For the estimation of dose equivalent and collective dose equivalent from veterinary radiographic diagnosis a nationwide survey of randomly sampled hospitals and clinics was carried out concerning number of radiographs and fluoroscopic examinations performed in 1985-1986. The resultant annual number of radiographs was 2, 310 thousand for small animals and 110 thousand for large animals with a total of 2, 420 thousand. The total time of fluoroscopic examination was 3, 000h. Animals were exposed to diagnostic X-rays according to technical factors of typical radiographic and fluoloscopic examinations obtained from a nationwide survey to estimate the dose equivalent to holding assistants whose doses were determined using ionization chambers and thermoluminescent dosimeters placed at the position of the chest pocket. The resultant annual collective dose equivalent was 1.06 man Sv for radiographs and 0.34 man Sv for fluoroscopic examinations with a total of 1.40 man Sv (140 man rem). The average annual dose equivalent per person was estimated to be 78μSv.
We have previously reported that the side effects on cardiovascular system such as the heart failure, increases of blood pressure and pulse accompanied with hypocalcemia occurred in rats when Zn-DTPA was injected intravenously, but those did not occur by Ca-DTPA. This is in the reverse that it is generally said that Zn-DTPA is more safe than Ca-DTPA. This study was carried out to examine whether the same side effects occurred in different animal species or not. Zn-DTPA or Ca-DTPA (30, 150, 300 and 600μmol/kg) was injected intravenously to beagle dogs. The hypocalcemia was observed in the dogs by Zn-DTPA injection, but it was not by Ca-DTPA. After Zn-DTPA injection, the increase of blood pressure and pulse, and heart failure was observed in 3 out of 5 dogs at 300μmol/kg dose, and in 3 out of 8 dogs at 600μmol/kg dose. These changes were the same degrees as those in rats. In the present study, it is suggested that the side effects induced by Zn-DTPA intravenous injection occur independently of animal species and the data obtained from animal experiments can be available to estimate DTPA toxicity in humans.
Ground level cosmic ray pulse height spectrum of a 7.5cm diameter spherical NaI (T1) scintillation detector was evaluated through stripping operation based on a pulse height spectrum measured on the sea and high precision response functions of the detector for U-series, Th-series and 40K. The exposure rate calculated from the determined cosmic ray pulse height spectrum was 0.21μR/h eq., which agreed well with that obtained from another method. The shape of the pulse height spectrum showed similarity to that measured at the altitude of 16, 000 ft, especially in the energy region of 0 to 3MeV. The principle of the adopted method is rather plain, however, the reliability of the spectrum is satisfactory. As the pulse height spectrum is a common information to any analytical method for environmental gamma ray using NaI (T1) scintillation detector, it is expected to be used for simple and precise separation of cosmic ray component involved in the enviromental pulse height spectrum.
It is important to know the over-all counting efficiency of measuring apparatus. In this work, the counting efficiency of ZnS (Ag) scintillation counter was discussed with regard for counting radon daughter products sampled on a filter paper. The results are as follows; (1) It is unsuitable to use a counting efficiency for sources such as U3O8 or Am-241 instead of using radon short-lived daughter products. (2) The counting efficiency of ZnS (Ag) scintillation counter is decided from results obtained by counting radon short-lived daughter products on a membrane filter with gridded ionization chamber. (3) The over-all counting efficiency is obtained from product of the counting efficiency of detector, the emerging efficiency and the sampling efficiency.