Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 64, Issue 2
Displaying 1-6 of 6 articles from this issue
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Opening Article
Originals
  • Comparsion with myocardial perfusion MRI and myocardial perfusion SPECT in the diagnostic performance of coronary artery disease: A meta-analysis
    Kunihiro Iwata, Makoto Kubota, Katsuhiko Ogasawara
    2008 Volume 64 Issue 2 Pages 251-258
    Published: February 20, 2008
    Released on J-STAGE: March 01, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.251
    JOURNAL FREE ACCESS
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    We compared the diagnostic abilities of stress myocardial perfusion MRI (myocardial perfusion MRI) and myocardial perfusion SPECT, using a meta-analysis method. We investigated the diagnostic abilities of MRI and SPECT in similar subject groups in reports written in English or Japanese. The reports to be used for analysis were selected according to a “screening standard,” which was established in advance. After consolidating the data from the selected reports, we compared (1) the integrated odds ratio, (2) the point estimation values of sensibility/specificity, and (3) the summary ROC curve. For the analysis, six reports were selected (subjects: 153, coronary-artery target sites: 447). Meta-analysis revealed that the diagnostic ability of myocardial perfusion MRI was superior to that of myocardial perfusion SPECT regarding each of the parameters (1)-(3). This is considered to be supportive evidence of the usefulness of myocardial perfusion MRI. (Article in Japanese)
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  • Investigation of Reduction of Exposure Dose in Digital Mammography: Relationship between Exposure Dose and Image Processing
    Yoshio Fujimura, Hikaru Nishiyama, Toshinori Masumoto, Shingo Kono, Ya ...
    2008 Volume 64 Issue 2 Pages 259-267
    Published: February 20, 2008
    Released on J-STAGE: March 01, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.259
    JOURNAL FREE ACCESS
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    In digital mammograms, granularity is an important image property for the detection of microcalcifications and masses. Therefore, we investigated the relationship between the conditions of various exposure doses and the detectability of RMI156 phantom images with and without image processing for the reduction of exposure dose. The images are processed with Gaussian filter and unsharp-masking filters to evaluate the effects on image properties by using the digital Wiener spectrum (WS) presampled modulation transfer function (MTF). In addition, observer performance tests for the detectability of microcalcifications and masses are performed. With Gaussian filtering, the WS value decreased to 50% at 2.0 cycles/mm and the detectability score of masses increased 80% and 12%, on 1.34 mGy and 2.62 mGy, respectively (p<0.05). With unsharp-masking (7×7 pixels), the MTF value increased to 126% at 2.0 cycles/mm, and the detectability of microcalcification to 32% and 5%, on 1.34 mGy and 5.28 mGy, respectively (p<0.05) compared with the original image. The optimal dose of simulated lesions with unsharp masking became 5.25 mGy. The unsharp masking could reduce 37% of the exposure dose without a loss of detectability of microcalcifications and masses. (Article in Japanese)
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Note
  • Basic Assessment of the CNR Measurement Method of MRI System in Phantom—Suggestion for Improvement in the CNR Evaluation Method—
    Yoichi Wada, Takanori Hara, Tosiaki Miyati
    2008 Volume 64 Issue 2 Pages 268-276
    Published: February 20, 2008
    Released on J-STAGE: March 01, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.268
    JOURNAL FREE ACCESS
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    Many methods of measuring contrast-to-noise ratio (CNR) in magnetic resonance imaging (MRI) have been proposed. However, it is not clear which method is best for evaluating clinical or phantom images. In this study we examined the characteristics of the methods of evaluation proposed in the past, and we proposed new CNR evaluation method that improved noise evaluation. We examined the relationship of theoretical CNR value and measurement value when measurement sensitivity was changed. We measured the relationship between number of signal averaged (NSA) and value of CNR. The CNR value changed greatly according to where noise was measured. The measuring method that we proposed in this study was superior for the following reasons: the measurement point of noise and signal are the same; the influence of the low frequency element is slight; and the correlation of measurements and theoretical value is high. The method that we proposed in this study is useful for evaluating phantom images. (Article in Japanese)
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Clinical Technology
  • MR Venography Using the 3D-MEDIC (Multi Echo Data Imaging Combination) Sequence for Lower Extremities
    Hisashi Kitagawa, Takayuki Kishi, Ryo Saito, Shohji Tomokazu, Keiji No ...
    2008 Volume 64 Issue 2 Pages 277-285
    Published: February 20, 2008
    Released on J-STAGE: March 01, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.277
    JOURNAL FREE ACCESS
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    It is possible to diagnose varicose vein from medical history and physical examinations including inspection and palpation. Non-contrast enhanced MRV (magnetic resonance venography) is becoming popular because it can be easily performed without being affected by the radiographer’s skill. We thought that the use of MEDIC (multi echo data imaging combination) would enable us to delineate varicose veins within a short acquisition time and without need for synchronization or contrast enhancement. We used the SIEMENS MAGNETOM Avanto 1.5-Tesla unit to acquire images. Our subjects were five healthy volunteers and five patients with varicose vein. The signal strength of deep veins and muscles were measured. The SNR (signal-to-nose ratio) of deep veins and the CNR (contrast-to-noise ratio) between deep veins and muscles were also measured. 1. a) flip angle, b) fat suppression methods, c) MTC (magnetic transfer contrast) pulse, and d) combined echo. Using the optimum image acquisition protocol following our preliminary study with varicose vein patients, the ability of the 3D-MEDIC method to delineate varicose veins was compared with that of the ECG-synchronized 2D-TOF method. We found that the following settings would enable us to acquire images from a wide range=coronal, within short acquisition time and needless ECG-triggering. 1. a) flip angle=20 degrees, b) fat suppression method=water excitation, c) MTC pulse=ON, d) combined echo=2. 3D-MEDIC was better than the 2D-TOF method in delineating the varicose vein itself and the connection between the varicose vein and deep veins. It is expected that 3D-MEDIC may be useful in the clinical diagnosis of varicose veins. (Article in Japanese)
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