The success of the MRI lies in its very favourable features:
- No chemicals need to be injected into the organism (if no contrast agent is applied), and no ionizing radiation is generated during the examination. Although the examination has, or may have physical effects, the health risks of these are incomparably lower than those of a CT study or of isotope-diagnostic techniques. Therefore, the examination practically does not affect the patient’s and the physician’s health.
- Several quantities can be measured (e.g. spin-grid relaxation, spin-spin relaxation, diffusion, flow rate, chemical composition), thus different contrasts can be achieved. Of all imaging techniques, MRI can give the best soft tissue contrast.
- Its resolution is good. A resolution of 1 mm can be achieved even under clinical circumstances, while in special devices spatial resolution can be below 100 μm.
- Slices in arbitrary directions can be measured.
Of course, this method has disadvantages as well:
- Investment costs are high.
- It is relatively slow. Although today methods exist for the examination of fast processes, e.g. the observation of the beating heart or of brain functions, a typical study lasts longer than thirty minutes.
- The examination involves particular discomfort. The machine is excessively noisy; it is inevitable for the patient to use earplugs. Patients have to lie in a relatively long, narrow tube, which may cause problems for claustrophobic patients.