Magnetic Resonance Imaging is a safe process of testing, with no surgery involved, to take informative images of a patient’s organs and tissues. Typically cardiac MRI takes images of the heart while in the process of beating and can give the doctor images still as well as moving images of the heart and the blood vessels. Generally cardiologists use these images to diagnose a problem and determine what form of treatment should be meted out for the patient. Cardiac MRI makes use of a potent magnetic field, radio waves and a computer to produce images of the heart, the blood vessel and immediate surrounding areas. Like CT scans and X-rays, MRI does not utilize ionizing radiation, so there is no risk of cancer either.
The Common Uses of Cardiac MRI
Today Cardiac MRI has become a rather common test and it can be used to help doctors to:
- Assess the structure and the working of the heart, its valves, the main blood vessels, etc
- Diagnose various cardiovascular ailments
- Identify and asses the results of a coronary heart conditions
- A damage that has resulted in the heart as an after effect of a heart attack
- Detect congenital heart defects
- Identify cardiac tumours
Cardiac MRI can also help a doctor assess the size of the chambers of the heart and the width of the wall of the heart. Doctors can also assess if there is any build-up of plaque or blocks in the blood vessels.
Preparations for Cardiac MRI
Not much preparation will be required before the patient goes for a cardiac MRI. In some cases the patient may have to have a contrast dye injected into one of the veins. The dye generally used for MRI is known as gadolinium which is not known to cause any sort of allergies or after effects. Unless specifically told, the patient can usually take all his medication and eat a regular diet before the MRI. He will be required to wear a loose fitting gown and all items like jewellery, watch, credit cards, hearing aids, pins, metal zips, hairpins and any other metallic items will have to be removed from the body because there are chances that these objects can hinder the magnets in the MRI equipment.
If the patient has fear of closed spaces it would be best if he is given a mild sedative just before the MRI examination. Pregnant women must inform their doctor of their condition before they go in for a cardiac MRI.
The Cardiac MRI Equipment
The MRI equipment is a big cylindrical tube that has circular magnet on all sides. The patient will be asked to lie on the examination table that slides into the centre of the cylindrical magnetic compartment. In some MRI equipments, the magnet does not completely enclose the patient, while still others have openings on the sides. These devices are particularly useful for those patients who are claustrophobic and also for those people who are on the bulkier side. The computer connected to the MRI unit will be located in another room from where it will process the images that are taken by the unit.
How does the Procedure Work?
As mentioned earlier, the MRI equipment does not use ionizing radiation like CT scans or X-ray mechanisms. When the patient is inside the magnetic unit, the radio frequencies transmit the axes of the revolving protons in a strong magnetic field. These protons are the nuclei of the atoms of hydrogen. Now the magnetic field is created when electric current is transmitted through the wired coils found inside the MRI equipment. There may be other coils that are placed in other parts of the machine too and some may even be placed on the part of the body being examined and it is these coils that collect and transmit the radio waves that create signals that are identified by the coils.
The signals that are sent are then processed by the computer which produces a set of pictures. Each of these pictures or images exhibits a part of the heart and they can be looked at from various angles.
How is the Procedure Performed?
The patient is made to lie on the examination table of the MRI equipment. To ensure that the patient maintain the correct position sometimes straps and bolsters are used. The patient may have some coils attached on and around the area to be examined so that these coils can send and receive radio waves. Electrocardiogram leads may also be placed on the chest so that the equipment can also assess the heart beats. A respiratory gating belt that aids the computer in keeping track of his breathing throughout the time he is inside the equipment is placed on the upper part of the abdomen of the patient.
In case some contrast dyes require to be used the technician or nurse will inject the same through the vein on the patient’s arm. Unlike a cardiac CT scan, the MRI scan can take more time and some times may require to be taken again.
Experience During and After the Procedure
Being a non-invasive process MRI tests are usually painless, but there are some patients who feel uneasy inside closed spaces so it would be better if they are offered a mild sedation, though very few people may need it. The patient could experience slight warmth around the area being examined. It is imperative that the patient stays absolutely still for the few seconds that each imaged is being taken. In some cases the patient will also be asked to hold hid breath.
As the images are being recorded the patient can hear thumping and tapping noises. This is the result of the radio waves being activated when they are generated by the coils. The patient is allowed to relax during the intervals when the images are being recorded, though he will have to maintain the same position.
Though the patient is alone inside the MRI unit, the technician is always able to see, hear and talk to the patient. If being injected with contrast dye the needle could cause irritation and the patient may experience coolness as well as a flush for a couple of minutes. There are patient who could experience a metallic taste in the mouth after the injection has been delivered.
Benefits and Risks
Since there is no surgery involved in the cardiac MRI there is no pain nor is the patient exposed to ionizing. Cardiac MRIs are generally extremely clear when compared to other imaging techniques. This method is said to be very effective in diagnosing a variety of heart conditions. In addition cardiac MRI allows the cardiologist to asses the anatomy and the functioning of the heart and its related blood vessels.
Usually MRI scanning poses no risks for the patient. However if there are any medically implanted metal devices in the body it could cause dysfunction of the magnetic field.
Limitations of Cardiac MRI
The greatest drawback is that MRI scanning can deliver high quality images only if the patient is absolutely still during the imaging process. People who are extremely large may probably not fit into the opening of the MRI machine.