For Ge (Li) γ-ray spectrometry performed in the presence of some Compton interferences, the estimation of optimum cooling interval by mathematical or graphycal method has been discussed, and the recommended cooling intervals available to the actination analysis of unknown samples, which has not been discussed so far, have been proposed, and applied to the non-destructive activation analysis of gold in pure copper. In the presence of Compton interferences, two kinds of optimum cooling intervals had been discussed by some authors. One is a cooling interval which maximizes the S/N ratio of a desired photo-peak. The interval had been originated by Isenhour, et al. with the computer technique, and in this work it is abbreviated as ts/N. The other is a cooling interval which minimizes the relative standard deviation (σs/S) of a net photo-peak counting rate of interest (S) . The interval had been originated by Tomov, et al. and Quittner, et al. and in this work abbreviated as topt or t'opt. All the equations derived by above authors, however, have a disadvantage from the practical viewpoint: of including the term relating to the intensity of the desired photo-peak, thus making it difficult to predict the optimum cooling interval before irradiation, because in the chemical analysis the concentration of the desired element, or the intensity of the photo-peak of interest, should be considered as “unknown”. In the present work, an approach to the selection of recommended cooling interval applicable to the unknown sample has been discussed, and the interval, topt, which minimizes the lower limit of detection of a desired element under given irradiation and counting conditions has been proposed. The topt can be obtained mathematically as the cooling interval which minimizes the σs/S of a fine photo-peak assumed near to detection limit. In the practical measurement, if the intensity of the desired photo-peak in the sample is not near to detection limit, the recommended interval of course does not agree with the “optimum”interval for the large photo-peak, namely t'opt shown by equation (8) for example. However, the error never leads to any trouble for the practical work, because even at topt all the photo-peaks larger than detection limit would be certainly measured with the satisfactory precision required for activation analysis. When the interfering nuclide is only one, topt is calculated by equation (7), where T1/2sand T1/2lare the half-lives of a desired nuclide and its interfering one, respectively, and N01is the interfering activity (counting rate) under the photo-peak of interest, and Nb is a natural background counting rate. On the other hand, as shown in Table 1, tS/N gives almost the same precision as topt, although not “optimum” strictly. Thus, it can be available instead of topt in the practical work, and the interfering nuclide being only one, tS/N is calculated by equation (9) . When the interfering nuclide is not one but a few, equations (7) and (9) can be sometimes available by simplifying the interferences as follows: (i) When there exist some interferences arising from very long half-lives nuclides (but relatively comparing to N01), they can be added in the term of Nb. (ii) There existing some interferences arising from the same or near half-lives nuclides to N01, they can be added in the term of N01. (iii) If T1/21>>T1/22and N01>N02, or T1/21>T1/22and N01>>N02,
Results are presented of investigations leading to the development of a procedure for the simple and rapid determination of trace amounts of tin in metallic antimony by neutron activation analysis. The irradiated target was rapidly dissolved with hydrochloric acid in the presence of potassium bromate. Tin was separated from matrix element antimony by the isopropyl ether (IPE) extraction from 0.8M hydrochloric acid containing 2M ammonium thiocyanate and the activity of123Sn (half life, 39.5m) or125Sn (half life, 9.8m) was counted. Since the extraction yield of tin is found to be quantitative, no yield correction is needed. Only about one-third hour is required for the analysis of trace amounts of tin in metallic antimony, including the time for irradiation of the sample. The limit of detection is estimated to be ca. 0.1ppm when the time of neutron irradiation and of the counting are 5min and 400sec respectively.
Scan conversion memory (SCM) has been applied to a method of the storage and the display for radioisotope imaging. Scan data were fed in SCM as pulse signal with X and Y axis from the scinti-scanner or the scinti-camera. Electric charge on the target of SCM is directly proportional to pulse density. A display by the TV system was immediately executed after the record of a radioisotope image. If necessary, seven additive color display to the image density was able to be obtained by a simple color slicer, and image can be hard-copied by a video hard-copy printer. The characteristics of the SCM has been experimentally clarified as follows: practical resolution was 700 line/TV, ten levels gray scale were discriminated on the video monitor, uniformity measured by an oscilloscope was less than 20%, and dead time of the pulse interval at the full scale signal was 5μsec. The SCM scnitigrams were observed as representation closely resembling conventional film scintigrams. Superimposed image of a X-ray picture and a radioisotope image can be realized by using the SCM, for an increase in anatomical localization on reading images. SCM scintigram can be applied fast and pre viewer of radioisotope imaging.
