A nuclear reactor at Kinki University is operated at the maximum of 1 W. It produces fission neutrons as much as γ-rays. To facilitate its use for neutron radiobiology, fast neutrons inside the reactor were measured with nuclear-track detectors TS 16 N and a pair of ion chambers. The angular dependence of TS 16 N response, an anisotropy of fast neutron fluxes in the reactor and misuse of the kerma factor assumed for radiation protection business are the major causes of discrepancy in measured doses by the two methods. Correction factors for the three causes are proposed. After correction, neutron doses estimated with TS 16 N and chambers agree within 5 %. The dose-rate at the reactor's center is about 20 tissue-cGy/h. This is the first in situ dosimetry of fast neutrons in a reactor with track detectors attached to biologic samples. Our routine usage has demonstrated that, if used with caution, TS 16 N elements are handy, reliable monitors for fast neutron dosimetry as they are insensitive to contaminated γ-rays and small enough to be attached to biologic samples.
We simplified procedures of in situ hybridization with riboprobes on serial sections of paraffne-embedded tissues. We found that when tissues were fixed with 4 % paraformaldehyde, embedded in paraffine, and cut serial sections with 5μm thick, excellent results were obtained without proteolytic, heat, or HCl treatment. With our simplified method, both EGF and NGF mRNAs were detected intensively and specifically in granular convoluted tubule (GCT) cells of a male mouse submandibular gland, but not detected in either the acini or ducts other than the GCT. Accumulation of the silver grains was localized in the basal side of the GCT cells. No significant hybridization was observed in those cells with the sense probe and in the parotid and sublingual gland even with the anti-sense probe. Since our results were not only very consistent with other data, but also much more excellent than other results obtained by in situ hybridization on the similar tissues, our simplified method should be very useful to study gene expression on tissue sections.
68Ga-EDTA (ethylenediaminetetraacetic acid) is simply and economically obtained without a cyclotron. We used renal blood volume (RBV) values obtained by C15O studies for blood activity subtraction on renal time activity curves using a positron emission tomography for the determination of the glomerular filtration rate (GFR) by intravenous68Ga-EDTA administration. Positive correlation was revealed between the GFR and RBV values, where the ratio of blood activity in whole renal activity increased relatively as GFR value decreased. The estimation using a correction equation derived from the correlation curve was possible without a C15O study.
In the unit housing of a compact cyclotron and positron emission CT (PET), positron emitting gas such as15O, 11C, C15O2, C15O etc. is supplied from a cyclotron to a PET room through a transportation pipe with an appropriate shield to reduce positron annihilation radiation. This paper discribes the effect of lead and concrete shields with various thickness. Using lead or concrete shield blocks with various thicknesses, radiation leakage through the shield was measured by an ionization chamber type survey meter during continuous and constant supply of15Ogas of 1.85 GBq/min concentration which is the maximum dose for clinical use. The leakage radiation measured was 213.7, 56.0, 15.3, 5.0 μSv/week for lead shield with 1, 2, 3, and 4 cm thickness, respectively, and 193. 3, 30.5 and 5.1 μSv/ week for concrete shields with thickness of 10, 20, and 30 cm, respectively. The present study shows that to keep less than 300μSv/week, which is the permissible dose rate of the boundary zone around the radiation controlled area by Japan Science and Technology Agency, it is required to use more than 8 mm thick lead shield or 7 cm thick concrete for continuous supply of 1.85 GBq/min15Ogas.