Magnetic Resonance Imaging

MRI is a relatively new imaging technique, having been in use in hospitals for around 25 years. However, NMR has a much longer pedigree.

The NMR phenomenon was predicted in the early part of the twentieth century on the basis of the quantum theory of the atomic nucleus. Key dates are as follows

1936 – NMR predicted and searched for by the Dutch physicist Cornelius Gorter

The experiment failed only because Gorter’s equipment was insufficiently sensitive.

1937 – NMR observed in molecular beams by Isidor Rabi

Rabi was assisted by Gorter, and received the Nobel Prize for Physics in 1944 for this work.

1946 – NMR observed in liquids and solids by Bloch and Purcell

Bloch and Purcell made this discovery independently at Stanford and Harvard, respectively. They were jointly awarded the Nobel Prize for Physics in 1952 for this work.

 

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NMR is not an imaging technique, but rather a technique for analysing chemical composition and structure. As such it rapidly became standard technique in analytical chemistry, which it remains today.

 In the 1950s, the samples studied using NMR came to include material of biological origin (due particularly to Erik Odeblad).

The development  of an imaging technique from NMR is usually attributed to Damadian, Lauterbur and Mansfield (see below). However, there were two earlier pieces of work that deserve mention.

1952 – In his PhD thesis, Hermann Carr described an NMR method using magnetic field gradients (see below) that prefigures their use in MRI.

Carr later claimed that his work had been overlooked, or even deliberately appropriated, by other researchers. Carr went on to make other important contributions to NMR.

1960 - Vsevolod Kudravcev, working at the National Heart Institute in the USA, used NMR to produce crude images of an egg. An NHI report noted that NMR might yield ‘…coarse pictures… of muscle, arteries and other structures’.

Kudravcev was discouraged from continuing with this ‘unimportant’ work, and his research was forgotten for many years.

 

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1971 – Raymond Damadian discovered difference between NMR signals from normal and cancerous tissues taken from in rats.

Damadian filed a US patent for an NMR machine to ‘scan’ the body in order to diagnose cancer. The patent did not specify precisely how the machine would work, or whether images could be produced.

Nevertheless, Damadian later enforced this patent against medical equipment manufacturers who had started to market MRI scanners. The settled with most companies, but General Electric fought him all the way to the US Supreme Court. Damadian won and was awarded $129 million in damages in 1997. The money was invested in Damadian’s company, Fonar, which still designs and sells innovative MRI systems.

 

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1973 – Paul Lauterbur demonstrated MRI using magnetic field gradients (see below) in a seminar paper in Nature

1974 – Peter Mansfield (University of Nottingham) produced the first human MR images, of a finger.

1977 – Damadian obtained the first MRI body images

1978 – Ian Young (Hammersmith Hospital) produces the first MRI head images

1980 – John Mallard (University of Aberdeen) develops ‘spin-warp imaging’, the imaging method in widespread use today

It will be noted that many of these early developments took place in UK universities and hospitals, although for financial reasons MRI was slow to become established clinically in the UK as compared to the USA and other countries.

 

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Major medical equipment manufacturers realised the potential of MRI in the early 1980s and began major investment. Although some of the early pioneers had established ‘spin out’ companies, with the exception of Damadian’s Fonar Corporation, these were unable to compete and today companies such as Philips, Siemens and General Electric dominate the market.

1988 – There were about 1,300 MRI systems worldwide (including one at Guy’s, installed in 1986)

2002 – There were about 22,000 MRI systems wordwide, performing 60 million examinations a year.

In the UK there are about 500 MRI scanners, performing over 1 million examinations a year. MRI is no longer the preserve of major university hospitals!

 

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2003 – The Nobel Prize for Medicine was awarded to Mansfield and Lauterbur.

Here is part of the Nobel citation:

In the beginning of the 1970s, they made seminal discoveries concerning the development of the technique to visualise different structures. These findings provided the basis for the development of magnetic resonance into a useful imaging method.

In reaction to this, a group representing Damadian took out whole-page advertisements in the The New York Times, The Washington Post, and The Los Angeles Times protesting that he had been excluded from the prize award. This was the culmination of a priority dispute over the invention of MRI that had been going on for some years.
But the citation was written carefully to stress that the prize was being given for development of a useful imaging method.

 

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