An effect of the electric charges on a radiation source in 4πβ and 27πβ gas flow counter was examined. This effect gave serious damage on counter characteristics such as plateau curve. The lower side anode of the box type 4πβ proportional counter was replaced by a source holder. A vibrating reed electrometer with resistor of 109-1013 ohms or a constant voltage power supply were connected between the source backing film and the cathode, and current on the backing film was measured or some potential was supplied on the backing film. At the same time, the plateau curves of upper half 2πβ proportional counter were taken. 60Co beta-ray source on an aluminum foil was placed on the source holder. The results were as follows: a) Plateau curves were shifted to higher supply voltage linearly with source potential. Ratio of the shift of starting voltage to source potential was 0.26-0.64, and it varied with the diameter of source backing film and anode shape. b) Higher electric resistance between the source backing film and the cathode of 22πβ counter gave higher plateau threshold voltage and longer plateau length, but the starting voltage was not changed. c) Finally, when the counting rate of 27πβ counter was about 104 cpm, electric resistance between the source backing film and the cathode should be maintained lower than 1010-1011 ohms.
The distribution of 228Th and 228Ra concentrations in the sediments around a river mouth was studied. High resolution gamma-ray spectrometry with a Ge (Li) detector made it possible to analyze the radionuclides in the sediment samples without chemical treatment. The activities of 228Th and 228Ra were determined from the activities of their daughters, i.e., 212Pb, 208Tl and 228Ac. Samples containing monazite sand of known activity were used as the standards in which the thorium series radionuclides were in secular equilibrium. It was shown that the radionuclides were mostly accumulated in a narrow band stretching along the stream from the river. The activity ratios of 228Th to 228Ra were large at the river mouth and at the places aside the band. The activity ratios of 228Th to 232Th were also measured with alpha-ray spectrometry using a double grid ionization chamber. These studies made clear the situation of the fractionation effect around a river mouth due to the difference of chemical properties between thorium and radium in the sea water.
The investigation has been carried out to find a proper sample preparation and a proper standard material for accurate determination of oxygen in organic substances by fast neutron activation analysis, wherein a serious systematic error due to Q-ray self-absorption is always in problem. It was confirmed from the present work that the error mainly depended on the difference in density between a sample and a standard material and that it was effectively eliminated by using a mixture of stearic acid and solid paraffin as a standard and also diluting the sample with solid paraffin. For most of organic samples, eight times dilution was found to be enough to lower the relative systematic error down to 2%.
As radiation due to radioisotope decay is discontinuously emitted, its data analysis can be done very easily by digital method. So it was rather early that a computer was applied in the field of nuclear medicine using radioisotope. Especially the processing of storage, calculation and display for radioisotope image data obtained by a scintillation camera and scanner was studied using a computer system. In order that processed images might become useful in clinical routine, an online computer system is indispensable which could obtain results at real time. Then we studied how much scale computer should be installed in an on-line system according to memory capacities and display resolution. An ideal plan should be on-line connecting with an image memory unit, a central processing unit and a display unit each other and of being controlled each part of them by the computer as a central processing unit. But at the present time, either a mini-computer or a small hard program computer is used both a memory unit and a processing unit. Memory capacities for calculation depend upon the purpose of processing but 8 kilo words were enough for complicated calculation. And as the capacities for the data storage 16-20 kilo memory elements (about 8 bits/element) were needed, and 5×104 counts or so must be accumulated to make an image. Also as the numbers of display points in an image using cathod ray tube (CRT) 16-100 kilo points might be necessary for a fine grain and continuous display according to a size of a spot on the CRT used now. For the purpose of increasing display points, it was considered as a reasonable solution to use an interpolation method instead of expansion of expressive magnetic cores.
Under standard clearance conditions, twenty-nine simultaneous measurements of 169Yb-diethylenetriamine pentaacetic acid (169Yb-DTPA) and exogenous creatinine clearances have been performed in dogs, in which renal function was varied by stenosing renal artery. A good correlation between both groups of comparative studies was found over a wide range of clearance values. (regression equation; y (169Yb-DTPA) =0.933×x (creatinine) +0.5, coefficient of correlation: 0.99) . However, compared with thiosulfate clearance in twenty-five patients with normal and impaired renal function, 169Yb-DTPA clearance showed lower value than that of thiosulfate. This discrepancy may be probably due to tubular excretion of thiosulfate, because an excellent agreement with 169Yb-DTPA clearance was found when thiosulfate clearance was estimated during high plasma concentration (25mg/dl), and thiosulfate clearance obtained during low plasma concentration (20 mg/dl) averaged 1.2 times as much as that of 169Yb-DTPA. From these results, it seems that 169Yb-DTPA provides convenient substance for measurement of glomerular filtration rate not only in animals such as dog but in clinical use.
A method of insulin radioimmunoassay with Sephadex-bound antibody (Phadebas® Insulin Test) was tested for the determination of serum insulin. The time to reach the maximal binding rate of insulin to the solid phase antibody was not so different to that of two antibody method. But enough accuracy for the practical purposes was obtained in overnight incubation. The insulin values obtained with this method was well in accord with that with the two antibody method in good conditions, and was not interfered by the presence of serum proteins, judged from the results of recovery test. Though this method was a little less sensitive and accurate as compared to the two antibody method, this method was simple and convenient and has enough sensitivity and reliability for the usual routine serum insulin assay.
The distribution patterns of tritiated trimetoquinol (AQL-208), its O-dibutyrylated derivative (BAQ-509) and glucuronide of AQL-208 (main metabolite) administered orally were studied in mice by whole body autoradiography. O-dibutyrylated derivative of trimetoquinol was more quickly absorbed from the gastrointestinal tract than trimetoquinol. But there were not essential differences between the disribution patterns of both compounds. The highest accumulation of radioactivity was recorded in the liver, kidney, lung, gall bladder and urinary bladder. The blood and the connective tissues displayed strong and stable amount of radioactivity. At 24 hr after administration hardly any radioactivity could be observed in the body of the mice.3H-BAQ-509 hardly passed the placental barrier and the blood-brain barrier. After oral administration of tritiated glucuronide of AQL-208, it was found that the absorption from the intestine was considerably small. Most part of the absorbed amount was circulated from the liver into intestinal lumen via bile, while minor part of it was excreted via kidney.