Absolute Contraindications

Implantable Pediatric Sternum Device

A new implanted sternal device system for pediatric patients is contraindicated for MRI. Dr. Michael Harrison (pediatric surgery UCSF) is currently running a phase 2 research procedure, The Magnetic Mini-Mover procedure. This research procedure utilizes the following products, “Magnimplant” and “Magnatract” in a combined system to correct for pectus excavatum or sunken chest deformity. An internal magnet is surgically placed behind the sternum for "Magnimplant," and “Magnatract” is an external brace with a magnet implanted. The devices combine to exert a magnetic force on the chest wall.

This device system is totally contraindicated for MRI at any field strength. Per Dr. Harrison: “The device is made for us by Texcel and stays in 18-30 months.” “It is implanted on the sternum through a small subxiphoid incision which will always be visible, so this would be the best marker in an unconscious patient.” “The patients are teen and preteen and they and their parents have verbal and written warnings about MRI. In addition the patients wear (or at least are given) a medi alert bracelet saying no MRI.” Parents of pediatric patients should specifically be asked if this magnet device has been implanted. Most devices have been for older children, but they may be seen in patients as young as 1 year old in the future. The devices may remain implanted for years, although studies are still ongoing to determine the best clinical usage. More information is available at: http://pedsurg.ucsf.edu/conditions--treatments/magnetic-mini-mover-procedure.aspx#a3 and http://clinicaltrials.gov/ct2/show/NCT00466206. Contact the principle investigator Dr. Michael Harrison with further questions.

Note that MRI can be performed if a patient has a Nuss bar for pectus excavatum repair made of titanium alloy plates.

Metallic Foreign Body in the Eye

Intra-ocular metal foreign bodies are a cause of major concern in MR safety. It is not uncommon for patients who have worked with sheet metal to have metal fragments or slivers located in and around the eye. Since the magnetic field exerts a force on ferromagnetic objects, a metal fragment in the eye could move or be displaced and cause injury to eye or surrounding tissue. A screening CT of the orbits for foreign body must be cleared by a radiologist prior to the patient entering the scan room (Zone 4).

"Triggerfish" Contact Lens

A new contact lens that allows for an automated recording of continuous intraocular pressures has come to market (http://www.sensimed.ch/en/). This device is MRI unsafe, and can result in severe eye burn.

Gastric Reflux Device

The LINX Reflux Management System is a series of titanium beads with a magnetic core implanted around the lower end of the esophagus to control gastro esophageal reflux disease (GERD). This implant is totally contraindicated for MRI in both the 1.5T and 3T. The FDA website has more information.

Insulin Pumps

There are two basic types of insulin pumps, one is used as an external device and the other is implanted. Both types currently pose hazards to patients referred to MRI procedures. For an external insulin pump, in general, the device typically needs to be removed and kept out of the MRI environment to ensure that there is no adverse impact on the functionality of the external pump. The implanted pump will be adversely affected by the magnetic field and will need to be removed prior to imaging.

Temporary Transvenous Pacing Leads

Temporary external transvenous pacing leads contain nonferromagnetic, but electrically conductive material. Radiofrequency pulses in MRI can induce currents that could lead to thermal injuries. They are contraindicated for MRI. The same is true for abandoned intracardiac pacing leads.

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