6-Deoxy-6-[18F]fluoro-L-threo-2,3-hexodiulosonic acid γ-lactone(6-[18F]fluoro-dehydroascorbic acid, 18F-FDHA)was synthesized by oxidation of 6-deoxy-6-[18F]fluoro-L-ascorbic acid(18F-DFA)with Br2, a route that is analogous to the original synthesis of FDHA, in order to develop a radiotracer for nuclear medical imaging. Tissue biodistribution of 18F-FDHA in fibrosarcoma-bearing mice showed a low accumulation of radioactivity in the brain, with both substantial in vivo defluorination and low tumoral uptake levels. Several organs of mice unfed for 24h showed a more significant increase in radioactivity postinjection of 18F-FDHA than did fed mice. Co-injection with 2-deoxyglucose of 18F-FDHA did not significantly alter brain and tumor uptake, as confirmed by tissue-to-blood ratios, and as compared to control experiments. Thus, 18F-FDHA does not exhibit desirable properties as a brain-targeting imaging agent for ascorbic acid bioactivity.
In order to understand the characteristics of terrestrial gamma ray dose rate levels in sedimentary rock areas of the Japanese Islands, statistical data were investigated for two parts in various areas, i.e., the Cenozoic sedimentary bedrock part and the corresponding hinterland in each area. As a result, the dose rates in sedimentary rock parts showed around 10% lower than those in the hinterlands. Furthermore, it was found that the ratio between the coefficients of variation for the above two parts depended considerably on geological time.
The analytical yield of gamma emitters in seawater by coprecipitation method with nickel hexacyanoferrate(II)and iron(III)hydroxide was confirmed using spiked radioisotope(137Cs)and stable elements. Ninety-nine% of spiked 137Cs was adsorbed on nickel hexacyanoferrate(II), and 88–94% of spiked Ce, Co, Mn, Ru, Zn, Zr was adsorbed on iron(III)hydroxide. This analytical method is considered to be very efficient and practical for environmental radiation monitoring from the view of quick and simple operation, especially easy analysis of plural samples.
The Medical Science and Pharmaceutical Committee of the Japan Radioisotope Association proposed to establish the national guidance for the clinical use of radiotracers labeled with short-lived positron emitting radionuclide in November, 1980, and started the Sub-committee on Medical Application of Cyclotron-Produced Radionuclide(re-named as Sub-committee on Application of Positron Nuclear Medicine in November, 2005). This sub-committee served to publish “recommendations on clinical use of ultra-short lived radionuclide produced by accelerators in medical institution or medical research facility”. It approved the radiotracers, which showed safety and clinical value, as established technique, and set the standards for production and quality control of the tracers. A total of 15 tracers have been approved as established technique.
As regards the application required for health insurance of PET, the Ministry of Health, Labour and Welfare indicates the following procedures : first, request a permission to the Ministry of Health, Labour and Welfare for the clinical use of the automatic synthetic instrument for PET drug, approved according to the Pharmaceutical Affairs Law. Second, put into practice the use of PET test, under the highly advanced medicine premises. Then, in case of gathered positive results, the health insurance is approved for this PET test. Thus, following the above mentioned procedures, first, the use of [15O]oxygen PET was approved in April 1996. Second, the use of [18F] FDG-PET was approved in 12 different diseases : epilepsy, ischemic heart disease and 10 different types of cancer, in April 2002. Third, in April 2006, an additional 3 types of cancer were approved. Now, we are in the process to get the health insurance of all kinds of malignant tumors(cancer and sarcoma)except for the early gastric cancer.