Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 69, Issue 11
Displaying 1-19 of 19 articles from this issue
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Opening Article
Editorial
Originals
  • Reduction of Radiation Exposure during Computed Tomography Perfusion Using an Iterative Reconstruction Method
    Tomomi Ohmura, Hideto Toyoshima, Yuichiro Sato, Takato Ishida
    2013 Volume 69 Issue 11 Pages 1218-1224
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1218
    JOURNAL FREE ACCESS
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    The purpose of this study was to evaluate the image noise reduction effect of iterative reconstruction (IR) when used to reduce radiation exposure during computed tomography (CT) perfusion. We scanned a contrast phantom using various radiation doses. Image reconstruction was via filtered back projection (FBP) and IR (adaptive iterative dose reduction 3D: AIDR3D). AIDR3D provided four levels of noise reduction (weak, mild, standard, and strong). We examined the accuracy of CTP map (cerebral blood volume: CBV, mean transist time: MTT, cerebral blood flow: CBF) low-dose IR images to create a digital perfusion phantom that simulates the dynamic curve of ischemic cases using reconstructed images. The optimal filter type of IR was evaluated in the low-frequency area of the NPS at low doses. We were able to obtain the optimal filter type of IR in the low-frequency area of the NPS that was equivalent to that of the reference (150 mA, FBP). The CTP map created using the optimal filter type of IR allowed dose reduction to 80 mA, much lower than the reference. We conclude that it is possible to reduce the dose to 46% of the reference level by using the NPS for dose reduction and IR. IR thus has the potential to contribute to reduction of radiation exposure during CT perfusion.
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  • A Fundamental Study of the Energy Subtraction Processing Using a Monochromatic Image for Computed Tomography Angiography after Coil Embolization of a Cerebral Aneurysm
    Daisuke Sasamori, Tadashi Nonaka, Akira Takahashi, Shingo Kayano, Tomo ...
    2013 Volume 69 Issue 11 Pages 1225-1231
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1225
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    Coil-embolized cerebral aneurysms are difficult to evaluate using computed tomography (CT) angiography (CTA) due to artifacts caused by the coil devices. This study was conducted to assess the practicality of energy subtraction processing using monochromatic images obtained using CTA after coil embolization of a cerebral aneurysm. In this study, the changes in the CT value of the contrast agent and the coil were analyzed not only at varying monochromatic energy levels but also by energy subtraction processing. Our analyses revealed an exponential change in the CT value of the contrast agent at any desired energy. We also found that the CT value of the coil was unchanged at the upper threshold of the grayscale limit. Based on these results, we were able to create images of changes in material-specific CT values and thus eliminate the material. Energy subtraction processing enabled us to distinguish between the contrast agent, the coil, and the artifacts from coil devices. We suggest that energy subtraction processing using monochromatic images can resolve the limitations of CTA after coil embolization of cerebral aneurysms.
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Notes
  • Examination of Factors Useful for Choosing a Method to Assist Coil Embolization of Unruptured Cerebral Aneurysm
    Takumi Kuriyama, Nobuyuki Sakai, Hajime Furukawa, Kumiko Oonishi, Hide ...
    2013 Volume 69 Issue 11 Pages 1232-1240
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1232
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    Background: In coil embolization of neurovascular aneurysms, we have noted that few wide-necked unruptured aneurysms are successfully embolized. This prompted us to search for useful factors to assist the choice of methods of coil embolization. Method: We first measured aneurysm size and volume using auto measurement (NVvol) and VER (NVver). Second, we calculated the volume (NVapp) and VER (NVapp) using approximation expressions. Third, we measured the end-on view neck angle using a 3 dimensional digital subtraction angiography (3D-DSA) image. Results: NVvol and NVapp were correlated (y=0.87x). NVvol VER and NVapp VER approached 24% in 41 clinical cases. The dome/neck ratio averaged 1.15. Length of neck and the end-on view neck angle were significantly different between the stent-assisted group and the balloon-assisted group. NVvol and NVapp showed a good correlation with basic examination results in 41 clinical cases. Conclusion: The end-on view neck angle is significantly different. This boundary neck angle was 100° for the two groups. The end on-view neck angle is thus a useful factor for deciding medical treatment strategy.
