"Once these precautions are better understood and further refined, we hope policy makers will see fit to review current restrictions on scanning anyone with a device," says lead author Saman Nazarian, M.D., a cardiac electrophysiology, clinical and research fellow at Hopkins.

"These images are critical to early diagnosis of certain cancers of the brain, head and neck, and to guide invasive procedures," he notes.


Of those scanned in the study, 31 had a pacemaker and 24 had an implantable defibrillator. Only modern devices - pacemakers made after 1996 and defrillators manufactured after 2000 - were tested, Nazarian says, because the latest models were deemed to be safer than older versions. Newer models are made of titanium, a non-magnetic metal, he points out, and they are smaller and more lightweight and have better protection from the radiofrequency energy of the MRI scanner.

Using a single scanner, a 1.5 Tesla by General Electric, the Hopkins group was able to help plan artery-opening procedures for more than a half-dozen in the test group; improve measurements of tumor growth in nine others; and detect two strokes, a benign brain mass and a blood clot in the spine that had been missed by alternative imaging from CT scanning.

Nazarian cautions that only physicians specially trained in MRI safety, or with access to specialists familiar with the specific precautions taken in his study, should undertake this approach. "It is also important at this time to restrict MRI use to those with implanted devices specifically tested, and scanners of the same type and magnetic strength as that used in our study," he adds.

All study participants were closely monitored during the scans with electrocardiography and pulse oximetry, and staff were on hand to resuscitate patients in the event of an emergency.

All subjects were over age 19 and were followed from three months to six months to look for any post-test heart damage or changes in the devices' programming.

Patients were disqualified from testing if they had any leads placed on the surface of the heart or leads that were capped with metal, and therefore not connected to the battery and at greater risk of overheating. Leads are the electrical components connecting the device to the heart muscle, and when the leads are attached to the battery or embedded in the blood vessels, they are less likely to be overheated by the MRI field.

An analysis of records showed that scans provided definitive answers to physicians' diagnostic questions 100 percent of the time for conditions affecting areas outside the chest, and 93 percent of the time for conditions that affected the heart and the upper body. In the latter category, the remaining 7 percent of the scans were too distorted by imaging artifacts from the implanted devices to make a clear diagnosis.

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