Development of a nickel plated aluminum krypton-81m target system.

A fully automated system was developed to produce rubidium-81 (81Rb), based on the natKr (p, n) 81Rb reaction. The energy incident on the target was 26MeV. Only 6MeV was stopped inside the gas and the remainder was stopped by a specially designed flange. The target body was characterized by its conical shape and its inner walls were chemically plated with 100±10µm of nickel (Ni). Ni is advantageous as a fairly good conductor of heat whose surface can resist solutions. Additionally, the Ni plated target allowed potassium chloride to dissolve 81Rb, with no further effect on the target body. The system produced 81Rb with a production yield of approximately 4.5mCi/µAh, which is close to the calculated expected yield of 5.3mCi/µAh. The system is able to deliver reliable and reproducible radioactivity for patients and can be operated up to 1500µAh before preventive maintenance is due. Key steps in designing the 81Rb target for selected energy ranges are reported here.

Production cross sections of radioisotopes from 3He-particle induced nuclear reactions on natural titanium.

Excitation functions were measured using the stacked-foil method for the natTi(3He,x)44mSc, 46m+gSc, 47Sc, 48Sc, 48V and 48Cr nuclear processes up to 68MeV. Our new cross-section data were compared with the earlier reported values as well as the evaluated theoretical predictions by means of the TALYS 1.6 code as compiled in the TENDL-2015 library. The new data show acceptable agreement with the previous experimental values in the overlapping energy regions, however only a partial agreement was found in the case of the results of the nuclear reaction model code. The present work not only strengthens the experimental datasets of the above processes but also provides new cross-section values above 36MeV where only one dataset is available for each reaction.

A singly charged ion source for radioactive ¹¹C ion acceleration.

A new singly charged ion source using electron impact ionization has been developed to realize an isotope separation on-line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive (11)C ion beams. Low-energy electron beams are used in the electron impact ion source to produce singly charged ions. Ionization efficiency was calculated in order to decide the geometric parameters of the ion source and to determine the required electron emission current for obtaining high ionization efficiency. Based on these considerations, the singly charged ion source was designed and fabricated. In testing, the fabricated ion source was found to have favorable performance as a singly charged ion source.

Cryogenic molecular separation system for radioactive (11)C ion acceleration.

A (11)C molecular production/separation system (CMPS) has been developed as part of an isotope separation on line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive (11)C ion beams. In the ISOL system, (11)CH4 molecules will be produced by proton irradiation and separated from residual air impurities and impurities produced during the irradiation. The CMPS includes two cryogenic traps to separate specific molecules selectively from impurities by using vapor pressure differences among the molecular species. To investigate the fundamental performance of the CMPS, we performed separation experiments with non-radioactive (12)CH4 gases, which can simulate the chemical characteristics of (11)CH4 gases. We investigated the separation of CH4 molecules from impurities, which will be present as residual gases and are expected to be difficult to separate because the vapor pressure of air molecules is close to that of CH4. We determined the collection/separation efficiencies of the CMPS for various amounts of air impurities and found desirable operating conditions for the CMPS to be used as a molecular separation device in our ISOL system.

[18F-FDG injections produced by a solid phase 18F-fluorination (FDG MicroLab): effects of 18F-FDG and the components on endotoxin and sterility tests].

Effects of 18F-FDG and components of the injections on endotoxin tests (Limulus tests) and sterility tests (Blood culture system) were determined with 18F-FDG injections produced by a solid phase 18F-fluorination (FDG MicroLab, GE). 18F-FDG injections with endotoxins shortened the time for gelling (turbidimetry), compared with that of the control (saline). Blood culture systems inoculated with 18F-FDG injections and microorganisms showed positive results within 72 h of incubation for every species of microorganisms used in the present study (Bacillus subtilis, Candida albicans, Clostridium sporogenes, Micrococcus luteus). These results were quite similar to those for the control samples inoculated with saline and the microorganisms. Consequently, 18F-FDG and the components of the injections produced by the present methods may not significantly affect the endotoxin tests and sterility tests.

Performance assessment of O-18 water purifier.

In the synthesis of 18F-FDG by the nucleophilic substitution method, 18O-H2O is usually used as target water. The target water should be recovered after synthesis and reused, because it is expensive, but recovered water contains impurities such as organic substances, and it must be purified before reuse. For this reason Sumitomo Heavy Industries, Ltd. developed an O-18 water purifier for elimination of organic substances in recovered water. This instrument consists of a UV irradiation unit and low-temperature distillation unit. Our institution had an opportunity to test use this instrument and evaluated its performance. The concentrations of organic substances after UV irradiation was greatly reduced, and recovery efficiency after distillation by the low-temperature distillation unit was very satisfactory at 99.3 +/- 0.5%. Furthermore, the yield of 18F-FDG from 18O-H20 purified with this instrument was sufficient for the clinical use.