The ionization measurement of γ-radiation

Abstract

In recent years there has come into being, in the borderland between physics and medicine, the subject of the quantity measurement of short-wave radiation in its application to therapeutic purposes. Such studies owe their origin mainly to the increasing use of X-rays and radium γ-rays in the treatment of cancer, applications which in this country have been largely fostered by the National Radium Commission and the Radium Beam Therapy Research. The importance of reliable measurement and skilful application in relation to successful treatment, as against failure or positive harm, is bound up with the fact that malignant cells are in general only slightly more sensitive to radiation than adjacent healthy cells. In the light of present knowledge, the fundamental conception of the quantity of radiation received at a point in a medium is based on the amount of electronic energy which is absorbed per unit volume at the point in question. It is further accepted that a related measure of the electronic energy absorbed at any point in a medium may be derived experimentally from the ionization produced in a minute air cavity situated at that point in the medium.