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Hidetake Hara,Hiroshi Muraishi,Hiroki Matsuzawa,Toshiyuki Inoue,Yasuo Nakajima,Hitoshi Satoh,Shinji Abe 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.1
We have recently developed a phantom that simulates acute ischemic stroke. We attempted to visualize an acute-stage cerebral infarction by using dual-energy Computed tomography (DECT) to obtain virtual monochromatic images of this phantom. Virtual monochromatic images were created by using DECT voltages from 40 to 100 keV in steps of 10 keV and from 60 to 80 keV in steps of 1 keV, under three conditions of the tube voltage with thin (Sn) filters. Calculation of the CNR values allowed us to evaluate the visualization of acute-stage cerebral infarction. The CNR value of a virtual monochromatic image was the highest at 68 keV under 80 kV / Sn 140 kV, at 72 keV under 100 kV / Sn 140 kV, and at 67 keV under 140 kV / 80 kV. The CNR values of virtual monochromatic images at voltages between 65 and 75 keV were significantly higher than those obtained for all other created images. Therefore, the optimal conditions for visualizing acute ischemic stroke were achievable.
Satoshi Wada,H. Kakemoto,K Yokoh,T Tsurumi,T Muraishi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
The phase transition behaviors of [111]-oriented barium titanate (BaTiO3) crystals were investigated as functions of temperature, uniaxial stress, and electric field. For the phase transition caused by temperature, with decreasing temperature above Tc, the paraelectric phase changed to an intermediate phase with a superparaelectric state and finally changed to a ferroelectric phase with randomly oriented spontaneous polarizations. Moreover, the phase transition caused by the uniaxial stress field above Tc was found to be almost similar to the one caused by temperature. On the other hand, for the phase transition caused by an electric field above Tc, with increasing electric field, the paraelectric phase changed to an intermediate phase and finally to a ferroelectric phase with an oriented polar direction. These results suggest that above Tc, a combination of uniaxial stress with an electric field may be effective as a poling treatment for BaTiO3 crystals. Thus, in this study, a new poling method for the BaTiO3 crystals by using control of the temperature, the uniaxial stress, and the electric field is proposed.t