Monte Carlo studies of x-ray scattering in transmission diagnostic radiology

Monte Carlo methods have been used to simulate the scattering of x rays in polystyrene and water phantoms. In particular, the ratio of the scattered to total x-ray fluence (scatter fraction) has been calculated for monoenergetic x-ray beams in the energy region relevant to diagnostic radiology and nuclear medicine (30--660 keV). Simulations have been made for representative values of the pertinent geometrical factors; phantom thickness from 5 to 21 cm, x-ray beam diameters of 10 and 25 cm, and scatterer-to-image-plane separations from 0 to 20 cm. As a function of x-ray energy, the scatter fraction was found to vary slowly between 30 and 100 keV, and to decrease between 100 and 660 keV. The present results were generated with a special transport code which included the effects of special geometries and the response of the x-ray detector. With the inclusion of these effects, the results resolved inconsistencies and showed good agreement with previous measured and calculated data