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Article type: Cover
1987 Volume 43 Issue 6 Pages
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Article type: Index
1987 Volume 43 Issue 6 Pages
Toc17-
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Article type: Index
1987 Volume 43 Issue 6 Pages
Toc18-
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Article type: Appendix
1987 Volume 43 Issue 6 Pages
App15-
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Article type: Appendix
1987 Volume 43 Issue 6 Pages
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TATSUSHI TOMOMITSU, SHINICHI YANAGIMOTO, NAOMASA NARIHIRO, HIROAKI MIM ...
Article type: Article
1987 Volume 43 Issue 6 Pages
667-671
Published: June 01, 1987
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In order to measure bone mass by dual photon absorptiometry (DPA) using ^<153>Gd as the radionuclide source, it is essential to determine accurately the counts of both energies at 44 and 100 keV. Therefore, the spill-over effect over 44 keV energy window, which is due to the scattering of the 100 keV photon, should be corrected. In this paper, the correction of the spill-over effect in a newly developed DPA instrument system using a gamma camera was studied. It was concluded that spillover effect (f(x)), on the central area (3×3 pixels) in the detector field, from the 100 keV energy to the 44 keV energy window was given by the following equation : f(x) =0.124・X+ 0.256 (where X was the phantom thickness (cm), and f(x) was expressed as the percentage of the counts at the 100 keV photopeak). Furthermore, the spill-over effect on the whole detector field was calculated as 1.5% of error.
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HIDEKI KATO
Article type: Article
1987 Volume 43 Issue 6 Pages
672-678
Published: June 01, 1987
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The Monte Carlo computer program has been used to analyze the characteristics of scattered radiation in a phantom irradiated by 10 MV X-rays. The program simulated an irradiation by 10 MV X-rays with a 0 area field upon a center of 30×30×30 cm^3 water phantom. The study distinguished energy distribution of the secondary electron which was set in motion by interactions in the ring with radius R and depth d. Using these results, spectrums of the secondary electron on the beam axis of the circular fields were calculated by means of the superposition principle. Ratios of the average collision mass restricted stopping power (water/air, acrylic/air, polystyrene/air) on the beam axis of circular fields were calculated based on the electron spectrum data. Stopping power ratios calculated on spectrum of electron, which were set in motion only by first interactions of the primary photon beam, coincided with the data in AAPM protocol (1983) within 0.5%. However, stopping power ratios, which were calculated on electron spectrums with full interaction, increased with the field radius, and differed from AAPM data beyond 2% at the maximum. For precise measurement or calculation of the absorbed dose for high energy radiation, it is better to apply the mass restricted stopping power based on the electron spectrum with full interactions.
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KESATO YANO, TOSHIO KASUGA, FUMIO MARUYAMA
Article type: Article
1987 Volume 43 Issue 6 Pages
679-689
Published: June 01, 1987
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The mean blood flow was measured with the mean transit time and vascular volume by DSA. Blood flow analyses reported up to now have not yet been put to practical use because of many clinical problems still not solved. We clarified those problems, developed a new method for relative blood flow measurement, and compared it with the conventional method. The new method is as follows : first, one ROI is set on the time image based on the parameter of time information in each pixel ; secondly, the mean transit time is determined by liner approximation of the time information and distance along the blood vessel by the least squares method. The relative vascular volume was determined by the time density curve. With this new method, the errors caused by a change in the regional blood flow velocity, noise and geometrical measurement could be decreased. Therefore, the accuracy of the blood flow measuremcnt compared with the conventional method was greatly improved. The phase information of the Fourier analysis far superior in accuracy than the other time parameters, because the accuracy did not drop when the measuring distance became shorter. The error of the relative blood flow measurement could be controlled below 10% for blood vesses of more than 3 mm in diameter and 3 cm length in continuous flow. Furthermore, for pulsatile flow, it may have excellent applications.
