Energy-selective reconstructions in X-ray computerised tomography

Abstract

All X-ray computerized tomography systems that are available or proposed base their reconstructions on measurements that integrate over energy. X-ray tubes produce a broad spectrum of photon energies and a great deal of information can be derived by measuring changes in the transmitted spectrum. We show that for any material, complete energy spectral information may be summarized by a few constants which are independent of energy. A technique is presented which uses simple, low-resolution, energy spectrum measurements and conventional computerized tomography techniques to calculate these constants at every point within a cross-section of an object. For comparable accuracy, patient dose is shown to be approximately the same as that produced by conventional systems. Possible uses of energy spectral information for diagnosis are presented.

The potential of dual-energy computed tomography for quantitative decomposition of soft tissues to water, protein and lipid in brachytherapy

“…Alvarez and Macovski (1976) separated the linear attenuation coefficient (LAC) of each voxel into the photoelectric and Compton scattering components using approximative analytic formulas for the cross sections. The authors, however, did not tune the method for usage in radiation treatment.…”

A review of X-ray explosives detection techniques for checked baggage

“…9. Schematic of a potential combined CT-multiple energy x-ray imaging system to further improve upon detail detectability Attempts to gain spectral information by separating raw bremsstrahlung spectra into photoelectric effect and Compton scattering dominated energy regions is not new (see for instance, Alvarez et al, 1976;Kelcz et al,1979;Lehmann et al, 1981). Here it is recognized that, for the typical wide energy bremsstrahlung spectrum provided by CT scanners, the Dual-energy x-ray imaging can be accomplished by varying the potential of the x-ray tube, by arranging for the beam to be recorded in sandwich detectors (Knoll, 2000), which have different sensitivities to high and low energy photon beams, or through the use of so-called Kedge filters.…”

PET/CT scanner instrumentation, challenges, and solutions

“…Collecting two (or more) scans with x-ray beams at different energies allows one to decouple the photoelectric absorption and Compton scattering components from the total linear attenuation coefficients [55]. These individual components can then be scaled separately to any energy, such as 511 keV for PET, and added to obtain the total attenuation coefficient.…”