Catheter-based device uses MR inside body to detect plaque

When established manufacturers five years ago told the young entrepreneurs of TopSpin Medical it was impossible to build a self-contained intravascular MR catheter, it only encouraged them to go on. They were right to do so. Clinical trials testing the safety and functionality of the device were to be complete by the end of 2004. FDA approval could come by mid-2005, according to Eyal Kolka, senior vice president of business development for the Israel-based company.

Kolka and Erez Golan, both in their early 30s, have designed a miniature handheld system that generates its own magnetic field and radio-frequency pulses and then records the data to be processed into images. The disposable intravascular MR (IVMR) catheter is intended primarily for interventional cardiologists to detect coronary plaque and characterize it as lipid-rich, which is vulnerable to rupture, or necrotic, which is considered stable.

The IVMR catheter is stabilized on the arterial wall by the inflation of a low-pressure (up to 1 atmosphere) side balloon. From there, it can achieve images with resolution of 100 microns or 0.1 mm - three to five times the resolution possible with state-of-the-art cardiac MR scanners.

Advantages of the technique include its low cost (estimated at $1000 with no expensive external setup), elimination of motion artifacts, accessibility to the patient during the procedure, compatibility with existing interventional tools, and resolution and diffusion contrast capabilities that are unattainable by conventional clinical MR imaging, Kolka said.

Kolka and Golan are now designing the next-generation probe, one that could be mass-produced and commercialized. Improvements include a smaller diameter and a better signal that will double the current thickness of 2 mm, enabling the imaging of a larger vessel segment.

"These changes, plus others, will enable us to bring a commercial product to market in the second half of next year," Kolka said in 2004.

Human clinical trials in Europe have documented the safety and efficacy of the catheter in 20 patients scheduled for catheter angiography. Clinical trials are slated to begin in the U.S. and Japan next year.

Studies in pigs have shown that the catheter's effect on the epithelium is no different from the effect of intravascular ultrasound. Preclinical ex vivo studies correlating the IVMR results with histopathologic staining of human carotid and coronary arteries showed an overall accuracy of 95%. Results have been good for in vivo experiments that examined lesions in the aortas of rabbits.

"We need to show more preclinical and clinical data," Kolka said. "Those studies should be published next year along with the introduction of the next-generation catheter."

Other potential applications of this technology include detection and staging of prostate cancer; imaging tumors in the colon, lung, and breast; and imaging the peripheral vasculature. For these applications, the technology is the same, but the device's design will change.

A transrectal device for prostate imaging would require a larger diameter than the one used in vascular applications. The safety implications for prostate imaging are less demanding than for the coronary arteries, and the clinical trials would reflect those differences, Kolka said.