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Article type: Cover
1997 Volume 53 Issue 2 Pages
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Article type: Cover
1997 Volume 53 Issue 2 Pages
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Article type: Index
1997 Volume 53 Issue 2 Pages
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Article type: Index
1997 Volume 53 Issue 2 Pages
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[in Japanese]
Article type: Article
1997 Volume 53 Issue 2 Pages
I-
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
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1997 Volume 53 Issue 2 Pages
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1997 Volume 53 Issue 2 Pages
III-IV
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1997 Volume 53 Issue 2 Pages
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
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1997 Volume 53 Issue 2 Pages
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
VI-VII
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
VIII-X
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KOICHI CHIDA, TATSUO NAGASAKA, HIROKI ISHIYA, HIROYUKI SATO, MASAHIRO ...
Article type: Article
1997 Volume 53 Issue 2 Pages
265-271
Published: February 20, 1997
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X-ray high-voltage generations have racently been developed. One type incorporating a monitoring unit for X-ray tube voltage and X-ray tube current, has been particularly popular. The output of the monitoring unit is said to be almost proportional to the X-ray tube voltage and current of the X-ray high-voltage generator. The output of the monitoring unit is obtained mainly by a built-in resistance bleeder. We compared the accuracy of the monitoring unit with conventional direct measuring using an invasive tube voltage and current meter(AB-2015D-MII, TOREX). For X-ray tube voltage, almost the same results were obtained with the monitoring unit and the conventional direct measuring method. But the results with inverter-type X-ray generators differed somewhat from those obtained by conventional direct measuring. The X-ray tube current signal measured by the monitoring unit has different overshoot and waveform from that obtained by the conventional direct measuring method. In the steady state, however, the data were almost in agreement. We conclude that the monitoring unit should be applicable to the quality control of X-ray high-voltage generators.
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TOSHIHARU SAKUMA, NAOAKI YAMADA, TOSHIHIRO NISHINO, HIROSHI OHTAKENO, ...
Article type: Article
1997 Volume 53 Issue 2 Pages
272-276
Published: February 20, 1997
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The pupose of this study was to evaluate blood oxygenation level-dependent(BOLD)contrast and the inflow effect in functional MRI. Nine normal volunteers underwent an activation test using right finger tapping on a 1.5T machine. A triple gradient echo sequence(TE=21, 44, 67msec)was repeated to obtain rest and activated images, and the functional image was calculated b subtraction. The excitation angle of the sequence was varied at 10 degree, 40 degree, and 70 degree. The activated region coincided with a cortical vein on 2D-TOF-MRA(v-group)or not (c-group). BOLD contrast was dominant in the both groups. The v-group had a larger inflow effect than the c-group. The activation ratio was independent of the excitation angle, which also suggested that BOLD contrast is dominant in functional MRI.
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YOH KATOH, HITOSHI SATO, TORU NEGISHI, HIROMI AOYAMA, KATSUHIRO NISHIK ...
Article type: Article
1997 Volume 53 Issue 2 Pages
277-283
Published: February 20, 1997
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Since the cadmium telluride detector has about fourfold the photeolectric absorption probability as compared to germanium, the detector area can be miniaturixed. However, it is difficult to increase the thickness of the particles because of the decreased positive hole mobility, resulting in the high probability of photon escape. When measuring the continuous spectum of the rradiation source with the detector, the spectrum form becomes distorted towards the lower energy region by reason of these problems. We applied an unfolding-method to the measured spetrum. This method presupposes that the tail region should be flat if measured by a mono-energy radiation source. A respoonse function and an efficiency curve were obtained easily from the spectrum distribution of standard sources. The reponse function was expressed with about a 200-degree square triangularmatrix. Since the absorption edge of cadmium and tellurium is around 30keV, characteristic X-rays emitted from standard sources were used for the determination of detection efficiency. The original spectrum was obtained easily by those xorrections. We consider that quality control of X-ray equipment and the assessment of exposure doses can be done correctly using this spectrum.
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TAKASHI WAKAMATU, HIROHARU OKADA, TOSHIYA SANO, SMIO ANZAI, FUMIHIKO F ...
Article type: Article
1997 Volume 53 Issue 2 Pages
284-290
Published: February 20, 1997
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A computer-assisted diagnosis(CAD)system has been developed by Katuragawa S, Morishita K, Doi K, et al. for the automated detection and characterization of interstitial infilitates based on the Fourier transformation of lung texture. The root-mean-square(RMS)variations and the first moments of power spectra correspond to the magnitude and coarseness of texture. They indicated that RMS variation was dependent upon the average optical density, though no obvious trend existed for the first moment of power spectrum of texture. We therefore tried to ivestigate the results by using the mathematical model of the Wiener spectrum of the radiographic screen-film system and the virtual power spectrum of texture for simulating performances of the RMS variation and the first moment. The results of the simulated investigation suggested that the amounts of information model of signal to noise ratio are as useful as the RMS variations of power spectra in texture analysis.
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TOSHIO TSUCHIHASHI, TOSHIO MAKI, TAKESHI SUZUKI
Article type: Article
1997 Volume 53 Issue 2 Pages
291-298
Published: February 20, 1997
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The fast inversion recovery(fast IR)pulse sequence was evaluated. We compared the fast fluid attenuated invertion recovery(fast FLAIR)pulse sequence in which inversion time(TI)was established as equal to the water null point for the purpose of the water-suppressed T_i-weighted image, with the fast short TI inversion recovery(fast STIR)pulse sequence in which TI was established as eaual to the fat null point for purpose of fat suppression. In the fast FLAIR pulse sequence, the water null point was increased by making TR longer. In the FLAIR pulse sequence, the longitudinal magnetization contrast is determined by TI. If TI is increased, T_2-weighted contrast improves in the same way as inreasing TR for the SE pulse sequence, Therefore, images should be taken with long TR and long TI, which are longer than TR and longer than the water null point. On the other hand, the fat null point is ot affected by TR in the fast STIR pulse sequence, However, effective TE was affected by variation of the null point. This increased in proportion to the increase in effective TE. Our evaluation indicated that the fast STIR pulse sequence can control the extensive signals from fat in a short time.
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Yasuhiko Tohyama
Article type: Article
1997 Volume 53 Issue 2 Pages
299-308
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
309-352
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1997 Volume 53 Issue 2 Pages
353-354
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
355-356
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1997 Volume 53 Issue 2 Pages
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Article type: Appendix
1997 Volume 53 Issue 2 Pages
358-359
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1997 Volume 53 Issue 2 Pages
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1997 Volume 53 Issue 2 Pages
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1997 Volume 53 Issue 2 Pages
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Article type: Cover
1997 Volume 53 Issue 2 Pages
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