For patients, implants are a blessed benefit of modern medicine, enabling hearts to beat properly, ears to hear again and hips to be replaced. But for radiology centers, it's an ongoing challenge to know which implants -- and therefore, which patients -- can safely undergo MR imaging.
Compounding the challenge is the fact that new implants are constantly coming onto the market. Now, this potentially dangerous knowledge gap is being addressed by a new web site, www.mrisafety.com.
The 5-month-old site represents the work of Frank G. Shellock, a PhD physiologist and adjunct professor of radiology at the University of Southern California in Los Angeles. He's also a consultant who literally writes the book on MR safety and implants, The Pocket Guide to Magnetic Resonance and Metallic Implants, now in its fifth edition from Lippincott, Williams and Wilkins Healthcare.
But even a pocket guide that is updated annually can't match the currency of a Web site, and Shellock is adding new material to his site regularly.
"New implants are added on an ongoing basis, based on my testing of them and/or published reports," Shellock said. "Since September, I've tested an additional 40 implants, with 35 more scheduled to be tested in January/February 2000."
The need for information is clearly vital, since many if not most patients have some condition that may preclude or hamper MR imaging.
"Every person that walks into the MR center with an implant has a potential safety issue, (which includes) probably 40%-60% of patients over 50 years of age," Shellock said.
Nor is the safety issue limited to implants. Patients with tattoos and cosmetic enhancements such as permanent eyeliner have been known to experience skin irritation or burning sensations, apparently caused by tattooed pigments that contained iron oxide or other similar ferromagnetic substances.
Other safety topics include preventing the "missile effect," in which metallic objects in a room can be drawn into a magnet "by considerable force," and anecdotal reports of discomfort for patients wearing drug delivery "patches" during scanning.
Shellock's site also includes a new downloadable pre-MRI screening form developed late last year by Shellock and Anne Marie Sawyer-Glover, manager, MR whole-body research systems, at Stanford University School of Medicine in Stanford, CA.
The need for up-to-date safety information is not likely to abate, Shellock noted, given the increasing sophistication of implants, especially electronically activated devices such as neurostimulators, and the increasing sophistication of MR systems with very high static magnetic fields and extremely fast gradient magnetic fields.
By Tracie L. ThompsonAuntMinnie.com staff writer
January 19, 2000
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