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What are artifacts

Q: The radiology report I have on my spinal MRI says a few things about "artifacts." What are those exactly?

A: Magnetic resonance imaging (MRI) is one of the best ways to take a look inside the spine and see what's going on without actually opening the body. The brain, spinal cord, discs, ligaments, bones, blood vessles, nerves, muscles, and joints can all be evaluated with this tool.

Information gained from MRIs is different than what is seen on X-rays or CT scans and is sometimes "complementary" to these others types of imaging studies. Multiple sclerosis plaques, loss of blood flow or blood hemorrhaging, edema (swelling), and torn spinal nerves are just a few of the other types of pathologies MRIs can reveal.

One of the best advantages of MRI (a pearl) is that it does not expose the body to ionizing radiation like X-rays and CT scans do. And it provides the only real way to look at the spinal cord. MRIs are better than X-rays for finding subtle or difficult-to-spot bone fractures. MRIs also show bone bruising and tumors that aren't readily seen on X-rays or CT scans.

One of the biggest downfalls (a pitfall) is the appearance of artifacts. Artifacts refer to anything that shows up on the MRI that isn't really there. An error on the part of the technician conducting the test can create artifacts. But so can the pulsations of blood or cerebrospinal fluid as they flow through the body.

Dental implants show up as dark spots. Fat and water in the body shift position causing artifacts. Even chemicals shifting in the body can become artifacts. Any of these factors creating artifacts can also result in a false positive meaning the MRI suggests a problem that doesn't exist.

MRIs provide valuable information but findings must be viewed with caution. The patient's history and clinical presentation (signs and symptoms) must be considered along with the imaging results when planning, assessing, and modifying treatment. Continued advancements in improving MRI systems may eventually eliminate artifacts. But until then, false positives and false negatives may delay or disguise an accurate diagnosis for some patients. Being mindful of artifacts is helpful in reducing diagnostic errors.

Reference: James Elliott, PT, PhD, et al. The Pearls and Pitfalls of Magnetic Resonance Imaging for the Spine. In The Journal of Orthopaedic and Sports Physical Therapy. November 2011. Vol. 41. No. 11. Pp. 848-860.