|How Accurate Are MRI's? Magnetic Resonance Imaging
The MRI is supposedly highly suited for imaging the musculoskeletal system. High signal intensity of fat planes and differences in signal intensity of various structures allow separation of the different tissue components including muscles, tendons, ligaments, vessels, nerves, hyaline cartilage, fibrocartilage, cortical bone, and trabecular bone.
Anyone who has had an MRI knows just how difficult it is to have an MRI. During the sometimes 45-minute examination it is absolutely vital to remain as still as possible. If this is not accomplished, the scan is fraught with motion artifact. Sometimes this artifact is just from the motion caused by breathing. Motion artifacts show up as image blurring and ghost images. Metallic objects, like surgical clips and prosthetic implants, may distort the local magnetic field due to a local change in magnet susceptibility and thus may cause image distortion. Another source of artifacts is the varying fat content of tissues. Fatty tissue is somewhat shifted in the images as compared to tissues mostly made up of water. This misregistration (chemical shift artifact) shows up at interfaces in the frequency-encoding direction; for instance, a dark border line may show up at one of the cortices, whereas the interface at the other side will appear bright.(1)The net effect of all of these artifacts is that a normal tendon is interpreted as a tear.
Limitations of MRI and CAT Scans
In the 1980s, modern medicine developed a high-tech diagnostic tool to look at vertebrae, nerves, and discs on filmùthe MRI
scan. It has been shown by various studies that more often than not, "abnormalities" on MRI were found on people with absolutely no symptoms. People were subjected to various treatments and surgeries for these "abnormalities" with the hopes of curing their pain.
physicians rely too heavily on diagnostic tests, especially for low back problems. Consequently, many who suffer from low
back pain do not find relief. The typical scenario is as follows: A person complains to a physician about low back pain that radiates down the leg. The physician orders x-rays and a CAT or MRI
scan. The MRI scan reveals an abnormality in the disc, such as a herniated, bulging, or degenerated
disc. Unfortunately for the patient, he/she may be subjected to treatments for this MRI finding which usually has nothing to do with the pain.
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