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Article type: Cover
1993 Volume 49 Issue 6 Pages
Cover17-
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Article type: Index
1993 Volume 49 Issue 6 Pages
Toc17-
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Article type: Index
1993 Volume 49 Issue 6 Pages
Toc18-
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Article type: Appendix
1993 Volume 49 Issue 6 Pages
i-v
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Article type: Appendix
1993 Volume 49 Issue 6 Pages
vi-xii
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HIROYUKI TAGASHIRA, SHIGERU NAKATA, MASAHIRO YOSHIMOTO, TOSHIAKI KAWAK ...
Article type: Article
1993 Volume 49 Issue 6 Pages
803-809
Published: June 01, 1993
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We evaluated the quantitative assessment of radiopasity of the maxillary sinuses using digitally processed images. The radiographs of the maxillary sinuses were exposed with Water's projection and the copper wedge filters were exposed simultaneously for the following data analysis. The original radiographs were converted to a digital image with a dedicated digitizer (TDF-500-B, Toshiba, Japan), and a quantitative analysis was performed with a medical image processor (GMS-550-U, Toshiba, Japan). The 4.2×4.2(mm)^2 of a region of interset (ROI) was selected 12mm under the infraorbital foramen and the mean pixel value was converted to the thickness of copper wedge filter width was difined as the fixed copperequivalent value (M_1) and the converted value of ROI drawn on the whole maxillary sinus was defined as the mean copper-equivalent value (M_2). The results showed that M_1 and M_2 were the useful indicators for a follow-up in the conservative theraphy against the chronic maxillary sinus.
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TOSHIAKI MIYACHI, HARUMASA KASAI, TOSHIAKI SAKAKIBARA, KATSUHIRO ICHIK ...
Article type: Article
1993 Volume 49 Issue 6 Pages
810-816
Published: June 01, 1993
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A study was carried out on studied the effects of conductive samples regarding experimental receiving sensitivity on 0.5T magnetic resonance imaging (MRI) system and the adaptability of these results to clinical imaging. The relationship among the sample size, conductivity and inductive loss (magnetic loss) was taken up. For the 0.5T-MRI system, inductive loss was in proportion to the electric conductivity of the sample and to the fifth power of the sample radius. Furthermore, the second power of the signal-to-noise ratio (SNR) of the image was inversely proportional to the fifth power of the sample radius. These results agreed well with the theoretical formulations. In addition, the maximum and minimum receiving sensitivity of each radio-frequency (RF) coil could be calculated from the ratio of the inductive losses observed. The experimental results could be applied for clinical imaging. Values for the observed inductive losses in human subjects reflected the characteristics of the particular organ being evaluated, and also reflected the characteristics of the particular RF coils. Calculating the inductive loss value in reference to the particular body part allowed for practical estimation of the coil parameters, and was useful in assurance of image quality.
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MITSUHIRO MATSUMOTO, YOSHINOBU MORI
Article type: Article
1993 Volume 49 Issue 6 Pages
817-824
Published: June 01, 1993
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A Computed Radiography (CR) with storage phosphor technology has advanced remarkably. Its application has been also discussed regarding the field of radiotherapy and studies have been made to shift from the film/screen system to the portal film using the CR system. The authors started to research CR portal imaging with high energy X-ray (10MV) on a regular scale in 1989. This paper deals with characteristics of high energy X-rays using the CR system. The results are : (1) The digital characteristic curve correspond with calculated value for dynamic range (L-value). (2) The monitor unit (MU) counts at pixel (digital) value saturation point were L-value 0.5 : 28MU, L-value 1.0 : 50MU, L-value 2.0 : 167MU, L-value 3.0 : 450MU, L-value 4.0 : 1614MU. (3) The image contrast with the Mix-Dp phantom was L-value 0.5 : about a 300 pixel value and L-value 4.0 : about a 30 pixel value by a phantom 10 to 18cm in thickness. (4) Optimum L-value was 0.5, and tone-scale was the straight type of CR portal imaging using the graphy count mode. (5) Optimum L-value was 4.0, and tone-scale was a rectangular wave type of CR portal imaging using theraputic doses, and those were also describe by the histogram analysis.
