Customer FAQ

Magnetic resonance imaging (MRI) uses radio-frequency waves and a strong magnetic field (rather than X-rays) to provide remarkably clear, detailed pictures of internal organs and tissues. It has proven invaluable in diagnosing a broad range of pathologic conditions, in all parts of the body.

The conventional MRI unit is a closed cylindrical magnet, in which the patient must lie totally still for a couple of minutes at a time. Some may consequently feel closed in or truly claustrophobic; fortunately, new patient-friendly designs are now coming into routine use. The short-bore systems are wider and shorter, so they do not fully enclose the patient - and open permanent magnet systems are open on all sides.

MRI is unique because, unlike the usual radiographs (X-rays), radioisotope studies or even computed tomography (CT) scanning, it does not rely on ionizing radiation. Instead, radio-frequency waves are directed at protons, the nuclei of hydrogen atoms, in a strong magnetic field. The protons are initially 'excited' and then 'relaxed,' emitting radio signals which can be computer-processed to form an image.

In the body, protons are most abundant in the hydrogen atoms of water (the H in H2O); an MRI image shows differences in the water content and distribution of various body tissues. Even different types of tissue in the same organ (such as grey and white brain matter) are easily distinguishable. Typically, an MRI examination consists of two to six imaging sequences, each lasting up to ten minutes. Every sequence has its own degree of contrast and shows a cross-section of the body in one of several planes.

It is important to mention any allergy or drug intolerance, in case a contrast agent is requested for your examination. Gadolinium, used in MRI, is very rarely allergenic.

If possible, have your MRI in a medical imaging centre equipped with an open magnet system.

If you arrive with someone else, that person may remain with you, if your examination is carried out with an open MRI. The technician will watch you all the time, while fully able to hear you and speak to you through a microphone. For further security, an alarm is placed in your hand, to be pressed, if necessary.

MRI uses receiver antennas which are very sensitive to the weak radio waves emitted from your body during a sequence. Radio waves coming from outside must be filtered out by a continuous shielding; this would be interrupted by opening the door, hence deteriorating image quality during the sequences.

There are no moving parts inside an MRI device. Noise is generated by the fast-inversion of electric currents in the radio wave emitters which obtain images. Sequences are fairly loud in a closed high-field MRI, but quieter in open systems. If noise is still a problem, just ask for ear protection.

High magnetic fields and electromagnetic waves (radio waves) induce multiple short-term magnetic orientation changes in a small minority of your body's atoms. Under normal examination conditions, no adverse effects have ever been proven, even in fetus, showing that this technique is safe. Every MRI machine is strictly controlled in a regular manner, to ensure safety and stable image quality.

Most sequences need a few minutes to complete; during this time, MRI builds a very precise body map to obtain an image. Any patient movement during this period will produce blurred imaging and lose information. MRI image formation can be compared with night-time photography, where a longer exposure period is necessary to gain enough light to expose the film (where light is likened to the MRI signal). The shorter the sequence, the less signal is obtained and the less precise the image will be.

Open magnets use a vertical field. This orientation increases the signal obtained from the patient. That is why image quality obtained by an AIRIS Elite 0.3T is equivalent to that of a 1T closed MRI unit.

Tell your doctor if you have a pacemaker or another electronic implant (eg an insulin pump), as well as any metal elements in your head or close to your eyes. Metal objects elsewhere do not pose a danger - just mention it to the technician in charge of your examination.

Although MRI has shown to be safe and does not generate any dangerous radiation, pregnant women should not undergo MRI imaging during the first two trimesters. This rule can be ignored if a life-threatening disease is to be investigated.