The Determination from Absorption Data of the Distribution of X-ray Intensity in the Continuous X-ray Spectrum

The empirical relation suggested by Silberstein to represent the transmission curve for a heterogeneous beam of X rays of initial intensity Io, when subjected to absorption by various thicknesses x of material, is critically examined. Attempts to apply the equation to experimental data in the deep X-ray therapy range have shown that a notable improvement in the agreement obtainable between experimental and empirical data results, if a constant d is included in the expression, so that the exponent becomes ). The method of evaluating the constants A, B and d is described, and it is shown how the spectral distribution of dosage rate in a heterogeneous X-ray beam may be calculated without recourse to spectrometric analysis. The method is suggested as being of special value in the deep-therapy region.