An MRI, magnetic resonance imaging, is a radiological examination using a high-power magnetic field.
Specifically, this non-invasive technique, which is not based on exposure to radiation, is used to visualize and examine soft tissues, the brain, spinal cord, muscles, joints and internal organs.
A cardiac MRI can detect heart problems early-on, especially in areas with a lack of oxygen supply.
Useful information: A clinical MRI (at 1.5 Tesla) is 30,000 times more powerful than the Earth’s magnetic field!
What is the difference between a CT scan and an MRI?
CT scans and magnetic resonance imaging (MRI) are two medical imaging technologies. But they have slightly different principles. MRI uses a magnetic field and radio waves to produce images, whereas a CT scan uses X-rays. An MRI is also generally used to obtain sharper and more detailed images.
How does an MRI work?
Our body is made up of water and tissues that contain abundant hydrogen atoms. The nucleus of these atoms is comprised of protons that vibrate and align as they approach the MRI magnet. An antenna captures these vibrations at varying speeds, depending on the type of tissue in which the atom is found. The signals emitted will then be used to create detailed cross-sectional images of the inside of the heart, which will then be reconstructed by a computer in two or three dimensions.
Why have an MRI?
An MRI may be prescribed as part of regular patient monitoring, to diagnose an illness, as well as to evaluate the effectiveness of a treatment or ensure follow-up after treatment. It is carried out in combination with other examinations and is used to obtain images with greater precision than other medical examinations.
What happens during an MRI?
An MRI is a painless examination.
It may be necessary to inject a contrast agent (most often gadolinium-based) during the MRI scan. This product is injected intravenously and makes certain parts of the body appear opaque so that they become more visible. Specifically, a contrast product makes it easier to visualize inflammations, scars left by a heart attack and other cardiomyopathies.
In practice, an MRI scan lasts 45 minutes. The patient is asked to remove any metal objects (jewelry, glasses, etc.) that may interfere with the magnetic field. It is recommended to wear clothing that is neither black nor synthetic, as this may possibly interfere with the taking of images, and to not apply ointments or balms to the area that will be examined.
The patient lies down on a mobile table that moves towards the horizontal tunnel of the MRI machine, which is approximately two meters long. The scanning magnet that produces the magnetic field is located inside this tunnel. In an adjacent room, the radiology technician performs the examination and communicates with the patient via loudspeakers.
The patient may be given hearing protection to attenuate the sometimes deafening noise of the machine. The patient must remain still and briefly hold their breath when asked.
At the Liryc Institute, a research project to revolutionize cardiac MRI scans
Led by Professor Aurélien Bustin, a researcher at the Liryc University Hospital Institute, the “SMHEART” project aims to revolutionize cardiac MRIs by making it possible to rapidly collect images of the whole heart, in one single click while the patient breathes as normal (i.e. without being asked to occasionally hold their breath during the exam), which is more comfortable for the patients. The project also plans to use artificial intelligence (AI) to automate the extraction and analysis of the anatomy, function and features of the cardiac tissues.
With SMHEART, there is no need to inject a contrast agent or hold your breath; the MRI of the future will be powerful, comfortable and completely automated to improve the care of patients with heart rhythm disorders.
Are there any side effects after an MRI?
An MRI does not pose any health risks.
In general, the contrast injection is well tolerated although it may cause side effects. Most often, these side effects are temporary and not serious: a metallic taste in the mouth, some nausea, even vomiting, a sensation of feeling warm, as well as a small bruise (hematoma) at the injection site. In some cases, these side effects may require treatment. Asthma, hives or allergic reactions may also occur, and patients with kidney failure may experience a progression of their condition.
How to prepare for an MRI
Except in certain specific cases, e.g. a stress cardiac MRI and which will be specified to the patient beforehand, it is not necessary to fast before this examination.
Pacemaker and defibrillators
Due to the extreme strength of the magnetic field, MRIs are strictly contraindicated in certain patients fitted with metallic equipment such as an implanted cardiac pacemaker. Such devices could be damaged or moved out of place.
If you have one of these devices*, it is essential that you inform the medical staff. They will be able to advise you on whether or not the examination can be performed.
*pacemakers, defibrillators, prostheses, transdermal patches, catheters, implantable pumps, artificial heart valves, hearing implants, neurostimulators, etc.
What is a stress cardiac MRI?
The heart’s arteries dilate during exercise to supply the heart with blood and oxygen. During a stress cardiac MRI, the effects of this physical effort will be reproduced using medication and it will be possible to detect the narrowing of certain arteries.
How is an MRI interpreted?
An MRI can be read immediately with the radiologist. However, it may also take longer to interpret an MRI, and in this case the doctor will contact the patient at a later time. In general, the printed images and examination report are sent by regular mail.
The radiologist will examine all of the image cross-sections, i.e. the image “slices” of the region examined. These images are usually shown in three dimensions and can be used to analyze the size, shape and exact location of any potential anomalies. The radiologist will then write a report that will be sent to the primary care physician.
