Magnetic Resonance Imaging (MRI) produces images of the internal organs without the use of x-rays and radiation. Anatomic images are produced using a strong magnet, radiofrequency signals, and sophisticated computer software. With MRI the body may be examined slice by slice in any desirable plane.
What is MRI used for?
MRI is a noninvasive imaging technique that allows visualization of very small structures, detection of soft tissue and connective tissue abnormalities, tumor detection, and a multitude of other diseases. By mapping the motion of water molecules, MRI can be used to detect acute stroke, often within 30 minutes from the onset of symptoms.
What Is MRA?
Magnetic Resonance Angiography (MRA) uses MRI to evaluate blood vessels. Typically in the head, neck, abdomen, and extremities. MRA does not obligatorily rely on the use of IV contrast and avoids the use of ionizing radiation.
What is the difference between MRI and CT?
CT uses x-rays/ionizing radiation. MRI uses magnetic fields and radio frequency signals thus avoiding exposure to ionizing radiation. In MRI, hydrogen atom alignment in the body is systematically disrupted with radio waves. As the alignment returns to its previous state, energy is emitted and measured. It is this data that is used to generate two-dimensional cross-sectional images and three-dimensional reconstructions. MRI and CT typically complement each other and provide different types of information about disease.
How long does an MRI or MRA take?
Depending on the purpose, an MRI scan can take anywhere from 10 minutes to over 2 hours. Typical scanning protocols takes about 45 minutes and are divided up into separate blocks of scans. The machine will run for roughly 5 minutes at time, and will then stop.
What should I expect during an MRI or MRA?
You may be asked to wear a hospital gown or clothing without zippers or snaps (such as sweatpants and a t-shirt). Certain types of metal can cause blurry images.
You will lie on a narrow table, which slides into a large tunnel-shaped scanner.
Some exams require a special dye (contrast). Most of the time, the dye will be given through a vein (IV) in your hand or forearm before the test. The dye helps the radiologist see certain areas more clearly.
Small devices, called coils, may be placed around the head, arm, or leg, or around other areas to be studied. These help send and receive the radio waves, and improve the quality of the images.
During the MRI, the person who operates the machine will watch you from another room. The test lasts about 45 to 60 minutes, but may take longer.
An MRA exam causes no pain. If you have problems lying still or are very nervous, you may be given a medicine (sedative) to relax you. Moving too much can blur images and cause errors.
The table may be hard or cold, but you can ask for a blanket or pillow. The machine produces loud thumping and humming noises when turned on. You can wear ear plugs to help reduce the noise.
An intercom in the room allows you to speak to someone at any time. Some scanners have televisions and special headphones that you can use to help the time pass.
There is no recovery time, unless you were given a medicine to relax.
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