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Allan Cormack

Picture of Allan Cormack

Date of Birth: 02/23/1924

Age: 91

Birthplace: Johannesburg

Citizenship: United States

Background

After high school, K. decided that "astronomy is not very promising from the 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 a bachelor`s degree of this discipline, and the next year - a master.

In the future, K. worked as an intern researcher at the Cavendish Laboratory at Cambridge University (UK), exploring the properties of the radioactive helium-led Otto Frisch and attending lectures PAM Dirac on quantum mechanics. Write a letter to the head of the Department of Physics, University of Cape Town, K. was invited to the position of teacher of physics. In 1956 he also began working part-time in the field of medical physics at the hospital Groote Schuur.

In Cape Town there was a perfect scientific equipment, both in Cambridge and, in addition, K. felt somewhat isolated from the rest of the scientists - specialists in nuclear physics. However, according to him, the head of the department of physics RU James gave him enough freedom for research and given the opportunity to publish more scientific papers. In the radiology department at the hospital Groote Schuur K. watched the use of radioisotopes and performed such works as, for example, calibration, special plates, which can be judged on the radiation dose received by the hospital staff. This observation of radiotherapy patients with malignant tumors have led him to the work for which he received the Nobel Prize.

K. realized that in order to calculate the dose of radiation to treat tumors, it is necessary to have accurate information on the absorption of X-rays by body tissues. In thinking about how it would be possible to measure the absorption of these characteristics, he concluded that they could also have diagnostic value, for example for more accurate tumor localization. Conventional X-ray images poorly served these purposes.

X-ray equipment was born in the end of XIX century. When Wilhelm Roentgen discovered the rays that he called X-rays, and with them won the first X-ray image of the hand of his wife`s hand. In these methods through a hand or other body part on the sensitive film takes a fairly wide beam of X-rays. The energy of these beams incident on the film is not uniform due to the fact that different tissues, through which the rays differently absorb them. These dense tissue like bone, have a very high absorption, and therefore beam passing through them strongly attenuated, soft tissue and absorb less fluid rays air - even less.

Radiographs represent only a general absorption of the rays on the path of each beam. At the same time it is not possible to determine which part in the overall absorption took tissue through which the beam is passed sequentially. This causes problems, for example, radiography of the head, ie. K. Skull absorb rays and hide very soft tissue image of the brain. K. came to the idea of ??the head that do if multiple x-ray measurements in which the beam will pass through the object from different angles, when this information is received separate internal ray absorbing portions.

Although it seemed quite reasonable to assume that with the help of numerous X-ray measurements can get the necessary information, there was still a purely mathematical problem: how to interpret the entire volume of the data to reconstruct the internal structure of the parts? This problem is somewhat easier provision that x-rays pass through the object is always in the same plane as would thus realizing a thin slice of tissue, thereby forming a two-dimensional cross section. By repeating such measurements in the series of closed parallel planes, it is possible to implement a three-dimensional object reconstruction.

This X-ray image, consisting of individual thin slices, called now tomogram (from the Greek. Tomos, which means "slice"), and the whole procedure is called computed tomography. K. developed mathematical methods for the analysis of data obtained by X-ray measurements, and continued to develop these methods for several years.

In 1956, Karl took a year off for research at the Harvard Cyclotron Laboratory in Cambridge (Massachusetts). (Cyclotron - a device that gives high speed atomic particles; at the same time 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 came close friendship with the director of the laboratory of Andreas Keller. In 1957, K. briefly traveled to Cape Town and then returned to the United States and was appointed assistant professor of physics at Tufts University in Medford (Massachusetts).

In Cape Town and Medford K. he continued experiments to verify his mathematical method. The first experiments used gamma ray of cobalt-60, which were characteristic for the same pattern as that for X-rays. K. rays collected into a thin linear beam and passed through a plaster cast of a human body; as a detector used a Geiger counter, rear dummy. In Cape Town, the dummy was a system of concentric aluminum cylinders enclosed in a wooden shell; thus, it was composed of two materials with different absorption properties. The radiation source and the detector are fixed, whereas the wood-aluminum cylinder located on a movable platform and able to move, taking different positions in relation to the scanning beams. This method not only gave the expected results, but beyond all expectations revealed in the aluminum structures of land with different density. Later, in Medford, K. repeated the experiment with more sophisticated hoax: it consisted of an aluminum shell ( "skull"), which is located inside the plastic, to simulate soft tissue ( "brain"), and two aluminum disk, the corresponding tumors. The experiments were successful again. In 1963 and 1964. K. published two articles on mathematical methods and results of the experiments, trying to arouse the interest of specialists in radiation physics. Articles, however, have not received a significant response. Whatever it was, K. proved the effectiveness of his method, received on the basis of differences in the absorption of X-ray images of cross-sections of the body with the internal structure of the parts. It was still only demonstration laboratory with mechanical dummies, but to speed up mathematical calculations have been used computers. The results of these calculations are not quoted in the form of similar images with photographs and in graph form. Meanwhile, K. continued studies in particle physics at Tufts University. In 1966 he became an American citizen. Having received the first title of associate professor, then full professor of physics at Tufts University, he went on to become head of the department of physics and led this department from 1968 to 1976

In the late 60`s - early 70-ies. Research Fellow of the English Association "Elektrikal End myuzikal instrument Limited