Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 66, Issue 9
Displaying 1-13 of 13 articles from this issue
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Opening Article
Program of the 38th Autumn Scientific Congress
Originals
  • A Computerized Method for Detection of Acute Cerebral Infarction on CT Images
    Hideki Saito, Shigehiko Katsuragawa, Toshinori Hirai, Shingo Kakeda, Y ...
    2010 Volume 66 Issue 9 Pages 1169-1177
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1169
    JOURNAL FREE ACCESS
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    This paper proposes a computerized method for automated detection of acute cerebral infarction (ACI) on CT images. This method is based on the difference value of image features in the two regions-of-interests (ROIs) selected at symmetrical positions. In our computerized method, first, we segmented the brain parenchyma by the thresholding technique after correction of inclination of the midsagittal plane with translation and rotation of the image. Then we selected the middle cerebral artery (MCA) region of the brain parenchyma. Moreover, many ROIs with a 32×32 matrix size were selected in the MCA region. In addition, image features in each ROI were determined from the statistical analysis, the co-occurrence matrix and the run length matrix. Finally, ROIs with ACI were classified by using a linear discriminant analysis with difference values of image features in two ROIs at symmetrical positions. Nineteen cases with ACI and normal 14 cases were employed in this study. As a result of our experiments, the sensitivity of detection of ACI was 88.0% with an average number of false positives of 4.6 per case. Our computerized method provided a relatively high performance for detection of ACI. Therefore, we believe this method would be useful for an algorithm of a computer-aided diagnosis to detect ACI on CT images.
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  • Influence of Imaging Parameters on the Measurement of Apparent Diffusion Coefficient
    Masanori Ozaki, Akio Ogura, Isao Muro, Tosiaki Miyati, Takayuki Tamura ...
    2010 Volume 66 Issue 9 Pages 1178-1185
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1178
    JOURNAL FREE ACCESS
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    The apparent diffusion coefficient (ADC) values are calculated by using signal intensity in diffusion-weighted images (DWIs) with two or more different b-value. Therefore, the signal to noise ratio (SNR) of DWI with higher b-value may have a big influence on the measured ADC value. We examined the influence of the imaging parameters on the calculated ADC values. The SNR of DWI increased by using a larger voxel size, by means of a decreased number of matrix, an increased slice thickness, and an increased field of view (FOV). However, when the number of excitations was increased to improve the SNR of DWI, the signal intensity of background noise was observed to be slightly increased. It was suggested that the consistency of measured ADC was not preserved when the signal of the DWIs with higher b-value dropped close to the noise level.
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  • Study of Setup Margins in Radiation Therapy: How Many Verification Times and Patients are Required
    Mitsuhiro Matsumoto, Seiichi Ohta, Yoshimi Ohno, Yuji Ogata
    2010 Volume 66 Issue 9 Pages 1186-1196
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1186
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    Introduction: The purpose of this research is to require suitable numbers of verification times and patients for calculating the setup margin (SM) in radiotherapy. Methods: 1) This simulation was performed using the standard normal distribution random number. The simulation used the seven levels of verification from 5 to 35 in 5 steps, and 35 patients. 2) The setup error in prostate radiotherapy at three hospitals was analyzed. Systematic error and random error were calculated from each patient’s average value and standard deviation. Furthermore, we used the formula of J Stroom to calculate SM. Suitable numbers of verification times and patients were obtained from statistical analysis of the simulated results. Results: 1) In the results of our simulations using random number, SM converged on 1.0 to 1.3 mm, regardless of the number of patients, when there were more than 15 verification times; 2) The results of clinical data were slightly different from the standard normal distribution, and more than 15 verification times and over 15 patients were required. Conclusions: In conclusion, calculation of the SM in radiotherapy required more than 15 verification times and over 15 patients.
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Notes
  • Simulation Study for Artifacts on Gd-EOB-DTPA-enhanced Liver Dynamic MR Imaging in Arterial Dominant Phase
    Takahiro Fukaya, Kenichi Naito, Hiroaki Saitoh, Munenori Takimoto, Aki ...
