EVENT AND DESCRIPTION OF EXPOSED GROUPS relationship to the surface dose and depth dose as does the air dose measured in a “point source” 9 source” beam air doses with comparable biologic effect are obtained : beam in the clinic or laboratory. It would appear under these circumstances and in most experimental conditions that the midline dose, rather than dose measured in air, wauld be the Rongelap, Group I.__--_-. Ailinginae, Group IT___-.__Rongerik, Group III --._-- Utirik, Group IV_-.----..-- 260 r 100 r 120 r 20 r too 3 \ wd <7 . 4m EXPOSURE, MANY SOURCES 1.35 aA aS Y g SL = < Se g 5 RATIO LSE Ye « ¥ al BILATERAL EXPOSURE, OIVERGING SOURCE 39% NX i 0 5 id is a 20 25 30 \ t 36 CM MASONITE DEPTH DOSE DISTRIBUTION IN CYLINORICAL PHANTOM, CO™ FACILITY, (NMR!) Fiaurge 1.4—Comparison of depth dose curves in masonite phantoms from bilateral exposure to a single point source, and simultaneous exposure to multiple aources with a spherical distribution around the phantom, better common parameter in terms of which to predict biological effect. On this assumption, the air dose values stated in Table 1.1 should be multiplied by approximately 1.5 in order to compare their effects to those of a given air dose from a “point source” beam geometry delivered bilaterally. If this is done, assuming a fallout of 12 hours, the following “point 381712 O—56-——2 The geometry of radiation from a fallout field is not identical either to the geometry of bilateral point sources or spherically distributed sources since the plane source delivers the radiation largely at a grazing angle. However, the total field situation is better approximated by solid than by plane geometry. Exposure geometry in a radioactive cloud would be spherical.