GC156 Reprinted from Rapiation Researcn, Volume 6, No. 5, May 1957 Acudenne Press Ine. Printed in 17.8.A. 4 Q ‘1 3 so A RADIATION RESEARCH 6, 554-572 (1947) The Medical Research Corner Brookhaven National Laborato.y The Influence of Exposure Geometry on the Pattern of Upton, L. L, New York Radiation Dose Delivered to Large Animal Phantoms’ V.P. BOND, E. P. CRONKITE, C. A. SONDHATS, G. DMTERIE, J. 8. ROBERTSON anp D. C. BORG Medical Department, Brookhaven National Laboratory, Upton, New York, and The Naval Medical Research Institute, Bethesda, Maryland INTRODUCTION In attempts to make quantitative comparisons of the effects of fallout y-radiation exposure received by the Marshallese with those of previous human and large animal exposure (1), it became necessary to consider the influence of exposure geometry on the tissue dose and on the pattern of dose deposition. It became evident that, for the same dose expressed as roentgens measured free in air, in terms of which exposures and LDs values have been generally reported in the literature, the tissue dose could vary by as muchas a factor of 2 or more. In the present work, the influence of exposure geometry on the depth-dose pattern in a large animal phantom was investigated systematically, under the several exposure conditions frequently encountered in situations where large animals or man have been exposed to penctrating radiations. A more detailed treatment of the problem may be found in a current Naval Medical Research Institute report (2). It will be apparent: that the biological effects of penetrating radiation must depend on the dose “absorbed” in the tissues (3), not on the exposure received by the ambient air. Thus, much of the confusion that results from expressing large animal exposures in terms of air dose could be alleviated by using tissue dose to characterize an exposure. The necessity of using tissue dose has been recognized for many years by radiologists and is set forth in the 1937 and 1953 reeommendations of the International Commission on Radiological Units (4) and in the 1940 Technical Bulletin of the Radiological Society of North America Standardization Committee (5). This practice has cleared up much of the confusion in clinical radio- 1This research was supported by the Atomic Energy Commission and the Navy Department. A portion of this work was performed while three of the authors (VPB, JSR. CAS) were at the U.S.N. Radiological Defense Laboratory, San Francisco. ? Presented as part of a symposium at the Radiation Research Society Meeting, Chicago, Dl., May 17-19, 1956. 554 nePositony —LN4L RECORDS COLLECTION ISLANDS BOXNo, MEQICAL DEPT. PUBLICATIONS Land LD oa a fr 20 | Lited FoLtpen UO - / 72