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Article type: Cover
1998 Volume 54 Issue 8 Pages
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Article type: Cover
1998 Volume 54 Issue 8 Pages
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Article type: Appendix
1998 Volume 54 Issue 8 Pages
App4-
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Article type: Index
1998 Volume 54 Issue 8 Pages
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Article type: Index
1998 Volume 54 Issue 8 Pages
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[in Japanese]
Article type: Article
1998 Volume 54 Issue 8 Pages
I-
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
III-V
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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Article type: Appendix
1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
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1998 Volume 54 Issue 8 Pages
XVII-XVIII
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MITSUJI HIGASHIDA, MASARU YAMAZAKI, AKIO OGURA, HIROSHI INOUE, TAKAHAR ...
Article type: Article
1998 Volume 54 Issue 8 Pages
947-952
Published: August 20, 1998
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The NEMA standard and AAPM method have been approved for the determination of slice thickness in diagnostic magnetic resonance imaging. In these methods, the slice thickness is obtained as the full width at half maximum of the slice profile. However, these methods are affected by the signal-to-noise ratio(SNR)and pixel size. In addition, the measurement procedure required for accurate evaluation is troublesome. Therefore, a new method of evaluation using the partial volume effect, called the PVE method, is proposed. With the PVE method, slice thickness can be evaluated without the slice profile. A comparison ofaccuracy and simplicity of measurement is made between the PVE method and the wedge method of the NEMA standard. Results showed the PVE method to be accurate and easier to use than the wedge method.
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MASUMI HATTORI, NOBUHARU TANADA, ISAO SAKAI, SHUJI KOYAMA
Article type: Article
1998 Volume 54 Issue 8 Pages
953-960
Published: August 20, 1998
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Stair-step artifacts in helical computed tomography(CT)are associated with inclined surfaces in the Zaxis direction. We evaluated stair-step artifacts on virtual CT endoscopy. A "Y"-shaped phantom was scanned with a helical CT scanner, and the images were shown by using virtual CT endoscopy with combinations of x-ray beam collimation(1, 3, 5 and 10 mm), table velocity(1, 2, 3, 5 and 10 mm/s), and reconstruction interval(0.5, 1.5, 2, 2.5, 3, 5 and 10 mm). Stair-step artifacts arose from two sources:aliasing effect and rotation effect, forming the rugged wall of isoclosed curves and the rugged wall of spiral-like patterns. To eliminate these artifacts, the reconstruction interval should be about half of the table velocity. To eliminate artifacts of similar circles at the "Y"-point, the reconstruction interval should be less than one-third the internal diameter of the phantom. To eliminate the torsional fold at the "Y"-point, the table velocity sould be less than 5 mm/s.
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TETSUO KIDA, HIDEO OONISHI, SATORU MATSUO, KAZUO NOMA, MASAHIRO YOSHIM ...
Article type: Article
1998 Volume 54 Issue 8 Pages
961-969
Published: August 20, 1998
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We evaluated the influence of scatter-rays on images using the power spectrum method and attempted to determine the best energy window for image acquisition. We acquired planar images of a phantom that had existing signals of known diameters, at different energy windows. We varied these according to the following two parameters:(1)width of the energy window and (2)level of the energy window. We then used ^<99m>Tc, ^<201>Tl, and ^<123>I as signal sources. We determined that the influence of scatter-rays on images decreased as Pr(n)on the same frequency that indicated each signal and the integral value of Pr(n)increased on frequency analysis. Results indicated that(1)with ^<99m>Tc and ^<123>I, depending on the width of the energy window, Pr(n)decreased, and with ^<201>Tl, Pr(n)varied less. (2)With ^<99m>Tc, ^<201>Tl, and ^<123>I, Pr(n)decreased at lower energy levels to photopeak.At upper energy levels, increases were noted with ^<99m>Tc and ^<201>Tl, whereas a decrease was noted with ^<123>I. From the standpoint of image quality, we consider that images acquired with an asymmetric energy window that included an upper rather than lower level to photopeak were less affected by scatter-rays on ^<99m>Tc and ^<201>Tl imaging and by a narrow energy window width on ^<123>I imaging.
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YASUYUKI TAKAHASHI, HIROYUKI SHINBATA, AKIRA MASUHARA, ISAO KAWAMATA, ...
