A Diagnostics & Imaging Week

NEW ORLEANS Among a variety of diagnostic technology studies presented at last week's annual scientific sessions of the Heart Rhythm Society (Washington), Biophan Technologies (West Henrietta, New York) released the results of its recent scientific studies that it said help explain what it termed "the widely varying reports on the MRI safety of implanted medical devices such as pacemakers, defibrillators, neurostimulators and other devices."

CEO Michael Weiner noted that Biophan was founded five years ago to solve the problems of pacemaker heating, "which have precluded millions of pacemaker patients from undergoing MRI, including for critical needs such as preparation for cancer treatment."

He said that over the last several years, the worldwide scientific community has been divided over whether there is or is not a real safety problem. "Biophan has identified a major inconsistency in the method of testing used by the industry to assess pacemaker heating during MRI, which helps to account for the wide variation of results observed in lead heating."

The company's study results indicate that some of the unintentional variance seen in testing is "due to limitations in the methods of testing and the very complicated physics associated with MRI."

Biophan said its scientists have characterized a wide array of variables related to devices, patients, MRI scan parameters and temperature measurement techniques that can affect lead heating. "For example, testing has determined that maximum heating occurs slightly into the tissue and not at the tip of the electrode where heating is typically measured, and that different types of approved temperature measurement probes can significantly understate actual heating due to their design."

When more accurate and more precise temperature measurement protocols are used, the company said "physiologically significant" temperature increases well in excess of currently allowable limits are observed.

The company's data released include studies of the temperature generated by a device and its dependence upon the location of the patient and device within the MRI scanner. Moving the pacemaker lead as little as 3 inches to 4.3 inches within the scanner can result in an increase in temperature at the tip of the lead of more than 10 degrees C, enough, Biophan said, to cause significant tissue damage. "This could occur clinically as a result of shifting a patient off center in the MRI bore to better image other tissues," it added.

Additional data show the effect of two different temperature probe designs, both of which are acceptable according to the current ASTM testing standard. "This information is significant," Biophan said, "since it also affects the way MRI-induced heating is measured in other devices, such as the safety testing of surgical tools used in the emerging field of MRI-guided interventional medicine."

Biophan said it has been discussing the findings with implantable-device manufacturers at this year's meeting. Weiner said, "We are pleased to see recognition by key industry and government experts, sharing our view that MRI safety cannot be guaranteed until devices are designed from the ground up, with rigorous scientific testing."

Also at the HRS meeting:

GE Healthcare (Waukesha, Wisconsin) reported that it to date has the largest global installed base of 64-detector volume computed tomography (CT) systems. The company said that installations of its next-generation system, the LightSpeed VCT, in 2005 would number in the hundreds.

In a single rotation, the LightSpeed VCT creates 64 submillimeter images, totaling 40 mm of anatomical coverage, which are combined to form a 3-D view of the patient's anatomy for the physician to analyze. "These highly detailed images can provide critical information to a physician analyzing less invasive treatment options," GE said.

Laura King, global vice president, interventional, cardiology and surgery at GE Healthcare, said the speed and accuracy of the LightSpeed VCT "has put GE at the forefront of diagnostic cardiovascular care."

She said that installations of LightSpeed VCT in general hospitals, cardiac centers, physician offices, children's hospitals and other facilities around the world "are revolutionizing imaging and transforming the delivery of healthcare."

GE Healthcare said its AW Card EP software option, available to cardiologists using the LightSpeed VCT, allows for greater precision in pre-planning for electrophysiology procedures (EP), even in the most complex anatomy. The company said the AW Card EP software provides cardiologists "a tool for quick and easy 3-D processing of CT images used in EP ablation planning and biventricular lead placement procedures."

The 3-D images obtained with the LightSpeed VCT system also can be processed with the Carto XP EP Navigation System manufactured by Biosense Webster (Diamond Bar, California), a Johnson & Johnson company, resulting, GE said, in "more accurate anatomical registration with 3-D map for greater confidence in navigation."

LightSpeed VCT, which GE introduced last year as the world's first volume CT system, also enables cardiologists to capture images of the heart in just five heartbeats something no other CT system can offer, according to the company.

"Cardiologists and [other] customers told us that imaging the heart in five or fewer beats was an urgent clinical need," said King. "The LightSpeed VCT is the only technology capable of five-beat cardiac imaging."