    2010 Volume 66 Issue 9 Pages 1197-1203
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1197
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    We performed a simulation for artifacts on liver dynamic MR imaging with the contrast agent gadolinium-ethoxybenzyl (Gd-EOB)-DTPA. The signal enhancement of the image by the contrast agent in the arterial dominant phase was assumed, and the time-enhancement curve was numerically generated. The data in k-space was obtained by the Fourier transform of a liver image. By assuming the scan timing and duration in the time-enhancement curve, the data set of each phase-encoding step in k-space was increased in proportion to the corresponding intensity in the time-enhancement curve. We obtained the simulated image by the Fourier transform of the k-space data, and investigated artifacts in the image. Assuming the use of the centric k-space filling scheme, blurring in the image is found when the scan timing is delayed. When the scan is started in an early timing, we observe the effect of edge enhancement in the image. These artifacts of blurring and edge enhancement are decreased by shortening the scan duration. Assuming the use of the sequential k-space filling scheme, those artifacts are not prominent. The use of the sequential scheme would be effective for the purpose of avoiding the artifacts. It is known that the contrast enhancement would not be sufficient without optimal scan timing; in addition, artifacts should be noted. For basic study of the contrast enhancement and artifacts, our simulation technique based on the time-enhancement curve would be useful.
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  • What Factors Affected Image Quality in Coronary Multidetector-row Computed Tomography?
    Takehiro Arai, Takeshi Kondo, Hitomi Morita, Tomonari Sano, Hideyuki M ...
    2010 Volume 66 Issue 9 Pages 1204-1212
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1204
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    Background: Although it is well known that we usually cannot acquire a high quality coronary MDCT in patients with arrhythmia or incomplete breath-hold, we sometimes also cannot obtain a high quality coronary MDCT in patients without arrhythmia or incomplete breath-hold. Purpose: We studied what factors other than arrhythmia or incomplete breath-hold affected image quality. Methods: Coronary MDCT and echocardiography were performed within one month in 2145 patients, and 452 cases of arrhythmia or 102 cases of incomplete breath-hold during scanning were eliminated. The remaining 1591 patients were studied. Those patients were divided into two groups (mid-diastolic phase reconstruction (MD) group (N=1377) and end-systolic phase reconstruction (ES) group (N=214)). Age, body weight, mean heart rate (HR) during scanning, temporal resolution (TR) and left ventricular ejection fraction (LVEF) by echocardiography were estimated. Image quality (A: Excellent (3 points), B: Acceptable (2 points), C: Unacceptable (1 point)) was evaluated. Results: The mean image quality points of the MD group (2.9±0.3) were significantly (P<0.0001) higher than the mean image quality points of the ES group (2.3±0.7), and the mean HR of the MD group (57±6 bpm) was significantly (P<0.0001) lower than that of the ES group (81±15 bpm). In the MD group, HR and TR were selected as significant factors affecting image quality by stepwise regression analysis. In the ES group, TR and HR were selected. In the ES subgroup with HR<90 bpm, TR and HR were selected; however, in the ES subgroup with HR≥90 bpm, TR and LVEF were selected. Conclusion: In the MD group, low HR was important for high quality coronary MDCT. In the ES subgroup with HR<90, short TR and low HR were important; however, in the ES subgroup with HR≥90 bpm, TR and LVEF were more important than HR.
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  • Result of the Onsite Dosimetry and Questioning about Quality Assurance/ Quality Control of Radiotherapy in the Hokuriku Area -A Comparison with Past Results-
    Akihiro Takemura, Naotaka Tsukamoto, Eiichi Yamamoto, Shinichi Ueda, Y ...
