Cherenkov counting efficiency has been considerably improved by a specified measuring geometry. Radioactive sample and wavelength shifter are separately dis positioned, where a butyl-PBD has been employed as a wavelength shifter in the form of liquid and solid solutions. This technique can get rid of the shortcoming of the method usually used, in which wavelength shifter is directly incorpolated to Cherenkov medium.
The sublimatographic separation of volatile β-diketone, pivoloyltrifluoroacetone (PTA), chelates of fission products was studied. When Zr carrier was added, the sublimated radioactive chelates deposited on only one zone at the position of 45-60 cm (85-50°C) from the position of the sample. The position agreed with the deposited position of inactive chelates of Zr. The nuclide presented in the zone was almost95Zr.On the other hand, when Y or Eu carrier was added, the sublimated radioactive chelates deposited on two zones at the position of 20-40 cm (150-120 °C) and 60-75 cm (50-25°C), respectively. The zone at higher temperature side agreed with the deposited position of inactive chelates of each carrier and the nuclei presented in this zone were mainly lanthanide elements (141Ce, 144Ce, 147Nd, 140La.103Ru, 95Zr) .The zone at lower temperature side was mainly carrier-free state of95Zr, but the position of carrier-free95Zrshifted to lower temperature side than the deposited position of inactive chelates of Zr carrier.
Macroautoradiographic studies on distribution of14C-pipemidic acid in the guinea pig ear were performed after administration of the drug to provide its disposition for its application in the otolaryngological field. Petrosal bone, cochlea and auditory ossicles contained extremely low levels of14C-pipemidic acid; blood, mucous tissues of tympanic cavity and tympanic membrane, low levels; tissues of external ear, moderate levels; and outer surface tissues of petrosal bone possibly including periosteum, significant levels. These otological tissue distributions of pipemidic acid suggest the effective applicability of the drug in the field.
Thorotrast amount deposited in patients, chiefly in the liver and the spleen, was determined with a NaI detector and a Computerised Axial Tomography (CT) . In the measurement of the γ-rays with the NaI detector, the geometry-factors, that are the distance from the detector to the source, the attenuation of the γ-rays in the tissue and the shapes of the liver and the spleen, were studied, and the mean amount deposited in the organs was determined. In the measurement with CT, the relationship of CT-Number and the amount of thorium was got, and the localized amount and the distribution in the organ were measured.