MRI (Magnetic Resonance Imaging)
An MRI (magnetic resonance imaging) is a radiology exam that uses a device that emits electromagnetic waves, thanks to a large magnet. Under these waves, the hydrogen atoms that make up the body’s tissues begin to vibrate. They then emit signals, captured by a specific camera and transcribed into images on a computer screen.
MRI is a painless exam that allows you to get images of the inside of the human body, in 2 or 3 dimensions. It is prescribed in particular to visualize “soft tissues” (brain, spinal cord, viscera, muscles, tendons, etc.)
This technology, which does not use X-rays, is without risk of irradiation for the patient.
How it works?
Magnetic Resonance Imaging (MRI) does not use X-rays, unlike CT scans or X-rays.
The principle of MRI is based on the magnetic properties of an atom, hydrogen, contained, to varying degrees, in all tissues of the human body.
By using very strong magnets, the protons of hydrogen atoms in the body are simultaneously stimulated, which has the effect of pointing all hydrogen atoms in the same direction.
Once this first step is accomplished, the atoms are put into resonance by causing them to undergo excitation by a magnetic field (radiofrequency).
Read also: Difference Between CT Scan and MRI? (Medical Imaging)
When the stimulation stops, the atoms release energy, the intensity of which is measured and analyzed.
Since not all tissue contains the same amount of hydrogen atoms, the level of energy released will differ depending on the tissue composition.
The analysis of this data by computers makes it possible to reconstruct images in 2 and 3 dimensions and in the three planes of space.
Conduct of the examination (the process)
With some exceptions, you do not need to be fasting and you must take your usual medication.
If you are claustrophobic or anxious at the idea of having an MRI, report it when making the appointment, a mild sedative may be prescribed, however in this case, due to the risk of drowsiness, you must be accompanied.
Before the exam
You will be asked to undress in a cabin provided for this purpose: a shirt will be made available to you.
All metal objects are left in the cabin (jewelry, watches, glasses, hearing and dental aids, piercing, etc.) as well as mobile phones and magnetic cards due to the risk of erasure.
It is recommended to go to the bathroom before entering the cabin, for more comfort.
Depending on the examinations to be performed in order to improve the quality of the images, the establishment of a venous line may be necessary for the injection of a contrast product.
Conduct of the examination
The device looks like an examination table that slides in a tunnel open at both ends.
The room you are in must be closed, but the radiologist and technicians see you through a window. Cameras and microphones allow constant surveillance to communicate with you at all times.
You are lying on your back or on your stomach depending on the region to be explored.
The machine makes a lot of noise: noise-canceling headphones improve comfort.
Your cooperation is essential: it is important to remain calm without moving and to breathe calmly so that the images are of good quality.
The exam lasts an average of 20 to 30 minutes.
After the exam
If you have had an intravenous injection for your examination, it is important to drink a lot after the examination (at least 1.5 liters of water or around 50 oz) and on the following days in order to promote renal elimination of the injected product.
Please be sure to report any redness or rash that may occur as a result of the exam.
As the number of images to be interpreted is large, the result will be available at the radiology office within 8 days.
Precautions
MRI has contraindications that must be clearly identified. For most MRI scans, preparation and precautions are necessary.
You will be asked to come with your prescription and the written list of your medications in order to:
- to explain the procedures to you
- to check the contraindications or to take the necessary precautions
- to give you, if necessary, the prescriptions for the products to look for in the pharmacy and to bring back on the day of the exam
- to give you the prescription if necessary to perform a blood test in the medical analysis laboratory before the examination
- In the event of a foreign body of a medical nature, present yourself with the card issued by the surgeon.
Contraindications to MRI
Wearing a pacemaker, pacemaker or cardiac battery
Wearing certain heart valves or a vena cava filter
Cochlear implants
Neurostimulators
Neurosurgical and vascular clips
Implanted automated injection equipment (insulin or morphine pump)
Recent surgery less than 2 months ago
Intra ocular metallic foreign bodies
The relative contraindications
Brain bypass valves: a neurosurgery consultation may be necessary after MRI to adjust the flow of the valve
The presence of metallic foreign bodies: staples, osteosynthesis materials
Joint prostheses
Metal shards
Claustrophobia: premedication may be prescribed
Major obesity> 130 Kg
Pregnancy: the examination is not performed during the 1st trimester
Contraindications and precautions for the injection of a contrast medium
Some tests require the injection of a contrast medium, Gadolinium.
In pregnant or breastfeeding women: the injection of contrast product should be avoided
In patients with renal insufficiency: a blood test before the examination will be necessary
A proven allergy to Gadolinium (rare) contraindicates the injection.
Price MRI test
The price starting from around US$ 500 to US$ 5000 and above. It depends on the specific type of exam and the area being imaged.
One factor that can greatly affect the cost of your MRI scan is whether you have it performed in an inpatient facility, like a hospital, or an outpatient surgery center.
Information: Cleverly Smart is not a substitute for a doctor. Always consult a doctor to treat your health condition.
Sources: PinterPandai, NHS UK, National Institutes of Health
Photo credit : Province of British Columbia / Flickr