    2010 Volume 66 Issue 9 Pages 1213-1220
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1213
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    Purpose: To analyze temporal changes in human resources in the radiotherapy section, quality assurance/quality control (QA/QC) and dose difference for radiotherapy in the Hokuriku area based on the results of past investigations and our investigation. Method: We visited radiotherapy sections of 17 hospitals in the Hokuriku area (5 in Toyama, 9 in Ishikawa and 3 in Fukui) to measure the dose at the reference point of a linear accelerator (LINAC), as we asked questions to a radiotherapist about human resources, QA/QC of LINAC, etc. We compared our results with past reports (1992 to 2007) on the dose difference, human resources and frequency of dose monitor system calibration. Results: The number of physicians has not changed since 1999, but the number of radiotherapists was significantly increased. Weekly dose monitor system calibration has been achieved in 80% of the institutions in our survey. This percentage was significantly higher than in the past surveys. The dose difference distribution from our onsite dosimetry did not significantly differ from that from the onsite dosimetry in 2007. 91% of the institutions have accomplished within 2% of the dose difference. Conclusion: We found that the number of physicians has not increased since 1999, but the number of radiotherapists has increased. We conclude that the increment of radiotherapists led to 80% achievement of the weekly dose monitor system calibration. Almost all institutions in Hokuriku area have properly performed QA of the dose monitor system.
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  • Fundamental Study of the Fat-suppressed Three-dimensional Coherent Oscillatory State Acquisition for the Manipulation of Image Contrast (3D-COSMIC) Sequence in the Knee Joint Cartilage
    Takuya Amakawa, Tooru Shinohe, Satoru Tominaga, Takashi Honda, Mitsuji ...
    2010 Volume 66 Issue 9 Pages 1221-1228
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1221
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    Fat-suppressed three-dimensional coherent oscillatory state acquisition for the manipulation of image contrast (3D-COSMIC) is a sequence that is based on fast imaging employing steady state acquisition (FIESTA) of balanced steady-state free precession (balanced SSFP). Since the data acquisition of steady-state transition is filled up with the center of k-space, improvement in the contrast of the cartilage, which is a low T2/T1 value domain, is expected. This time we report on the usability in applying the above sequence to cartilage imaging of the knee joint and comparing and examining this sequence with the sequence in the past from the viewpoints of the contrast and scan time. As a result, compared with fat-suppressed three-dimensional spoiled gradient echo (3D-SPGR), the contrast of marrow and synovial fluid was equivalent to that of the cartilage, and imaging time was shorter than half of that with the cartilage. Compared with a fat-suppressed two-dimensional proton density weighted image (2D-PDWI), the contrast of the cartilage and synovial fluid was significantly improved, and spatial resolution was also excellent. As a short imaging time and a high resolution image pick-up are possible for fat-suppressed 3D-COSMIC, and it can describe minute damage of the cartilage since it depicts synovial fluid as high-level signals, I think this technique is useful.
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Clinical Technology
  • Development of the Method for the Similarity Detection of Descriptions in Radiology Reports Using Structuring Technology
    Hikaru Futami, Hiromasa Yamagishi, Osamu Kawaguchi, Nobuhiro Tsukamoto ...
    2010 Volume 66 Issue 9 Pages 1229-1236
    Published: September 20, 2010
    Released on J-STAGE: October 21, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.1229
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    Radiologists often spend much time for re-reading some of the past free-text radiology reports and determining interval changes in the physical findings when creating a report for long term cases. The aim of this study was to propose the method to detect semantic similar descriptions in the free-text reports using the structuring method based on text-mining technology. In a previous study, we had developed the structuring method that can semantically analyze the free-text reports and convert them into the description unit consisting of five items: finding/diagnosis, modifier, region, regional modifier, and confidence. Our developed prototype system extracted similar descriptions from the free-text reports by calculating the similarity index between description units. We confirmed similar descriptions extracted by the system applied to free-text reports of cases which had more than one chest CT examination written in actual clinical situation. As a result, it became available to identify candidates of similar descriptions from free-text reports. In some cases regarding practical use, the similar descriptions could not be identified in the sentences which used paraphrasing or where the findings had status changes. A solution of identifying similarity in these cases was necessary to improve the method. With the presented method here, it is expected that interval changes in the findings can be visualized and applied it to support diagnosis.
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