External exposure of veterinary staffs and owners in veterinary nuclear medicine was estimated by monitoring the surface dose rate (SDR) and ambient dose rate (ADR) from the feline renal patient (n=20) and controls (normal cats, n=8) during and after renal scintigraphy with 99mTc-mercaptoacetyl triglycine (MAG3, dose 93-141 MBq/head). The highest SDR was at the ventral side of abdomen and its SDR-time course followed within the degradation curve with physical half-life (6.01 h) ADR demonstrated significant decrease up to about 100-fold by keeping distance from the patient at 100 cm. All cats showed acceptable SDR which was less than 115 µSv/h in 24 h post injection, where cumulative SDR till infinity was less than 1 mSv (=dose limit to the public). Urination had a conspicuous effect on SDR at 24 h (0.38–9.6 µSv/h) and all urinated cat showed less than 1/10 of the limit of the yearly external public exposure. These results satisfied current legislation in Japan, while the 24 h post-dose regulation was considered over-regulated in the case of sufficiently lower maximum SDR. From the perspective of overburdening animals, their owners, and veterinary clinics, it was considered desirable to determine criteria based on the maximum SDR for each patient.
A semiconductor preamplifier for use in intense radiation monitors has been developed. Semiconductor devices, particularly those using integrated circuits, are prone to failure in high radiation environments. This preamplifier consists of radiation tolerant junction gate field effect transistors (J-FETs) and a differential pair of J-FETs with regulated bias current for reducing radiation effects on the input circuit. The resulting semiconductor preamplifier can withstand more than 100 kGy of gamma radiation.
Behavior of radioactive caesium, derived from Fukushima Dai-ichi Nuclear Power Plant Accident, in river water and sediment investigated during 2012–2016. Concentrations of radioactive caesium in river water and sediment were decreased with time exponentially. The residence half-life of radioactive caesium in the river water and sediment were 0.788–1.50 year for 134Cs, 1.22–2.17 year for 137Cs. Any decrease in radioactive caesium concentration in the Tama river is because of weathering effect than radioactive decay. Concentrations of suspended radioactive caesium temporarily increased when sediments were resuspended due to rain. On the other hand, dissolved radioactive caesium is not easily impacted by this factor. Radioactive caesium concentration in sediments was considerably higher than that in river water. It indicated that much of the radioactive caesium in the Tama river existed in the sediments. Sequential extraction, elemental and crystal phase analysis were performed on the sediments and examined the chemical state of radioactive caesium as well as the adsorption mechanism. Radioactive caesium in sediment was present in a stable chemical form, and there is possibility that radioactive caesium was incorporated in biotite.
Digital luminescence radiography with Imaging Plate (IP) invented in Japan eliminated the drawbacks of conventional X-ray film radiography and has supported X-ray diagnostics over more than a quarter century in the world. The excellent features of IP extended its application fields to X-ray non-destructive testing and scientific research field. Although IP expelled conventional X-ray film, flat panel detector is nowadays mainly used in medical field. Technological advancement has prompted the exchange of the leading role. In the field of scientific research, IP has been still heavily used.
The Expert Committee on Promotion of RI Utilization, Science and Engineering/Life Science Committee, Japan Radioisotope Association, conducted a survey of academic conferences held from 2018 to 2019 in order to understand the usage status of radioisotopes (RIs) for research in Japan and overseas. We surveyed 8 international conferences and 7 domestic conferences, and extracted a total of 304 lectures that reported the use of RIs. We analyzed the production and application status of RIs in Japan and overseas, and discussed the promotion of RI use in Japan.
Pharmacokinetic (PK) parameters of stable caesium (SCs) were determined in adult Japanese Black Cattle (JBC, n=20). They were divided into two groups, i.e, intravenous (IV) and oral (PO) administration groups, and each of them was administered 133CsCl solution (20 mg/kg b.w.). SCs in biological samples was measured by ICP-MS, and their concentration-time courses were monitored for 182 days. The PK parameters determined in plasma and blood in each group were as follows (mean±SD); area under the concentration-time curve (AUC;µg/L·h): 0.54±0.06 (IVp), 0.42±0.05 (POp), 0.87±0.11 (IVb), and 0.71±0.33 (POb), mean residence time (MRT; day); 20.9±3.2 (IVp), 19.3±2.9 (POp), 24.7±3.6 (IVb), and 23.6±5.2 (POb), bioavailability (F%); 82±29 and 83±38, clearance (CL; mL/min/kg): 0.46±0.05 (IVp), 0.49±0.06 (POp), 0.29±0.04 (IVb), and 0.31±0.08 (POb), and distribution volume (Vd; L/kg) was 3.3 (Vdp) and 4.4 (Vdb). The biological half-life of the terminal elimination phase (T1/2) was estimated to be approximately 30 days. The urine recovery for the dose was 28±6 (IV) and 28±8 (PO), and the fecal recovery was 85±21 (IV) and 122±42% (PO). The time course via both routes of administration showed similar biphasic distribution and elimination profile in any biological samples and elucidated by compartment analysis with consideration of background level. Based on the PK parameters, elimination profile of radioactive caesium (RCs) from the JBC kept long in the RCs contaminated area can be explained.
We have proposed a new concept of time/position correlation type tomographic method based on a directionality-sensitive gamma camera, which can identify incident γ-ray direction. This method utilizes the correlation between two γ-ray photons and provides the radioactivity concentration in the body with a high resolution and a high signal-to-noise ratio. 111In is known as a cascade γ-ray emitting nuclide. Besides 111In, we have explored new candidates and found some other nuclides with different lifetimes. A focused lead collimator was designed and coupled to a pixelated detector array for this new coincidence imaging modality. The method shows a significant background rejection and an improved spatial resolution in comparison with the single-photon analysis.
FLASH Radiotherapy is an ultra-high dose rate irradiation, and has a characteristic of reducing the normal tissue damage. Therefore, it overturns the conventional concept of radiotherapy, and if it can be applied clinically, it has the potential to produce a paradigm shift in the field of radiotherapy. In this review, we introduce the background, biological aspects, mechanism, and efforts for clinical application.
Analysis of carbon and nitrogen isotope ratios are now popular among many study fields mainly due to the development of EA-IRMS. It is difficult to run the tiny samples or the samples with low carbon or nitrogen concentrations with the normal EA-IRMS setting. Here we introduce the modification of EA-IRMS for the tiny samples. The analytical system with the narrow oxidation and reduction tubes allows better peak shapes for carbon and nitrogen, which increases the sensitivity of EA-IRMS. This system is now available for the users in Center for Ecological Research, Kyoto University without any big troubles in the analysis. Because the modification introduced here is not so complicated and the users can also use the normal settings whenever required, many EA-IRMS users can apply this system relatively easily.
Difficulties in treating water containing tritium were investigated. Adaption of radioactivity for the measure quantity of material seems essential source of the issue. Use of space-time density of action as a controlling quantity in safety management with rdioactive material was proposed. Concept of action and related new dose, basic dose, were also presented. Protocol of diagnosis with radioactive substance was made. Thought experiments showed likelihood of safety of the current criteria with water containing tritium are sufficiently high.