NOBEL PRIZE: MEDICINE
Developing a tool with multifarious applications
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Paul Lauterbur discovered the possibility of creating a 2D picture by introducing gradients in the magnetic field. Sir Peter Mansfield further developed the use of gradients in the magnetic field and showed how the signals could be mathematically analysed, which made it possible to develop a useful 3D imaging technique.
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MAGING OF human internal organs with exact and non-invasive methods is important for medical diagnosis. This year's Nobel Laureates in Physiology or Medicine have made seminal discoveries concerning the use of magnetic resonance to visualise different structures. These discoveries have led to the development of modern magnetic resonance imaging, MRI. Magnetic resonance imaging, MRI, is now a routine method within medical diagnostics. It is often superior to other imaging techniques and has improved diagnostics in many diseases.
Discoveries of importance to medicine
This year's Nobel Prizes in Physiology or Medicine are awarded for crucial achievements in the development of applications of medical importance. In the beginning of 1970s, the laureates made seminal discoveries concerning the development of the technique to view different structures. These findings provided the basis for the development of magnetic resonance into a useful imaging method.
Paul Lauterbur (born 1929), Urbana, Illinois, U. S., discovered the possibility to create a 2D picture by introducing gradients in the magnetic field. By analysis of the characteristics of the emitted radio waves, he could determine their origin. This made it possible to build up 2D pictures of structures that could not be visualised with other methods.
Peter Mansfield (born 1933), Nottingham, England, showed how the signals could be mathematically analysed, which made it possible to develop a useful imaging technique. Mansfield also showed how extremely fast imaging could be achievable.
Nuclei of hydrogen atoms
Water constitutes about 2/3 of the human body weight, and this explains why magnetic resonance imaging has become widely applicable to medicine. There are differences in water content among tissues and organs. In many diseases the pathological process results in changes of the water content, and this is reflected in the MR image.
Water is a molecule composed of hydrogen and oxygen atoms. The nuclei of the hydrogen atoms are able to act as microscopic compass needles. When the body is exposed to a strong magnetic field, the nuclei of the hydrogen atoms are directed into order stand ``at attention''. When submitted to pulses of radio waves, the energy content of the nuclei changes. After the pulse, a resonance wave is emitted when the nuclei return to their previous state.
Sir Peter Mansfield
The small differences in the oscillations of the nuclei are detected. By advanced computer processing, it is possible to build up a 3D image that reflects the chemical structure of the tissue, including differences in the water content and in movements of the water molecules. This results in a very detailed image of tissues and organs in the investigated area of the body. In this manner, pathological changes can be documented.
The resonance phenomenon is governed by a simple relation between strength of the magnetic field and frequency of the radio waves. For every type of atomic nucleus with unpaired protons and /or neutrons, there is a mathematical constant by which it is possible to determine the wavelength as a function of strength of the magnetic field.
Examining brain, spinal cord
A great advantage with MRI is that it is harmless according to all present knowledge. The method does not use ionising radiation. However, patients with magnetic metal in the body or a pacemaker cannot be examined with MRI due to the strong magnetic field, and patients with claustrophobia may have difficulties undergoing MRI.
MRI is used to examine all body organs. The technique is valuable for detailed imaging of the brain and spinal cord. Nearly all brain disorders lead to alterations in water content, which are reflected in the MRI picture. A difference in water content of less than a percent is enough to detect a pathological change.
Paul C. Lauterbur
In multiple sclerosis, examination with MRI is superior for diagnosis and follow-up. The symptoms associated with multiple sclerosis are caused by local inflammation in the brain and the spinal cord. With MRI, it is possible to see where in the nervous system the inflammation is localised, how intense it is, and also how it is influenced by treatment.
Another example is prolonged lower back pain, leading to great suffering for the patient. It is important to be able to differentiate between muscle pain and pain caused by pressure on a nerve or spinal cord. MRI examinations have been able to replace previous methods which were unpleasant. With MRI, it is possible to see if a disc herniation is pressing on a nerve and to determine if an operation is necessary.
Important pre-operative tool
Since MRI yields detailed 3D images, it is possible to get distinct information on where a lesion is localised. For instance, in certain microsurgical brain operations, the surgeon can operate with guidance from MRI results. The images are detailed enough to allow placement of electrodes in central brain nuclei to treat severe pain or to treat movement disorders in Parkinson's disease.
Improved diagnostics in cancer
MRI examinations are important in cancer diagnosis and treatment. The images can exactly reveal the limits of a tumour, which contributes to precise surgery and radiation therapy. Before surgery, it is important to know whether the tumour has infiltrated the surrounding tissue. MRI can differentiate between tissues and help in improved surgery. It has improved the possibilities to ascertain the stage of a tumour, and this is important for the choice of treatment.
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