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Article type: Cover
1998 Volume 54 Issue 11 Pages
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Article type: Cover
1998 Volume 54 Issue 11 Pages
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Article type: Index
1998 Volume 54 Issue 11 Pages
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Article type: Index
1998 Volume 54 Issue 11 Pages
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[in Japanese]
Article type: Article
1998 Volume 54 Issue 11 Pages
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Article type: Appendix
1998 Volume 54 Issue 11 Pages
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1998 Volume 54 Issue 11 Pages
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1998 Volume 54 Issue 11 Pages
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1998 Volume 54 Issue 11 Pages
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1998 Volume 54 Issue 11 Pages
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1998 Volume 54 Issue 11 Pages
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Article type: Appendix
1998 Volume 54 Issue 11 Pages
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DAISAKU TATSUMI, JUNJI SHIRAISHI, HIROYUKI TSUSHIMA, KEN'ICHI KUS ...
Article type: Article
1998 Volume 54 Issue 11 Pages
1273-1280
Published: November 20, 1998
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Practical experiments were done to quantify basic properties of the imaging plate(IP). The relation was investigated between incident dose on the IP and the S value associated with computed radiography. An acrylic phantom and uniform exposure were used for this study. The effects of the properties of incident dose(tube voltage, exposed dose, and grid application) and IP(fading time and period of use) on the S value were measured. Results indicated that determination of the S value depended on tube voltage and fading of the IP, but not on exposure dose or period of IP usage. The effects of grid use could be estimated with the grid's bucky factor and scattering factors. We concluded that these results were useful for research using the IP as an x-ray detector and for estimating incident dose by using the S value.
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HIROAKI ARAI, TAKASHI UENO
Article type: Article
1998 Volume 54 Issue 11 Pages
1281-1286
Published: November 20, 1998
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We examined the digital image resolution of an indirect radiographic system with an I.I. and television camera by using the ratio of contrast to square wave output. Because the output medium of the last image was a CRT with variable contrast, the output value was digitized. In terms of the ratio of contrast of the rectangular wave of digital images obtained from this device, the vertical direction was found to be better than the horizontal direction. This is because sampling is done after removing the high-frequency ingredient for the series signal provided by scanning at the time of digitizing. Further, the field of view of the I.I. was small, and the ratio of contrast to the rectangular wave was high. However, the value became almost the same as that obtained when a cross axis of the contrast ratio was converted into space frequency per pixel in the digital image. Resolution deteriorated when pixel size decreased. Therefore, it is important to determine the size of the pixel in digital images.
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YUN SHEN, TETSUYA HORIUCHI, FUMIKO KIMURA, FUMIKAZU SAKAI, MAKOTO GONO ...
Article type: Article
1998 Volume 54 Issue 11 Pages
1287-1294
Published: November 20, 1998
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Cardiac pulsation is the most important cause of serious image degradation on high resolution CT(HRCT) images of lung adjacent to heart and cardiac images. The purpose of this study was to propose a special high temporal resolution reconstruction(HTRR) algorithm, and to assess the effects on the reduction in motion artifacts caused by cardiac pulsation on HRCT images of lung and cardiac images by using this algorthm combined with sub-second CT. The HTRR algorithm was developed on the basis of a special weighting function. The results of phantom and clinical studies demonstrated that the HTRR algorithm can provide high temporal resolution, substantially reduce moting artifacts and noise, and markedly improve the quality of cardiac images and HRCT lung images at the cost of a slight degradation in spatial resolution. Further, the HTRR algorithm can obtain phase information by combining subsecond CT with the overlapping cine reconstruction technique and ECG information. Using the HTRR algorithm, the effective temporal resolution(FWHM) is 0.4 sec for a 0.8 sec scan.
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TAKESHI NII, TAKUJI NISHIDA, JUNKO KAKIZAKI, SYUJI SUGIHARA
Article type: Article
1998 Volume 54 Issue 11 Pages
1295-1300
Published: November 20, 1998
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We examined whether or not it is better to use delayed myocardial SPECT images in determining the varability in myocardial uptake(ΔTF) of^<99m>Tc-tetrofosmin under the one-day protocol. We injected 370 MBq of ^<99m>Tc-tetrofosmin at peak exercise, and initial(TF1) and delayed(TF2) exercise SPECT images were acquired 30 min and 3 hr, respectively, after the injection. Then, 740 MBq of ^<99m>Tc-tetrofosmin was reinjected soon after TF2 acquisition, and rest SPECT images(TF3) were obtained 30 min later. Myocardial counts of TF1, TF2, and TF3 were defined as C1, C2, and C3, respectively, and ΔTF was determined by the following formula:ΔTF(A)=[{C1×R-(C3-C2')}/(C3-C2')]×100(%). ΔTF(B)=[{C1×R-(C3-C1')}/(C3-C1')]×100(%), where R is dose ratio, A is the procedure of imaging with delayed exercise SPECT, and B is the procedure of imaging without delayed exercise SPECT. The combination in which the delayed image was used better clari-fied the decreased uptake of ^<99m>Tc-tetrofosmin at the hypertrophied myocardium, and thus proved to by useful.
