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Article type: Cover
1991 Volume 47 Issue 6 Pages
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Article type: Index
1991 Volume 47 Issue 6 Pages
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Article type: Index
1991 Volume 47 Issue 6 Pages
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Article type: Appendix
1991 Volume 47 Issue 6 Pages
i-iii
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Article type: Appendix
1991 Volume 47 Issue 6 Pages
iii-iv
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MASAKI ASAHARA, AKIRA YOSHIDA, HIROOMI SUMIDA, NOBUE NAKAMURA, SETSUO ...
Article type: Article
1991 Volume 47 Issue 6 Pages
797-803
Published: June 01, 1991
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A new-type phantom for several methods of observer performance examinations was developed. The phantom consists of 121 plastic block pieces, each of a different size and depth cylindrical hole as the signal object. When these signal blocks are lined up sequentially, they construct a conventional C-D diagram phantom. In addition, the specific size and depth of the signal block is able to be picked up and employed as a signal object in the ROC analysis or AFC procedure. We investigated the effect of the signal arrangement of the C-D diagram phantom on observer performance. Results indicate that the signal arrangement is significant due to the affects the variability of the threshold contrast. The percent standard deviations due to the within-observer variations were about 8.7 and 10.7% for the conventional and random arrangements, respectively. It was also compared the conventional C-D diagram method to the 18-AFC procedure using the new phantom. We found that the threshold contrasts obtained from the 18-AFC procedure have lower values than those from the C-D diagram method.
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SUSUMU MURAKAMI
Article type: Article
1991 Volume 47 Issue 6 Pages
804-810
Published: June 01, 1991
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We have developed a new method for obtaining exposure data for X-ray film caracteristic curves. The system holds neutral density attenuater (NDA) between film and screen in a cassette. The main feature of this method is using the fluorolucent intensity method while the conventional way applies the inverse square method. As the result of this experimentation, we proved that this method shows excellent correllation with the conventional inverse method. The advantage of this method over the conventional one is it allows wider exposure range of more than 1000-fold, does not require any special equipment other than an ordinary cassette and X-ray apparatus, and therefore, enables us to examine the film caracteristics very easily.
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AKIO OGURA, HIDEHARU NIIDA, KENICHI OGAWA, YOSHINORI KOMAI, HIDEHIKO T ...
Article type: Article
1991 Volume 47 Issue 6 Pages
811-817
Published: June 01, 1991
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One of the important factors affecting radiographic image quality is the film contrast of the recording system, which may be expressed by the gradient of its characteristic curve. The methods for measuring the gradient have been investigated with regard to their accuracy. It has been published that the most accurate measurement of the sensitometric curves of screen-film systems is an intensityscale X-ray sensitometer employed in the inverse square law of distance. However, in this method, the measuring is rather laborious. In this study, the accuracy of sensitometric curve by the bootstrap method using an aluminium step wedge was examined. The influences on the shape of its curve affected by several factors such as X-ray energy and the scatter factor were examined. We also compared the accuracy of the bootstrap method with the inverse square method by the standard deviation of each density at ten times the sensitometry. The measurements indicated that those factors failed to change the shape the sensitometric curve. At high density of sensitometric curves, the standard deviation at ten times of the bootstrap method were less than the inverse square method using the X-ray tube employed during daily clinical examinations. It is concluded that the bootstrap method is simple and effective to measure the gradient of sensitometric curves except for a laborious type measurement.
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YUKIHIRO MATSUDA, KAZUHIRO MASUDA, HIROSHI HASHIMOTO
Article type: Article
1991 Volume 47 Issue 6 Pages
818-824
Published: June 01, 1991
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Measurement for effective atomic number (Zeff) and electron density (ρ_e) was made using a monoenergetic image from dual energy scanning with the Rapid kV Switching (RKS) method. Measurement was conducted on the phantom and a human body. During the phantom measurement, the resulted value of ρ_e that was obtained corresponded to the calculated value within a 1% accuracy. The resulted Zeff differed average 1.5% from the calculated value by Mayneord's formula in each rod measurement into the linearity phantom using a single composition. Also the difference from the calculated value was 4.8% on the average in the composite material phantom based on the calcium carbonate and polyurethan. The mean reproducibility during 10 measurements indicated 1% or below for ρ_e and 2% or below for Zeff. In the measurement on soft human body tissue, the mobile coefficient that resulted showed a small variation from 1% to 3% for 18 cases, which almost equals to Zeff's calculated from a formation such as in NBS. The above results show an improvement in the measuring accuracy compared with the conventional method. Consequently, this is clinically applicable to various quantitative analyses.
