Cardiac niche holds promise in expanding MRI applications

GE sponsors cardiac work at Milwaukee clinic

One of the most promising new applications for MRI lies in cardiacimaging. The increasing speed of MR image acquisition and processingprotocols have enabled MRI scanners to conduct cardiac applicationstraditionally reserved for modalities such as nuclear medicineand echocardiography. If cardiac MRI does live up to its potential,however, radiologists may find that they must share its benefitswith cardiologists, several of whom are becoming ardent championsof the technology.

Cardiologists are calling the shots at the Cardiovascular MagneticResonance Imaging Research Unit at St. Luke's Medical Center inMilwaukee. The center opened in June and is dedicated solely todeveloping clinical applications for cardiovascular MRI, accordingto Dr. Samuel Wann, director of the unit. The center uses a 1.5-teslaGE Signa scanner that has been optimized for cardiac scanningand scans about four or five patients a day. It is not currentlycharging for scans.

MRI can complement or even replace echocardiography, cardiaccatheterization or scintigraphy for a number of applications,Wann said. MRI angiography is an obvious winner, being less invasiveand less expensive than catheterization.

Coronary MRA, particularly breath-hold imaging, is the center'sHoly Grail. GE has developed a breath-hold imaging package thatallows measurement of wall motion and ejection fractions in ashort period of time, Wann said. The center is also anxiouslyawaiting the installation of an echo-planar imaging package forits Signa.

"To be able to do meaningful coronary artery imaging,one needs to be able to do it in a breath-hold," Wann said."Ideally, we'd like to do it in real time. You can't makeit too fast for us. It is a constant trade-off between cost andprice."

Another site dedicated to the clinical practice of cardiovascularMRI is at the University of Alabama, which has installed a 1.5-teslaPhilips Gyroscan ACS. The site focuses primarily on ventricularfunction, according to Dr. Gerald Pohost, director of the divisionof cardiology, where the scanner is located. Pohost is both acardiologist and a professor of radiology.

Pohost sees cardiac MRI as providing more diagnostic informationat a cost only slightly higher than echocardiography. MRI's handas a cost-effective modality for cardiac imaging will be thatmuch stronger as MRI perfusion applications develop, he said.

"If you can do MRI of structure and function and thenadd perfusion to it, you've made it much more cost-effective,"Pohost said. "Everything before an intervention that youneed to know can be learned by one or another or all MRI approaches."

The site has done about 60 MRI perfusion studies, he said.

Vendor activity. While still in its infancy, cardiac MRI coulddevelop into a powerhouse application for the modality, and scannervendors are making sure they don't miss the boat. GE has thrownits support behind the St. Luke's center in the hope that applicationsdeveloped at the unit will form the basis for a cardiac imagingplatform that can be released as a commercial product.

"GE is supporting an aggressive works-in-progress programtargeting cardiovascular MR applications," said GE spokespersonBrian Johnson. "We see cardiac MR as an important growthopportunity for the business."

Another vendor dipping a toe in the cardiac MRI water is SiemensMedical Systems. The company recently released a software package,developed by its Siemens Corporate Research software R&D lab,designed to optimize cardiac MRI. The program uses MR images togenerate dynamic 3-D models of the human heart, then calculatesdifferent cardiac functions, such as ejection fractions and measurementsof the myocardial mass. Siemens reports that its software cancomplete an analysis in five minutes.

Siemens is planning a fourth-quarter release of the softwareas part of its new diagnostic visual console (DVC), a collectionof packages for use in cardiac analysis.

Philips is also pursuing cardiac applications for its lineof compact NT MRI scanners, introduced last year (SCAN 12/29/93).

Other vendors have been more circumspect in their cardiac MRIefforts. One company rumored to be developing a cardiac MRI scanneris echocardiography vendor Hewlett-Packard. The company has notmade a public announcement as to whether it is developing a cardiacMRI scanner, but HP representatives were on hand at the Dallasmeeting of the Society of Magnetic Resonance this year (SCAN 4/6/94).

MRI has taken a beating over the past year as an example ofhigh-cost medicine run amok, but the University of Alabama's Pohostbelieves that the modality can prove itself as a cost-saver inthe cardiac niche.

"There is a brilliant future for MRI if politics and turfdon't get in the way. With health-care reform, it's a golden opportunity,"Pohost said. "We always see such bad press for MRI, becauseit's thought of as an expensive technology. The instrumentationmay be expensive, but once it's in place it lasts for a long time."