ABC of Vascular Disease
Magnetic Resonance Imaging
1. What is an magnetic resonance imaging?
Magnetic resonance imaging (or MRI) is a new method of taking very detailed
images of the inside of the body but without using x-rays. The images are
created using sophisticated computer analysis of radiowaves that are directed at
the patient, but in order to create useful images the patient must lie inside a
very strong magnetic field which is controlled by the computer as the patient is
scanned. The whole process is completely painless and requires no contact
with the patient. Occasionally a special dye is injected into the vein in
the arm and allowed to circulate in the blood to enhance the images of the blood
2. Are there any special precautions to take before having the MRI?
Most MRI machines consist of a tunnel that the patient must lie in during the
scan. You must lie still during the scan to avoid "blurring" the
pictures and some patients find this a bit claustrophobic. The MRI machine
uses very, very strong magnetic field which you cannot feel, but if you have any
metal on (or in) you, it may be affected by the magnetic field and can be
hazardous. Patients with metal implants may not be able to have an MRI
3. What are MRI scans used for?
MRI scans are very good at looking at the "soft" tissues that do not
show up very well on x-rays and often very poorly on ultrasound. MRI
images can be generated by the computer so that you literally can be looked at
from all directions! Modern MRI machines can also detect the flow of blood
in the arteries and veins without repeated injections of dye into the artery (as
is needed for an angiogram) and these pictures of the blood vessels can be
looked at in three dimensions.