Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 64, Issue 4
Displaying 1-12 of 12 articles from this issue
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Opening Article
Originals
  • Influence of Count Rate on Image Quality in Three-dimensional PET Acquisition
    Hiromitsu Daisaki, Kazufumi Suzuki, Hiroyoshi Fukukita, Hitoshi Fukush ...
    2008 Volume 64 Issue 4 Pages 407-416
    Published: April 20, 2008
    Released on J-STAGE: May 02, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.407
    JOURNAL FREE ACCESS
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    Objective: In FDG-PET examinations, optimization of the injected dose and duration of acquisition are important in determining the physical performance of PET or the PET/CT scanner. This study was intended to elucidate the influence of count rate on image quality. Methods: Three PET/CT scanners (Biograph sensation 16, Discovery ST, and Aquiduo) were used in this study. Body and scatter phantoms (NEMA 2001) and a cylindrical phantom (for QC use) were also used. Data acquisition was performed repeatedly for about 6 h to achieve a fixed 15 million counts of true plus scatter. The count rate performance and image quality (signal-to-noise ratio and contrast) of each frame were analyzed after data acquisition. The relationship between the count rate and image quality was also analyzed. Results: A positive correlation between the random fraction (ratio of random to prompt count rate) and signal-to-noise ratio was found in all PET/CT scanners, but with differing effects of the count rate’s influence on image quality. Image contrast was not correlated with count rate. Conclusion: Acquisition parameters must be determined by considering each scanner’s effect on how count rate influences image quality. (Article in Japanese)
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  • Proposal and Verification of Presampled MTF Measurement by the Simple Analysis Method Using the Edge Method
    Ryo Higashide, Katsuhiro Ichikawa, Hiroshi Kunitomo, Michito Sawada
    2008 Volume 64 Issue 4 Pages 417-425
    Published: April 20, 2008
    Released on J-STAGE: May 02, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.417
    JOURNAL FREE ACCESS
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    The edge method adopted by the International Electrotechnical Commission (IEC) for presampled modulation transfer function (presampled MTF) measurement has the advantage that the complexity and limitations of image acquisition are less than those of the slit method. On the other hand, it has the disadvantage that the maintenance of accuracy is difficult because of the noise amplification caused by the differentiation. In order to reduce this disadvantage, we proposed an effective method in which many edge profiles are synthesized and then the synthesized edge profiles are bound into regular interval bins. Furthermore, the influences of some factors in edge profile analysis on measurement accuracy were examined. The appropriate width of one bin was 10-20% of the sampling interval. Measurement error of the inclination angle of the edge should be made up to 0.05°. The range of the angle was allowed to be from 1 to 5 degrees. If these conditions were fulfilled, accurate measurement up to the Nyquist frequency (fn) was possible. Using an actual computed radiography (CR) system, the presampled MTF was obtained by the slit method and our edge method. The two results showed good agreement. (Article in Japanese)
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  • Influence of Smoothing Process on Statistical Brain Function Image Analysis
    Yuki Matsutake, Hideo Onishi
    2008 Volume 64 Issue 4 Pages 426-433
    Published: April 20, 2008
    Released on J-STAGE: May 02, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.426
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    Spatial smoothing performed after spatial normalization on the easy Z-score Imaging System (eZIS) is considered to affect signal size. The purpose of this study was to analyze quantitatively the influence of the smoothing process on eZIS using the voxel of interest (VOI) method. A normal database (NDB) was established using 99mTc-Hexamethylpropyleneamine oxime (HMPAO) brain perfusion SPECT images of thirty healthy volunteers. Then the NDB was smoothed with various Gaussian kernels (2, 4, 8, 12, 16 mm). Artificial lesions with known volumes and reduction of tracer uptake were made on one of the healthy volunteer images, and eZIS analysis was performed on the NDB of the same Gaussian kernel, respectively. The signal size of small-sized lesions was expanded 5.1 times to the true signal size of a 12 mm Gaussian kernel. On the other hand, the medium lesion size, which was approximately the same size as the posterior cingulate gyrus, was expanded 2.9 times to true signal size. Estimation of the false positive area using the extraction estimation method at lesion size medium indicated the lowest value at 8, 12 mm Gaussian kernel smoothing. The smoothing procedure at 8-12 mm Gaussian kernel is effective to detect a focal abnormality in the brain SPECT of Alzheimer’s disease. (Article in Japanese)
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  • Evaluation of Non-linear Adaptive Smoothing Filter by Digital Phantom
    Kazuhiro Sato, Mitsunori Goto, Hiroki Ishiya, Ryosuke Oshita, Issei Mo ...
    2008 Volume 64 Issue 4 Pages 434-441
    Published: April 20, 2008
    Released on J-STAGE: May 02, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.434
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    As a result of the development of multi-slice CT, diagnoses based on three-dimensional reconstruction images and multi-planar reconstruction have spread. For these applications, which require high z-resolution, thin slice imaging is essential. However, because z-resolution is always based on a trade-off with image noise, thin slice imaging is necessarily accompanied by an increase in noise level. To improve the quality of thin slice images, a non-linear adaptive smoothing filter has been developed, and is being widely applied to clinical use. We developed a digital bar pattern phantom for the purpose of evaluating the effect of this filter and attempted evaluation from an addition image of the bar pattern phantom and the image of the water phantom. The effect of this filter was changed in a complex manner by the contrast and spatial frequency of the original image. We have confirmed the reduced effect of image noise in the low frequency component of the image, but decreased contrast or increased quantity of noise in the image of the high frequency component. This result represents the effect of change in the adaptation of this filter. The digital phantom was useful for this evaluation, but to understand the total effect of filtering, much improvement of the shape of the digital phantom is required. (Article in Japanese)
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Clinical Technology
  • Automatic Selection of Optimal Cardiac-phase in Coronary CT Angiography—Its Clinical Usefulness for Patients with Atrial Fibrillation
    Ryota Matsumoto, Hiroshi Narita, Hirofumi Anno, Yoshihiro Ida, Yoshihi ...
    2008 Volume 64 Issue 4 Pages 442-449
    Published: April 20, 2008
    Released on J-STAGE: May 02, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.442
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    The optimal cardiac phases for coronary CT angiography (CTA) are end-systole and mid-diastole, in which cardiac movement is slow. In conventional methods, these cardiac phases are determined by visual selection. We have compared the images in the optimal cardiac phases that were selected by the conventional method and cardiac-phase search software (Phase Navi), and examined the clinical usefulness of Phase Navi in patients with atrial fibrillation. The subjects were 38 patients (regular rhythm: 20, atrial fibrillation: 18). The continuity scores of patients with regular rhythm (Phase Navi, conventional methods) were 2.4±0.3–2.5±0.3 in end-systole and 2.4±0.5–2.4±0.4 in mid-diastole. The scores of patients with atrial fibrillation (Phase Navi, conventional methods) were 2.3±0.4–2.3±0.4 in end-systole, and 2.2±0.5–2.1±0.6 in mid-diastole. Because the continuity scores of the optimal images from Phase Navi were similar to those from the conventional method, Phase Navi had clinical usefulness in patients with atrial fibrillation. (Article in Japanese)
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Educational Lecture—Interpreting Medical Images for Radiological Technologists
Basic Lectures—The Image Processing Technology that You Should Learn on Examination
Clinical Technology Course
Series—Law and Medicine (9)
Report of Research Group
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