In computed tomography (CT), any reconstruction algorithm relies upon input data that accurately reflect true line integrals of some physical quantity. In x-ray transmission tomography, x-ray beam hardening alters the polychromatic x-ray source spectrum resulting in inconsistent data if simple exponential attenuation is assumed. Four models relating intensity of the emerging polychromatic beam to thickness of the absorber are examined in this paper. A cubic polynomial relation suggested by Macovski et allis compared with more physically motivated models of Greening2, Joseph3 and the present authors. Results given indicate that for moderate x-ray prefiltering (.75mm Cu), all models provide better than .05% accuracy for computing thickness of a single material; while for small material thicknesses and lighter x-ray filtration (<6.mm Al), Greening's formula is most accurate.

Date Published: 23 December 1976
PDF: 7 pages
Proc. SPIE 0096, Application of Optical Instrumentation in Medicine V, (23 December 1976);

Published in SPIE Proceedings Vol. 0096:
Application of Optical Instrumentation in Medicine V
Robert K. Cacak; Paul L. Carson; Gregory Dubuque; Joel E. Gray; William R. Hendee; Raymond P. Rossi; Arthur Haus, Editor(s)