This study was carried out to design a new collimator for the present123I-IMP SPECT imaging of the brain, which is hindered by the contamination of124I and126I. In this study we intended to increase spacial resolution along the transaxial direction and, at the same time, to compensate for the decrease of sensitivity by sacrificing the resolution along the axial direction to some extent. For this purpose, we developed 4 kinds of slat type units; ultrahigh resolution (UHR), high resolution (HR), high sensitivity (HS), and ultrahigh sensitivity (UHS) . In practice, either UHR or HR is set to the detector together with either HS or UHS. After testing 4 kinds of combinations, we found that the combination of UHR-HS gave us far better images than those obtained with the conventional medium energy parallel hole collimator and was best suited for123I-IMP SPECT imaging of the brain at present. We are now thinking of fusing these two units together into one collimator.
Translocation of131I to ears of rice plant at the end of milky stage was investigated. A small piece of absorbent cotton wool containing 185 kBq (5μCi) of Na131I solution was placed on the flag leaf (n-th leaf) surfaces. Three days after that, 131I was detected in the ears autoradiographically. In the same way, the cotton was placed on the lower leaf surfaces. More than 10 days were needed to find131I in the ears. A 20 μl of Na131I solution (3.7 kBq (0.1μCi) ) was administered to the basal part of the flag leaf by using micropipet. Only two days after administration, 131I was clearly found in the ears also autoradiographically though the dose was only one-fiftieth for foliar administration. It can be supposed that the translocation of131I to the ears from basal part of the flag leaf is faster than that from the leaf surfaces. Rice plants were grown in the beaker containg 25 ml of deionized water with 740 kBq (20 μCi) of Na131I for 0.2, 1 and 2 days. Iodine-131 was detected almost all parts of the plants. In general, there are two transport systems in the plants, that is, xylem system and phloem system. Foliar and basal part uptake-translocations are taken place through the phloem system, while root uptake-transport is through the xylem system. It was observed that131I in the xylem system was transported to hull, while that in the phloem system more to brown rice than to hull.
The decomposition yields for crystalline alkali metal oxalates and some oxalates by γ-ray irradiation in the presence of air at room temperature were determined by UV and IR spectro-photometry. A logarithmic plot of the yields for alkali metal oxalates against metal-oxygen bond energy gave a good correlation, except for rubidium oxalate.
The additional absorbed radiation doses to total body from radioactive impurities in radiopharmaceuticals were estimated for a total of 10 samples (i.e., 99mTc generator eluates, 99mTc solutions, 67Ga, 81mKr generator eluates, 111In, 123I, 201Tl, 75Se, 197Hg, 198Au) selected from commonly used radiopharmaceuticals. The radioactive impurities in radiopharmaceuticals used in this estimation were previoulsy identified. The radiation doses were calculated according to the MIRD procedures, assuming each radionuclide to be uniformly distributed throughout the body. In the case of the cyclotron-produced radioisotopes and198Au, the additional total body absorbed doses from impurities were found to be rather high: 280% for123I, 55% for81mKr, 5% for198Au, 4% for111In and 2% for201Tl. The absorbed doses due to impurities in the other radioisotopes were less than 1%.