A low noise charge-sensitive preamplifier for scintillation detector system using the photodiode read-out of scintillation light has been developed. The input stage of the preamplifier consists of four selected FFTs (2 sk 505, gm=26 mS) . The characteristics of the preamplifier are obtained as: (1) rise time is less than 10 ns, (2) ENC (equivalent noise charge, FWHM) =1.1×10-16C with connected to the S 1723-06 photodiode (Hamamatu photonics, sensitive area 10 mm×10 mm), (3) open loop gain =2.4×104. Using this low noise preamplifier, the scintillation spectrometer system has been constructed with a 10×10×10 mm3 CsI (Tl) scintillator and S 1723-06 photodiode, the energy resolutions of which have been 6.1% and 42% (FWHM) for 662 keV and 60 keV gamma-rays respectively. As another application, the α-ray detector has been successfully constructed using the present low noise preamplifier attached to the S3204 photodiode with ZnS (Ag) scintillator, where the equivalent noise charge of the system was as low as 3×10-16C.
Synthesis of 14C-labeled 4-ethoxy-2, 3-benzodioxin-1-ol (EtO-BD) from [1 (4, 5, 8) -14C] naphthalene and the decomposition behavior of the labeledEtO-BD are described.14C-EtO-BD is stable over months as long as kept at . -40°C as a solid state, and over weeks in acetonitrile. The decomposition ofEtO-BD is facilitated by the presence of H2O giving rise to two major decomposition products, o-phthalaldehydie acid and its ethyl ester. Thus the generation ofOHradical is expected on its decomposition path and is enhanced as increasingH2O concentration.Fe (II) seems to facilitateEtO-BD decomposition through the electron transfer reaction.
201Tl myocardial SPECT were performed to evaluate of cardiomyopathy in Duchenne type o progressive muscular dystrophy (DMD) . Follow up SPECT images of the same patients were also obtained about 1 year after the first scan. Cases subjected to study were 10 DMD. At the first study the hypoperf usion area of the left ventricular muscle were observed in 6 cases (60%) out of 10. At the second study the hypoper fusion areas became wider and lower in 4 out of 6 cases (66.7%) . The new hypoperfusion area which was not demonstrated at the first study was observed at the second study in one case of these cases. These results suggested that the positive rate of cardiomyopathy in DMD by 201Tl myocardial SPECT was high, and 201Tl myocardial SPECT is a useful examination to detect the change of myocardial damage in DMD.
The authors developed an integrated system for managing the safe use of radioisotope laboratory facilities, users' access to controlled areas, and the control of air-conditioners. This system consisted of a personal computer, an access controller, an eye retinal verifier, magnetic card readers, hand foot cloth monitors, video tape recorders and a fire alarm system. The access controller was set as the central unit to operate the whole system including 13 gates and air-conditioners. Under this program, only registered persons were permitted to enter the laboratories; the exact records on access were easily obtained; and electricity and fuel expenses were largely reduced. We expect that the system would facilitate the safe use of radioisotopes and the utilization of laboratory facilities.
In connection with low-level γ-ray counting of natural samples, background due to 220Rn-and 222Rn-daughters was monitered. The results obtained for 4 months showed that the background γ-ray from 222Rn-daughters was more variable than that of 220Rn-daughters. An efficient air-conditioning was helpful to keep the background stable. It was practically equivalent to the use of N2-gas. Radiometric data for dust samples filtered from the laboratory air suggested that Rn-daughters tended to be removed by air-conditioning.
Improving the smear efficiency and the stability of smear method on the monitoring of radioactive floor surface contamination, wet smear method by a water sprayer was designed and examined. And as the temporary decontamination method applied to the wide spread radioactive floor surface contamination, the method by a vacuum cleaner (vacuum cleaner method) was examined. These examinations were carried out by the experiment using the lonleum floor sheets waxed and the various types of pharmaceutical compounds labeled with 99mTc. On wet smear method, the smear efficiencies were larger than 50% and coefficient of variations by far smaller than that of dry smear method (usual smear method) : for all the radiopharmaceuticals examined. These results showed the effectiveness of wet smear method. On vacuum cleaner method, the decontamination coefficients were comparatively large and almost same to that by wet duster method (decontamination method by using the wet duster) except Ringer's solution and DMSA what had less removable part of contamination. These results showed the effectiveness of vacuum cleaner method for the removable parts of contamination.