This invention relates generally to x-ray imaging processes and systems that use two or more x-ray spectra.
Conventional x-ray imaging uses a single kVp during a scan and represents an observed object in terms of its attenuation. However, this information is not sufficient to precisely characterize the observed object, since attenuation is energy dependent. In the diagnostic energy range, x-ray attenuation is the combination of two photon-matter interactions: the photoelectric effect and Compton scattering. These two interactions are energy-dependent and reflect the effective atomic number and electron density of the object. Accordingly, two measurements at distinct energy spectra can separate the attenuation information into these two basic components, which allows for better identification of the materials present in the object, contrast material specific images, or a weighted sum of the two interactions.
Larger spectral separation of the low and high energy spectra is favorable to image variance deduction, therefore it contributes to reducing the total radiation dose of each scan while maintaining the same noise level of the output image.