Cardiac MRI Provides New 3-D Images of Beating Heart
DURHAM, N.C. -- For Karen Pressley, Duke's new Cardiovascular Magnetic Resonance Center revealed critical details of her heart that could enable her to have an angioplasty.
Physicians at her home medical center in Fort Walton Beach, Fla. were reluctant to perform a heart procedure on 55-year-old Pressley because conventional techniques could not determine the extent of possible heart muscle death from a recent silent heart attack. So Pressley was referred to Duke University Medical Center, where cardiologists used magnetic resonance imaging (MRI) technology to clearly distinguish dead from damaged, but still living, heart muscle.
"My doctors in Florida didn't want to perform an angioplasty until they could get a better view of my heart," Pressley said. "The MRI scan they performed at Duke showed that there was very little muscle death. That meant there was a good chance that angioplasty could restore function to my heart. It is a great relief to know that I can have the procedure."
Duke cardiologists estimate that about 30 percent of patients with heart disease -- like Pressley -- find that conventional methods for imaging the heart fall short in providing accurate information on which to guide treatment. The cardiologists believe that cardiac MRI can help this significant number of heart patients.
Pressley is among the first patients to have their hearts "scanned" at the new Duke Cardiovascular Magnetic Resonance Center (DCMRC), the only facility in Duke's service region -- and the first of its kind nationwide -- devoted exclusively to cardiovascular MRI. Unlike similar facilities where MRI machines may be used for many different clinical problems, the Duke scanner is devoted entirely to imaging the heart.
The DCMRC is directed by biomedical engineer Robert Judd, Ph.D., and cardiologist Raymond Kim, M.D. They say that MRI provides crisp 3-D views of cardiac anatomy with no interference from adjacent bone or air. Its image quality surpasses that of echocardiography -- a more common imaging technique -- and MRI is able to capture views that echocardiography cannot.
Cardiac MRI can show physicians how well the heart muscle is contracting, as well as precisely reveal areas of damaged tissue. The non-invasive, radiation-free technique is especially useful for evaluating such conditions as coronary artery disease, heart failure and congenital heart disease.
Already a valuable diagnostic technique, cardiac MRI is still in its infancy, according to Judd.
"It wasn't until a few years ago that engineers developed scanners fast enough to clearly capture a beating heart," Judd said. "The discipline is still defining itself. We want to advance the field by improving existing cardiovascular imaging techniques and also by creating entirely novel ways to look at the heart and its vessels."
During an MRI examination, a patient is guided through the cavity of a large doughnut-shaped magnet. The magnet causes atomic nuclei in cells to vibrate and give off characteristic "radio" signals, which are then converted by computers into three-dimensional images of the heart and its structures. While MRI technology itself is 20 years old, only in the past few years has technology improved to the point where accurate images of moving tissues can be taken.
"For the first time, we can look at the heart in a totally non-invasive way with a precision not available with other techniques," said Pascal Goldschmidt, M.D., chief of the division of cardiology at Duke. "It's a like an astronomer being able to use the Hubbell telescope for the first time to look at galaxies never visible before. The detail MRI provides is the big difference -- the exquisite definition of layers of tissue that form the heart and the membranes that surround the heart is unique to MRI."
In addition to using the machine to help cardiologists diagnose heart problems, the DCMRC will also be the site of concentrated research aimed at developing new applications of MRI technology for cardiology. Just as importantly, the researchers say, the center offers to first advanced cardiac MRI training program to teach the next generation of cardiologists in the promising new technology.
The center will devote about 40 percent of its resources to research, including basic research to improve the detection of salvageable heart tissue, research to improve imaging technology and clinical trials that use MRI to determine how new therapies affect heart function.
For Kim, being able to distinguish damaged from dead heart tissue is one of the main early benefits of MRI technology.
"With other techniques, damaged tissue can look dead," Kim explained. "Being able to distinguish dead tissue from damaged -- but still alive tissue -- is crucial, because with techniques like angioplasty or bypass surgery, we can re-supply the tissue with nourishing blood flow.
"MRI can take the guesswork out of diagnosing heart problems -- we can see exactly what disease processes are going on," Kim continued. "The MRI is not just providing better pictures of the heart -- which it does -- but it also provides new and better forms of information, such as the metabolism of heart muscle cells."
For Pressley, the cardiac MRI was able to provide her physicians with the detailed answer they needed for a specific clinical problem. As more research is conducted at the DCMRC, the Duke investigators believe that cardiac MRI will revolutionize their ability to diagnose heart problems.
"For the future, we foresee a 'one-stop shop' where any question about the heart and its vessels can be answered definitively using this technology," Kim said. "Unlike the other imaging technologies, cardiac MRI can be used to answer many different issues we face daily in treating our patients."
The DCMRC currently operates the $2.6 million, four-ton scanner in its outpatient clinic. A second scanner will be installed later this year in the inpatient area of Duke Hospital to better serve patients who are hospitalized.