Moving Hearts are a Different Story Magnetic resonance imaging seems like a natural medium for studying the brain, but testing the heart, says MRI head David Bluemke, M.D., Ph.D., is “a different story.” In principle, multiple images—like brain MRIs—should be able to tell right away if the heart’s threatened by an imminent attack. A problem lies in a basic characteristic of hearts: They move. And movement in MRI is like bringing your mother-in-law on your honeymoon. Additionally, because of an intrinsic limit in MRI, the most narrow coronary vessels defy clear imaging. “For the heart,” Bluemke says, “we need a completely different approach.” For the last eight years, Bluemke, Department of Radiology director Elias Zerhouni, M.D., and a team of 40 radiologists, cardiologists, physicists and engineers have worked to develop one. “You obviously can’t stop the patient’s heart,” declares radiology fellow Sal DeSena. “But we’ve learned enough to compensate for its motion. At certain parts of the cardiac cycle, the heart doesn’t move as much. We’re trying to instruct the computer to select images from that part.” “To say we’ve had to be clever to do this,” adds Bluemke, a modest man, “is an understatement.” To monitor heart muscle, Zerhouni developed what he calls MR cardiac tagging. Based on the idea that the motion of heart muscle reflects its health, he programs the machine to magnetize selected bands through a patient’s heart tissue and image the whole heart as it’s beating. The sequence lasts a fraction of an eye blink, but as the heart contracts, he’s able to see how such bands move in relation to one another. Examining more than 200 normal and heart-damaged patients has given him an idea of how to identify pathologies. The benefits of using MRI on the heart are clear. Patients aren’t sedated, and there’s no incision or worry that a catheter moving through an artery will knock off plaque, causing potentially damaging results. The software goes one step further by visualizing the vessels and their surroundings in 3-D. “It’s the gold standard for assessing the anatomy and the function of the heart,” attests cardiologist Joao Lima, M.D., “and even predicting whether trouble lies ahead.” The latest software, fine-tuned in conjunction with General Electric (which is also funding a new lab here) and the Department of Biomedical Engineering, aims for high-quality angiograms in the vessels of beating hearts. Bluemke’s also testing several easily injected liquids that act like a dye to reflect local circulation. With a few touches of the console, the monitor reveals systems as intricate as the blood vessels in a teen-age girl’s lungs. They look like sharply defined strands of frayed rope. With the new Navigator program, you can view a large blood vessel from the inside out, as though the blood cells contain mini-camcorders. Push the right panels and you’re traveling inside someone’s aortic arch, observing how the openings for the carotids resemble the holes in an ocarina. Says Bluemke, “People with anginal pain or elevated cholesterol come to the hospital, and what do they get? The state-of-the-art echocardiogram, an exercise stress test, an angiogram—multiple tests. But with MRI, we're looking right at perfusion to the heart - is the blood supply OK? Then we're looking at the motion of individual elements of the heart - is it moving in the right way? Put all that together and you can do the tests in an integrated manner. Plus, the patient only has to come in once. Within an hour, we should know if a person's a candidate for a heart attack."