Trace amounts of zinc were determined by the radioactivation analysis based on the quantitative isotope dilution principle. The irradiated sample is divided into two parts, and a known amount of carrier M is added to one. An amount m which is less than the amount of the element in question Mx is separated from each part, and then radioactivities of both parts a and a' are measured. The unknown amount Mx is calculated from Mx=a'M/ (a-a') The experiment to determine the reaction ratio between zinc and dithizone was carried out at various conditions and it was observed that the ratio was constant in the solution of pH 8.5. It was also shown that the specific activity was proportional to the amounts of zinc added, and the reproducibility of the results was satisfactory. Then, this method has been applied to the determination of zinc in the zinc doped gallium arsenade as semiconductor material and satisfactory results were obtained.
As a fundamental study of thickness-gauge, level- or density-meter by means of backscattered gamma-rays, the spectra of the gamma-rays which were scattered by steel plates with or without water behind these plates, were measured. The incoming beam from 137Cs 0.1 Ci was collimated by a hole 6 mm in diameter. The experimental condition was based on the calculated results of the intensity of singlescattered rays in the incident plane. In calculation, the geometrical condition of the apparatus (the sizes of detector and collimator etc.) was taken into account. When the scattering angle was not large, the energy spectrum showed two main peaks: the higher energy peak by single-scattered rays and the lower energy one by multiple-scattered rays. It was found that the energy band of the higher peak was suitable for thickness measurement of vessel wall. It was also possible by some ways of geometrical arrangement of the apparatus to detect mainly the scattered rays by the vessel wall. It was shown that geometrical arrangement in wall-thickness measurement by means of backscattered gamma-rays could be evaluated from the standpoint of the error caused by presence of liquid in the vessel. Hereby, the experimental results about the geometrical effects were examined, and the optimum geometrical arrangement was found.
A description is given of the structure and some characteristics of the whole body counter at Kyoto University. The counter is intended for use in radiation protection and medical diagnostic investigations. Three types of detectors are set for whole body counting of human subjects: (1) one 8 in.×4 in. NaI (Tl) crystal scintillation probe, (2) four sets of probes consisting of a 1.5 in.×1.5 in. NaI (Tl) crystal and a photomultiplier tube, (3) four plastic scintillation probes. Output signals from the detectors are analyzed in a 400 channel pulse-height analyzer and a dual-channel pulse-height analyzer. Some data of this counter are presented.
It is desirable for radioisotope scanning of organs to use the nuclide which gives more photon output while reducing the absorbed radiation dose to the patient. Although99mTC, a short-lived nuclide is nearly ideal from this point of view, it is not necessarily widely used because of short half life (2.8 days) of parent nuclide99Mo as well as expensiveness of99Mo-99mTc cow for its short shelf life of 10 days. 113Sn-113mIn cow is extremely useful in this respect because that113Sn is a long-lived nuclide (118 day half-life), daughter nuclide113mIn decays with a half-life of 1.7 hrs. by emitting 390-keV mono-energetic gamma rays (no beta emission) and milking of 113mIn from the cow with dilute HCl can be practiced twice a day. By simple procedure the various-sized particles of113mIn can be prepared very quickly. The authors followed the radiopharmacological methods reported by H.S. Stern, et al. for lung, liver scanning and besides succeeded in preparing113mIn-microcolloid (tentatively named) for bone marrow scanning recently. 113mIn is one of the most promising short-lived nuclides and113Sn-113mIn cow will be widely accepted in future.