A thin 4πβ-counter with five anode wires was operated by supplying negative high voltage to the inner wall and showed good plateau characteristics in the case of using only the center anode to take out signals in the previous experiments. This counter, as the 4πβ-counter and both 2πβ-counters, showed good plateau characteristics in these detailed experiments and no dependency on the disintegration rates examined up to 6000 dps. Then a 4πβ-γ coincidence equipment was set up using this 4πβ-counter and one NaI (Tl) scintillation detector with size of 76 mmφ×76 mm. The radioactivities that were measured for β-γ and electron capture-γ decay nuclides by this coincidence equipment were coincided with those measured by the other one. The improvement of the γ-ray detection efficiency to aim was achieved by that the efficiency obtained by this system was the same as one by the other system having two NaI (Tl) detectors with the same size.
In order to determine the optimum irradiaton condition for the production of67Ga and68Ga, used in nuclear medicine, excitation function and thick-target yield curves were obtained for alpha and helium-3 reactions of natural zinc. With the initial alpha energy of 25 MeV, the thick-target yield of67Ga was found to be 165 μCi/pA⋅hr at the end of bombardment and the66Ga contamination could be reduced to less than 1% after about 3 days of cooling.68Ga could be obtained by milking from68Ge. With the alpha energy range of 17-40 MeV, the thick-target yield of68Ga was 1.2 μCi/μA⋅hr at the end of bombardment.
The optimum irradiation conditions were investigated for the production of61Cu and62Zn by alpha and3He particle bombardment of natural nickel. Formation cross sections and thick-target yields were obtained for reaction products in the energy range of 10 to 40 MeV. For the production of61Cu and62Zn, the alpha particle bombardment was found superior to the3He particle bombardment in so far as the yield was concerned. When the incident alpha energy of 21 Me V was chosen, after 2.4 hours of cooling, 2.1 mCi/μA⋅h of61Cu could be produced with less than 1 % of60Cu contamination. For the production of62Zn, when the incident alpha energy of 35 MeV and the target thickness of 57 mg /cm2 were chosen, 97, 5 μCi/μA⋅h of62Zn could be produced. Radiochemical purity of62Zn was the highest at 12 hours after the end of bombardment.
Pollen grains of Bz strain of maize were exposed to 14 MeV neutrons with single or fractioared treatments, and pollinated on the recessive stock. Mutation frequency from Bz to bz was observed after harvest of F1 seeds. No clear difference in the mutation frequencies between single and fractionation series was observed. To investigate the effects of water content upon mutation frequency of neutron and gamma-rays, seeds heterozygous for the Yg2-gene were used. Moisture-stabilized (13%) seeds and seeds steeped in water for 24 hrs were exposed to neutrons or to gamma-rays, and mutation from Yg2 to yg2 was detected as color change green to yellow-green in the seedlings. In the gamma-ray treatments, the mutation frequency of wet seeds was about 1.5 times higher than that of corresponding lot of dry seeds. In the neutron treatment, on the other hand, no clear difference in frequency between wet and dry seeds was observed. It may be concluded that no change or no recovery in neutron-induced mutation was observed not only in the fractionation treatment but also in the dryy and wet seeds treatments.
99mTC-Pertechnetate was used for the diagnoses of the upper gastrointestinal tract. Oral administration was useful for the detection of the stenosis and obstruction on the esophagus and the pylorus to the poor risk patients. Mucosal imaging of the stomach was clearly revealed by intravenous administration, and the scintigram of the patient with stomach cancer showed a cold region. Taking the gastric scintiphoto, temporal radioactivity in the stomach region was recorded (gastrogram) . This seems to be a new and prospective approach to the clinical gastroenterology.