When Do I Need an MRI Study of My Body? A Discussion Guide for Patients and Caregivers

Richard C. Semelka, MD


September 12, 2005

In This Article

Body MRI: What the Fuss Is About

At some point during the telecast of any major sporting event, one of the commentators will announce that one of the players will be getting or has gotten a magnetic resonance imaging (MRI) study of some musculoskeletal injury, and that will determine when the player will be able to play sports again. So, virtually everyone knows about this mysterious entity called MRI and that it detects abnormalities with such clarity that it can foresee when athletes can play again, like some modern Delphian oracle.

What is it that makes MRI so powerful, and how do you know when you should be getting one to investigate a medical condition?

Basically, MRI has unparalleled soft tissue contrast resolution compared with other imaging modalities, which means that it can visualize -- in the case of sports injuries, muscles, tendons, ligaments, and cartilage -- with precise anatomic detail. This same soft tissue contrast resolution has also made MRI the technique of choice to look at most diseases of the brain and spinal cord. This heightened soft tissue contrast resolution has been slower to be fully recognized by physicians as regards the body -- that is, abdomen, pelvis, and chest -- because of problems with motion artifact (primarily breathing) which are more of an issue in the torso than in the head, spine, or arms and legs.

In this review, we focus on imaging the torso with MRI, which is what we radiologists generally refer to as body MRI.

The classically recognized strength of MRI is soft tissue contrast resolution, as mentioned above, which is much greater than that of its competitor imaging modalities of computed tomography (CT) and ultrasound. Soft tissue contrast resolution refers to the ability of a modality to distinguish the appearance of different normal components of soft tissues (such as grey and white matter in the brain) but also between diseased tissue (such as cancer or degenerative disease) and background tissue. This advantage is greatest with soft tissues (ie, anything that is not solid dense [cortical] bone or tissue with a sizable air content, such as lungs). In general, any disease process, whether it be cancer, degenerative disease, or inflammatory disease, that occurs in solid organs or muscles is shown with greater conspicuity, or contrast resolution, on MR images. In addition to the greater intrinsic soft tissue contrast resolution, MRI is more sensitive to the presence or absence of intravenously administered contrast agents (generally gadolinium-based agents) than is CT to its contrast agents (iodine-based). The combination of high intrinsic soft tissue contrast resolution and greater sensitivity to the contrast agent enhancement render MRI superior to CT and ultrasound for many applications.

Why is it, then, that MRI is not routinely used in studying possible disease in the chest, abdomen, and pelvis? There are a variety of factors that account for this, which include: (1) MRI experiences more problems with image quality from patient motion; (2) MRI studies are longer in duration; (3) patients need to cooperate more to undergo a successful MRI study; (4) there is greater familiarity among radiologists and physicians to interpret MRI findings; (4) and CT machines are more plentiful and therefore readily available.


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