Jacobs, Melville L.; Pape, Leon
Dosimetry for a Total-Body Irradiation Chamber
Dosimetry for a Total-Body Irradiation Chamber 1 Melville L. Jacobs , M.D. and Leon Pape , M.Sc. City of Hope Medical Center Duarte, Calif. ↵ 1 From the City of Hope Medical Center (M. L. J., Chairman of the Department of Radiology; L. P., Chief Physicist), Duarte, Calif. Presented at the Forty-sixth Annual Meeting of the Radiological Society of North America, Cincinnati, Ohio, Dec. 4–9, 1960. Excerpt In the past few years there has been a rapidly growing interest in the problems of radiation protection in cases of exposure of large areas of the human body. In addition, much work has been done in the field of organ transplants, particularly with respect to the management of leukemia with bone-marrow transplants. It is of interest to note that more success has attended the studies on experimental animals than on man. It is postulated that one of the problems in evaluating the efficacy of total-body irradiation of man has been the difficulty of obtaining a fairly uniform dose of radiation throughout the entire volume of a patient. Certainly a system which provided such a uniform energy deposition would eliminate a variable in the ultimate evaluation of total-body irradiation. It is the object of this paper to describe a physical system designed and constructed with this in view and to report the initial results of the dosimetry connected with it, as well as the problems encountered. The irradiation chamber measures approximately 11 × 11 feet. In its center is a treatment area defined by four upright posts (Fig. 1), which is approximately 2 feet wide and 6 feet long, representing a horizontal plane 3 feet above the floor of the treatment chamber. The radiation is produced by eight cesium sources with an initial strength of 300 curies each. When in treatment position, the sources are housed in the four upright posts and are located in the corners of the treatment area; they are so placed that four of the sources form a plane 3 feet above, and four form a plane 3 feet below the treatment area. Each pair of upper and lower sources is contained in a seamless steel tube which, in turn, is mounted in a steel well casing (Fig. 2). The four casings are sunk to a depth of 12 feet in the ground below the chamber and are encased in concrete jackets. The source tubes rise to a point 7 feet above the chamber floor. Each tube supports an independent chain-drive mechanism which is used to bring the sources from “safe” position in the underground wells to “treatment” position. Each set of sources can be positioned independently or all four sets can be positioned for treatment simultaneously. The counterweights are adjusted so as to provide for source return to “safe” position in case of power failure. The sources are housed in standard international treatment capsules which, in turn, are mounted in carrier capsules. The carrier capsules for each set are connected through a rigid steel bar which maintains a fixed separation of 6 feet between sources. Movement and positioning of each pair of sources are therefore simultaneous. Each treatment portal has a removable beam-absorber holder to which a wide variety of absorbers and beam-shaping blocks can be secured. Finally, the control panel contains a row of lights for each column. Copyrighted 1961 by The Radiological Society of North America, Inc.
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