Two Diagrams for the Computation of Dosage Rates from Linear Radium Sources

In Radium Therapy it is frequently necessary to calculate dosage-rates at various points near rectilinear sources. Such sources include not only the single needle or container, but also intracavitary tubes and rows of needles in plaques and implants. The Parker-Paterson methods are satisfactory in many cases, but they only give the average dosagerate in a strictly defined area or volume, and also it is not always possible to conform to their rules for the distribution of the radium. The two types of diagrams for calculating dosagerates near rectilinear sources, described in this paper, are easy to construct and simple to use, and have been found useful in this department. One diagram of either type will deal with all sources which have the filtration for which it is designed. The dosage-rate, D r/hr., at a point P (Fig. 1), near a radium source AB, of unit linear density and with a wall thickness equivalent to d mm. of platinum, is given by the equation: μ=the absorption coefficient of γ radiation in plat...