DOSIMETRY FOR TOTAL-BODY IRRADIATION OF RHESUS-MONKEYS WITH 300 KV X-RAYS

Purpose: To obtain more accurate information on the dose distribution in rhesus monkeys for total body irradiation with orthovoltage X-rays. Materials and methods: Dose measurements were performed with an ioniz ation chamber inside homogeneous cylindrical and rectangular phantoms of various dimensions and in phantoms containing lung-equivalent mater ial. The irradiations were carried out with reference to a monitor ion ization chamber placed alongside the phantom or the irradiation cage. Results: Correction factors for mass and lung dose relative to the ave rage dose in a homogeneous reference phantom, showed linear relationsh ips with the effective diameter of the monkey. The lung dose correctio n factor relative to the homogeneous phantom was about 1.12 for a 3.5 kg monkey. The stated values for the average absorbed dose in the anim al of standard weight should be multiplied by a factor of 0.93 for exp eriments performed before 1983. All publications on total body irradia tions of monkeys at TNO after 1983 contain the corrected dose values. Conclusion: Dose distributions are reported for phantoms of different diameters and of cylindrical or rectangular shape. The new dosimetry h as also resulted in a revised statement of the LD50 for the occurrence of bone marrow syndrome after X-irradiation; 4.9 Gy instead of 5.3 Gy .