Article type: Article
1998 Volume 54 Issue 8 Pages
970-974
Published: August 20, 1998
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When SPECT images are reconstructed, 60 projection data-sets are produced if data are collected in a 360-degree sweep at a sampling angle of 6 degrees. This in involves 30 projection(=60×1/2)because data are also collected by the opposing detector located opposite(180 degrees)the primary detector. With the off-set reconstruction method, data are collected in a 360-degree sweep at angles of 6 degrees, but one detector collects data from 0 to 180 degrees, and the opposing detector collects data at two non-opposing angles, which are 183 degrees instead of 180 degrees from each other. When images obtained using this method were compared with conventional SPECT images, it was found that the off-set reconstruction SPECT images were superior in terms of uniformity of the columnar phantom, the ability to image hot spots, uniformity of the myocardial phantom, and the ability to quantify defects. When this technique was used in healthy individuals, the ability to image the cardiac lumen was better than ever, and high-quality images were obtained. Although the off-set reconstruction method is based on data collected at a sampling angle of degress, the apparent projection data obtained by this method resemble data collected at a sampling angle of 3 degrees.
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YASUYUKI TAKAHASHI, HIROYUKI SHINBATA, HISASHI SHINOHARA
Article type: Article
1998 Volume 54 Issue 8 Pages
975-979
Published: August 20, 1998
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Continuous-mode SPECT can be characterized by the collection of data using movable detectors. We examined the effects of movement of the detector on SPECT images. Projection data collected in step mode at a sampling angle of 2 degrees were serially added, and images at sampling angles of 4, 6, 8, and 10 degrees were reconstructed. In this manner, data were collected using a method resembling continuous-mode SPECT. Our experiment using phantoms revealed that, as the sampling angle increased, the resolution of hot spots in the periphery of the columnar phantom decreased slightly, and that the relationship between the sampling angle and the variance of the data in a given direction of projection was defined by a regression equation of y=0.51x+47.66(r=0.98). When a myocardial phantom was used, the imaged area of the defect created in the anterior wall increased as the sampling angle increased(y=12.63x+78.54;r=0.99), when the imaged area at a sampling angle of 2 degrees was set at 100%. No changes were observed in the ability to obtain images of the area near the center of the columnar phantom, the ability to obtain images of the defect in the inferior wall of the myocardial phantom, or the quality of the image of normal myocardium obtained by Tc-99m Tetrofosmin SPECT. These results suggest that although this method is not equivalent to continuous-mode SPECT, its resolution in the tangential direction and its ability to image in this direction are affected by the movement of the detectors and that these effects are associated with the sampling angle.
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EIJI MATSUDA, TAIZO SANADA, GO HITOMI, KOUSHI ISHII, AKIRA YOSHIDA
Article type: Article
1998 Volume 54 Issue 8 Pages
980-985
Published: August 20, 1998
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We have experienced variiations in the shape of the cinesensitometric curve when the exposure field is greatly altered. The veiling glare that arises from the scattering of x-ray photons, electrons, and light in the x-ray image intensifier(X-I.I.)depends on the size of the exposure field. Also, the effect adjacent chemicals that occurs during the develoment process depends on the size of the exposed area on film. The veiling glare in the X-I.I.and the adjacent chemical effect on cine film processing may be responsible for these phenomena. This study investigated the influences of veiling glare on the shape of the cinesensitometric curve. Results showed that the veiling glare of the X-I.I.acts to increase the sensitivity of the cinesensitometric curve on the X-I.I.whenthe exposed area on the X-I.I.is larger.
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TSUTOMU GOMI, MASAKAZU AKAHORI, YOSHIHIRO KITOH
Article type: Article
1998 Volume 54 Issue 8 Pages
986-990
Published: August 20, 1998
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We constructed a multipurpose network system and connected our digital fluorography(DF)system to it. A PC-UNIX computer was used as a file server and file transfer protocol(FTP)server. Still images generated by the DF system were transferred from the gateway computer connected to the DF system to the file server with a DICOM storage service. Images can be easily retrieved and modified by utilizing the functions that the network system makes it possible to share, such as the file-sharing system and the on-line viewer of the WWW browser. Thus, it should be easy to expand the network and improve its quality in the future. Our network can also be easily and effectively connected to other hospital network systems.
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Takashi Wakamatsu
Article type: Article
1998 Volume 54 Issue 8 Pages
991-997
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NAGAAKI OHYAMA
Article type: Article
1998 Volume 54 Issue 8 Pages
998-1007
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[in Japanese]
Article type: Article
1998 Volume 54 Issue 8 Pages
1008-1011
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[in Japanese]
Article type: Article
1998 Volume 54 Issue 8 Pages
1012-1014
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Article type: Bibliography
1998 Volume 54 Issue 8 Pages
1015-1016
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Article type: Appendix
1998 Volume 54 Issue 8 Pages
1017-1018
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Article type: Appendix
1998 Volume 54 Issue 8 Pages
1019-1020
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Article type: Appendix
1998 Volume 54 Issue 8 Pages
1021-1023
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1998 Volume 54 Issue 8 Pages
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Article type: Cover
1998 Volume 54 Issue 8 Pages
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