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SHINJI ABE, IZUMI OGURA, TAIJI AOYAGI, YOH KATOH, FUTOSHI YANO
Article type: Article
1991 Volume 47 Issue 6 Pages
825-831
Published: June 01, 1991
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Up to now in Japan, Capacitor discharge generators have mainly been used in mobile X-ray generators, but recently, the stored battery energy inverter X-ray generators are being widely used in this area. This time, the tube voltage, tube current, X-ray output and reproducibility were measured, and were examined using the them with this new type generator. Furthermore, a comparison was made between the inverter generator and the capacitor discharge generator, and as a result, the usefulness of the inverter generator was confirmed.
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HIROSHI FUJITA
Article type: Article
1991 Volume 47 Issue 6 Pages
832-834
Published: June 01, 1991
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As an introduction of this symposium, four different subjects related to the image evaluation of digital radiography are discussed, which are (1) appearance of different types of DR systems and the survival systems, (2) necessity of the image evaluation of digital radiography, (3) development of the methods of digital image evaluation, and (4) content and speakers of this symposium.
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KIYOSHI SAKAMOTO
Article type: Article
1991 Volume 47 Issue 6 Pages
835-840
Published: June 01, 1991
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Characteristic curves are useful in the comparison of system speeds and in the linearization of the system response for measurement of the modulation transfer function and other physical quantities. The characteristic curve of a digital radiographic imaging system can be defined as the relationship of the output in terms of pixel value to the input in terms of relative x-ray intensity. Several different methods for determining the characteristic curve of digital radiography systems are available. We used four methods and two methods in order to determine the characteristic curve of digital subtraction angiography system (DSA) and computed radiography (CR) system. Because luminous intensity increases in proportion to X-ray intensity in these systems, we could use the time-scale method. We had to choose most suitable method in DSA system. In CR system, we can treat in a way similar to that of a screen-film system.
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JUNJI MORISHITA
Article type: Article
1991 Volume 47 Issue 6 Pages
841-847
Published: June 01, 1991
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The modulation transfer function (MTF) has been used successfully to characterize the resolution properties of conventional analog X-ray imaging systems such as screen/film systems. However, the interpretation of MTF in digital radiographic imaging systems requires caution because of non-shift invariance and the aliasing effect due to the discrete data sampling with insufficient rate. To overcome these problems, the concept of presampling MTF, which shows inherent resolution property of digital imaging system including the unsharpness of detector and the blurring effect of sampling aperture, was introduced by Giger and Doi. Two different methods for determining the presampling MTF beyond Nyquist frequency were developed and measured for I.I.-TV system and computed radiographic system with photostimulable phosphors by Fujita et al. The purpose of this paper is to show some problems of MTF analysis for digital imaging system and to show the methods for determining the presampling MTF briefly. We also discussed various component MTFs of CR system such as digital MTFs, laser-printer MTFs and overall MTFs.
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YASUNOBU FUKUNISHI
Article type: Article
1991 Volume 47 Issue 6 Pages
848-853
Published: June 01, 1991
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Multi-format camera or laser printer is important device of digital radiography. We have investigated the characteristics of the resolution for multi-format camera. It is said that the diameter and the luminance distribution of electron beam spot of the cathode ray tube (CRT) are the fluctuating factors which depend upon cathode current. In this study, we have taken a photograph of slit image which is one pixel, and after generating the luminance distribution curve of that photograph. We assessed the characteristics of the spatial resolution by using modulation transfer function (MTF). Results are as follows : 1) The brightness of CRT is controlled with cathode voltage and current. Deterioration of the resolution of CRT was caused by the expansion of the diameter of electron beam spot, which is induced by increment of the cathode current. 2) The contrast is adjusted with amplification of image signals. The maximum value of line spread function (LSF) is variable with ajustment of the contrast, however the diameter of electron beam spot is constant. The MTF was improved with increment of amplification of the image signals. But, this tendencies did not observed in CRT with low resolution. 3) The spatial resolution was inconstant on the locations of the CRT. Especially it was remarkably decreased in the peripheral area of the CRT.
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KENJI KISHIMOTO
Article type: Article
1991 Volume 47 Issue 6 Pages
854-858
Published: June 01, 1991
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In digital radiography, we showed the cause of noise product and the factor that influences it, and indicated that what process are noise of computed radiographic (CR) system caused by. In addition, we measured the overall Wiener spectrum (WS) varying some factors concerned with noise product in CR image. With the increase in X-ray exposure to the imaging plate (IP), the noise was reduced, whereas at high exposure level the noise amounted to constant value. Futhemore the greater is pixel size, the noise was reduced. Compared the CR image with the screen/film system (BMIII/Cronex-10, BHIII/Cronex-10), the noise of CR image was smaller than that of screen/film system.
