Milestones:The First Two-Dimensional Nuclear Magnetic Resonance Image (MRI), 1973

Title

The First Two-Dimensional Nuclear Magnetic Resonance Image (MRI), 1973

Citation

Researchers at Stony Brook University produced the first two-dimensional image using nuclear magnetic resonance in 1973.The proton distribution of the object, a test tube of water, was distinctly encoded using magnetic field gradients. This achievement was a major advance for MRI and paved the way for its worldwide usage as a noninvasive method to examine body tissue for disease detection.

Street address(es) and GPS coordinates of the Milestone Plaque Sites

Medical Research and Translation (MART )building Lauterbur Drive Stony Brook ,NY 11790-3400

Latitude N40.908141 , Longitude W73.117410, 40.9126624, -73.1298849

Details of the physical location of the plaque

It will be on the ground floor and mounted on a wall in a prominent place in the MART building.

How the plaque site is protected/secured

The wall mounting will be secure.. The place where it will be mounted is available to the general public. No appointment will be needed to visit it and there are no security issues.

Historical significance of the work

September 2, 1971. Paul Lauterbur’s original idea for obtaining two-dimensional and three- dimensional images showing the distribution of magnetic nuclei relaxation times and diffusion coefficients were recorded in his notebook. A copy of this entry is found in Appendix A. His subsequent experiments resulted in producing the first two- dimensional magnetic resonance image (MRI) and the results were published in the March 16, 1973 issue of Nature. Appendix B is a copy of that article.

Prior to his effort, when NMR measurements were made on substances, there was no way to identify where the resonances occurred because a fixed magnetic field was applied. He realized that if a linear gradient was added to the fixed magnetic field it would be possible to spatially encode the substance in one dimension. By rotating this linearly varying magnetic field, he could get responses in other single dimensions.By doing so with three 45 degree rotations ,he was able to fill a two dimensional space.

This groundbreaking achievement drew on several prior technologies.

Availability of nuclear magnetic resonance (NMR) spectroscopy equipment to measure the properties of chemical substances.
Tomography algorithms previously developed for X-Ray CT scanning.

We will briefly review the prior knowledge that Lauterbur needed to accomplish his goal.

A. Nuclear Magnetic Resonance (NMR)

NMR is a physical phenomenon in which nuclei absorb and re-emit elecromagnetic radiation, typically in the 60-1000 MHz region. This occurs at a specific frequency which is proportional to the applied magnetic field. It can be used to study he properties of a wide range of chemical substances. However, in the case of MRI for medical application, one is usually concerned hydrogen protons contained in water molecules. NMR was first observed by Isadore Rabi in 1938 in gases. Felix Bloch and Edward Purcell demonstrated its use in liquids and solids. They all received Nobel Prizes for their work. The resonant behavior can be observed by applying electromagnetic radiation at the same frequency of the precession of the protons.

B- NMR Equipment

Lauterbur’s two-dimensional images were produced by using a Varian A60 NMR spectrometer with coils added to produce magnetic field gradients. Photos of the A60 and Lauterbur doing his early research on that equipment are found in Appendix C and an upload file-PLauterbur. The slope of the gradient corresponded to 700Hz per cm. The sample to be imaged received electromagnetic (RF) radiation at a nominal frequency of 60MHz. This frequency was varied to get a linear projection. Lauterbur imaged a water tube such that resonant interaction occurred only with the waters hydrogen protons. He then rotated the gradient field at three additional 45degree intervals to obtain sufficient data to construct a satisfactory two-dimensional image. His final step was to construct an image from these data. He realized that the problem had been solved for X-Ray CT scans and suitable algorithms were available. Lauterbur used one described by Gordon and Herman which is found in Appendix D. While he did not do so in his early work, he realized that previously developed Fourier transformed NMR and FFT algorithms could speed up image formation.

While the current MRI equipment is vastly more complex, Lauterbur’s achievement had much to do with spurring these developments.

C- Scanning and Transient NMR

While Lauterbur’s original work was done by scanning the RF signal, he noted that transient (Fourier transform) methods could be used as well, as described below.

Since the introduction of a magnetic field gradient will enable the resonance of a substance to be a function of distance; in Lauterbur’s case, he was imaging two 1mm inside diameter glass tubes filled with water. Thus, if we vary the frequency of the applied electromagnetic (RF) energy, we could get a one-dimensional projection of the water. Lauterbur rotated the magnetic field at 3 additional 45 degree intervals. These four linear projections filled up the two-dimensional space. Lauterbur was able to construct a two-dimensional image with the aid of an algorithm developed by Gordon and Herman. (see Appendix D). The algorithm had been developed to obtain two-dimensional images from X-Ray CT scans.

The transient method would involve pulse modulation of the RF signal. The pulse width would have to short enough to produce a frequency spectrum that would encompass the maximum shift in resonant frequency due to the gradient magnetic field change. If such a pulse were applied to the substance to be imaged and a Fourier transform of the response is performed, it would generate the desired linear projection. Using Fourier transform NMR clearly speeds up the process of determining the image.

At the time of Lauterbur’s 1973 Nature article, he used frequency scanning. Fourier Transform NMR was a known technique when he produced the first image and he did indeed use it in his later work.

D- Summary

While many improvements in speed and image quality have been made since this early work, Lauterbur’s demonstration of two- dimensional imaging was a major spur to make MRI the valuable development to the medical field that it is today. Researchers are continuing to find new applications for diagnostic imaging and more exciting discoveries undoubtedly lie ahead.

Media:Appendix A- Lauterbug Notes.pdf

Media:Appendix B - Lauterbur's First MRI Publication.pdf

Media:Appendix C - Varian A-60.pdf

Appendix C - second page

Media:Appendix D - p759-gordon.pdf

Media:Appendix E - NY Times Article - Nobel Prize.pdf

Features that set this work apart from similar achievements

Prior to this work, only one dimensional NMR images had been realized by point by point techniques many years earlier. Once Dr Lauterbur showed that 2D images could be obtained ,faster and higher resolution images became a reality,mostly due to Mansfield at the University of Nottingham .Lauterbur and Mansfield shared the Nobel Prize for Physiology or Medicine in 2003 for their MRI research..Lauterbur's first images were a key achievement that contributed to making MRI what it is today.

Significant references

Appendices A -E and a file-PLauterbur which have been uploaded and are referred to in the Historical Significance portion of this proposal..

Supporting materials

Appendices A-E can be made publically available on the IEEE History Center's website.

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