MAGNETIC RESONANCE IMAGING

SAFER THAN AN X-RAY, KEENER THAN A CAT-SCAN, IT’S BECOMING THE DIAGNOSTIC TOOL FOR THE 21st CENTURY.

Magnetism, a basic force of life, holds a strange fascination for us all, like some naturally occurring magic trick. The mysterious allure of magnetism has produced such concepts as “animal magnetism” and “magnetic personality,” each with connotations of an exotic, uncontrollable power.

Today medical scientists are harnessing that universal force to peer inside the living body. Powerful cylindrical magnets, large enough to position a human body within their cores, are being used to take “pictures” without X-rays. The resulting images are cross-sections of the head or body recorded with remarkable clarity and a level of detail never before achieved.

This high-quality imaging of human anatomy is called magnetic resonance imaging (MRI) or nuclear magnetic resonance imaging. It is allowing doctors at the University of Dallas Health Science Center to see the thinning of heart walls after a heart attack, tumors growing inside bone and fetal disorders inside a mother’s womb.

The precision of detail in these images is so improved over other imaging techniques that many scientists believe the technique may even someday replace the now-commonplace computerized X-rays known as CAT scans. In fact, for imaging of the head and spine, MRI is currently the method of choice in some hospitals.

“Most imagers believe that CAT scanning has plateaued, while MRI has just barely scratched the surface of its potential,” says Dr. Kenneth Maravilla, a health science center radiologist and MRI authority.

With its scientific uses rapidly expanding, MRI is becoming a new must-have diagnostic device for high-tech hospitals. Even the most basic MRI units provide improved imaging of the brain, spinal column and pelvis, and they can be adapted to keep up with the latest advances through added computer software. CAT scanners, on the other hand, have to be totally replaced every few years to stay abreast of new developments.

Across the nation MRI sales have risen dramatically-from 90 machines sold in 1984 to about 200 in 1985 – and manufacturers predict that in five years 1,500 will have been sold for a total of $3 billion.

Still, the average cost of an MRI unit – at least twice that of a CAT scanner-is more than most hospitals can bear. The race is on to increase the number of practical uses of magnetic resonance imaging, and the health science center is at the forefront of that research.

Last fall, the university’s Biomedical Magnetic Resonance Center received a five-year, $2.7 million grant from the National Institutes of Health to become a regional biotechnology resource, to which investigators from Texas and surrounding states will have access. The grant will enable the center to purchase a truly state-of-the-art MRI unit that will operate at a magnetic field more than double that of other whole-body MRI machines. The center will be one of only nine such federally funded facilities for MRI research in the United States.

Scientists at the health science center are among a handful of researchers worldwide who are improving magnetic resonance imaging while also developing a new class of technology called “MR spectroscopy.” This technology involves the use of even more powerful magnets to measure amounts of chemicals within a given tissue. Scientists can monitor intricate metabolic, or chemical changes within cells by knowing what constitutes normal amounts of these chemicals.

Whereas magnetic resonance imaging produces CAT scan-like pictures, in MR spectroscopy results appear as graphs composed of peaks and valleys. The MRI machine’s radio pulse is changed to a different frequency to detect specific chemical elements, which appear as spikes or dips in a graph according to their quantities in a particular tissue. These graphs can be visualized on a television screen or printed out on paper.

MR spectroscopy is now being used experimentally at the health science center to determine how drugs are metabolized in unhealthy tissue and how diseases can be detected early for preventive treatment. For example, researchers are investigating ways of using spectroscopy to assess the amount of injury to the heart after a heart attack.

Indeed, it was to further cardiac research that Drs. James Willerson, director of the Ischemic Heart Center, and Robert Parkey, chairman of the Department of Radiology, decided to purchase the health science center’s first research magnet in 1978.

Willerson-together with Parkey and Drs. Ron Peshock and Craig Malloy in the Department of Internal Medicine-continues to pursue an extensive program of heart research using MR spectroscopy as well as imaging techniques. He is particularly hopeful about the prophylactic potential of MR spectroscopy.

“MRI may allow us to identify patients at risk of having heart attacks so that we can subsequently prevent heart attacks from happening in the future,” says Willerson. “This may be done by non-invasive evaluation of changes in coronary blood flow and metabolism and serve as a warning of blood vessel narrowing.”

