Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 63, Issue 9
Displaying 1-6 of 6 articles from this issue
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Opening Article
35th Autumn Scientific Congress
Note
  • Study of Susceptibility-weighted Imaging (SWI) Using a Simple MR Phantom
    Ayako Ohta, Kenichi Naito, Masaki Ohkubo, Masami Inomata, Yukio Ohgosh ...
    2007 Volume 63 Issue 9 Pages 1093-1098
    Published: September 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.1093
    JOURNAL FREE ACCESS
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    We evaluated the visibility of hypointensity regions on susceptibility-weighted (SW) magnetic resonance imaging (MRI). A commercial simple phantom filled uniformly with a gel material was demonstrated to include small regions affected by different magnetic susceptibilities compared to their surroundings. For detection of these regions in the phantom, the three-dimensional SW imaging (SWI) technique is superior to a conventional two-dimensional gradient-recalled-echo (GRE) MRI technique. The mean contrast between the hypointensity regions and their surroundings on GRE images (T2* weighted images) of 4 mm slice thickness is approximately 88% less than that on SWI of 4 mm effective slice thickness. When the effective slice thickness of SWI is increased more than 4 mm, the contrast on SW images is decreased. While the mean contrast on SWI of 7 mm effective slice thickness is approximately 75-65% compared to that of 4 mm effective slice thickness, its contrast of 7 mm is determined to be higher than that on GRE images of 4 mm slice thickness; this suggests that the SWI technique could be applied to whole brain examination by reducing the acquisition time. The quantitative results in this article are considered to be useful for evaluating the visibility of hypointensity regions on SWI, when comparing them with GRE images and varying the effective slice thickness of SWI. [Article in Japanese]
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Data
  • Method of SNR Determination Using Clinical Images
    Akio Ogura, Tosiaki Miyati, Masato Kobayashi, Hiroshi Imai, Kouzou Shi ...
    2007 Volume 63 Issue 9 Pages 1099-1104
    Published: September 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.1099
    JOURNAL FREE ACCESS
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    Parallel magnetic resonance imaging (MRI) with arrays of receiver coils such as those of sensitivity encoding (SENSE) are being widely used. However, conventional methods of image signal-to-noise ratio (SNR) determination cannot be used for parallel MRI, and a novel method has been reported in JSRT. However, this method of SNR determination is for phantom images not for clinical images. Therefore, we researched accurate measurement of the image noise of parallel MRI reconstruction including the unfolding process and uniformity filters. The possibility of a subtraction method using clinical images and the accuracy of standard deviation (SD) of clinical images for optimum ROI were studied because it was not possible to use the air-signal method. The results indicated that the position of the ROI was selected for uniformity of signal intensity area and that the size of the ROI was about 50 pixels. However, under these conditions, the noise value of SNR was higher than that using the phantom-subtraction method. In addition, the tissue-subtraction method was useful when the two scanning images were in agreement. [Article in Japanese]
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