Magnetic Resonance Imaging (MRI)

What Is Magnetic Resonance Imaging (MRI)?

Magnetic Resonance Imaging (MRI) uses radiofrequency waves and a strong magnetic field to provide remarkably clear and detailed pictures of internal organs and tissues. There are no X-rays used at all in creating the images. The technique has proven very valuable for the diagnosis of a broad range of pathologic conditions in all parts of the body, including cancer, heart and vascular disease, stroke, and joint and musculoskeletal disorders.

How is MRI used in diagnosis?

MRI is the diagnostic imaging tool of choice for evaluation of the brain and spinal cord. Because it provides excellent soft tissue contrast without ionizing radiation, MRI is exceptionally useful for evaluating brain tumors of all kinds, multiple sclerosis and other white matter diseases, brain infections, aneurysms, and vascular malformations. MRI is also valuable in examining the orbital structures, pituitary gland, and the soft tissue structures of the neck.

Because MRI gives such clear pictures of soft-tissue structures near and around bones, it is the most sensitive exam for evaluating spinal and joint problems. MRI is widely used to diagnose sports-related injuries, especially those affecting the knee, shoulder, hip, elbow and wrist. The images allow physicians to see even the smallest tears and injuries to ligaments, tendons and muscles. MRI also excels in the diagnosis of disc herniation and spinal stenosis.

MRI of the heart, aorta, and peripheral blood vessels is a fast, noninvasive tool for evaluating atherosclerotic disease and other cardiovascular problems. MRI enables evaluation of the size and thickness of the chambers of the heart and can determine the extent of damage caused by a heart attack. MRI is useful in evaluation of aortic aneurysms (abnormal dilatations) or dissections (abnormal tears of the aortic wall).

Organs of the abdomen, including the liver, kidneys, spleen, and pancreas, can also be examined in high detail with MRI, enabling the diagnosis of tumors and other disorders. MRI is growing in popularity as an adjunct to traditional x-ray mammography in the early diagnosis of breast cancer. Because no radiation exposure is involved, MRI is often the preferred diagnostic tool for examination of the male and female reproductive systems, pelvis, hips and urinary bladder.

How should you prepare for the procedure?

Since MRI uses a strong magnetic field, patients will be asked if they have any metallic objects in their body. Any patient with a cardiac pacemaker, old pacemaker wires, an implantable defibrillator, cochlear implant, neurostimulator, or non-MRI compatible aneurysm clip is not a candidate for MRI. Also, any patient with shrapnel in their body or a metallic foreign body in or around their eyes should not undergo an MRI study. If there is any question of metal fragments being present, you may be asked to have an x-ray that will detect any such objects. In most cases, cardiac stents, artificial heart valves, prosthetic joints, and surgical staples, plates, pins and screws pose no risk during MRI if they have been in place for more than four to six weeks. Dental fillings and braces are not affected by the magnetic field, but they may distort images of the facial area or brain so that the radiologist should be aware of them. If you would like more information about the safety of a particular medical device for the MRI exam, please go to www.mrisafety.com. Before the exam, you will be asked to remove anything that might degrade MRI images of the head, including hairpins, jewelry, eyeglasses, hearing aids and any removable dental work.

Female patients should not have an MRI during the first trimester of pregnancy. If there is a chance of pregnancy, a pregnancy test should be performed prior to the exam. MRI can be safely performed in the second and third trimesters with prior approval of your physician. Some patients who undergo MRI may feel claustrophobic. If this is the case, a sedative may be administered to help you through the exam. Music is also available during the exam, and you may bring your own CD to listen to.

What can a person expect during the MRI study?

The patient is placed on a sliding table by the technologist and positioned comfortably for the study in the bore of the scanner. The technologist leaves the room and programs individual MRI sequences that typically last between 2 and 6 minutes each. A tapping or knocking noise will be heard during the imaging process. An intercom allows the patient and technologist to communicate with each other at any time during the study. Depending on the number of images necessary, the study will generally take 20-30 minutes. You will be asked not to move during each sequence while breathing normally.

Depending upon the study, a contrast material (gadolinium) may be injected intravenously in an arm vein. This material will enhance certain tissues or blood vessels, making them more conspicuous and aiding diagnosis.