The University Record, March 18, 1998

Today's imaging machines have exciting potential

David Kuhl (left), talked with a reporter after he delivered the Russel Lecture last week, the highest honor the University bestows on a senior faculty member. Photo by Bob Kalmbach

By Karen Thomas
Health System Public Relations

Aging baby boomers can breathe a bit easier. The 21st century could bring advances in medical research that will make the process of growing older more pleasant.

David E. Kuhl, widely regarded as the "father" of the PET scanner, focused on the development of reconstruction tomography in his March 10 Henry Russel Lecture. The process, used every day in medical diagnosis, involves taking a three-dimensional object--the human body or part of the body--and duplicating it exactly on a display like a computer screen. To accomplish that, images are taken from all different sides and back-projected through the display device. Computers then correct the data so that the final images, which can be viewed in cross-sectional "slices," precisely match the measurements of the object being viewed.

Kuhl, chief of the Division of Nuclear Medicine in the Department of Internal Medicine and professor of internal medicine and radiology, began his talk with a look at the more mundane activities of well-known painters like Piero della Francesca, Leonardo da Vinci and Rembrandt. As Renaissance men, their interests extended to fortress design which, in turn, led to attempts to sketch cross-sectional views of round buildings. Displaying a della Francesca sketch of a floor tile design and another of a human head, Kuhl noted that "many of the ideas these men introduced dominated the development of art, and also laid the foundations for the imaging machines we use today."

Computers provided the final missing piece in the tomography puzzle. The Eniac, the world's first electronic digital computer, was introduced in 1947, Kuhl noted. The machine was developed, like the sketches of Piero della Francesca 400 years earlier, for defense purposes--in this case, to analyze ballistic projection paths for the U.S. Army. The computer gave scientists much-needed number-crunching power to make accurate representations of the inner workings of the brain.

Admitting that today's imaging machines, while sophisticated and powerful, are "kind of boring," Kuhl showed TV films of early scanners. The 1963 Mark II, the first clinical tomography machine, had only two detectors, which looked like giant cafeteria coffee dispensers turned upside down. The 1975 Mark IV, which had 32 detectors, represented progress, but patients may have thought they were being examined by a whirring windmill with red-painted blades.

Kuhl then focused on the exciting potential of today's imaging machines and ongoing research at the U-M that may ultimately help ameliorate, prevent or cure diseases that afflict the elderly brain. Advanced reconstruction tomography techniques, for example, have allowed researchers to study the glucose metabolic rate in the brain, which in normal aging barely slows down. In patients with Alzheimer's disease, however, the rate typically slows while other forms of dementia show still different patterns of abnormality.

"The pictures are immediately understandable and extremely valuable," Kuhl said, because they show that the dementia disorders are caused by many different diseases, a fact that was not obvious from simply studying symptoms. In addition, in what may have implications for future treatment, researchers discovered that in patients with early Alzheimer's the first part of the brain to suffer from lower glucose metabolism is the posterior portion.

U-M researchers also have developed a new radioactive tracer that targets acetylcholine neurons in the brain (they're associated with memory). The one consistent neurochemical feature of Alzheimer's involves an abnormality of acetylcholine synthesis. Until recently scientists could only examine these neurons during pathology studies of the deceased. Now that the tracer allows researchers to look at this activity in living patients, the results have challenged the postmortem data.

"The postmortem material, may, in fact, have exaggerated, especially in early Alzheimer's disease, the number of neurons that are dead. And that's good news," Kuhl explained. "This could mean that many neurons at that stage are sick, not dead. Researchers can then focus on 'How do we keep them well?' and 'How do we help them heal?'"

The Henry Russel Lectureship has been awarded annually since 1925 and is the highest honor the University gives to a senior faculty member. It is awarded for distinguished achievement in research and teaching.