Cormack (Cormack), Allan

genus. February 23, 1924 g.Amerikansky physicist Allan MacLeod Cormack was born in Johannesburg (South Africa), the son of an engineer and teacher, George Cormack Amelia Cormack (McLeod). Allan was the youngest of three children. His parents emigrated from Scotland to South Africa before the First World War. When Allan was 12 years old, his father died and the family moved to Cape Town. Here K. enrolled in secondary school for boys. During his studies he was especially interested in astronomy, physics and mathematics. He also liked to play tennis, participate in discussions and perform on stage amateur theater.
After high school, K. decided that "astronomy is not very promising from a material point of view ', and entered the University of Cape Town to study electrical engineering. Two years later, he realized that he was more interested in physics, and in 1944. received the discipline bachelor's degree, and next year - the Masters.
Later K. worked as an intern researcher at the Cavendish Laboratory at Cambridge University (UK), investigating the properties of the radioactive helium under the leadership of Otto Frisch and attending lectures P.A.M. Dirac on quantum mechanics. Written the letter head of the Department of Physics, University of Cape Town, K. received an invitation to the post of professor of physics. In 1956, Mr.. He also began working part-time in the field of medical physics at the hospital Grote-Shur.
In Cape Town was not the same sophisticated scientific equipment, both in Cambridge, and, in addition, K. felt a certain isolation from the rest of scientists - experts in nuclear physics. However, according to him, the head of the department of physics R.U. James gave him enough freedom to research and provided an opportunity to publish several scientific papers. In the department of radiology at the hospital Grote Shur-K. watching the use of radioisotopes and perform such work, such as the calibration of the special plates on which one could judge the dose of radiation received by hospital personnel. This observation of the radiation treatment of patients with malignant tumors led him to the work for which he received the Nobel Prize.
To. realized that in order to calculate the dose of radiation to treat tumors, it is necessary to have accurate information about the absorption of X-rays by different tissues of the body. Thinking about how one could measure such absorption characteristics, he came to the conclusion that they could have a diagnostic value, for example, for a more precise localization of tumors. Conventional X-ray images poorly served those purposes.
. X-ray technique originated in the late XIX century. When Wilhelm Roentgen discovered the rays which he called X-radiation, and with their help, obtained the first X-ray image of the hand of his wife
. With such techniques through the hand or other body part on the sensitive film is a fairly broad beam of X-rays. The energy of these rays that fall on the film varies due to the fact that different tissues, through which the rays differently absorb their. Such dense tissue, like bone, have a very high absorption, and therefore passes through the beam are greatly weakened, soft tissue and fluids absorb less radiation, air - even less.
. X-rays show only the total absorption of radiation on the path of each beam
. In this case it is impossible to determine what part of this overall absorption took tissue through which this beam passes successively. This causes difficulties, such as x-ray head, t. to. absorb the rays of the skull bones are very strong and hide the image of soft tissues of the brain. K. had the idea that if you make several X-ray measurements, in which the beam passes through an object from different angles, then when it will provide information on the absorption of radiation by individual internal regions.
. Although it seemed reasonable to assume, . that with the help of numerous X-ray measurements can provide the necessary information, . there was still a purely mathematical problem: how to interpret the entire volume of the data to recreate the details of internal stroeniyaN This problem is somewhat easier position, . whereby X-rays always pass through the object in the same plane, . how to exercise with a thin tissue sections, . thus generating a two-dimensional cross-section,
. Repeating such measurements in a series of closed parallel planes can carry a three-dimensional reconstruction of the object.
Such X-ray image, which consists of individual thin sections, is currently tomograms (from the Greek. tomos, which means 'cut'), a technique generally called computed tomography. K. developed mathematical methods to analyze data obtained by X-ray measurements, and continued to develop these methods for several years.
In 1956, Mr.. K. took a year off for research at the Cyclotron Laboratory at Harvard University in Cambridge (Massachusetts). (Cyclotron - a device which gives the high-speed atomic particles, while they are faced with any 'targets', such as other particles, which makes it possible to obtain valuable information about the structure and interactions of atoms.) Here K. studied the interaction between protons and neutrons. Here, he had a close friendship with the director of the laboratory, Andreas Kohler. In 1957. K. long trip to Cape Town, and then returned to the United States and was appointed assistant professor of physics at Tufts University in Medford (Mass.).