The isolation and characterization of metabolites excreted in urine of rat were studied following oral administration of14C-glipizide. Five metabolites and a small amount of the unchanged compound were isolated from urine samples of rat and their structures were elucidated by thin-layer chromatography and by various spectroscopic analysis. As the results, 3-cis-, 4-trans-hydroxycyclohexyl derivatives, decyelohexyl derivative, hydroxymethyl derivative and hydroxyethyl derivative were identified or suggested. The relative amount of each metabolite excreted in the urine differed remarkably according to the species of animals used: in rat and mouse major metabolites were 4-trans-, 3-cis-hydroxycyclohexyl derivatives and decyclohexyl derivative; in guinea-pig 4-trans-, 3-cis-hydroxycyclohexyl derivatives and hydroxymethyl derivative; and in rabbit hydroxymethyl derivative. In dog, cat and monkey N- (4-carboxymethyl-benzene-sulfonyl) -N'-cyclohexyl-urea was suggested to be a major metabolite.
Five cases are presented in which lesions affecting the spleen were suspected either clinically or on routine99mTc-sulfur colloid liver scans. Using99mTc, transmissionemission scans were performed on these patients; these scans were all abnormal. Subsequent diagnostic studies confirmed three real lesions. The other two patients had intrathoracic abnormalities producing the abnormal scans. The technique, advantages, and limitations of transmission-emission scanning for detecting space-occupying lesions of the left upper quadrant area are discussed.
Since first suggested in 1964, 131I-labeled macroaggregated albumin (MAA) has been used as a pulmonary perfusion scanning agent. 99mTc has the favorable physical characteristics of high photon yield, low radiation dose and easily collimated 140 keV gamma-ray emission. Many reports have appeared in the literature on the preparation and use of99mTc-MAA for lung scintigram. However, there has been technical difficulties that preclude the use of99mTc-MAA in routine clinical practice. Recently, a kit for99mTc-labeled stannous macroaggregated albumin has become supplied commercially. The purpose of this study is to evaluate animal tissue distribution, clearance and clinical utility of99mTc-Sn-MAA. In comparison with99mTc-human albumin microspheres which was the first commercially available agent of this type, its preparation is easier and labeling efficiency is better. In experiment of mice, 96.5% of the particles were deposited in the lung and few per cent, which was in the liver and the kidney, was increased at 2 hours after injection. Biological clearance from the lung occurred with a T50% of about 7 hr contrary to the simultaneous increase in hepatic activity, in rabbits. In clinical experience, the quality of lung image was excellent and lesions were more distinctly defined with99mTc-Sn-MAA than131I-MAA And no severe reactions were observed in a series of 124 patients with a variety of pulmonary disorders. Liver and kidney activity never interfered with interpretation of the lung scintigram obtained immediately after injection. 99mTc-Sn-MAA should prove to be a very useful agent for pulmonary perfusion imaging.
198Au-colloid has been widely used for liver scanning in Japan but it is not the best scanning agent because of large exposure dose to the patients. We performed a few basic experiments about99mTc-phytate, of which preparation is very easy. The labeling efficiency was found to be 97.5% immediately after preparation and it remained fairly stable in the course of time. As a result, the compound can be used within 6 hours after preparation without fear of chemical instability. Liver scanning with93mTc-phytate was done in 116 patients and was compared with198Au-colloid liver-scanning. Scans made with99mTc were found to be superior to those made with198Au in the resolution of surface defects in the liver, while at increasing depths the resolution with99mTc dropped rapidly, apparently due to absorption of its relatively low energy photon. This indicates the importance of taking multidirectional views. The degrees of splenic concentration of99mTc-phytate were fairly close to those of198Au-colloid. Therefore, liver scanning with99mTc-phytate is useful in the diagnostic evaluation of diffuse parenchymal liver disease.