[en] Non-uniformity of resolution and quantification on micro single-photon emission tomography (SPECT) system were improved greatly by using the design of light path to take a photograph and the solid reconstruction program based on statistics. Concentration distribution of radioactive medicine in a small animal body became to be able to measure accurately in comparison with positron computed tomography (PET). Two light paths imaging device, which answers for complete data, was manufactured for an assurance of the solid reconstruction program. The quantity evaluation of tissue blood flow rate in myocardium of rat and the bone scanning on mice were possible by imaging the physiological function of animal as it is alive, although the sensitivity of the micro SPECT was inferior to that of the PET. (M. Suetake)

[en] MRI (magnetic resonance imaging) with ¹²⁹Xe has gained much attention as a diagnostic methodology because of its affinity for lipids and possible polarization. The quantitative estimation of net detectability and stability of hyperpolarized ¹²⁹Xe in the dissolved phase in vivo is valuable to the development of clinical applications. The goal of this study was to develop a stable hyperpolarized ¹²⁹Xe experimental 3T system to statistically analyze the dissolved-phase ¹²⁹Xe signal in the rat lungs. The polarization of ¹²⁹Xe with buffer gases at the optical pumping cell was measured under adiabatic fast passage against the temperature of an oven and laser absorption at the cell. The gases were insuffiated into the lungs of Sprague-Dawley rats (n=15, 400-550 g) through an endotracheal tube under spontaneous respiration. Frequency-selective spectroscopy was performed for the gas phase and dissolved phase. We analyzed the ¹²⁹Xe signal in the dissolved phase to measure the chemical shift, T₂^*, delay and its ratio in a rat lungs on 3T. The polarizer was able to produce polarized gas (1.1±0.47%, 120 cm³) hundreds of times with the laser absorption ratio (25%) kept constant at the cell. The optimal buffer gas ratio of 25-50% rendered the maximum signal in the dissolved phase. Two dominant peaks of 211.8±0.9 and 201.1±0.6 ppm were observed with a delay of 0.4±0.9 and 0.9±1.0 s from the gas phase spectra. The ratios of their average signal to that of the gas phase were 5.6±5.2% and 4.4±4.7%, respectively. The T₂^* of the air space in the lungs was 2.5±0.5 ms, which was 3.8 times shorter than that in a syringe. We developed a hyperpolarized ¹²⁹Xe experimental system using a 3T MRI scanner that yields sufficient volume and polarization and quantitatively analyzed the dissolved-phase ¹²⁹Xe signal in the rat lungs. (author)

[en] We report 12 cases of acute encephalopathy associated with influenza H1N1-2009 treated according to Japanese guideline (2009). In all 12 cases, electroencephalogram presented diffuse or localized high-amplitude slow waves. Brain CT and MRI showed abnormalities in 4 and 6 cases, respectively. We used hypothermia therapy for 5 patients. One patient showed impairment in short term memory, while the rest of the patients showed no sequelae. These 12 cases presented here suggest the early recognition and therapy according to the newly proposed guideline may reduce severe sequelae and mortality by acute encephalopathy associated with influenza H1N1-2009. (author)

[en] A small plasma focus device was constructed for the EUV radiation experiment. The storage energy of capacitor bank is 3.4 kj, and the maximum discharge current is 140 kA. Although the device was not well optimized for strong pinch, EUV radiation was observed from the focus plasma. The plasma dynamics was affected by electrode material, and the use of Sn electrode was proved to be effective for producing Sn plasma

