Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 64, Issue 11
Displaying 1-16 of 16 articles from this issue
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Opening Article
Originals
  • Optimization of Helical Pitch in Cardiac MDCT Acquisition in Patients with Arrhythmia Requiring ECG-edit
    Hideyuki Matsutani, Tomonari Sano, Takeshi Kondo, Takako Sekine, Takeh ...
    2008 Volume 64 Issue 11 Pages 1343-1351
    Published: November 20, 2008
    Released on J-STAGE: December 06, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.1343
    JOURNAL FREE ACCESS
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    The ECG-edit is necessary in cardiac MDCT in arrhythmias [premature atrial contraction (PAC) or premature ventricular contraction (PVC)]; however, it sometimes results in a data deficit. Therefore, a thinner helical pitch (HP) should be set to avoid data deficits. The thinner helical pitch creates more radiation exposure. The purpose is to optimize HP in PAC or PVC. In a phantom study, an acrylic phantom (10×10×500 mm) was scanned by MDCT (Aquilion 64) using an artificial pacemaker at various gantry rotation speeds (r) and HP. We evaluated the relationships between HP and the maximal table moving length (Lmax) in the border of data deficit, and among r, HP, and the maximum data collection time interval (Tmax). In the clinical study, cardiac MDCT was performed in 44 cases (M/F: 26/18, 71.4±10.6yrs) including 30 PAC and 14 PVC using the optimal HP derived from Tmax+10%. In the phantom study, there were significant correlations between HP and Lmax (Lmax=34.94–0.32 HP... (1), r=0.999, P<0.0001), and Tmax [Tmax= (69.88/HP–0.64)×r] was calculated using formula (1). In 42/44 patients, high-quality images were obtained using the optimal HP; however, it resulted in data deficits in 2 patients, because of heart rate decreasing and a couple of PAC during scanning. Optimal HP significantly (P<0.0001) reduced radiation dose (–11.4%) compared with conventional HP. In conclusion, the optimal HP in PAC or PVC was calculated from the phantom study, provided fine images in 95% patients, and could reduce radiation dose.
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  • Development of Semi-automated Segmentation of the Brain and CSF Region on MR Images
    Norio Hayashi, Keita Sakuta, Shigeru Sanada, Masayuki Suzuki, Yukihiro ...
    2008 Volume 64 Issue 11 Pages 1352-1360
    Published: November 20, 2008
    Released on J-STAGE: December 06, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.1352
    JOURNAL FREE ACCESS
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    MR imaging (MRI) is an important method for the diagnosis of abnormalities of the brain. In the present report, a semi-automated method is presented to segment the brain and CSF region on brain MR images. MR images were obtained from 6 subjects by SE sequence and 8 subjects by GRE sequence. The semi-automated method consisted of the following three steps: (1) segmentation of the intracranial region using the region-growing technique, (2) segmentation of the brain region using histogram analysis and mathematical morphology, and (3) segmentation of the CSF region using the top-hat transformation technique. The average ratio of a correctly recognized region (CRR) between the semi-automated method and manual method was 87.9%, 85.1% for the intracranial region (IRR), and 94.8% and 86.8% for the brain region in the SE and GRE sequences.
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  • Comparison of OS-EM Reconstruction Algorithms among Different Processors Using a Digital Phantom Dedicated for SPECT Data Evaluation
    Norikazu Matsutomo, Hiroaki Furuya, Taichirou Yamao, Norimi Nishiyama, ...
    2008 Volume 64 Issue 11 Pages 1361-1368
    Published: November 20, 2008
    Released on J-STAGE: December 06, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.1361
    JOURNAL FREE ACCESS
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    Objective: In the OS-EM method, reconfigured images may be different among reconstruction image processors because the programs are highly arbitrary. The purpose of this study was to evaluate the difference in OS-EM algorithms among four different image processors using a digital phantom dedicated for SPECT data evaluation. The image processors used were GMS-5500A/PI (Toshiba), GENIE Xeleris (GE), e.soft (Siemens), and Odyssey FX (Shimadzu). Methods: Multiple images were reconstructed with OS-EM fluctuating the number of subsets and iterations. A region of interest (ROI) was placed on each image. The average counts, contrast, root mean square uncertainty (%RMSU), and normalized mean squared error (NMSE) of each ROI were calculated and compared with those of different image processors. Results: There was no significant difference in contrast among the algorithms. However, the average counts and (%RMSU were significantly different among algorithms as the number of updates increased. In addition, the minimums of NMSE were also different among algorithms. Conclusion: In the OS-EM method, careful evaluation is necessary when using multiple image processors in research studies on the standardization of nuclear medicine imaging or in clinical applications.
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Note
  • Stereometry of the Prostate Using MRI–A Comparison Between TRUS, CT, and MRI–
    Chikara Noda, Toshiyuki Takahashi, Keigo Okabe, Hajime Saito, Kyoichi ...
    2008 Volume 64 Issue 11 Pages 1369-1374
    Published: November 20, 2008
    Released on J-STAGE: December 06, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.1369
    JOURNAL FREE ACCESS
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    I-125 permanently implanted sealed-source radiotherapy is one of the treatments for early localized prostate carcinoma. In order to choose treatment parameters such as the number of implanted sources, accurately determining the volume of the prostate is vital for this type of therapy. We compared the usefulness of transrectal ultrasound (TRUS), computed tomography (CT), and magnetic resonance imaging (MRI) for preoperative stereometry of the prostate, and we further reviewed the utility of the MRI measurement. We performed prostate stereometry with TRUS, CT, and MRI in each of 45 patients who had provided informed consent. Taking TRUS stereometry as the standard, we computed the correlation of the MRI results with TRUS, and that of the CT results with TRUS, and found that MRI had a higher correlation.
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Clinical
  • Influence of the Difference in Start-up Echo on Signal Intensity in the FIESTA Sequence
    Takanori Naka, Mitsuyuki Takahashi
    2008 Volume 64 Issue 11 Pages 1375-1382
    Published: November 20, 2008
    Released on J-STAGE: December 06, 2008
    DOIhttps://doi.org/10.6009/jjrt.64.1375
    JOURNAL FREE ACCESS
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    The FIESTA sequence is a fast imaging method used for various parts in recent years. A constant flip angle (CFA) or linear flip angle (LFA) are used as the start-up echo in many cases. It is reported from CFA, which is the conventional method, that the T1 value and T2 value influence the speed that reaches steady state. However, there is no such report in LFA. Therefore, we examined the influence of the difference of start-up echo method upon signal intensity. In phantoms other than vegetable oil, the difference was not accepted in the change of speed that reaches steady state and the signal intensity in steady-state transit. In LFA, signal intensity of vegetable oil was clearly lower than CFA. The same result was obtained regardless of on or off resonance. From the result, it was thought that it depended on T2/T1 for the speed that reaches steady state. Moreover, the difference in resonant frequency was considered to greatly influence LFA but not CFA. That is, it was suggested by the difference in start-up echo that the signal intensity of fat changes greatly.
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The 63rd Annual Scientific Congress
The 63rd Annual Scientific Congress
The 63rd Annual Scientific Congress
Educational Lecture—Interpreting Medical Images for Radiological Technologists
Basic Lecture—Permanent Implant Brachytherapy of the Prostatic Cancer Using I-125 Radiation Source
Clinical Technology Cource
Report from the Scientific Research Group
Science Exchanges Committee News
JIRA Topics
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