Spectral Fluence of Scattered Radiation in a Water Medium Irrradiated with Diagnostic X-Rays

Abstract

The spectral fluence of scattered photons in water irradiated by diagnostic X-ray beams has been measured by using scintillation spectroscopy techniques. For beams generated at kilovoltages in the range 70 to 105 kvp, measurements were carried out as a function of water depth, irradiating area, and scattering angle. Distortions introduced into the spectra by the NaI(Tl) spectrometer due to finite energy resolution, escape of iodine characteristic radiation, etc., were removed by using digital computer techniques. Angular integration of the scattered spectra determined the spectral fluence of all scattered photons reaching various points in water. Based on available depth-dose data, the integrated scattered spectra were combined with appropriately attenuated primary spectra to yield the total spectral fluence of photons at various points within the water medium. Effective half-value layers were calculated from these spectra. The scattered component becomes increasingly hard as depth increases, shows little...