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SHU IKEDA, KOJI MUNAKATA, KUNIHIRO YOSHIDA, MAMORU HAYAKAWA, YOSHITERU ...
Article type: Article
1998 Volume 54 Issue 11 Pages
1301-1308
Published: November 20, 1998
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Multiplanar reformation(MPR) images of helical CT suffer from poor longitudinal resolution and the "stair-step" artifact. We attempted to solve these problems by studying five scanning modes(1 mm collimation with 1 pitch; 1 mm collimation with 2 pitches; 3 mm collimation with 0.5 pitch; 3mm collimation with 1 pitch; and 5 mm collimation with 1 pitch). Longitudinal resolution was found to be affected more by slice collimation than table feed. The stair-step artifact consists of a rotation effect and aliasing effect. The rotation effect was a cyclic artifact, and the cycle was dependent on table feed. In order to solve these problems, we employed a restoration filter to improve longitudinal resolution and a band filter to remove the stair-step artifact. In the clinical images, we used three scanning modes(1 mm collimation with 1 pitch; 3 mm collimation with 0.5 pitch; 3 mm collimation with 1 pitch). In conclusion, these problems in scanning images were completely solved by using 1 mm collimation with 1 pitch. However, we were not able to solve the problems in scanning images using 3 mm collimation with 0.5 and 1 pitch.
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TOSHIO TSUCHIHASHI, MINORU NAKATA, ISAO FUJITA, MICHIKO CHIBA, SATOSHI ...
Article type: Article
1998 Volume 54 Issue 11 Pages
1309-1315
Published: November 20, 1998
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Differences in magnetic susceptibility produce artifacts and signal loss in magnetic resonance imaging(MRI). This study was undertaken to compare the degree of artifacts on MRI caused by metallic dental materials. The influence on MRI of six types of dental alloys, a dental implant, orthodontic appliance, and magnetic attachment was investigated. Among the dental metals, nickel-chromium alloy and cobalt-chromium alloy, which have ferromagnetism, caused significant metal artifacts. Gold-platinum alloy, gold-silver-palladium alloy, silver alloy, and amalgam alloy produced slight metal artifacts. The orthodontic appliance mainly consisted of iron, and the keeper for its magnetic attachment was made of stainless steel. For these reasons, marked metal artifacts and signal loss could be seen in both of them owing to their ferromag-netism. These results suggest that orthodontic appliances and magnetic attachments impair evaluation of the GRE and EPI techniques. It is therefore preferable to use predominantly diamagnetic or paramagnetic dental materials for MRI of the head and neck. Removable keepers should be used more widely to prevent metal artifacts and enhance safety on MRI.
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KAORU MORIKAWA, [in Japanese], [in Japanese], [in Japanese], [in Japan ...
Article type: Article
1998 Volume 54 Issue 11 Pages
1316-1321
Published: November 20, 1998
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YASUMITSU KAWAGOE, [in Japanese], [in Japanese], [in Japanese], [in Ja ...
Article type: Article
1998 Volume 54 Issue 11 Pages
1322-1335
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YOSHIHIRO ONISHI
Article type: Article
1998 Volume 54 Issue 11 Pages
1336-1341
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[in Japanese]
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1998 Volume 54 Issue 11 Pages
1342-1343
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[in Japanese]
Article type: Article
1998 Volume 54 Issue 11 Pages
1344-1348
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[in Japanese]
Article type: Article
1998 Volume 54 Issue 11 Pages
1349-1351
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Article type: Appendix
1998 Volume 54 Issue 11 Pages
1352-1353
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Article type: Appendix
1998 Volume 54 Issue 11 Pages
1354-1355
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Article type: Appendix
1998 Volume 54 Issue 11 Pages
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Article type: Appendix
1998 Volume 54 Issue 11 Pages
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Article type: Cover
1998 Volume 54 Issue 11 Pages
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