Research Papers in Physics and Astronomy


Date of this Version

February 1983


Published in Health Physics 44:2 (February 1983), pp. 173–175. Published by Pergamon Press Ltd. Used by permission.


The International Commission on Radiological Protection (ICRP77) and the International Commision on Radiation Units and Measurements (ICRU70) have recommended that the evaluation of radiation hazards be based on the “dose equivalent” defined as the product of the absorbed dose and some modifying factors, the most important of which is the quality factor (Q). The quality factor is intended to allow for the effect on the resulting detriment of the microscopic distribution of the absorbed energy. It is therefore defined as a function of the collision stopping power (L) in water at the point of interest. Thus Q rises monotonically with increasing LET until 175 keV/μm where it achieves a value of 20 and remains at 20 for all higher values of LET.

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