Prof.Paul Lauterbur and the invention of MR gradients

In March 1971, Science published Dr. Raymond Damadian's first paper on the topic of NMR , titled "Tumor Detection by Nuclear Magnetic Resonance." In that manuscript, Dr. Damadian described how he had used an NMR machine to study tumors and normal tissue taken from rats. He found that nuclei in the tumors took longer to revert back to their orientation after being nudged by a magnetic field than did the nuclei in healthy tissue. Malignant cancer, he concluded, could be detected by NMR measurements.

That suggestion caught the attention of many people, including Donald P. Hollis, then a researcher at the Johns Hopkins Medical School.. The Hopkins group set out to study various types of rat cancers.

Just before Labor Day in 1971, Leon A. Saryan, a graduate student of Mr. Hollis's, loaded up a box of live rats and flew to Pittsburgh to perform experiments on the machine used by Dr. Damadian. He killed the healthy and diseased rats, took biopsies from each, and measured the "relaxation times" -- the period that it took the nuclei to flip back to their original orientation following a magnetic pulse.

By chance, another scientist was watching Mr. Saryan's experiments that day. Mr. Paul Lauterbur was on a break from his teaching position at the State University of New York at Stony Brook. As he watched Mr. Saryan's efforts, Mr. Lauterbur was struck by the distinct NMR difference between the various normal tissues and the malignant ones.

But Mr. Lauterbur wondered if he could locate the source of an anomalous NMR signal. Was there a way, using NMR, to map out different tissues without cutting into a person?

He knew already that atomic nuclei would wobble at a specific frequency determined by the strength of the magnetic field in an NMR machine. But most experimenters tuned their magnets to create a uniform field, so that all parts of the sample would resonate at the same frequency. That produced the clearest signals.

Mr. Lauterbur recognized, however, that he could get different regions in a sample to wobble at their own individual frequencies by applying a graduated magnetic field instead of a uniform one. As nuclei in the sample produced signals at different frequencies, the value of each frequency would serve as an address, indicating where in the sample each signal had originated. By using gradients in various orientations, he could map out the structure of a sample inside an NMR machine.

That night, on September 2, 1971, Mr. Lauterbur bought a notebook, wrote down his idea, and had it witnessed by a colleague. Then he set out to perform the experiment using magnetic gradients. Nature rejected a first draft of his paper, but he published a second version in March 1973. Only five paragraphs long, the paper suggested using NMR to map the position of malignant tumors inside the body.

The era of imaging through magnetic resonance began to shape up ..