Criteria for the Applicability of LET

Linear energy transfer is only one of the factors which determine energy deposition in microscopic regions.Other factors are the range of charged particles, energy loss straggling, and energy dissipation by delta-rays.Graphs are presented delineating those regions of site diameters and particle energies for which the individual factors are important.In the case of protons and other heavy ions one finds a substantial interval of site diameters and particle energies for which the LET concept is appropriate, i.e., where LET is the only relevant factor.No such interval exists for electrons.