As it happened, after leaving Argonne, David had some six months to fill before he could begin work on his project at the University of Illinois in Chicago. So, in the interim, Albert Crewe, director of Argonne National Laboratory and a distinguished faculty member at the University of Chicago, took him on as a special assistant. “He was working on his own project,” David recalls, “and he said, ‘Use your ideas to help me with my project while you wait.” The project in question? Development of the scanning electron microscope.
This work was important to David’s development as a researcher—in more ways than one. Crewe had gathered around him a group of wildly talented scientists and David enjoyed getting to know “these marvelous, marvelous people.” Among them was another member of “Crewe’s crew”: Venezuelan researcher Humberto Fernández-Morán, who in 1955 had invented the diamond knife, which was used to show microscopic photos of the brain.
Fernández-Morán also lived in the Cloisters, so he and David got to know each other socially as well as professionally. “I was a new guy in a new field of research and here was this world-famous scientist. He asked me to walk with him every Sunday afternoon and we talked science as we walked up and down the streets on the south side of Chicago. He gave me his views of science and how he did science. I learned so much from him as to how to succeed.
“He convinced me to push ahead as I wished and not to listen to the people saying, ‘Oh, David, you’re crazy for wanting to measure very weak magnetic signals. It can’t be done.’ Humberto taught me to listen to my own voice.”
Finally, the time came to begin work on his shielded room, so he could start measuring the very weak magnetic signals emanating from the human body. Flush with the money allotted to him by Winsberg, he hired a group of students and university carpenters to build the room itself. He had already worked out the mechanics, he says. With no precedents in medical imaging, he had looked outside the discipline and learned of work in the field of geology. In 1962, researchers Bob J. Patton and John L. Fitch had reported a significant innovation, a magnetically shielded room they had designed and built mainly for geophysical (oil) research. This proved an excellent starting point for David, who adapted the concepts Patton and Fitch had described for use in the human body.
He also employed a different type of detector than the Syracuse team had. The latter had used two identical coils connected to one another, each with several millions of turns around a ferrite core in opposition to each other. The idea here was that currents induced by any background noise would be identical in the two coils and would cancel each other out. The magnetic field of the heart, in contrast, has a gradient over the chest, and thus would produce a net measurable signal. Still, the resulting recordings were very noisy, even after signal-averaging.
David took a different approach. In addition to reducing background noise using his now-completed magnetically shielded room, he employed a smaller coil than the Syracuse team had, and a better amplifier. Thus, he was able to record the magnetic signal produced by the heart with far less noise. The noise was still too large to allow recording of clear heart traces, but the results were encouraging enough that they warranted sharing.
In early 1967, two years after joining the university faculty, he published a paper in the journal Science detailing his first measurements of the magnetic signals produced by the heart: “Magnetic Fields around the Torso: Production by Electrical Activity of the Human Heart.” In this study, per the paper’s abstract, “A search was made outside the torso for fluctuating magnetic fields produced by the heart. Detector and subject were housed in a highly shielded enclosure. Magnetic signals with amplitudes of 10-8 to 10-7 gauss were detected synchronously with the electrocardiogram, confirming previous reports.”
It was an important study, and big news. Letters and phone calls started pouring in, and a number of news outlets picked it up. Not least was the New York Times, which described the work and highlighted its promise for diagnosing disease. It was still too early to assess its “long-range potential,” David told the Times writer. “But it now looks, while it has not been proved, that the detection of currents by their magnetic fields does give new information about the heart’s electrical activity above and beyond what one might get from the more routine forms of electrocardiography.”
(“Actually,” he clarifies today, “it gives different information, eliminating the radial component of the heart’s signal and emphasizing the tangential signal.”)
The writer spoke with a variety of others for the article, including Dick McFee, one of the Syracuse University researchers, as described earlier. In the article, McFee made an interesting observation about the technique: that it might in fact be most useful in detecting the electrical activity of the brain.
“Bone in the skull is a good insulator of electricity, making it difficult to detect the small electrical currents within the head,” he said. “But bone has no effect on the magnetic field produced by currents and this device ultimately might be of use in tracing brain waves.”
Indeed, by now David was also growing more interested in measuring the magnetic fields produced by electrical activity in the human brain. This would present a bit of a challenge. He knew the magnetic field of the brain should be about 100 times smaller than that of the heart, “so it would be a tough thing to measure,” he says. “I spent much of the next year figuring out how to do it.”
Here again, he found help navigating the new (to him) area of inquiry. John Hughes was a well-known neurologist in Chicago and a professor at Northwestern Medical School. David doesn’t recall how he and Hughes first connected but notes that in Chicago at the time there was a robust community of physicians and researchers engaged in the science of bioelectricity. Thus, word of David and his work, of “this guy doing this crazy thing of measuring enormously weak magnetic fields,” could easily have gotten to the neurologist.
In any event, Hughes took an interest and offered his assistance in teaching David how the brain works from a bioelectrical perspective. “He and I sat night after night talking and planning,” David says. “And it worked. In 1968, I was able to measure the magnetic field of the brain. That was a really thrilling time, sitting night after night and watching the signal slowly emerge out of random magnetic noise.” As with the earlier heart measurements, the signal was noisy and wasn’t yet high enough for practical use, but as a proof of principle the study was an unambiguous success.
He published his findings, again in Science, in the paper “Magnetoencephalography: evidence of magnetic fields produced by alpha rhythm currents.” And again, the New York Times published an article about the work.
David was thrilled with the progress he was making. His idea of measuring the very weak magnetic signals produced by the human body was proving successful. But he knew he was working on borrowed time. With a series of political upheavals in the physics department, the promise of tenure he had received when he joined the university had been withdrawn.
It started when Winsberg, the new chair who had filled out the department with his own hires, David included, essentially demoted several of the old guard in the physics faculty. “He lowered their salaries,” David says, “because he thought they weren’t good.” Winsberg may not have realized that, by the rules of the university, faculty could vote a chair out of office. When he ruffled their feathers, they did just that.
It turned out that the dean who had endorsed Winsberg’s offer to David had also left. “Suddenly I was without support,” David says. The old guard who remained weren’t sold on the idea of measuring very weak magnetic signals in the body. “They thought I should be doing classical physics in a traditional physics department, that I shouldn’t be fooling around with this new stuff.” When the time came to vote on his tenure, tenure was denied. Even amidst two big successes in measuring the magnetic signals produced by the human body, David found himself without a secure job.