In Cape Town, and Medford to. continued experiments to test his mathematical method. In the first experiments used gamma radiation of cobalt-60, for which were characterized by the same pattern as for X-rays. K. collecting rays in a thin line bundle and passed through a fake human body as a detector used a Geiger counter, located behind mock. In Cape Town, this dummy is a system of concentric aluminum cylinders, enclosed in a wooden shell, so it consisted of two materials with different absorbing properties. Radiation source and detector are fixed, while the aluminum-wooden cylinder was placed on the mobile platform and could move around, taking different positions relative to the scanning beams. This method not only gave the expected results, but beyond all expectations revealed in aluminum structures with different density plot. Later, in Medford, K. repeated the experiments with more complex hoax: it consisted of an aluminum shell ( 'skull'), inside of which was plastic, simulated soft tissue ( 'brain'), and two aluminum disk, the corresponding tumors. Experiments were successful again. In 1963 and 1964. K. published two articles on mathematical methods and results of experiments in an effort to arouse the interest of specialists in radiation physics. Articles, however, have not received significant response. In any case, K. proved the effectiveness of its method, based on differences in the absorption of X-ray images of cross sections of the body with the details of the internal structure. It was still only a lab demonstration with mechanical dummies, but to speed mathematical calculations have been used computers. The results of these calculations are set not in the form similar to the photographs of images, and in the form of graphs. Meanwhile K. continued research in particle physics at Tufts University. In 1966, Mr.. He became an American citizen. When you become first an associate professor and then full professor of physics at Tufts University, he later became head of the department of physics and head of the department from 1968 to 1976
In the late 60's - early 70-ies. Fellow of the British associations 'Electrical End myuzikal Tool Limited' (EMI) by Godfrey Hounsfield developed a similar but more practical method of CT scan. Important role in this was played by the emergence of modern computers. In 1971, Mr.. Wimbledon at Atkinson Morley's Hospital (UK) was installed first clinical CT scanner and began the study of patients with tumors and other diseases of the brain. In April 1972, Mr.. EMI has announced the production of the first commercial computer tomograph - EMICT-1000. Clinical trials of the imager immediately showed that computed tomography - a big step forward compared with other methods of obtaining X-ray images of human tissue.
. Serial CT scanner consists of four main units: the X-ray generator, a scanning element (X-ray tube and detector); computer, . expecting the degree of attenuation of X-rays due to its absorption of tissues; oscilloscope with printer, . designed to display pictures obtained by X-ray absorption,
. The patient in the study of stationary, . a radiation source and scanning element revolve around his head, . while making hundreds of measurements of the absorption of rays of brain tissue, . on the basis of which further constructed two-dimensional image of a cross section,
. For three-dimensional image the patient gradually shifts along the axis of rotation, . that leads to successive section, . from which then reconstructed three-dimensional image (in some models a large number of fixed detectors in a circle and performed a rotation of the radiation sources).,
. According Hounsfield, CT scanner is 100 times more efficient than conventional X-ray machine, tk
. processes all the information it receives, and the usual X-ray machine - only about 1%. CT scanner sensitive, and requires less energy per shot than the regular X-ray machine, although the total dose is approximately the same due to the fact that the imager must be a lot of pictures. However, the main advantage of tomography is that it can be used to clearly distinguish soft tissue from the tissue surrounding them, even if the difference in the absorption of radiation is very small. Therefore, the device to distinguish healthy tissue from infected. Initially computer tomography were used to scan the brain, and they are currently used to study virtually all parts of the body.
In 1979. K. with Hounsfield was awarded the Nobel Prize in Physiology or Medicine 'for the development Computed Tomography'. In his Nobel lecture to. spoke about the motives, . which prompted him to do this work: 'I had an idea about, . that for, . to more accurately chart the treatment plan, . need to know the distribution of the absorption coefficient in various tissues of the body, . and this distribution must be measured with the help of external devices,
. I soon realized that such information would be useful for diagnosis and, in fact, confined to a tomography, or a sequence of tomograms, although I did not know that particular word for many years. "
In 1980. K. was awarded the title of University Professor Tufts University - the highest professorial rank at this institution. In the same year he received an honorary doctorate.
In 1950, Mr.. K. Barbara married a CV. In the family they have one son and two daughters. K. preferred 'home' life and he loves swimming and boating, devotes a lot of time reading. While still in college, K. become an avid mountain climber and a great lover of music. K. - Assistant editor of the Journal of Computed Tomography '(' Journal of Computed Tomography '), he is a member of the South African Institute of Physical, American Physical Society and American Academy of Arts and Sciences.