A constant request from doctors is for a non-intrusive map of the densities and internal interfaces within a human body. The main non-invasive examination tools are MRI and positron-emission, gamma-ray and X-ray tomography. Although these medical imaging techniques rely on different physical principles, they all depend entirely on mathematical processing to complete the information, extract it from noise and eliminate artefacts.
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MRI and CT scans
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The hydrogen atom, the lightest in nature, behaves like a magnet that can readily be aligned by a magnetic field. When stimulated by an electromagnetic pulse, it resonates at a frequency proportional to the strength of the magnetic field. If a body is subjected to a magnetic field that varies from point to point in space, measuring the atom's frequency makes it possible to locate it.
