Challenges of 21st century medicine and healthcare systems require accurate quantitative determination of physiological and pathological parameters at histological, metabolic, and even molecular levels in human tissues. Modern medical imaging devices have been evolved and even revolutionized to address these challenges by using sophisticated manipulation of known physics processes. In this category, advanced radiation-based imaging devices are using either transmission X-Rays (Computed Tomography) or gamma-photons emission (Positron Emission Tomography). Special detection techniques have been developed to enable spectral analysis of the measured wide-band X-ray spectrum in Computed Tomography. Splitting of the X-Ray spectrum to two or more bands enables decomposition of the reconstructed images to those associated with Compton Scattering in the scanned object and to those associated with Photo-Electric absorption, and even to specific images of high K-edge materials administered to tissues. This enables accurate clinical separation of different tissues type, characterization of tumors, segmenting calcifications in blood vessels for cardiovascular diseases assessment, analysis of vulnerable plaque, accurate stroke assessment and more. Furthermore, adding a special, gratings based, interferometer to an X-Ray CT systems, enables Phase-Contrast imaging in addition to the conventional absorption imaging, leading to more capabilities to see micro-structures in human tissues. This usage of X-Ray diffraction using a non-coherent polychromatic source is in the frontiers of modern X-Ray imaging and is still in a research stage.

While X-Ray based CT utilizes the physics of radiation interaction with matter, Positron Emission Tomography (PET) is using phenomena from nuclear and particles physics to measure metabolic and molecular processes in human tissues, by measuring up-take of special radioactive tracers that emit positrons, leading to positron-electron annihilation at a very close proximity to the emission location. This is detected through a coincidence measurement of to 511 keV gamma photons emitted from the annihilation events. New detection and reconstruction technologies enable measurements of the time of flight (TOF) of each of these photons, leading to high accuracy in quantification, and characterization of cancerous tumors, neuro-degenerative diseases, and cardiovascular lesions.