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big idea at big boy

Paul C. Lauterbur, Nobel Laureate and University of Pittsburgh Ph.D. passed away on March 27 at the age of 77. Lauterbur was largely responsible for inventing Magnetic Resonance Imaging (MRI), which changed the world of medical diagnostics forever.

Lauterbur's quest for a non-invasive method of tissue analysis came during a set of experiments involving the sacrifice of laboratory animals, a custom to which Lauterbur, trained as a chemist, was disinclined. Lauterbur’s solution to the problem came as an epiphany one evening while eating dinner in the New Kensington Big Boy. Struck with inspiration, he rushed out to a late-night drug store to buy a makeshift scientific notebook, began jotting his thoughts down, had them witnessed the next day and began the arduous process of studying the idea’s feasibility.

In his 2003 Nobel Lecture, Lauterbur explained that his preliminary work involved answering three fundamental questions: First, would the magnetic signal be sufficiently responsive to human tissue? Second, if there was sufficient signal strength, could the data be manipulated mathematically to produce an image and; Third, could a magnet large enough for a human body be made. Working before the age of desktops and laptops, Lauterbur used pencil, paper and hard-copy literature searches to determine that the answer to all three questions was, in principle, yes. Thereafter he dedicated himself fully to the development of magnetic resonance imaging.

Armed with the seldom-asserted knowledge that hydrogen nuclei are particularly susceptible to magnetic influence and the average human body is composed of more than 50 percent water and each molecule of water contains two hydrogen nuclei, Lauterbur’s approach sought to answer two elementary questions about the elemental and spatial characteristics of very small areas inside the human body non-invasively. Those questions were: What is it? And where is it? He addressed both questions by looking at two characteristics of hydrogen nuclei: spin and magnetism.

Put simply, Magnetic Resonance Imaging employs two sets of magnets to align the body’s array of chaotically arranged hydrogen nuclei in specific orientations. The first is the large (powerful enough to lift a car) homogenous magnet, which surrounds the whole body and forces the axes of the body’s hydrogen nuclei to align head to toe with some poles up and some down. Due to hydrogen’s single proton characteristic, most of the protons pair up with oppositely oriented neighbors, thereby negating any magnetic susceptibility or influence. However, there always remains a small fraction of nuclei that, for a number of very complicated reasons, do not find mates. These nuclei are particularly susceptible to manipulation by magnetic forces.

Once the big, homogenous magnet has aligned the body’s hydrogen atoms and all the pairing is done, a second set of much weaker gradient magnets direct magnetic forces toward very specific slices of the body to energize the unpaired nuclei, which causes their spin angles to tilt. When the magnet is turned off, the nuclei relax, shedding the energy they absorbed during the excitation process in the form of wavelength-specific electromagnetism, which corresponds to a spectroscopic signature for each element. When imaged against the uniform field of head-to-toe nuclei, the position of unpaired nuclei can be determined mathematically and converted into a visual image.

In his Nobel Lecture, delivered in Stockholm in 2003, the dry-humored Lauterbur pondered the wisdom of his decision to devote his full energies to the development of magnetic resonance imaging, some 30 years earlier. “In retrospect, you could say it was a foolish decision,” he said with a wry smile. “But since I'm here, obviously it did have some potential.”

This article first appeared in Tom Imerito’s TEQ column, Innovation Chronicles.

© Copyright 2007, Thomas P. Imerito / dba Science Communications

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