: “ Loi dae . Lot tae . ee Tea Meas be ba el Eee Beec da atiehales! 100 TABLE 35. . Animal Age of burden Man Code | Liver . Kidney Spleen Lung / Cortical 100 253 49d 03 100 100 lly 66 100 134 0.5 0.9 26d 48d 26y 83 85 166 100 100 100 66 65 604 0.7 1.0 0.2 0.4 1.t 0.5 0.8 1.3 100 205 0.6 0.7 1.0 100 100 100 100 100 100 100 175 213 580 204 44] 252 316 0.4 0.8 0.9 100 312 07 67 72 73 TH2‘>) TH3) TH4® TH5) Average marrow _| 02 41d 35d 38d 18m 22m 12m 22m Bone? + “bone 49d Average Rat Tissce DistrinutTion oF THoROTRAST™ | Red bone marrow —_ 8.4 19.1 2.4 1.9 5.0 5.8 14 Il 7.1 12.5 | ‘*) Concentration of thorium (?"Th)/g of tissue as % of liver concentration. ®) Ratios are based on 7Ra activities assuming equal f; values for all the soft tissues. ‘) Rib and vertebra, respectively. TABLE 36. OrGan DistTRIBUTION OF THOROTRAST IN Man (222TH) W, Organ Organ Liver Spleen Kidney Lung Cortical bone Red bone marrow Total Bone -++ marrow wt in Standard Man, kg 1.7 0.15 0.3 1.0 7.0 1.5 10.0 least about the physical and chemical prope C, Thorium conc. rel. to liver % in organ Cw (100 CW/ 100 205 0.6 0.7 1.0 12.5 170.0 30.8 0.2 0.7 7.0 18.8 v 13.6 0.1 0.3 3.1 8.3 7.1 227.5 71%) (from tions and approximations must be made. The s mathematical model, and the one which assun Table 35) 227,5) 100 (9) The figures in the right hand columngivethe fractional retention of #%2Th in the organ, relative to the amount in the whole body. Amounts of Thorotrast contained in organs other than those listed are assumed to be negligible. Thorotrast in lymphnodes, though probably not negligible, has been ignored because of inadequate data. ») The danger in extrapolating from the figure for bone which contains marrow, is demonstrated. This value for the whole skeleton is approximately three times that obtained by extrapolating separately for cortical bone and red bone marrow. not be carried out rigorously since they depend on metabolic parameters which are inadequately understood. For this reason a numberof simplifying assump- Thorotrast, is presented in an Appendix to this The following results have been obtained on th of the equations contained therein. RESULTS AND DISCUSSION Tissue distribution of Thorotrast (732Th) Measurements were made of *3?Th concentrat tissues from 6 humans and 7 rats. Average conc tions in the various organs are summarized in 30, All have been normalized with respect to the — content of the liver, the organ which containstl. jor fraction of the total body burden. In this way of the difficulties which arise in making extrapoi to the whole body can be minimized, e.g., those nonuniform distribution of activity in each orga certainty in the ratio between the weight of the s measured and that of the whole organ (particul: the case of bone marrow), and inaccuracies quoted amounts of Thorotrast injected. On this no significant differences between man and the r evident in the extremely meagerdata. Extrapolation from the data for man (Table . the whole body has been made by assuming weights for the standard man in accordance wr recommendations of ICRP.‘The pattern of dis perh MENS R tS