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Article type: Cover
1999 Volume 55 Issue 10 Pages
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Article type: Index
1999 Volume 55 Issue 10 Pages
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Article type: Index
1999 Volume 55 Issue 10 Pages
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[in Japanese]
Article type: Article
1999 Volume 55 Issue 10 Pages
I-
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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1999 Volume 55 Issue 10 Pages
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1999 Volume 55 Issue 10 Pages
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1999 Volume 55 Issue 10 Pages
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1999 Volume 55 Issue 10 Pages
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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NORIAKI OUCHI, [in Japanese]
Article type: Article
1999 Volume 55 Issue 10 Pages
973-979
Published: October 20, 1999
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NOBUO OKAZAKI
Article type: Article
1999 Volume 55 Issue 10 Pages
980-983
Published: October 20, 1999
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NAGARA TAMAKI
Article type: Article
1999 Volume 55 Issue 10 Pages
984-988
Published: October 20, 1999
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KATSUHIKO YAMADA
Article type: Article
1999 Volume 55 Issue 10 Pages
989-998
Published: October 20, 1999
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TAKEYUKI HASHIMOTO
Article type: Article
1999 Volume 55 Issue 10 Pages
999-1002
Published: October 20, 1999
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JYUNICHI KIMURA
Article type: Article
1999 Volume 55 Issue 10 Pages
1003-1004
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[in Japanese]
Article type: Article
1999 Volume 55 Issue 10 Pages
1005-1006
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[in Japanese]
Article type: Article
1999 Volume 55 Issue 10 Pages
1007-1008
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TOSHIO TSUCHIHASHI, ISAO FUJITA, TOSHIO MAKI, MATSUO KlTAGAWA, TAKESHI ...
Article type: Article
1999 Volume 55 Issue 10 Pages
1009-1017
Published: October 20, 1999
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The T_2 relaxation effect of the fast spin echo sequence (FSE) was investigated using Superparamagnetic iron oxide (SPIO) particles. When even echoes were used as the effective TE of FSE, the signal intensity ratio [signal intensity of FSE/signal intensity of conventional spin echo sequence(CSE)] of FSE and CSE increased, whereas the T_2 relaxation effect of SPIO with FSE was reduced. However, when odd echoes were used, neither signal intensity changed, and weakening of the T_2 relaxation effect, considered a problem with FSE, was reduced. This phenomenon was not observed when the refocusing flip angle was changed to 30 and 60 degrees. However, it was observed when the refocusing flip angle was 120 and 150 degrees. Thus, this phenomenon can be considered to be related to oscillation in longitudinal magnetization when using the Carr-Purcell-Meiboom-Gill(CPMG) technique.
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YASUNOBU FUKUNISHI, SHIGEYA SHIMADA
Article type: Article
1999 Volume 55 Issue 10 Pages
1018-1026
Published: October 20, 1999
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Images with reduced rib shadows can be obtained on chest radiography by using a higher voltage or applying an additional filter, owing to an increase in effective energy. Although images with poor discriminative ability result from radiography at a high effective energy level when screen/film systems are used, a result of a general decrease in the contrast of the subject, shadows of soft tissues are apparently emphasized when the CR system is used. Because tone is adjusted according to the width of the histogram by the exposure-data-recognizer (EDR) mechanism, a higher effective energy level is expected to be advantageous in chest radiography using the CR system. As long as the incident dose to the imaging plate (IP) is maintained at a nearly fixed level using a phototimer, EDR-enhanced noise, soft tissue signals, and the SNR in the lung field are reduced, with an increase in effective energy. All in all, the high effective energy technique has reduced the ability to diagnose low contrast masses. Increasing the dose is extremely efficient in the high SNR of the lung field and maintains the advantage of high-voltage radiography in the CR system using the EDR mechanism. The increase ratio requisite for exposure is about 1.4 in Cu 0.1mm+Al 2 mm, about 1.6 in Cu 0.3 mm using 141 kV, with the proviso that the increase ratio is 1.0 when the sensitivity of the phototimer is normal.
