We performed myocardial scan using201TlCl and 99mTc-methoxy isobutyl isonitrile (99mTc-MIBI) in 16 patients of myocardial infarction and compared their diagnostic value. In view of image quality, 99mTc-MIBI scan was superior to201Tl scan in 11 cases, and201T1scan was superior in no case. There was no statistically significant difference between99mTc-MIBI scan and201T1 scan in sensitivity (88.9% and 83.3%, respectively) and specificity (83.9% and 80.6%, respectively) . It is concluded that99mTc-MIBI enables us to perform high quality myocardial scan and is clinically useful.
In the measurement of environmental radioactivities by Ge detector, the calibration curve of the full-energy peak efficiencies needs to be obtained from standard γ-ray sources. When high energy γ-ray emitters viz., 60Co or88Y are used as standard sources, the correction of coincidental summing effects is necessary for estimating true peak efficiencies. It, however, requires complicated calculations and a simpler way to obtain the ralibration curve has been desired very much. It is well known that the more the distance between a counting sample and a detector endcap is, the less becomes the summing effect, though the efficiency of the measurements may increase. This interrelation, however, seemed still indistinct and the present paper intended to find the optimum source distance to minimize the measurement error and the summing effects without the complicated calculation for the correction. The results indicates that the error of the measurements can be practically low enough without the correction of coincidental summing effects for our detecting system, when the source distance from the detector endcap is about 3 cm.
We bored four samples (5cm diam. by 50cm length) from concrete side walls in the operating radiation facilities. And the gamma rays of radioisotopes induced in samples were measured with a pure Ge detector. So we identified eight radioactive nuclides of46Sc, 59Fe, 60Co, 65Zn, 134Cs, 152Eu, 54Mn and 22Na. From the measurement it was confirmed that the radionuclides induced by thermal neutrons through the (n, γ) reaction are dominant, and that the induced activity by thermal neutron is higher at 5 to 10 cm depth rather than at the surface of concrete and decreases rapidly according to the exponential function beyond about 20 cm depth.