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KOUSUKE UEDA, MASAHIRO YOSHIMOTO, TOSHIAKI KAWAKAMI
Article type: Article
1987 Volume 43 Issue 6 Pages
690-693
Published: June 01, 1987
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KUNIO DOI
Article type: Article
1987 Volume 43 Issue 6 Pages
694-729
Published: June 01, 1987
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Observer performance experiments using ROC analysis indicated that the detectability of subtle microcalcifications in digitized mammograms was improved by unsharp-mask filtering. However, the processed mammograms still provided lower accuracy than the original mammogram. Similar studies with mild interstitial infiltrates and subtle pneumothoraces in chest radiographs showed that the use of a pixel size substantially larger than 0.1 mm may result in some loss of diagnostic accuracy, and that a 2048×2048 matrix may be a satisfactory compromise for digital chest radiography. The unsharp masking may improve diagnostic accuracy for pneumothorax, while radiologists' performance in identifying interstitial infiltrates was degraded by the image processing. The contrast-detail (C-D) diagram was measured by using simulated square patterns superimposed on radiographic noise. Experimental variations in conventional C-D curves due to observer differences, within-reader variability, and image noise outcomes were quite large, and therefore it was necessary to increase the total number of observations in order to obtain reliable results. The relationship between physical and visual image quality for the task of detecting plastic beads was studied on thirty-seven different radiographic imaging conditions using a 2AFC visual detection experiment. Results indicated that human observer detection performance most closely resembled that of a sub-optimal statistical decision process. The effects of imaging and display conditions on the detectability of low-contrast objects in DSA images were investigated by using 18AFC experiments. We found that the SNR obtained from the perceived statistical decision theory model, which includes the observer's internal noise, can accurately predict the detectability of low-contrast objects in DSA images. The effect of pixel size on the SNR and threshold detection of low-contrast radiologic pattern was investigated theoretically for digital radiographic systems. No substantial difference between 0.1 and 0.2 mm pixel sizes was found in threshold contrasts for square objects. No substantial difference between 0.1 and 0.2 mm pixel sizes was found in threshold contrasts for square objects ranging from 0.1 to 20 mm, and thus we conclude that 0.2 mm pixel would be sufficiently small for visualization of most image detail in many radiologic examinations. The effects of image processing with unsharp masking, Metz filters, matched filters and optimal statistical filter on the detection of simulated square objects superimposed on radiographic mottle were studied theoretically and experimentally. The usefulness and limitations of these filters were discussed.
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
730-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
730-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
730-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
730-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
730-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
730-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
730-731
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
731-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
731-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
731-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
731-
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
731-732
Published: June 01, 1987
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
732-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1987 Volume 43 Issue 6 Pages
733-
Published: June 01, 1987
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1987 Volume 43 Issue 6 Pages
733-
Published: June 01, 1987
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[in Japanese], [in Japanese], [in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
733-
Published: June 01, 1987
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Article type: Article
1987 Volume 43 Issue 6 Pages
733-
Published: June 01, 1987
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Article type: Article
1987 Volume 43 Issue 6 Pages
733-734
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
734-
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Article type: Article
1987 Volume 43 Issue 6 Pages
734-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
734-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1987 Volume 43 Issue 6 Pages
734-
Published: June 01, 1987
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
735-
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
735-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1987 Volume 43 Issue 6 Pages
735-
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Article type: Article
1987 Volume 43 Issue 6 Pages
735-
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
735-736
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Article type: Article
1987 Volume 43 Issue 6 Pages
736-
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Article type: Article
1987 Volume 43 Issue 6 Pages
736-
Published: June 01, 1987
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[in Japanese], [in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
736-
Published: June 01, 1987
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Article type: Article
1987 Volume 43 Issue 6 Pages
736-737
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Article type: Article
1987 Volume 43 Issue 6 Pages
737-
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Article type: Article
1987 Volume 43 Issue 6 Pages
737-
Published: June 01, 1987
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1987 Volume 43 Issue 6 Pages
737-
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1987 Volume 43 Issue 6 Pages
737-
Published: June 01, 1987
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1987 Volume 43 Issue 6 Pages
737-738
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Article type: Article
1987 Volume 43 Issue 6 Pages
738-
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Article type: Article
1987 Volume 43 Issue 6 Pages
738-
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[in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
738-
Published: June 01, 1987
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[in Japanese], [in Japanese]
Article type: Article
1987 Volume 43 Issue 6 Pages
738-739
Published: June 01, 1987
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