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ATSUSHI TAKIGAWA, HIROSHI TERADA, MASAE SHINYA
Article type: Article
1991 Volume 47 Issue 6 Pages
859-864
Published: June 01, 1991
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It is not yet clear that how the Wiener spectrum of Fuji computed radiography (FCR) varies with image processing. Overall Wiener spectra were measured changing 3 parameters of spatial frequency processing, frequency rank : RN, frequency type : RT, degree of enhancement : RE. Influence of rotation amount : GA, that is one of 4 parameters of gradation processing, was also studied. We investigated processing conditons for mammography using FCR, from a viewpoint of granularity. RN, RE, GA contributed strongly to Wiener spectra, but the contribution of RT was small. When we process clinical images, we have to choose adequate parameters, with aims of diagnosis and parts of body.
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SHUICHI YAMAUCHI
Article type: Article
1991 Volume 47 Issue 6 Pages
865-869
Published: June 01, 1991
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The image quality in a computed radiography system (CR) was evaluated with observer performance tests using receiver operating characteristic (ROC) analysis. The detectability of low-contrast object (2mmφ beads) was compared CR with screen-film system. Effects of incident exposure to the imaging plate (IP) and image processing (contrast enhancement, unsharp masking) on the detectability of low-contrast object were also studied. The results indicated that the detectability of low-contrast object in a CR system was comparable to that of the medium-speed screen-film system. However, the detectability of low-contrast object in a CR system depended on IP size and decreased with incident exposure decreasing and increased by using contrast enhancement or unsharp masking.
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SHIGERU SANADA, KUNIO DOI, XIN-WEI XU, FANG-FANG YIN, MARYELLEN L. GIG ...
Article type: Article
1991 Volume 47 Issue 6 Pages
870-874
Published: June 01, 1991
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In an attempt to clarify the diagnostic quality of images obtained with a computed radiography (CR) system (TCR 3030A) in comparison with that obtained with conventional screen-film systems, we devised a dual-image recording technique. With this technique, a CR imaging plate is placed behind a screen-film system in a conventional cassette. This makes it possible to obtain two images simultaneously, one from each system, in a clinical examination with the same patient positioning, the same degree of patient motion, the same geometric unsharpness, and no additional exposure. The modulation transfer functions (MTFs) of the CR system with and without the dual-image recording technique were greater at low frequencies, but lower at high frequencies, than the MTFs of the screen-film systems used. The noise Wiener spectra of the CR images at the plane of the imaging plate were greater than those of the screen-film systems, but were comparable to those of the screen-film systems at the plane of the printed film due to the reduction in image size. Clinical chest images obtained with the dual-image recording technique appeared comparable, probably because of the image size reduction and the use of mild unsharp mask processing.
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[in Japanese]
Article type: Article
1991 Volume 47 Issue 6 Pages
875-876
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1991 Volume 47 Issue 6 Pages
877-899
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[in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 6 Pages
900-
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Article type: Article
1991 Volume 47 Issue 6 Pages
900-
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Article type: Article
1991 Volume 47 Issue 6 Pages
900-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 6 Pages
900-901
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1991 Volume 47 Issue 6 Pages
901-
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Article type: Article
1991 Volume 47 Issue 6 Pages
901-
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Article type: Article
1991 Volume 47 Issue 6 Pages
901-
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Article type: Article
1991 Volume 47 Issue 6 Pages
901-
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1991 Volume 47 Issue 6 Pages
901-902
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Article type: Article
1991 Volume 47 Issue 6 Pages
902-
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1991 Volume 47 Issue 6 Pages
902-
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Article type: Article
1991 Volume 47 Issue 6 Pages
902-903
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1991 Volume 47 Issue 6 Pages
903-
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1991 Volume 47 Issue 6 Pages
903-
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1991 Volume 47 Issue 6 Pages
903-
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1991 Volume 47 Issue 6 Pages
903-904
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1991 Volume 47 Issue 6 Pages
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1991 Volume 47 Issue 6 Pages
904-
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1991 Volume 47 Issue 6 Pages
904-905
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1991 Volume 47 Issue 6 Pages
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1991 Volume 47 Issue 6 Pages
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1991 Volume 47 Issue 6 Pages
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1991 Volume 47 Issue 6 Pages
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1991 Volume 47 Issue 6 Pages
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1991 Volume 47 Issue 6 Pages
906-
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1991 Volume 47 Issue 6 Pages
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1991 Volume 47 Issue 6 Pages
906-
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1991 Volume 47 Issue 6 Pages
907-
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Article type: Article
1991 Volume 47 Issue 6 Pages
907-
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1991 Volume 47 Issue 6 Pages
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