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Article type: Cover
2002 Volume 58 Issue 5 Pages
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Article type: Index
2002 Volume 58 Issue 5 Pages
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Article type: Index
2002 Volume 58 Issue 5 Pages
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[in Japanese]
Article type: Article
2002 Volume 58 Issue 5 Pages
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Article type: Appendix
2002 Volume 58 Issue 5 Pages
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Article type: Appendix
2002 Volume 58 Issue 5 Pages
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2002 Volume 58 Issue 5 Pages
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2002 Volume 58 Issue 5 Pages
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Article type: Appendix
2002 Volume 58 Issue 5 Pages
IV-VI
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MASAKAZU KAWASHITA, [in Japanese]
Article type: Article
2002 Volume 58 Issue 5 Pages
585-591
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Jumpei Tsujiuchi
Article type: Article
2002 Volume 58 Issue 5 Pages
592-600
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Junichiro Toriwaki
Article type: Article
2002 Volume 58 Issue 5 Pages
601-612
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Tohru Hirano, Kazunari Shimizume, Harumi Sugimoto, Tsunehiko Saikawa, ...
Article type: Article
2002 Volume 58 Issue 5 Pages
613-625
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SHINICHI GOTOH
Article type: Article
2002 Volume 58 Issue 5 Pages
626-630
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FUMIAKI SHINOHARA, [in Japanese], [in Japanese], [in Japanese]
Article type: Article
2002 Volume 58 Issue 5 Pages
631-633
Published: May 20, 2002
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HIDEAKI YAMAMOTO, [in Japanese], [in Japanese], [in Japanese], [in Jap ...
Article type: Article
2002 Volume 58 Issue 5 Pages
634-639
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HIDEHARU NIIDA
Article type: Article
2002 Volume 58 Issue 5 Pages
640-650
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KATSUMI TSUJIOKA
Article type: Article
2002 Volume 58 Issue 5 Pages
651-657
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KENICHI TAKANO
Article type: Article
2002 Volume 58 Issue 5 Pages
658-663
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RIE TANAKA, SHIGERU SANADA, MASAYUKI SUZUKI, TAKESHI MATSUI, YOSHINORI ...
Article type: Article
2002 Volume 58 Issue 5 Pages
665-669
Published: May 20, 2002
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To develop a new method of screening chest radiography that would provide respiratory kinetics easily and automatically using flat-panel-detector capacitated fluoroscopy, we carried out a motion analysis of the diaphragm at several respiratory phases. We obtained five chest radiographs of healthy volunteer at five respiratory phases, from maximum inspiration to normal expiration. The edges of the diaphragm were enhanced by the first derivative filter, which select edge graduents within a limited range of orientations, and were detected by thresholding and analysis of connectivity in the horizontal direction. We measured the distance from the apex to the diaphragm as well as the changes at each phase. The apex was determined previously at the step of lung-region recognition. At the costophrenic angle, the change in the distance from the apex to the diaphragm was 2.44 cm on the right and 3.06 cm on the left, while at the paramedian region the changes were 0.74 cm on the right and 1.36 cm on the left. This new method of chest examination with computer analysis can provide information on diaphragm kinetics during respiration. In addition, it may aid in the early diagnosis of diseases such as chronic pulmonary emphysema and phrenic nerve paralysis.
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KEIICHI MATSUMOTO, TORU FUJITA, KOJI OOGARI
Article type: Article
2002 Volume 58 Issue 5 Pages
670-678
Published: May 20, 2002
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Maximum likelihood expectation maximization (ML-EM) image quality is sensitive to the number of iterations, because a large number of iterations leads to images with checkerboard noise. The use of median filtering in the reconstruction process allows both noise reduction and edge preservation. We examined the value of median filtering after reconstruction with ML-EM by comparing filtered back projection (FBP) with a ramp filter or ML-EM without filtering. SPECT images were obtained with a dual-head gamma camera. The acquisition time was changed from 10 to 200 (seconds/frame) to examine the effect of the count statistics on the quality of the reconstructed images. First, images were reconstructed with ML-EM by changing the number of iterations from 1 to 150 in each study. Additionally, median filtering was applied following reconstruction with ML-EM. The quality of the reconstructed images was evaluated in terms of normalized mean square error (NMSE) values and two-dimensional power spectrum analysis. Median filtering after reconstruction by the ML-EM method provided stable NMSE values even when the number of iterations was increased. The signal element of the image was close to the reference image for any repetition number of iterations. Median filtering after reconstruction with ML-EM was useful in reducing noise, with a similar resolution achieved by reconstruction with FBP and a ramp filter. Especially in images with poor count statistics, median filtering after reconstruction with ML-EM is effective as a simple, widely available method.
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EMI WATANABE, TOMONARI FUNATA, HAJIME SAITOU, KYOUICHI KATOU, MASARU N ...
