Removal of239Puwith or without accompanying fission products from aqueous solution by coprecipitation with iron (III) hydroxide has been studied as functions of solution pH and the concentration of239Pu, the coprecipitant, and sodium nitrate added to the mixed system. It has been shown that239Puis removed in a more extent with the increased pH throughout the range of pH 5-8, beyond which the decontamination factor is saturated to give a constant value of (3-4) ×102up to pH 12. An addition of the electrolyte, sodium nitrate, did not affect the removal of239Puthroughout the concentration from 0.1 to 1 M, whereas at the concentration of 0.01 M, iron (III) hydroxide was dispersed finely to result in the formation of a colloidal solution, that led to a decreased DF value. The coprecipitant concentration required for the sufficient removal was found to be ca. 500 ppm. The DF value was not much dependent on the239Puconcentration in the range of 1×10-4to 2×10-1μCi/ml. DF of239Puremained unchanged by the addition of fission products to the contaminant solution. An additional procedure for the subsequent removal gave approximately the same DF value as the first treatment for removing239Puor95Zr-95Nb, whereas the successive removal of144Ce, 90Sr-90Y, or106Ruwas effected scarcely by the second treatment in comparison with the first.
Transmission scintiphoto was taken using a gamma-ray point source and a convergent 1261 hole focusing collimator. In addition, X-photo and scintillation image taken by keeping X-ray tube-film distance equal to focus-scintillator distance had the same rate of magnification and both the images were superimposable. If we use an attachment to reproduce the same geometry in recording scintillation image and X-photo, these images can be double exposed on the same X-ray film. Thus the localization of scintillation image can be easily determined by the present method, especially in combination with X-photo. The present method would be useful not only for diagnosis, but also for therapy.
The 5 in. dual headed whole body scanner, which we use in routine tests, has three operation modes of addition, subtraction, and positron scanning besides ordinary one. We studied diagnostic usefulness of the latter two, subtraction and positron modes. The word“subtraction scanning”in this study has different meaning from the usual subtraction technique. In our subtraction method, the image on the scintigram can be made by counting differences of output signals from upper and lower detectors. Therefore, two scintigrams, positive and negative, can be obtained simultaneously. Collimators of good resolution are not always necessary for this technique. Positron scanning is one of the established scanning techniques. However, unless the sensitivity of crystal is large enough, it is usually difficult to get a good result. So they don't use much in our country till today. We used two detectors, one with a focusing collimator and the other with no collimator. Both scannings, subtraction and positron ones, have less counting dots on the scintigrams compared with the ordinary scanning. If we use larger doses of radioisotopes with shorter half-lives and with no beta particles, the scintigram of good contrast and sharp quality can be obtained by these techniques.
In isosensitive radioisotope scanning system the delineation of the radioisotope distribution is completely independent of depth. Coupling of 4, 096-word multi-channel analyzer to the isosensitive scanner makes it possible to evaluate radioisotope distribution in vivo quantitatively and provides various new diagnostic tools; for example, spleen/liver ratio, pancreas/liver ratio, profile histogram of lung perfusion scan and tumor net counts in brain scan and so on.
For easy measurement of thyroid hormone (Thyroxine: T4) in blood, Res-O-Mat T4Kit method, an in vitro assay method using radioisotope, has been developed by Mallinckrodt Chemical Works. We studied 374 cases of various thyroid diseases using this kit in comparison with four other assay methods: Thyroid-131I uptake, Tetrasorb (T4), Triosorb (T3), and Thyopac 3 (T3) methods. A very good correlation between Res-O-Mat T4Kit method and Thyroid uptake (24-hour value) method was obtained. It was observed that the values obtained by Res-O-Mat T4method were equal to those obtained by Tetrasorb method multiplied by 0.915. It was required in this method to keep the room temperature at 25°C, and to be incubated (rotated) exactly for 60 minutes.