, Volume 31, Issue 1-4, 1 June 1990, Pages 211–215, https://doi.org/10.1093/rpd/31.1-4.211
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Abstract
Regions with nanometre dimensions differ greatly from micrometre regions with regard to the contribution of delta rays to the fluctuation of energy deposition, because the fraction of delta rays escaping from their region of origin increases with decreasing size of the region. Under these geometric conditions, the delta ray term of the distribution of energy deposition in a nanometre region traversed by a primary particle is essentially determined by low energy delta rays originating and stopping within the region. This distribution is found to be practically independent of the mass and energy of the primary particle. The remaining primary-particle-dependent variable determining the fluctuation of energy deposition in the nanometre region is linear primary ionisation density or its energy equivalent, restricted LET. Restricted LET should therefore have the properties of a characteristic parameter of radiation quality. This fundamental conclusion is proven by evaluating the predictive potential of restricted LET for energy deposition fluctuation of electrons, protons and alpha particles in nanometre targets, and with regard to the yield coefficient a for radiation-induced chromosome aberrations in human cells. Methods for the determination of restricted LET are discussed briefly.
