Spectral Distributions of 280 kVp X Rays

Spectral distributions of both primary and scattered 280 kVp X rays have been measured with a scintillation spectrometer and are presented in tabular form. The attenuation of the primary beam was calculated from the primary spectra and found to be in good agreement with measured attenuation data. Scattered radiation spectra were measured at depths of 2, 5 and 15 cm below the surface of a water phantom using field sizes of 50 cm2 and 300 cm2. Variation in depth and field is found to produce rather small changes in the shape of the scattered spectra. Primary and scattered radiation spectra were normalised and added together to obtain the spectral distribution of the combined radiation. These combined spectra were used to calculate the relative energy absorption in bone and muscle at the various depths.