Visible light is made up of many different wavelengths known as a spectrum. We observe these wavelengths as different colors, or all wavelengths together as white. The same principle can be used for x-rays. Although invisible to the naked eye, these different x-ray wavelengths or colors can be captured by some digital devices.
Standard radiographs and conventional CT measure how much of the x-rays are stopped or attenuated by the object the x-rays pass through. However, different materials (even with the same density) stop or attenuate different wavelengths differently, which is not captured by standard radiographs and CT – this is equivalent to measuring the brightness (density) but not the color (material composition). Spectral photon-counting CT measures how specific x-ray wavelengths are attenuated, which is used to determine material composition. For example, if iodinated contrast is administered to the patient, spectral CT can distinguish iodine from body tissues (bone, fat) and determine the amount present.
The combination of a color spectrum with extremely high spatial resolution means spectral photon-counting CT contributes significantly more information compared to conventional x-ray imaging. We aim to revolutionize medical imaging and significantly improve healthcare worldwide. Spectral CT, bringing color to x-rays, is analogous to that of the complex technological innovations that enabled the move from black/white television to color television.