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TOSHIAKI MIYACHI, YOSHIYUKI HANAFUSA, HIROYUKI NARITA, YUJI Kondoh, YU ...
Article type: Article
1993 Volume 49 Issue 6 Pages
825-832
Published: June 01, 1993
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An attempt was made to evaluate the imaging quality of various magnetic resonance imaging (MRI) modalities. Eight models were measured (four 0.5T and four 1.5T machines) using the same phantom. The results were then compared considering signal-to-noise ratio (SNR), image uniformity, T1, T2 and slice thickness. The results showed a little disparity with the projected values in T1 and T2 values. T1 and T2 values did not contribut to the differences in SNR among the models using the same magnetic field strength. The relative superiority of the SNR differed depending on the methods used to determine SNR. Coil diameter contributed to the differences in SNR among the different models. No difference in slice thickness existed for any of the models tested. Image uniformity reflected the characteristics of the radio frequency coil in each particular model. The phantom remained stable for the duration of assessment for all cases.
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[in Japanese]
Article type: Article
1993 Volume 49 Issue 6 Pages
833-839
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Article type: Article
1993 Volume 49 Issue 6 Pages
840-844
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Article type: Article
1993 Volume 49 Issue 6 Pages
845-848
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Article type: Article
1993 Volume 49 Issue 6 Pages
849-852
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
1993 Volume 49 Issue 6 Pages
853-857
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Article type: Article
1993 Volume 49 Issue 6 Pages
857-864
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1993 Volume 49 Issue 6 Pages
865-870
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1993 Volume 49 Issue 6 Pages
871-876
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1993 Volume 49 Issue 6 Pages
876-879
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1993 Volume 49 Issue 6 Pages
880-886
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Article type: Article
1993 Volume 49 Issue 6 Pages
886-888
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Article type: Article
1993 Volume 49 Issue 6 Pages
889-891
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Article type: Appendix
1993 Volume 49 Issue 6 Pages
892-
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Article type: Article
1993 Volume 49 Issue 6 Pages
892-
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Article type: Article
1993 Volume 49 Issue 6 Pages
892-
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Article type: Article
1993 Volume 49 Issue 6 Pages
892-
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Article type: Article
1993 Volume 49 Issue 6 Pages
892-
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Article type: Article
1993 Volume 49 Issue 6 Pages
892-
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Article type: Article
1993 Volume 49 Issue 6 Pages
892-893
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Article type: Article
1993 Volume 49 Issue 6 Pages
893-
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Article type: Article
1993 Volume 49 Issue 6 Pages
893-
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1993 Volume 49 Issue 6 Pages
893-
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1993 Volume 49 Issue 6 Pages
893-
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1993 Volume 49 Issue 6 Pages
893-
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1993 Volume 49 Issue 6 Pages
893-894
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1993 Volume 49 Issue 6 Pages
894-
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Article type: Article
1993 Volume 49 Issue 6 Pages
894-
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Article type: Article
1993 Volume 49 Issue 6 Pages
894-
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Article type: Article
1993 Volume 49 Issue 6 Pages
894-
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1993 Volume 49 Issue 6 Pages
894-
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1993 Volume 49 Issue 6 Pages
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1993 Volume 49 Issue 6 Pages
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1993 Volume 49 Issue 6 Pages
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1993 Volume 49 Issue 6 Pages
895-
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1993 Volume 49 Issue 6 Pages
895-
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1993 Volume 49 Issue 6 Pages
895-
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1993 Volume 49 Issue 6 Pages
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1993 Volume 49 Issue 6 Pages
895-896
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Article type: Article
1993 Volume 49 Issue 6 Pages
896-
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Article type: Article
1993 Volume 49 Issue 6 Pages
896-
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1993 Volume 49 Issue 6 Pages
896-
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