of tc 99m labeled materials images were acquired of each animal using 34 spot 34 views over the upper and lower portions of the body with conjugate views i e 180 degree opposed views for each the resulting image data was analyzed by creating regions of interest roi 39 s for each organ and determining the sum of the recorded gamma photons for each organ in each view from the transmission view an attenuation correction factor was derived for each organ and the activity in the organ determined by taking the square root of the product of the roi sums for conjugate views of the organ and then multiplying by the attenuation correction factor for that organ and then by the efficiency factor each animal was imaged with tc 99m l l n n 39 1 2 ethylenediylbiscysteine diethyl ester in order to serve as its own control one test isomer was then administered to each of the monkeys frequent blood samples were drawn from a peripheral leg vein regions of interest were drawn around all pertinent organs and time activity curves were constructed the accumulated radioactivity in various organs is recorded in the tables below table i______________________________________biodistribution in rhesus monkeys after 30 minutes numbers expressed as a percentage of the initialinjected.