Escape probabilities of radiations from slab and spherical homogeneous sources covered with shields are calculated for three different absorption characteristics of radiations; step functionally decreasing absorption characteristic, linearly decreasing one and exponentially decreasing one. When the probabilities are not expressed in elementary functions, numerically calculated results are given in figures.
In the radiochemical determination of137Csin the sea water sample, it is expected that impurities such as40K and87Rbco-precipitate with137Csin relation to the employed chemical separation. In order to determine137Csin the sample as accurately as possible, the low back-ground β-ray spectrometer was utilized. The β-ray spectrum, which was measured by the low back-ground β-ray spectrometer on the counting sample after chemical separation, was identified by the stripping method using the standard sample of interested radionuclide and the radioactivity of137Cswas determined spectrometrically by the weighted least squares analysis. The obtained results by the conventional method usinga low back-ground GM counter after chemical separation showed 1.15-1.9 times as much as those from the low background β-ray spectrometer. It was found that overestimation from the conventional counter after chemical separation, Ni2Fe (CN) 6-AMP-H2PtCl6method, was arisen by87Rb.And the net radioactivity of137Cscould be determined by the β-ray spectrometry without completely removing impure87Rb from the counting sample.
The present paper deals with a method of preconcentration necessary for the activation analysis of trace elements in water samples and its application. As it is difficult to determine volatile elements and short-lived nuclides by the instrumental neutron activation analysis using the evaporation residue of water samples, the preconcentration by coprecipitation withFe (OH) 3, Al (OH) 3andPbSwas tried for the analysis of these elements. The recovery of these elements was examined in advance by means of radioactive tracer. It was found convenient that the precipitation is made from a solution of pH 6 in theFe (OH) 3orAl (OH) 3coprecipitation or from a weakly acid solution in thePbScoprecipitation. γ-Ray spectrometry by a coaxialGe (Li) detector connected to a 4096 channel PHA was performed on the irradiated sample without any further chemical separation. This preconcentration method was applied to the river water sample taken from a comparatively clean river in Okutama district in the Tokyo Metropolis. About 30 elements in it were thus determined.
Neutron-irradiatedCo (acac) 3or Cr (acac) 3was dissolved in benzene containing various metal acetylacetonates as additives and the change in the apparent60Co-or51Cr-retention with the time after the dissolution was investigated at various temperatures. Unstable metal acetylacetonates such asMg (acac) 2were found to enhance thermal reactions (or the apparent retention) in the solutions. The behavior of the recoil species was very similar in both the irradiated benzene solutions and benzene solutions of the irradiated solids of these complexes. The reactions of the recoil species in solutions of the irradiatedCo (acac) 3orCr (acac) 3and the effects of various additives in such systems (especially the correlation between the apparent scavenging power of metal salts and the stability constant of their acetylacetonates) were explained in terms of recombination, scavenging and ligand transfer reactions.
Recently there appeared several99mTc labelled liver scanning agents. They were99mTc2S7colloid, 99mTc-Sn-colloid, 99mTc-microaggregated albumin and more recently99mTc-phytate, and could be used with simple labelling procedure. These were relatively small particles, and uniformity of these liver scanning agents was difficult to assess, and it was somewhat difficult to use these agents as quantitative liver scanning agents. In this regard, colloid seemed to be useful because of its uniformity of the particle size (about 4μ in diameter) . The authors intended to label colloid with99mTc by electrolytic method of Ikeda, et al., and performed basic and animal experiments and clinical evaluation of99mTc-colloid as liver scanning agent 99mTc-colloid labelled by Ikeda's original method showed marked macroaggregation within one hour after labelling. So the authors modified the original method in the point of pH adjustment usingNaHCO3immediately after labelling (pH=1.2→pH=6-7) . The labelling efficiency of the99mTc-colloid was over 94-99%. Particle size of the colloid observed with microscope was about 4μ and fairly uniform. The half time of blood disappearance and peak accumulation time in the liver of99mTc-colloid in man were 1.1 min and 10 min respectively. The linear scans showed clear single peak at the level of the liver, and body background of the chest was slightly higher than that of abdomen. Animal experiments showed about 20% of the total dose remained in the lungs, and it seemed difficult to use99mTc-colloid clinically. However, none of the liver scans of the clinical cases showed such marked lung uptake. The effective half life in the liver in experimental animal and in man were 6 hr and 5.5 hr, and in the spleen, 4.8 hr and 3.2 hr, respectively. Splenic visualization was more marked in99mTc-colloid than in99mT c-Sn-colloid. From these results, 99mTc-colloid prepared by electrolytic method seemed to be useful in clinical application.
Serial hepatobiliary scintigraphy has been generally used to differentiate the hepatocellular disease from extrahepatic biliary tract disease, especially when other nontraumatic radiological methods could not offer any information. However, the difficulty in differentiation between these two diseases has been frequently occurred. On the other hand, the blood clearance study has been considered to provide additional information for that purpose. In the present study, a ratio expressed as a percentage obtained by dividing the 20 min. count rate by 5 min. count rate was used as representing the blood retention not as yet cleared from the liver, and the combined study of this blood retention ratio of131I-BSPtogether with serial hepatobiliary scintigraphy was performed to achieve maximal effectiveness for the differentiation of hepatobiliary diseases. The obtained results are as follows: 1) It was almost pathognomonic of medical or nonsurgical jaundice if blood retention ratio showed 85 per cent or greater, in spite of the serial scintigram results. 2) In the case of 70-85 per cent range, the existence of131I-BSPintestinal excretion was the most important finding. The renal image without intestine, which was considered to represent the complete obstruction, suggests the high probability of complete extrahepatic obstruction. The delayed intestinal activity favours the diagnosis of hepatocellular disease or intrahepatic cholestasis. 3) Blood retention ranged from 40 to 70 per cent indicates an indeterminate type of hepatobiliary disease. However, a markedly delayed excretion, later than 4 hours, suggests the probability of extrahepatic biliary tract diseases. 4) Normally, blood retention ratio is less than 40 per cent. However, the extrahepatic biliary tract disease is not excluded when delayed131I-BSPexcretion into gut, later than 60 min, is found. From the present eombintion study, more accurate information for the differentiation of hepatobiliary disease could be provided than each of these only, and this nontraumatic method was considered to be valuable as an earlier examination method for the diagnosis of surgical or extrahepatic biliary tract disease than that of traumatic examination such as percutaneous eholangiography or celiac angiography.