The invention: Procedure that uses hydrogen atoms in the human body, strong electromagnets, radio waves, and detection equipment to produce images of sections of the brain.
The people behind the invention:
Raymond Damadian (1936- ), an American physicist and inventor
Paul C. Lauterbur (1929- ), an American chemist Peter Mansfield (1933- ), a scientist at the University of Nottingham, England
Peering into the Brain
Doctors have always wanted the ability to look into the skull and see the human brain without harming the patient who is being examined. Over the years, various attempts were made to achieve this ability. At one time, the use of X rays, which were first used by Wil-helm Conrad Rontgen in 1895, seemed to be an option, but it was found that X rays are absorbed by bone, so the skull made it impossible to use X-ray technology to view the brain. The relatively recent use of computed tomography (CT) scanning, a computer-assisted imaging technology, made it possible to view sections of the head and other areas of the body, but the technique requires that the part of the body being “imaged,” or viewed, be subjected to a small amount of radiation, thereby putting the patient at risk. Positron emission tomography (PET) could also be used, but it requires that small amounts of radiation be injected into the patient, which also puts the patient at risk. Since the early 1940′s, however, a new technology had been developing.
This technology, which appears to pose no risk to patients, is called “nuclear magnetic resonance spectroscopy.” It was first used to study the molecular structures of pure samples of chemicals. This method developed until it could be used to follow one chemical as it changed into another, and then another, in a living cell. By 1971, Raymond Damadian had proposed that body images that were more vivid and more useful than X rays could be produced by means of nuclear magnetic resonance spectroscopy. In 1978, he founded his own company, FONAR, which manufactured the scanners that are necessary for the technique.
Magnetic Resonance Images
The first nuclear magnetic resonance images (MRIs) were published by Paul Lauterbur in 1973. Although there seemed to be no possibility that MRI could be harmful to patients, everyone involved in MRI research was very cautious. In 1976, Peter Mansfield, at the University of Nottingham, England, obtained an MRI of his partner’s finger. The next year, Paul Bottomley, a member of Waldo Hinshaw’s research group at the same university, put his left wrist into an experimental machine that the group had developed. A vivid cross section that showed layers of skin, muscle, bone, muscle, and skin, in that order, appeared on the machine’s monitor. Studies with animals showed no apparent memory or other brain problems. In 1978, Electrical and Musical Industries (EMI), a British corporate pioneer in electronics that merged with Thorn in 1980, obtained the first MRI of the human head. It took six minutes.
An MRI of the brain, or any other part of the body, is made possible by the water content of the body. The gray matter of the brain contains more water than the white matter does. The blood vessels and the blood itself also have water contents that are different from those of other parts of the brain. Therefore, the different structures and areas of the brain can be seen clearly in an MRI. Bone contains very little water, so it does not appear on the monitor. This is why the skull and the backbone cause no interference when the brain or the spinal cord is viewed.
Every water molecule contains two hydrogen atoms and one oxygen atom. A strong electromagnetic field causes the hydrogen molecules to line up like marchers in a parade. Radio waves can be used to change the position of these parallel hydrogen molecules. When the radio waves are discontinued, a small radio signal is produced as the molecules return to their marching position. This distinct radio signal is the basis for the production of the image on a computer screen.
Hydrogen was selected for use in MRI work because it is very abundant in the human body, it is part of the water molecule, and it has the proper magnetic qualities. The nucleus of the hydrogen atom consists of a single proton, a particle with a positive charge. The signal from the hydrogen’s proton is comparatively strong.
There are several methods by which the radio signal from the hydrogen atom can be converted into an image. Each method uses a computer to create first a two-dimensional, then a three-dimensional, image.
Peter Mansfield’s team at the University of Nottingham holds the patent for the slice-selection technique that makes it possible to excite and image selectively a specific cross section of the brain or any other part of the body. This is the key patent in MRI technology. Damadian was granted a patent that described the use of two coils, one to drive and one to pick up signals across selected portions of the human body. EMI, the company that introduced the X-ray scanner for CT images, developed a commercial prototype for the MRI. The British Technology Group, a state-owned company that helps to bring innovations to the marketplace, has sixteen separate MRI-related patents. Ten years after EMI produced the first image of the human brain, patents and royalties were still being sorted out.
Consequences
MRI technology has revolutionized medical diagnosis, especially in regard to the brain and the spinal cord. For example, in multiple sclerosis, the loss of the covering on nerve cells can be detected. Tumors can be identified accurately. The painless and noninvasive use of MRI has almost completely replaced the myelogram, which involves using a needle to inject dye into the spine.
Although there is every indication that the use of MRI is very safe, there are some people who cannot benefit from this valuable tool. Those whose bodies contain metal cannot be placed into the MRI machine. No one instrument can meet everyone’s needs.
The development of MRI stands as an example of the interaction of achievements in various fields of science. Fundamental physics, biochemistry, physiology, electronic image reconstruction, advances in superconducting wires, the development of computers, and ad-
vancements in anatomy all contributed to the development of MRI. Its development is also the result of international efforts. Scientists and laboratories in England and the United States pioneered the technology, but contributions were also made by scientists in France, Switzerland, and Scotland. This kind of interaction and cooperation can only lead to greater understanding of the human brain.
See also Amniocentesis; CAT scanner; Electrocardiogram; Electroencephalogram; Mammography; Ultrasound; X-ray image intensifier.
