<unk> is an umbrella term for energy-resolved X-ray imaging in medicine. The technique makes use of the energy dependence of X-ray attenuation to either increase the contrast-to-noise ratio, or to provide quantitative image data and reduce image artefacts by so-called material decomposition. Dual-energy imaging, i.e. imaging at two energy levels, is a special case of<unk> and is still the most widely used terminology, but the terms<unk>  imaging" and<unk>  CT" have been coined to acknowledge the fact that photon-counting detectors have the potential for measurements at a larger number of energy levels.
Spectral imaging 
Iatrochemistry
Diffuse optical imaging
Orthogonal polarization spectral imaging
Multispectral optoacoustic tomography
Photoacoustic imaging
Functional near-infrared spectroscopy
Multiple scattering low coherence interferometry