Article type: Article
2002 Volume 58 Issue 5 Pages
679-685
Published: May 20, 2002
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Heat accumulation in X-ray tubes results in disarrangement of focus owing to heat expansion of the anode. CT scanners with automatic focus alteration capability have been developed to counteract this problem. We compared CT scanners with and without focus alteration capabilities and discuss the effect of focus disarrangement on the CT images. Images were obtained when heat accumulation was high and low. Subtraction images were made to define the disarrangement of focus. A comparison was made between CT scanners with and without automatic focus alteration capability. ROI was selected and changes in CT values, SD, and slice thickness were observed under changing anode heat accumulation. Results indicated that images from both scanners showed disarrangement of the focus and elevation of CT values as anode heat accumulated. However, the scanner with automatic focus alteration produced images with less focus disarrangement from the center of the slice and less elevation of CT values. Scanners with automatic focus alteration are less prone to the focus disarrangement and elevation of CT values caused by anode heat accumulation and enable reproducible images to be obtained.
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YUJI ENDOH, TOSHIO ITOH, MITSUFUMI KIKUCHI, MASAMICHI ISHIZAWA, JUNICH ...
Article type: Article
2002 Volume 58 Issue 5 Pages
686-693
Published: May 20, 2002
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In 54 cases of stereotactic irradiation (STI) seen at our hospital from April 2000 to March 2001, we examined the deficit in top-of-the-head computed tomography (CT) images and the influence that this deficit had on calculation of the STI dose. Results showed a slice deficit of more than 5 mm in 16 of the 54 cases and a maximum deficit of 25 mm. In most cases, the Gill-Thomas-Cosman (GTC) frame was used. The error in total dose monitor unit(DMU)calculation can be ignored if the top-of-the-head CT image deficit is less than 10 mm. If the deficit is more than 20 mm, it is possible that the total DMU calculation error will exceed 2%. In cases in which the deficit was greater than 30 mm, the average calculation error was 2.00%, and, in one case, the error was more than 7%. The GTC frame tends to produce CT image deficits in top-of-the-head images, whereas such images do not suffer this loss when a Brown-Roberts-Wells(BRW) head ring is used. When the CT image deficit is large, it is necessary to reduce the ratio of the arc that passes the area of the CT image deficit and to decrease the dose weight of the arc.
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HIROAKI ARAI, NAOYA HOSONUMA, MISAKO GOU, TAKASHI UENO
Article type: Article
2002 Volume 58 Issue 5 Pages
694-699
Published: May 20, 2002
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At cardiac catheterization, analog images obtained using cinefilm are translated into digital images, and images appearing on the CRT are filtered by a sharpen filter. We investigated the effect of the sharpening filter on vessel diameter as measured by quantitative coronary arteriography. We acquired images of a vessel phantom filled with contrast material using an X-ray image intensifier. Vessel diameters measured by quantitative coronary arteriography were 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, and 6 mm. Results showed that vessel diameters were decreased when the sharpening filter was used and that more intense filtering decreased the measured diameter further. When the diameter of the vessel phantom was less than 4 mm, the diameter was smaller and the ratio of decrease was larger. Vessel diameters of 2 mm, 3 mm, 4 mm, and 6 mm measured a maximum of 2.9% smaller, while those of 1 mm and 1.5 mm measured a maximum of 9.2% smaller.
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SHUJI YAMAMOTO, SEIKI HAMADA, TOMOHIRO NISHINO, SHOGO AZEMOTO, HIROAKI ...
Article type: Article
2002 Volume 58 Issue 5 Pages
700-704
Published: May 20, 2002
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Dynamic computed tomography is one of the methods used for the functional analysis of blood flow information. We devised a simple method of visualization for dynamic CT. Re-sliced images were stacked as multi-slice images for the different acquisition times to show a continuous spatial arrangement with dynamic data. Images processed into re-sliced images termed 2D-CT Chronograms were observed in many directions and were useful for comprehending the blood flow function of the target organ. Time-density curves with motion dependency and color displays similar to those of ultrasound images are easily acquired from the 2D-Chronogram. We introduce some clinical applications of the 2-D Chronogram.
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MASAKI OHKUBO, YUKIO OHGOSHI, TOMOKO INOUE, KENICHI NAITO, YUHKO YAGIS ...
Article type: Article
2002 Volume 58 Issue 5 Pages
705-710
Published: May 20, 2002
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In our study of three-dimensional contrast-enhanced MR angiography, we performed a computer simulation to quantitatively investigate vessel visibility according to scan timing. To construct the simulated MR images, we varied the position (scan timing) and range (enhancement-duration) of k-space data assumed to be acquired during contrast enhancement. In the present study, either the sequential or centric phase-encoding order in k_y and k_z on k-space was assumed to be used. When scan timing was shifted from the optimal timing, the visibility of thick vessels decreased, and the signal intensity in thin vessels was higher than that in thick vessels. We found that the appropriate setting of scan timing was an important factor in the visibility of thick vessels. Meanwhile, we also noted that extending the enhancement-duration (or shortening the scan time) could increase the visibility of thin vessels. Our results and the simple technique used for simulation are considered to be useful for the study of three-dimensional contrast-enhanced MR angiography.
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Article type: Appendix
2002 Volume 58 Issue 5 Pages
711-713
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Article type: Appendix
2002 Volume 58 Issue 5 Pages
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2002 Volume 58 Issue 5 Pages
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2002 Volume 58 Issue 5 Pages
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2002 Volume 58 Issue 5 Pages
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Article type: Appendix
2002 Volume 58 Issue 5 Pages
716-717
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Article type: Appendix
2002 Volume 58 Issue 5 Pages
718-719
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Article type: Cover
2002 Volume 58 Issue 5 Pages
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