Magnetic resonance imaging (MRI)
What
is Magnetic Resonance Imaging (MRI)?
How
Long will an MRI Take?
How safe in an MRI exam?
Pregnancy and pacemakers
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Magnetic resonance imaging (MRI) What
is Magnetic Resonance Imaging (MRI)? | |
What is magnetic resonance imaging?
Magnetic Resonance Imaging is a technique that uses a magnetic field and radio frequency to create detailed images of the body.
Our bodies are primarily made up of fat and water molecules. In turn, fat and water contain many hydrogen atoms, each of which carries a magnetic resonance signal. MRI measures these signals to capture cross-sectional images, or slices, of the body. A computer then reconstructs these signals into digital images. During the exam, there is a knocking noise that can be loud enough to require earplugs. The noise is the sound of the gradient coils.
MRI is well suited for obtaining pictures of soft tissues, including the brain, the heart, spinal cord, muscles, tendons, and joints. One of the main features of MRI is its ability to differentiate between tissues that are very similar in density, such as the musculoskeletal system (muscles, tendons, cartilage) or the gray and white matter of the brain.
Depending on the type of exam being done, an MRI study can last from a few minutes up to a full hour. Unlike a CAT scan where images are produced one at a time, MRI images are collected in a sequence, which take approximately 2-7 minutes to produce. Exams usually require 3-4 sequences. Because the MRI scanner acquires multiple images in a sequence, it is very sensitive to patient motion. It is very important to lie absolutely still. Because of the MRI scanner's sensitivity to motion, CAT scans are often the examination of choice when images of the lungs or abdomen are requested.
An MR magnet's strength is measured in a metric unit called a "tesla." Most magnets have a field strength between 0.5 and 1.5 tesla. This is about 30,000 times stronger than the Earth's natural magnetic field. Unlike conventional x-ray, MRI does not expose the patient to radiation. In addition, the strength and frequency of the radio waves used in MRI have not been shown to have any harmful effects.
Newport Imaging Center uses a new State-Of-The-Art 1.5 tesla scanner manufactured by General Electric Medical Systems.
Pregnant women and patients with pacemakers may often be excluded from undergoing MRI exams. If you are pregnant or think you may be pregnant, please notify your doctor before scheduling your MRI procedure.
A patient with a cardiac pacemaker may be excluded from an MRI study because the magnetic field can cause the pacemaker to move within the chest wall, change its operating mode, or shut down.