What is MRI ?
MRI stands for magnetic resonance imaging. It is a scanning modality performed by using a strong magnetic field. The hydrogen atoms in the body react to this magnetic field and emit signals which are then analyzed by a computer to produce images. It can provide sectional images in any plane of any part of the body. No ionising radiation is involved, and air or bone represent no obstacle to imaging.
What should I tell the doctor before scanning ?
No harmful effects of the static or fluctuating magnetic fields used in MR imaging are known; however, an important contraindication is the presence of ferromagnetic intra cranial aneursymal clips and intra ocular Ferro magnetic foreign objects. The presence of a pacemaker represents an absolute contra indication to MR imaging. First trimester pregnancy is also considered by some as an absolute contra indication to MR imaging due to possible heating of the foetus. Thus, you must inform the doctor about the presence of a pacemaker, or whether any foreign body had ever entered the eye. Also, you must inform the doctor if you have a cochlear (inner ear) implant, heart valve and any metallic implant.
What is the preparation required ?
There is usually no restriction on diet or medication. If an intra venous contrast has to be given, you may need to be on an empty stomach for four hours. A body scan may need you to be fasting for 4-6 hours. You should avoid eye makeup and ornaments as they may interfere with images to be obtained.
How is it performed ?
You are made to lie on a table which then passes through a narrow tunnel. You need to keep still. You may hear knocking sounds during the procedure. The entire test takes about 30-90 minutes depending upon the part scanned. There are no side effects. A few patients get a claustrophobic feeling during scanning, and may require sedation.