[en] Cerebral metabolic rate of oxygen (CMRO₂), oxygen extraction fraction (OEF) and cerebral blood flow (CBF) images can be quantified using positron emission tomography (PET) by administrating ¹⁵O-labelled water (H¹⁵₂O) and oxygen (¹⁵O₂). Conventionally, those images are measured with separate scans for three tracers C¹⁵O for CBV, H¹⁵₂O for CBF and ¹⁵O₂ for CMRO₂, and there are additional waiting times between the scans in order to minimize the influence of the radioactivity from the previous tracers, which results in a relatively long study period. We have proposed a dual tracer autoradiographic (DARG) approach (Kudomi et al 2005), which enabled us to measure CBF, OEF and CMRO₂ rapidly by sequentially administrating H¹⁵₂O and ¹⁵O₂ within a short time. Because quantitative CBF and CMRO₂ values are sensitive to arterial input function, it is necessary to obtain accurate input function and a drawback of this approach is to require separation of the measured arterial blood time-activity curve (TAC) into pure water and oxygen input functions under the existence of residual radioactivity from the first injected tracer. For this separation, frequent manual sampling was required. The present paper describes two calculation methods: namely a linear and a model-based method, to separate the measured arterial TAC into its water and oxygen components. In order to validate these methods, we first generated a blood TAC for the DARG approach by combining the water and oxygen input functions obtained in a series of PET studies on normal human subjects. The combined data were then separated into water and oxygen components by the present methods. CBF and CMRO₂ were calculated using those separated input functions and tissue TAC. The quantitative accuracy in the CBF and CMRO₂ values by the DARG approach did not exceed the acceptable range, i.e., errors in those values were within 5%, when the area under the curve in the input function of the second tracer was larger than half of the first one. Bias and deviation in those values were also compatible to that of the conventional method, when noise was imposed on the arterial TAC. We concluded that the present calculation based methods could be of use for quantitatively calculating CBF and CMRO₂ with the DARG approach

[en] The reproducibility of neurite orientation dispersion and density imaging (NODDI) metrics in the human brain has not been explored across different magnetic resonance (MR) scanners from different vendors. This study aimed to evaluate the scan–rescan and inter-vendor reproducibility of NODDI metrics in white and gray matter of healthy subjects using two 3-T MR scanners from two vendors. Ten healthy subjects (7 males; mean age 30 ± 7 years, range 23–37 years) were included in the study. Whole-brain diffusion-weighted imaging was performed with b-values of 1000 and 2000 s/mm2 using two 3-T MR scanners from two different vendors. Automatic extraction of the region of interest was performed to obtain NODDI metrics for whole and localized areas of white and gray matter. The coefficient of variation (CoV) and intraclass correlation coefficient (ICC) were calculated to assess the scan–rescan and inter-vendor reproducibilities of NODDI metrics. The scan–rescan and inter-vendor reproducibility of NODDI metrics (intracellular volume fraction and orientation dispersion index) were comparable with those of diffusion tensor imaging (DTI) metrics. However, the inter-vendor reproducibilities of NODDI (CoV = 2.3–14%) were lower than the scan–rescan reproducibility (CoV: scanner A = 0.8–3.8%; scanner B = 0.8–2.6%). Compared with the finding of DTI metrics, the reproducibility of NODDI metrics was lower in white matter and higher in gray matter. The lower inter-vendor reproducibility of NODDI in some brain regions indicates that data acquired from different MRI scanners should be carefully interpreted.

[en] Patlak analysis, which estimates the net 6-fluoro-3,4-dihydroxyphenylalanine (FDOPA) influx constant (K_i) by linear regression of data acquired from [¹⁸F]FDOPA positron emission tomography (PET) study, is widely employed in the diagnosis of neurological disorder, such as Parkinson's disease. In K_i estimation by Patlak analysis, it is assumed that the metabolites of radioligand do not diffuse out of the tissue during PET scan. However, [¹⁸F]F-Dopamine, synthesized from [¹⁸F]FDOPA, is rapidly metabolized and its metabolites diffuse from the tissue. We aimed at the evaluation of the effect of dopamine metabolism and the clearance of its metabolites on K_i estimated by Patlak analysis. For this purpose, we developed a model describing the detailed pathway of dopamine kinetics in the striatum, and a standard time-activity curve (TAC) was generated based on this model and [¹⁸F]FDOPA PET data of a monkey. And TACs in case of altering the dopamine metabolism or the clearance of its metabolites were simulated. Then, we evaluated K_i values estimated by Patlak analysis for these simulated TACs. K_i was increased when the dopamine metabolism to 6-fluoro-3,4-dihydroxyphenylacetic acid (DOPAC) (k₉^dopac) and the clearance of DOPAC and homovanilic acid (HVA) (k₁₁^dopac, k₁₁^hva) were altered. The results suggest that K_i could be biased by the influence of the metabolism of dopamine and clearance of its metabolites. Therefore, it is important to consider these biases in the interpretation of K_i value estimated Patlak analysis. (author)

