Magnetic resonance imaging (MRI)
Table of Contents
What is Magnetic Resonance Imaging?
The Magnetic Resonance Imaging (MRI) is used to image human body without using x-rays. MRI consists of a superconducting magnet and Radiofrequency (RF) system. The strength of Magnetic field and RF pulses used for human imaging are harmless.
MRI uses hydrogen atoms as signal source within the human body to generate images.
How do we perform MR I?
In the tube-like magnet is a 60-80 cm large hole, where the patient is placed. If you have claustrophobia you can receive a Beruhigungsmittel.
During the examination you can hear loud sounds that derive from the electromagnetic phenomenon. These sound are completely normal and depend on the examed area and used imaging technique. You are provided with ear plugs or headphones to protect you from any inconvenience caused by this sound.
During the exam it is important that you stay calm and do not move in order to reduce movement artifacts. Some examinations require breathing instructions or ECG monitoring to generate the images without breathing or pulsation artifacts.
It usually takes 30-50 minutes to complete one examination during which several hundred images are acquired.
What is to consider?
Before the examination:
The used magnetic field and the high frequency is under certain circumstances dangerous, because metal items are drawn into the magnet or can be destroyed by the radio frequency.
Especially in patients with certain implants MRI-exams are not possible.
These are patients with:
- cardiac pacemakers
- implanted heart defibrillators
- electronic implants (spinal cord stimulators, cochlea implants and so on)
- magnetic activated implants (insulin pumps or implanted infusion pumps etc.)
- not MRI-compatible protheses/implants
- metal splints or foreign bodies
Metal items that are introduced into the magnetic field, can cause injuries and picture artifacts. Therfore all metal or magnetic items should be removed in advance to the exam.
Especially the following items should be removed:
- wristwatches, glasses, keys, (piercing-)jewellery, hairpins
- moneybags, loose coins in pockets, credit cards (magnetic stripe will be erased and card will be useless!)
- metal items on clothing (belts, zippers, metal buttons, -lock e.g. bra)
- removable dental prostheses
- hearing aids
- acupuncture needles
After the examination:
If you have received a tranquillisation, you should not drive your car during the following hours. You also should not use dangerous machines that require your full attendance. Please let yourself get picked up if you received a tranquillisation.