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SHUJI KOYAMA, TAKAHIKO AOYAMA, HISASHI MAEKOSHI
Article type: Article
1999 Volume 55 Issue 10 Pages
1027-1035
Published: October 20, 1999
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Detectors of at least several centimeters long are required for accurate dosimetry of patient exposure from x-ray computed tomography (CT) devices, since scattered x-rays are largely distributed in the human body and their contribution to total absorbed dose is significant. The present paper describes the development of a novel dosimeter for x-ray CT devices that uses a tissue-equivalent thin plastic scintillating fiber as a detector. In usual scintillating fiber detectors, the lightemitted in the fibers is transformed to an electrical signal by a photomultiplier tube (PMT) attached to the end of the fiber. In this case, uniformity of sensitivity along the fiber axis cannot be obtained because of the attenuation of light intensity in the fiber. To obtain uniform sensitivity of the scintillating fiber detector, we developed a new method using two PMTs attached to both ends of the fiber and processed coincident signals from both PMTs. Using this method we were able to construct a long scintillation detector with an effective detection length of 880 mm for x-ray CT dosimetry. The measurement of absorbed dose in a human phantom for x-rays from CT devices indicated that the absorbed dose obtained with CT ion chambers was approximately 30% less than that measured with our new dosimeter.
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SHINICHI GOTOH, AKIKO HATTORI, AKIKO OHTSUKA, RIKA ONIKI, YOSHIAKI FUK ...
Article type: Article
1999 Volume 55 Issue 10 Pages
1036-1041
Published: October 20, 1999
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We describe the results of dose measurements and image quality evaluation in mammography using a phantom for the ACR accreditation program. Screen-film images, were obtained with the following systems: Min-R 2000 screen and Min-R 2000 film (Kodak), and UM Mammo Fine and UM-MA HC film (Fuji). CR images were obtained with the FCR 7000 (Fuji). Compared with the Mo filter system, mean glandular dose with the Rh filter at 28 kV and 30 kV decreased 22% and 10%, respectively. However, at 32 kV and 34 kV, there was no significant difference between the dose with the Mo filter and that with the Rh filter. Area exposure product correlated well with entrance exposure dose and seemed to be useful for approximating glandular dose. Although the quality of images obtained with the Mo filter at 28 kV was acceptable, images obtained with the Min-R 2000 system were superior to those obtained with the other two. According to the mammography quality assurance program established by JSRT, mean glandular dose could be calculated by measurement of the entrance exposure dose for a mammographic phantom.
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ISAO MURO, TAKASHI YAMASHITA
Article type: Article
1999 Volume 55 Issue 10 Pages
1042-1048
Published: October 20, 1999
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We describe a method to measure MTF using Fourier analysis with a square wave chart. This method has the advantage of being able to easily and accurately measure MTF without Coltman's formula by computing the Fourier spectrum of the fundamental frequency of each square chart. It took just 8 sec to automatically obtain measurements of MTF using the square wave chart. To evaluate the usefulness of this method, the contrast method was used to confirm its accuracy and reproducibility using computer-simulated data. MTF data for each sample were measured five times by 10 persons. We analyzed the accuracy and reproducibility of these two methods by using known MTF data with white noise. Our results demonstrated that error for the contrast method was psychologically affected by much noise and unfavorable MTF. The contrast method showed that the MTF obtained from data in which the error was more than 0.01 between the real and measured value was less than 0.2. However, MTF was less than 0.02 with our method. There was a difference between the two methods in terms of accuracy. Because of its superior accuracy and shorter measuring time, we consider our method better for determining MTF than the contrast method.
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
1049-1050
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
1051-1052
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
1054-1055
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
1056-1058
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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Article type: Appendix
1999 Volume 55 Issue 10 Pages
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1999 Volume 55 Issue 10 Pages
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Article type: Cover
1999 Volume 55 Issue 10 Pages
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