Loss of137Cs and potassium, by dry ashing and by hydrochloric acid treatment was studied on large amounts of total diets. Total diets were collected from 1963 to 1965 and samples for 2 or 5 days were treated as a whole. In this study, radioactive cesium was not added to the samples as a tracer, but fallout137Cs contained in them was used to check the recovery. The amounts of both137Cs and40K were determined by gamma-spectrometry. Ashing at 600°C for 10 hours gave several per cent of loss for137Cs, and no loss for potassium. In the process of dry ashing for 2 to 20 hours, no significant diferenc was found between 450°C and 600°C. By the hydrochloric acid (1: 1) treatment of the ashed sample, 90 to 80 per cent of137Cs was leached out but 10 to 20 per cent remained in the residue, while potassium was dissolved perfectly.
A human counter has been designed and constructed which has wide applicability in clinic. This does not have a steel shielded room but four detectors using 3×2 in NaI (Tl) crystals instead of single large crystal. In addition to whole body counting it can be used for almost all kinds of external countings such as temporal scanning, linear scanning and area scanning and it is therefore called “Medical Universal Human Counter (MUHC for short) ”. In whole body counting, two detectors are placed over the lying patient and the other two beneath the bed. After the first counting for a certain fixed time the detectors are transferred to another place for the second counting. These two countings give the geometrical arrangement equivalent to the whole-body counting with 8 detectors arrayed symmetrically in line above and below body axis provided that counting time is short enough for neglecting the changes of radioisotope distribution. Distance between the detectors adjoining each other is 50cm and that between the detectors opposing is 100cm. The spatial distribution of measurement efficiency is fairly uniform (100±5%) in the limits of 10cm above and below from the mid-point between two opposing detectors and 150cm along the longitudinal axis, in the insertion of a subject, however, intensity of γ-rays decreases exponentially with depth provided that pure photo-peak from a nuclide in the subject is counted. Since the measurement efficiency should be uniform in the opposed combination of two isoresponce curves which decrease linearly with depth, the width of spectrum was studied by which the counting rate of γ-rays decreases linearly with depth. As a result, reduction in water was proved to be linear in the width of 240-400 keV for131I, 525-725 keV for137Cs and 1.05-1.45 MeV for60Co. Generally for the lower energy γ-rays, uniform distribution (100±10%) of measurement efficiency was obtained in the water phantom of 20cm thick by a differential counting including Compton scattered region in addition to photopeak. According to the above-mentioned results, in the practice of whole-body counting with MUHC, the optimal spatial arrangement of the detectors and the optimal channel width of spectrometer should be taken into account. If so, the amount of radioisotope can be measured precisely not influenced by a state of internal distribution of radioisotope. 0.1μCi of131I in vivo can be measured with relative errors 5% by whole body counting for an hour.
The comparative study of distribution of orally administered35S-O-benzoyl thiamine disulfide (35S-BTDS) and35S-thiamine (35S-B1) has been carried out in adult mice by means of whole body autoradio graphic method. The autoradiogram revealed that the uptake of35S after administratijon of35S-BIDS was more rapid in various organs than that after administration of35S-B1and higher level of radioactivity continued for long time in the case of35S-BIDS than35S-B1. Dose relationship showed that uptake of35S-BTDS into organs increased remarkably while the increase in uptake of35S-B1 was limited.
When administrated35S-BTDS (35S-O-benzoyl thiamine disulfide) and35S-thiamine orally, the absorption rate of BTDS from the rat digestive tract was about 62% and that of thiamine was about 38% in one hour. It was found that the absorption of BTDS injected into the ligated loops of the rat intestine was greater than that of thiamine in all portions of intestine tested. This was especially remarkable in the lower portion of intestine, where thiamine was hardly absorbed.
Nowadays radiations finds its routine use in medicine and industry and has been used more and more extensively. The development of methods for protecting the living body from radiation reaction has thus become an urgent problem. The author has studied the -SH protecting agent among others. Disorder due to radiation is caused by ionization and activation of water and in the course of this process some radicals are liberated as intermediate products, to which we gave special attention. Since the -SH protective agents are capable of eliminating free radicals thus produced, we conducted experiment by means of ESR (Electron Spin Resonance) which permits to determine only free radicals. The radiation effect and protective effect were determined on the liver and tumor in mouce. Systemic radiation of60Co gamma rays was given once in a dose of 600 R, After, irradiation the animals were fixed with dry ice, then the liver and tumor were extirpated, dried by lyophilization and powdered. Samples thus obtained were determined for the quantity of free radicals per one gram by ESR and compared. Results: Free radicals were demonstrated in the liver of non irradiated mice, while they were found about 7 times as much in the liver of those mice fixed 5 min after irradiation. In the case of fixation done at 24 hours after irradiation free radicals were found markedly reduced but still more than those detected in the non-irradiated liver. Similar results, but lesser increasing in free radicals, were obtained on tumor. Favorable results in eliminating free radicals in the liver were obtained with glutathione, MEA and cystine in that order, when they were administered 30 min before irradiation. Especially with glutathione were obtained values near those obtained in the non-irradiated animals, its protective effect was found greater with decreasing time interval between the administration and irradiation, and less satisfactory when administered more than 30 min prior to irradiation. Also in tumorous tissues a reduction in the radiation effect was produced by glutathione but not so marked as seen on the liver.
Recently some scintigrams with RI scanning are made comparatively easy, but to gain quantitative data at the same time is difficult. In this paper, a simple way to get quantitative data is reported. The apparatus is made up of ratemeter, integrator, capacitance relay and X Y recorder. Scintillation pulse after spectrometry is detected by the high speed ratemeter (time constant 0.5 sec), then the out put of ratemeter is integrated by the simple electrical integrator. This integrator is operated by capacitance relay set in the scanner. The capacitance relay works when the scintillation head comes in the center of each scan. The curves recorded on X-Y recorder show the quantitative value in human body of radioisotopes. Practising lung scanning with131I-MAA in this method, measured pulmonary blood flow volume ratio of right to left lung, and the data are useful for clinical diagnosis of pulmonary diseases as well as the morphological aspects by scintigram. In 30 cases, the results of this method coincided by the difference of under ±2 percents with the acounts of dots counting with scintigram. In 10 normal cases, the results of pulmonary blood flow volume ratio showed 0.55 with the right lung and 0.45 with the left lung making total lung 1.00. However, there was a change in ratio shown in morbid cases.
Direct intercomparison of the distribution of colloidal198Au, Cr32PO4and177LuC13administered in normal and Ehrlich ascites tumor bearing mice was made under identical condition, and the results obtained were reported in detail including autoradiographic findings. Following intraperitoneal administration in normal mice the translocation of the Cr 32PO4into liver was the least among the three compounds. Following intraperitoneal administration in the Ehrlich ascites tumor bearing mice the translocation into the liver was less as compared with that in normal mice. Thus the difference of distribution of colloidal substance between normal and ascites tumor bearing mice was demonstrated. Autoradiographic findings disclose a considerable amount of deposition of the colloidal substance in the milky spot of the omentum as well as in free macrophages and on the peritoneal membrane.