For an MRI examination, the patient is placed in a large magnet. Then, using radiofrequency magnetic field pulses at the appropriate “resonant” frequency, hydrogen atoms are tipped out of their equilibrium. The MRI scanner detects the signal induced by the hydrogen atoms (mainly from water and fat) during their return to equilibrium. A computer then transforms this signal to produce anatomical and functional images of the human body.
All this takes place without exposing the patient to ionizing radiation. MRI has been used routinely to produce detailed anatomical images of patients for more than 30 years. For about 25 years, it has been possible to use MRI to study the microscopic diffusion of water molecules in the human body (diffusion weighted MRI technique) as a means for obtaining clinically useful information . The first clinical application of diffusion weighted MRI was in the detection of stroke in the brain, but in the last 10 years diffusion weighted MRI has seen growing use in cancer imaging throughout the body .
Thanks to technological developments in the last few years, it is now possible to capture images of the whole body with the diffusion weighted MRI technique in a short time, giving rise to the Diffusion Whole Body (DWB) examination . The execution of DWB examinations, and the interpretation of the resulting images have been standardised in the main research centres  and the technique has progressively become available for cancer patients .
Recent scientific publications report a diagnostic accuracy of DWB comparable to that of other and older whole body imaging techniques that use radiation and contrast agents, such as Positron Emission Tomography (PET) and Computed Tomography (CT) [6-7].
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