Magnetic Resonance Imaging (MRI) of the Bones, Joints, and Soft Tissues

By Sara Foster

(MRI Scan of the Bones, Joints, and Soft Tissue)

Procedure Overview

What is magnetic resonance imaging (MRI)?

Magnetic resonance imaging (MRI) is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

How does an MRI scan work?

The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. The magnetic field, along with a radiofrequency, alters the hydrogen atoms' natural alignment in the body. Computers are then used to form a two-dimensional (2D) image of a body structure or organ based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use radiation, as do x-rays or computed tomography (CT scans).

A magnetic field is created and pulses of radio waves are sent from a scanner. The radio waves knock the nuclei of the atoms in your body out of their normal position. As the nuclei realign back into proper position, they send out radio signals. These signals are received by a computer that analyzes and converts them into an image of the part of the body being examined. This image appears on a viewing monitor. Some MRI machines look like narrow tunnels, while others are more open.

Magnetic resonance (MRI) may be used instead of computed tomography (CT) in situations where organs or soft tissue are being studied, because with MRI scanning bones do not obscure the images of organs and soft tissues, as does CT scanning.

Reasons for the Procedure

In orthopedics, an MRI may be used to examine bones, joints, and soft tissues such as cartilage, muscles, and tendons for injuries or the presence of structural abnormalities or certain other conditions, such as tumors, inflammatory disease, congenital abnormalities, osteonecrosis, bone marrow disease, and herniation or degeneration of discs of the spinal cord. MRI may be used to assess the results of corrective orthopedic procedures. Joint deterioration resulting from arthritis may be monitored by using magnetic resonance imaging.

There may be other reasons for your physician to recommend an MRI of the bones, joints, or soft tissue.

Risks of the Procedure

Because radiation is not used, there is no risk of exposure to radiation during an MRI procedure.

Due to the use of the strong magnet, MRI cannot be performed on patients with implanted pacemakers, some older intracranial aneurysm clips, cochlear implants, certain prosthetic devices, implanted drug infusion pumps, neurostimulators, bone-growth stimulators, certain intrauterine contraceptive devices, or any other type of iron-based metal implants. MRI is also contraindicated in the presence of some internal metallic objects such as bullets or shrapnel, as well as surgical clips, pins, plates, screws, metal sutures, or wire mesh.

If you are pregnant or suspect that you may be pregnant, you should notify your physician. In general, there is no known risk of MRI in pregnancy.  However, particularly in the first trimester, MRI should be reserved for use only to address very important problems or suspected abnormalities.

If contrast dye is used, there is a risk for allergic reaction to the dye. Patients who are allergic to or sensitive to medications should notify their physician. Studies show that eighty-five percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your physician know if you have ever had a reaction to any contrast dye, and/or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast.

MRI contrast may have an effect on other conditions such as allergies, asthma, anemia, hypotension (low blood pressure), kidney disease, and sickle cell disease.

Nephrogenic Systemic Fibrosis (NSF) is a very rare but serious complication of MRI contrast use in patients with kidney disease or kidney failure.  If you have a history of kidney disease, kidney failure, kidney transplant, liver disease or are on dialysis, you must inform the MRI technologist or radiologist prior to receiving contrast.

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