Development of magnetic resonance imaging and spectroscopy is proceeding at such an impressive rate at the health science center that San Francisco-based Diasonics, Inc., a leading manufacturer of MRI hardware and software, has entered into a five-year, $1 million contract with the institution to develop marketable technology.

Through cooperative agreements with Diasonìcs, researchers at the university’s Biomedical Magnetic Resonance Center already have developed the first MRI surface coil to be approved by the U.S. Food and Drug Administration. The surface coil, an enhancing device, is the primary technique for imaging the lumbar and thoracic spine. As a result of the FDA approval, Medicare is expected to begin reimbursing costs for MRI using the spinal surface coil sometime this year.

Under the five-year Diasonics contract, health science center researchers are working on a combination of MR spectroscopy and imaging that can be applied to clinical use. The idea is that imaging and spectroscopy can compliment each other: MR imaging can be used to define a particular tissue area while spectroscopy provides detailed chemical information.

Dr. Ray Nunnally, the MRI centers research director and leader of the team working with Diasonics, says the project involves streamlining an imag-ing/spectroscopic process to provide the two forms of information faster and better. Only a few research centers are currently able to acquire MR imaging and spectroscopic information simultaneously, says Nunnally, and the process has never been refined for fast data retrieval and high-quality spatial resolution.

The radiology department has benefited from several relationships with industry through the years, says Parkey. “Cooperative agreements with industry have enabled us to purchase expensive state-of-the-art equipment for research and clinical use at reasonable prices,” he says.

The Diasonics agreement centers around a new MR imaging and spec-troscopy hardware system with a high-strength magnet made in Oxford, England. It is the centers second large magnet. In 1983, the first unit large enough for human body imaging (several smaller units are used for animal research) was purchased from Diasonics with private funds.

This original unit is now being used to capacity for both clinical diagnosis and research. While it is technically an “off the shelf” model, the technology for its use is still evolving. Special techniques developed here for enhancing images and for extracting more information from images are continuing to improve results.

The new magnet to be purchased with the NIH grant will be the health science centers most powerful to date. The new MRI unit, expected to be delivered by late 1986 or early 1987, will be a very powerful tool for research but is too small for most clinical applications.

The university’s diagnostic imaging team is composed of five staff physicians and four postdoctoral fellows along with a support staff of biochemists, physicists, engineers and technicians.

Dr. Jeffrey Weinreb, director of MR body imaging, cites several projects in his area now receiving national attention. Among the most exciting are those using MRI in pregnant women for diagnosis of growth retardation, lung immaturity and congenital abnormalities in the fetus. Because it doesn’t involve radiation exposure or injections, MRI also holds great promise as a routine method of safely imaging children with chronic illnesses, such as cancer, who must be monitored over an extended period. Indeed, Weinreb says that no hazards of MRI use have yet been demonstrated “at any level of exposure.”

So far. MRI’s primary function has been as a problem solver, Weinreb says, and the more the physician knows about what he or she is looking for-a tumor or other abnormality, for instance-the easier it is to find it by setting up the machine properly.

MR imaging of the brain has many advantages over other techniques says Maravilla, director of neurologic MRI. Head injuries and neurologic disorders involving anatomical abnormalities can be seen with greater clarity than with CAT scans, making diagnosis more accurate and at times eliminating the need for surgery.

Today, however, CAT scanning equipment leads in affordability and availability. Patients suspected of having a brain disorder routinely get a CAT scan first and then MRI if the diagnosis remains unclear, says Maravilla.

As MRI research at the health science center gains momentum, funding agreements fortunately are keeping pace with the progress of scientific investigation. In addition to the Diasonics agreement and the NIH grant, The Uni-versity of Texas System has tentatively approved a grant to the magnetic res-onance center for the construction of a special building to house the MRI research team and equipment, which currently are scattered among several locations. Additional research support also will be provided to the MRI center. “The new funds, together with pre-vious generous community contribu-tions and an existing NIH research grant, will place the health science center at the forefront of MRI research technology,” says Parkey. “We look for-ward to a future of exciting develop-ments, with our researchers remaining on the leading edge of change.”

Newsletter

Keep me up to date on the latest happenings and all that D Magazine has to offer.

Comments