Performance of miniature pgs after partial body irradiation.

Thirty-two miniature pigs were trained by shock avoidance conditioning to traverse a two-chambered shuttlebox. Eight unshielded pigs (whole-body exposed) received midline tissue doses (MTD) of about 13, 000 rads of pulsed, mixed gammaneutron radlations to the head and trunk. Eight head-shielded and eight trunkshielded pigs received doses to the unsh!eldcd part of the body that were equivalent to the doses received by unshielded animals. Four trunk-shielded pigs received 6000 rads to the head, and four others received 3000 rads to the head. MTD behind the shield (at the middle of the head or trunk) %is less than 7 percent of the MTD to the same point without a shield in place. Postirradiation performance was evaluated. All unshielded pigs suffered early transient incapacitation (ETI) or immediate, permanent complete incapacitation (PCI): several early deaths (within 4 hours) occ.:rred among these animals. Head shielding prevented ETI, i: r?-eite PCI. and e',rly deaths, but trunk shielding did not. tlowever, trunk--shielded subjects tha: scaped the early death performed and survived longer than most head-shielded or unshielded pigs. ETI occurred in all of tle trunk-shieided pigs that received 6000 rads and in one of four that received 3000 .'ad.; however, early deaths did not occur and suIrvival times were much longer than those previously reported for unshielded pigs that received comparable doses.