What is MRI?
Magnetic resonance imaging MRI shortened. MRI machine consists of a powerful magnet, a radio transmitter, a radio receiver (antenna) and a computer. These components work together in such a way that it produces images of the interior of the body. The machine is open at both ends and is well lit. When the investigation is done, you're inside the machine and are in a strong magnetic field. The machine simultaneously transmits radio waves towards the area to be examined. Depending on the tissue in the body these radio waves hit, different amounts of radio waves captured, absorbed. In the strong magnetic field detected by this antenna / radio receiver in your computer. The signals in this way is captured, sent to the computer which produce images.
Computer technology makes it possible to produce images in many planes as well as in three-dimensional images. There are many variations and special techniques which can be used to affect the MRI signal to emphasize specific types of tissues. Procedures for image acquisition varies from center to center. MRI is still under development and improvement.
In contrast to CT and X-rays are not radioactive radiation. There is no evidence of harmful effects on humans of the magnetic field and radio waves used for the MRI.
MRI of the heart
Among the imaging methods, MR is the one who can provide the most comprehensive information about the heart's structure (anatomy) and function. Without sticking needles or catheters into you, and without the use of radioactive rays, MRI can provide important and often unique contributions in the diagnosis of both congenital and acquired heart disease by.
MRI scan of the heart can provide excellent images of the heart seen in different planes. In addition, MRI can provide information on several aspects of cardiac function, eg.
- how well the heart contracts and work - the heart or parts of the heart
- how well the heart valves work
- how well the heart pumps blood into cycles
- how freely and quickly blood flows through the heart
- how good is the blood supply to the heart muscle (myocardium) at rest and under stress
There are signs of damage to the heart muscle
Each of these issues, however, requires separate, specific human rights record and to avoid unnecessary investigation takes a long time, it must be tailored to the individual patient.
Usually it is not required dietary measures or other preparations. Patients with pacemakers, cochlear implant (apparatus of the middle ear) and metal clip attached to the blood vessels in the brain after surgery for subarachnoid hemorrhage ( bleeding in the brain ) can not be performed MR. The same may be true for patients with implanted drug pumps and nerve stimulators. Should you, for example. a metal splinter in your eye, you know. Do you have other metal implants, you should ask your doctor or nurse if it has any significance.
Hearing aids, dentures, jewelry, piercing, hair pin, wig, etc. must be removed before the survey. Certain types of cosmetics (mascara) contains bits of metal and can cause discomfort - you should not wear make-up before the study.
Most MRI machines are tunnel-shaped with an opening at both ends. Modern magnets are shorter and wider than the older versions. As a result, claustrophobia become a minor problem in MR investigations. During the survey stock machine high bank sounds. Earplugs and / or headphones where you hear music, routinely used to suppress the noise. If only a small area as required depicted (eg heart), added an antenna that captures radio wave signals directly to the skin of the part to be examined.
Although modern MRI machines are more open and less frequent and claustrophobia than older versions, there are some patients who experience survey uncomfortable. To mitigate claustrophobia feeling may in some patients be necessary to give a sedative. Bidirectional communication with the investigators created - you can thus talk to them even if they are sitting in a control room adjacent to the examination room. Try and relax as best you can. The survey is painless.
You lie on a specially designed motorized bench. When you are comfortable, move the bench into the machine. It is very important that you lie still during the examination, so that images are sharp. Because heart constantly moving, be the capture is synchronized with the heartbeat. In some cases given contrast medium into a vein to enhance the images. Study time varies, but usually takes 30-45 minutes.
What changes are sought after?
In congenital heart disease, MRI of the heart to help identify heart failure and cardiac function. MRI can also be used for control after a heart operation.
At present (2004) have cardiac MRI some important place in the study of patients with narrow coronary arteries (coronary artery disease - angina pectoris and myocardial infarction), but it is expected that the investigation in the future will be very important in this area. It appears that the method can provide very reliable information about the blood supply to the different areas of the heart without having to do cardiac catheterization. The method also seems to provide good information about functioning and non-functioning heart muscle, information that is important when considering the extent of damage after a heart attack.
At the heart muscle (cardiomyopathy) also appear MRI to provide better images than the methods that are commonly used today. Otherwise, cardiac MRI is used to assess valvular abnormalities, disease of the heart lining (pericardial disease), and other rarer diseases.
MR is going to be an important method in the diagnosis of heart disease. The various MRI techniques are also steadily improved, they are faster and gives better picture quality. With further improvements may also coronary arteries could be made well enough that MRI can replace cardiac catheterization.
MRI in the assessment of cardiovascular disease is not prevalent in this country. This is due partly to a lack of capacity - most of the country's many MRI machines are in continuous use in investigations of the central nervous system and musculoskeletal system. It depends, however, on the lack of expertise. For most of our radiology departments and institutes, cardiovascular diagnostics limited to x-ray of the chest (thorax), while lack of experience with more advanced imaging of the heart.
Good reasons to do a scan of the heart can be congenital heart disease , coronary artery disease , weakening of the heart muscle ( cardiomyopathy and some other myocardial diseases), valvular abnormalities, diseases of the heart lining (pericardial disease) and tumor in and around the heart.