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Article type: Cover
1991 Volume 47 Issue 4 Pages
Cover13-
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Article type: Index
1991 Volume 47 Issue 4 Pages
Toc13-
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Article type: Index
1991 Volume 47 Issue 4 Pages
Toc14-
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Article type: Appendix
1991 Volume 47 Issue 4 Pages
i-ii
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Article type: Appendix
1991 Volume 47 Issue 4 Pages
iii-iv
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AKIYOSHI OHTSUKA, JUNJI MORISHITA, KATSUHIKO UEDA, MASAHIRO HASHIDA, S ...
Article type: Article
1991 Volume 47 Issue 4 Pages
610-619
Published: April 01, 1991
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A new concept found successful for improving the image quality of computed radiography (CR) is presented. It is shown theoretically and experimentally that radiographic contrast and sharpness can be improved by reduction in scattered X-rays without increasing patient exposure. ST (imaging plate : IP) combined with high-ratio antiscatter grids (the Low-Scatter System : LSS) and low-ratio grids (the High-Scatter System : HSS) for general radiography, and HR (IP) combined with antiscatter grids (LSS) and without grids (HSS) for mammography, were used in this study. In LSS, radiographic noise can be increased by a factor of about 2 due to reduction in the incident dose to IP. However, radiographic contrast and response can also be increased by a factor of 1.4-1.6. Images by LSS were found to those by HSS in visual detection of low contrast test objects and also in clinical application. This method is simple and has the advantage of not requiring special devices such as a moving slit assembly.
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JUNJI SHIRAISHI, KAZUHISA KOSAKAI, MASAKATSU HATAGAWA, MITSUJI HIGASHI ...
Article type: Article
1991 Volume 47 Issue 4 Pages
620-626
Published: April 01, 1991
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Free-response receiver operating characteristic (FROC) analysis, which is measured by detecting existence and location of multiple signals, has the possibility of providing a more accurate evaluation than receiver operating characteristic (ROC) analysis which is measured by merely detecting the existence of signal. However, the FROC uses more allows complex procedures to make samples and there is greater difficulty to use the observed data observation. In this study, we improved the FROC analysis using a personal computer so as to simplify these experimental procedures. Then, we evaluated 3 types screen-film combinations by using this method, and obtained useful results.
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MITSUHIRO MATSUMOTO, MICHIHIRO SASAGAKI, YOSHINOBU MORI
Article type: Article
1991 Volume 47 Issue 4 Pages
627-629
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KOZO KUMAGAI, KENJI ISHIMATSU, TATSUYA OHTSUKA, FUJIO ARAKI, TAKUMI IS ...
Article type: Article
1991 Volume 47 Issue 4 Pages
630-636
Published: April 01, 1991
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JARP announced officially the protocol for absorbed dose measurement at 1986. We presented a modified procedure that includes two items simplified for easy calculation in the protocol. In the first item, the ionization to absorbed dose conversion factors for electron irradiation with the JARP's ionization chamber are applied for all cases in which any other commercially available cylindrical chambers are used. In the second one, the electron mean energy at the phantom surface is determined directly with the ionization half-depth in the water phantom. The amount of calculation to be done is greatly decreased compared with that of the JARP's protocol. Results with the simplified procedure agreed well with those of JARP's. We applied the simplified procedure to an exercise in JARP's protocol. As a result, the simplified procedure corresponded to JARP's protocol in the range of ±1 at the last digit of the values for percentage depth dose. The mean energy determined in 16.7 MeV shown in the exercise. The Bremusstralung background has been neglected in JARP's exercise for the mean energy determination. The resultant error in the mean energy caused by the disregard of the bremusstralung background has come about twice that arising from the simplified procedure.
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FUJIO ARAKI, KOZO KUMAGAI, TAKUMI ISERI, TSUTOMU KAWANO
Article type: Article
1991 Volume 47 Issue 4 Pages
637-642
Published: April 01, 1991
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Dose calculations of irregularly shaped fields can be made by the Clarkson technique, which, however requires considerable time and is thus not practical. We investigated a simple approximation method for determining field factors (F_A) and tissue-peak ratios (TPRs) for irregularly shaped fields. By this method, we approximated scatter dose by the ratio of area for an irregularly shaped field to that for the overall field (without blocking). Maximum error of equivalent square fields as determined by this method for irregularly shaped fields was-1.3% for field factors, +2.1% for TPRs and +1.4% for the F_A×TPRs.
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[in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
643-647
Published: April 01, 1991
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HIDEKI KATO
Article type: Article
1991 Volume 47 Issue 4 Pages
648-652
Published: April 01, 1991
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
653-669
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Article type: Appendix
1991 Volume 47 Issue 4 Pages
670-
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[in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
670-
Published: April 01, 1991
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
670-
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[in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
670-
Published: April 01, 1991
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
670-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
670-671
Published: April 01, 1991
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[in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
671-
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[in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
671-
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[in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
671-672
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
672-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
672-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
672-
Published: April 01, 1991
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
672-
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[in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
672-674
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
674-
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Article type: Article
1991 Volume 47 Issue 4 Pages
674-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
674-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
674-
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Article type: Article
1991 Volume 47 Issue 4 Pages
674-675
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Article type: Article
1991 Volume 47 Issue 4 Pages
675-
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Article type: Article
1991 Volume 47 Issue 4 Pages
675-676
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Article type: Article
1991 Volume 47 Issue 4 Pages
676-677
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Article type: Article
1991 Volume 47 Issue 4 Pages
677-
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Article type: Article
1991 Volume 47 Issue 4 Pages
677-
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[in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
677-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
677-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
677-678
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[in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
678-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
678-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
678-
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Article type: Article
1991 Volume 47 Issue 4 Pages
678-679
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
679-
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Article type: Article
1991 Volume 47 Issue 4 Pages
679-
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[in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
679-680
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
680-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 4 Pages
680-
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[in Japanese]
Article type: Article
1991 Volume 47 Issue 4 Pages
680-
Published: April 01, 1991
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