It is the most sensitive exam for spinal and joint problems because it can provide clear pictures of soft tissue structures near and around the bones. MRI is oftentimes used to diagnose injuries, especially those affecting the clavicles, elbows, wrists, pelves, and knees. The images allow the physician to view even the very small injuries and tears to ligaments and muscles.

MRI of the thoracic section of the body is a fast, noninvasive alternative tool to x-ray angiography for diagnosing coronary artery disease and heart problems. Medical doctors can examine the size and thickness of the chambers of the heart and determine the extent of damage caused by a heart attack or progressive heart disease. Organs located in the chest and abdomen such as lungs, liver, kidney, spleen, pancreas and abdominal vessels can also be examined in vivid details with MRI, allowing the diagnoses and evaluations of tumors and functional disorders. MRI does not involve radiation exposure. It is often the preferred diagnostic tool for examination of the male and female reproductive organs, pelves, and bladders.

The standard unit of MRI is a closed cylindrical magnet in which the patient lies down totally still for several seconds at a time. The later models were not as closed as the old models. Patients are generally required to remain still for only a few seconds to a few minutes at a time.

When using a contrast injection, the patient may be uncomfortable at the injection site and may have a cool sensation. The loud tapping or knocking noises heard at certain phases of imaging are most bothersome to many patients. Earplugs may be of help.

MRI contrast material is less likely to produce an allergic reaction than the iodine-based materials used for conventional x-rays and CT scanning.

Normally an MRI examination consists of two to six imaging sequences, each lasting 15 minutes. Each sequence shows a cross-section of the body in one of several planes and has its own degree of contrast. The exam generally takes 15 to 45 minutes, depending on the number of images needed, albeit a very detailed study may take much longer.

MRI has its own limitations such as it may not always distinguish between tumor tissue and edema – an accumulation of an excessive amount of watery fluid in cells or intercellular tissues. It does not detect calcium when it is present within a tumor. Bone is better imaged by x-rays in some cases and CT scan is preferred for patients with severe bleeding.

MRI typically costs more than CT scanning.