[en] Cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO₂), oxygen extraction fraction (OEF), and cerebral blood volume (CBV) are quantitatively measured with positron emission tomography (PET) with ¹⁵O gases. Kudomi et al. developed a dual tracer autoradiographic (DARG) protocol that enables the duration of a PET study to be shortened by sequentially administrating ¹⁵O₂ and C¹⁵O₂ gases. In this protocol, before the sequential PET scan with ¹⁵O₂ and C¹⁵O₂ gases (¹⁵O₂-C¹⁵O₂ PET scan), a PET scan with C¹⁵O should be preceded to obtain CBV image. C¹⁵O has a high affinity for red blood cells and a very slow washout rate, and residual radioactivity from C¹⁵O might exist during a ¹⁵O₂-C¹⁵O₂ PET scan. As the current DARG method assumes no residual C¹⁵O radioactivity before scanning, we performed computer simulations to evaluate the influence of the residual C¹⁵O radioactivity on the accuracy of measured CBF and OEF values with DARG method and also proposed a subtraction technique to minimize the error due to the residual C¹⁵O radioactivity. In the simulation, normal and ischemic conditions were considered. The ¹⁵O₂ and C¹⁵O₂ PET count curves with the residual C¹⁵O PET counts were generated by the arterial input function with the residual C¹⁵O radioactivity. The amounts of residual C¹⁵O radioactivity were varied by changing the interval between the C¹⁵O PET scan and ¹⁵O₂-C¹⁵O₂ PET scan, and the absolute inhaled radioactivity of the C¹⁵O gas. Using the simulated input functions and the PET counts, the CBF and OEF were computed by the DARG method. Furthermore, we evaluated a subtraction method that subtracts the influence of the C¹⁵O gas in the input function and PET counts. Our simulations revealed that the CBF and OEF values were underestimated by the residual C¹⁵O radioactivity. The magnitude of this underestimation depended on the amount of C¹⁵O radioactivity and the physiological conditions. This underestimation was corrected by the subtraction method. This study showed the influence of C¹⁵O radioactivity in DARG protocol, and the magnitude of the influence was affected by several factors, such as the radioactivity of C¹⁵O, and the physiological condition. (author)

[en] The results of a survey of radiation workers suggest that they are worried about the effects of radiation exposure on health, and approximately 30% of Fukushima Daiichi Nuclear Power Plant (FDNPP) workers have anxiety. This questionnaire survey reveals that the higher the frequency of radiation education, the higher the knowledge of radiation the workers will have, and that the higher the level of knowledge, the lower the anxiety. To reduce anxiety, it is important to increase knowledge about radiation through radiation education. However, even those workers who had radiation education several times still had anxiety. According to the Ordinance on the Prevention of Ionizing Radiation Hazards, the time spent on education about the effects of radiation on the human body is only about 30 minutes. This education is not enough to reduce anxiety. FDNPP workers needed more effective education to increase their knowledge and to reduce their anxiety. (author)

[en] Unique properties and potential applications of 2D materials draw much attention for mass production of thin-layer 2D materials. Ball milling exfoliation of 2D materials has been rarely used, in spite of a promising dry phase production method, because of the superficial information in the mechanism and the effect of the operating parameters on the yield, size and thickness. Here, we investigate systematically the ball milling operating parameters in the exfoliation of bulk MoS₂ in the presence of sodium cholate (SC) as an exfoliant. The yield and dimensions of the exfoliated MoS₂ nanosheet were monitored by changing the parameters such as the weight ratio of bulk MoS₂ and SC (SC/MoS₂), the filling ratio in the volume of milling ball and container (φ), milling ball size (d _B), milling revolution speed (n _R), and initial mass of bulk MoS₂ ($m_{{\mathrm{M}\mathrm{o}\mathrm{S}}_2}$). The yield of exfoliation is found to be 95% at the optimum ball milling conditions (SC/MoS₂ = 0.75, φ = 50%, $m_{{\mathrm{M}\mathrm{o}\mathrm{S}}_2}$ = 0.20 g). In addition, yield and size of the exfoliated MoS₂ were controlled by the conditions of the ball milling. As for the evaluation of the exfoliated MoS₂, we developed a novel method by use of the XRD profile to determine the size and thickness of the ball-milled MoS₂ powder with less than 30% difference from those determined by the well-known absorption method. Finally, the size and thickness of the MoS₂ nanosheets prepared by ball milling exfoliation were correlated with their electrocatalytic and photoelectrocatalytic activities. (paper)