A new delayed coincidence method, which was based on selective counting of relatively short-lived nuclide, 216Po with a half life of 145 ms in Th series members, was applied to the absolute determination of low-levels of Th series. Every 45 ml portion of hot spring waters from Tamagawa area in Akita Prefecture was mixed with a liquid scintillation cocktail (55 ml) and all a decay events occurred were selectively counted by discriminating low energy β rays. When a decay events were detected, the time data were recorded on a computer memory to make disk files. The multiple time analysis on the collected time data was applied to obtain a simplified time spectrum. On the time spectrum, decay events220Rn→216Po→were selectively extracted.224 Ra were determined to be 3.41±0.38 (Bq/l) at the upper stream and 0.60±0.08 (Bq/l) at the lower stream.228 Th activities were also determined by the same method, which resulted in 0.36± 0.04 and 0.09±0.02 (Bq/l) at the upper and the lower stream, respectively. The activity ratios of224Ra to 229Th at each sampling point showed the preferential precipitation of224Ra relative to228Th.
The purpose of this study is to examine quantitatively the relationship between visual image quality and degradation in spatial resolution for a gamma camera by the increase in distance from collimator. The relationship between the proportion (p) of images identifced the difference of image quality and the difference (ΔFWHM) in FWHM between paired images was showed in a sigmoid curve. Using Dendy's method, minimum level to be correctly identified the difference of image quality on three out of four occasion (p= 0.75) was corresponded to 0.4 mm in ΔFWHM. Using fuzzy theory, the level to be identified the difference of image quality was examind under various conditions. The truth-value of fuzzy sets-degraded or slightly degraded and not-degraded in image quality between paired images-was gained the peak at 0.5 mm of JFWHM. It was founded that changes o f 0.4-0.5 mm in FWHM-corresponding about 2 cm distance from collimator-could be sufficiently identified in the difference of image quality.
The relation among the blood clearance of99mTc-phytate (99mTc-P), the hepatic uptake of99mTc-P and the severity of hepatic injury was investigated by using the rats with carbon tetrachloride (CCl4), D-galactosamine (Gal N), α-naphthylisothiocyanate (ANIT) or DL-ethionine (EthN) induced hepatic injury. After the administration of CCl4, GalN or ANIT, serum GPT activity increased significantly with the increase of dose level, and the degree of this increase was in the order: GalN>CCl4>ANIT. However, the mild increase in serum GPT activity was observed after EthN administration. The blood clearance rate of99mTc-P and the hepatic uptake ratio of 99mTc-P decreased with the increase of dose level after CCl4, GalN or ANIT administration, but significant changes were not found after EthN administration. The degree of decrease in the blood clearance rate of99mTc-P was in the order: GalN≅CCl4>ANIT, and the degree of decrease in the hepatic uptake ratio of99mTc-P was in the order: GalN≅CCl4>ANIT. These results suggest that the disorder in the hepatocytes may be one of causes for inducing the decrease in the hepatic uptake of99mTc-P, and the consequence of this decrease may induce the decrease in the blood clearance of99mTc-P.
Both67Ga citrate and201 Tl chloride accumulated in a parathyroid tumor of a 62 year-old woman with primary hyperparathyroidism. Histological studies disclosed that the tumor was a parathyroid carcinoma. The use of both tumor scanning agents, 67Ga citrate and201Tl chloride to visualize parathyroid carcinoma in a patient with primary hyperparathyroidism has not been reported as far as we could determine.