506 BOND, CRONKITE, SONDHAUS, IMIRIE, ROBERTSON, AND BORG A word should be said initially regarding the possible application to the problem of the vast amount of dosimetry data that has been published in connection with clinical radiation therapy. Most clinical radiotherapy exposures differ fundamentally from the ‘total-body” exposures considered here in that the object of the one is to obtain localized, cireumseribed partial-bodyirradiation of a diseased aren, whereas the object of the other usually is to obtain the same degree of ex- posures to afl tissues of the body. The one usually attempts to narrow the beam by collimation or by the use of ports; the other requires a beam sufficiently broad to expose the entire irradiated object. Thus, the numerous depth-dose figures published for radiotherapists (9) usually cannot be carried directly to the ‘‘totalbody” exposure situation, although the curves obtained with very large area ports apply approximately in some situations. Since the depth-dose pattern with ‘total- body” irradiation is highly dependent on the precise conditions of exposure, it is not practical to compile complete tables of depth-dose values for reference. The patterns to be presented here obviously apply strictly only to the specific conditions emploved, EXPERIMENTAL PROCEDURE The exposure geometries considered, all described more fully below, include unilateral, bilateral, multiport, rotational, ring, and 42 exposures in the laboratory, and exposure to immediate and fallout y-radiations in the field. A cylindrical Masonite phantom 26 em long and 26 em in diameter, corresponding to a 32-inch waist, Was exposed under each of the laboratory conditions listed. The density of the Masonite was 1.05. This phantom obviously does not represent exactly the essentially oval configuration of man in cross section in the region of the trunk, but it was felt to be a sufficiently close approximation. A diagram of the exposure conditions for a “point” source is shown in Fig. | for reference purposes. A targetto-“skin’’ distance (TSD) of 100 em was used for all exposures unless otherwise indicated. Studies showed that lengthening the eylidrical phantom bevond the o- wy ww RA d=!00.cm ANS A.ia a\ voy VN a “oy B PIAA» > "POINT" SOURCE Wr, Al ciao rk, oY WAAAa cr Fig. §. Schematic diagram showing method of exposure of a Masonite phantom to a “point” source of X- or +-radiation.