The Determination of Tissue Dosaqe

The basis for any rational scheme of x-ray therapy is a knowledge of the dose at every point throughout the treated tissue. The purpose of this paper is to review the data and methods available to make such dosage assessments. In a problem of such complexity, it is helpful to consider first a simple case, the case in which the irradiated tissue is homogeneous and, effectively, infinitely large. To anticipate, we will conclude that under these restrictions the available data and methods are adequate for clinical purposes. There is general agreement that for radiotherapeutic purposes such a homogeneous block of tissue may be approximated by a tank or phantom of water. It would thus be possible — but most laborious — for each radiotherapist to calibrate every port and every setting of his own equipment by direct measurement in a water tank. Fortunately it has been found that, in so far as the distribution of dosage in the beam is concerned, an x-ray beam can be characterized for clinical purposes by the targ...