RADIALLY RESTRICTED LINEAR-ENERGY-TRANSFER FOR HIGH-ENERGY PROTONS - A NEW ANALYTICAL APPROACH

Radially restricted linear energy transfer (LET) is a basic physical p arameter relevant to radiation biology and radiation protection. In th is report a convenient method is presented for the analytical computat ion of this quantity without the need for complicated simulation. The method uses the energy-restricted LET L(Delta), as recently redefined in a 1993 ICRU draft document and supplements it by a relatively simpl e term that represents the energy of fast delta rays lost within dista nce r from the track core. The method provides a better fit than other models and is valid over the entire range of radial distance from tra ck center to the maximum radial distance traveled by the most energeti c secondary electrons. L(r) computed by this approach differs only a f ew percent from the values obtained from explicit Monte Carlo simulati ons. The concept applies equally to heavy ions and to electrons.