The Good Health Magazine
It’s easy to see why doctors are so taken by Magnetic Resonance Imaging. Apart from providing a way to avoid repeated exposure to X-rays, which carry an accumulating risk (albeit slight) even in small doses, it reveals aspects of the body that can’t be visualized by the most sophisticated CT scanners. It shows the subtle differences between the brain’s white and gray matter. It reveals the smallest lesions in the spine and brain stem. It is fast becoming the method of choice for detecting herniated disks, knee injuries and tiny blood vessel blockages.
MRI is especially useful in neurological examinations. At Huntington Medical Research Institutes, Dr. William G. Bradley reports that nearly a third of patients over 60 who had undergone cranial scans at his unit showed indications of vessel blockages in the brain, yet they displayed no external sign of any problem. Such “mini strokes,” as Bradley calls them, are unlikely to have been picked up by a CT scan. (Don’t say “cat” scan; using that abandoned term will mark you as a medical illiterate.)
MRI can also detect small tumors and other abnormalities of the central nervous system, which until now could only be revealed by biopsy--a surgical probing that doctors and patients understandably prefer to avoid when the suspect tissue happens to lie within the brain or spinal cord. It can also resolve very faint areas of inflammation in the brain, such as those associated with viral encephalitis, a sometimes deadly disease if it isn’t caught soon enough. An especially compelling demonstration of MRI’s diagnostic power is its ability to spot, at a very early stage, the minuscule brain plaques that are the mark of multiple sclerosis, a degenerative disease of the central nervous system . Though MS can’t be cured yet, early detection can lead to a more comfortable management of the disease with the help of drugs to ease some of its symptoms.
In spite of MRI’s advantages, however, CT scans aren’t likely to disappear soon. They remain the preferred diagnostic method for certain skeletal disorders such as arthritis because X-rays are better able to visualize the knots of calcification characteristic of that ailment. They also retain an edge over MRI in diagnosing changes in blood flow caused by arterial blockages or bleeding in the brain. And scans work more rapidly and are much less expensive than MRI. A CT unit can be purchased for a few hundred thousand dollars, a fraction of an MRI unit’s cost. The difference is reflected in the bill for each service. A typical X-ray session runs from $200 to $300, while an MRI workup can range from $600 to $1,500.
Even so, many doctors feel the extra money may be well spent. Apart from sparing the patient exposure to X-rays, MRI often identifies illnesses earlier, thereby avoiding the expense of further tests, and sets the stage for quicker treatment, increasing the chances of success. And for smaller hospitals reluctant to foot the full bill for acquiring an MRI unit, there is a money-saving alternative. They can share with like-minded hospitals a mobile unit, such as GE’s MAX scanner. Resembling an outsized Winnebago, these MRI-systems-on-wheels come self-contained with magnets, computers and dressing rooms. The unit pulls into a hospital’s parking lot, plugs into the power supply, cranks up its magnets and, in short order, starts receiving patients. When the unit is finished with the hospital’s patient load, it moves on. .
One such mobile--shared by five hospitals in Cape Cod, Mass--was recently observed in action at the Falmouth, Mass., community hospital. As patients entered the van, most weren’t aware they’d stepped outside the hospital walls. An airport-type docking gate had been installed at the rear of the building to accept the unit. The patients had been shown a film on MRI or had been told by their doctors what to expect. The technicians simply reminded the patients to remove anything sensitive to magnetic fields, such as credit cards, mechanical watches, even intrauterine devices (IUDs) and false teeth. (Loose metal objects can become dangerously hurtling missiles if they’re caught in the magnet.) Anyone with a pacemaker or other type of ferromagnetic material in his body, such as joint pins and surgical clips, would automatically be excluded. So would pregnant women, unless the doctor deemed the examination essential; even though there is no known risk to the fetus, physicians are cautious in their use of the procedure.
Not all people take to lying quietly in what may seem like medicine’s version of a culvert. The first patient turned out to be severely claustrophobic. Only minutes into the examination, she insisted on leaving the machine. The technicians complied. “We never compel a patient to stay,” explains Dr. James Condon, head of the hospital’s five-man radiology group. About 5% of patients who undergo scanning discover they can’t tolerate the confines for the hour or so it takes to do the imaging.