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  • Tackling Hemodynamic Analysis of the Carotid Artery Using Open-source Software and Computational Fluid Dynamics
    Tatsunori Saho, Hideo Onishi, Toshihiko Sugihara, Yoshitaka Nakamura, ...
    2013 Volume 69 Issue 11 Pages 1241-1249
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1241
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    Purpose: The aim of this study was to evaluate the impact of wall share stress (WSS) in the carotid artery using a computed fluid dynamics analysis system and adopting open-source software. Methods: The dependence of element number (computation time and analytical accuracy) were considered with simple vessel models. We evaluated WSS and flow velocity using a carotid artery model that was based on the outcome of simple vessel models. Results: When the number of elements was 105 or more, the flow velocity error of the outlet decreased to 0.5% or below when using simple vessel models. The carotid bifurcation model showed a whirlpool and a decrease in flow velocity in the carotid bulb part. Conclusion: An analysis system was built using open source software. The results from the carotid bifurcation model suggested that hemodynamics contributes to the development of carotid stenosis.
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  • Clinical Evaluation of Automatic Contours for Head and Neck Region Using Deformable Image Registration Software
    Motoharu Sasaki, Masahide Tominaga, Takeshi Kamomae, Hitoshi Ikushima, ...
    2013 Volume 69 Issue 11 Pages 1250-1260
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1250
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    The purpose of this study was to clinically evaluate the automatic outline extraction properties using general-purpose deformable image registration (DIR) software for the head and neck region. To this end, we evaluated the following: (1) the difference between manual outline extraction carried out by a radiation therapy specialist and automatic outline extraction using the DIR software, and (2) the precision of the automatic outline extraction for the diachronic figure change and change in the organ shape. The manually-extracted outline and that extracted using the DIR software closely resembled each other at 0.70. Further, in the same case, the automatic outline extraction precision of the DIR software was greater at about 0.80. Our findings suggest DIR software to be useful for lessening the work involved in outline extraction.
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  • Non-gated Vessel Wall Imaging of the Internal Carotid Artery Using Radial Scanning and Fast Spin Echo Sequence: Evaluation of Vessel Signal Intensity by Flow Rate at 3.0 Tesla
    Manami Nakamura, Takeshi Makabe, Masaki Ichikawa, Ryohei Hatakeyama, H ...
    2013 Volume 69 Issue 11 Pages 1261-1265
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1261
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    Vessel wall imaging using radial scanning does not use a blood flow suppression pulse with gated acquisition. It has been proposed that there may not be a flow void effect if the flow rate is slow; however, this has yet to be empirically tested. To clarify the relationship between the signal intensity of the vessel lumen and the blood flow rate in a flow phantom, we investigated the usefulness of vessel wall imaging at 3.0 tesla (T). We measured the signal intensity while changing the flow rate in the flow phantom. Radial scanning at 1.5 T showed sufficient flow voids at above medium flow rates. There was no significant difference in lumen signal intensity at the carotid artery flow rate. The signal intensity of the vessel lumen decreased sufficiently using the radial scan method at 3.0 T. We thus obtained sufficient flow void effects at the carotid artery flow rate. We conclude this technique to be useful for evaluating plaque if high contrast can be maintained for fixed tissue (such as plaque) and the vessel lumen.
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Clinical Technologies
  • Development of an Automated Method for Analysis of Winston-Lutz Test Results Using Digital Radiography and Photostimulable Storage Phosphor
    Kousuke Nagafuchi, Hidemichi Kawata, Kazutaka Nashiki, Sunao Ohkura, K ...
    2013 Volume 69 Issue 11 Pages 1266-1273
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1266
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    Stereotactic radiosurgery (SRS) and radiotherapy (SRT) are intricate techniques that deliver a highly precise radiation dose to a localized target, usually a tumor. At our hospital, we perform SRS and SRT on brain tumors using a linear accelerator (linac) mounted with an external micro multi-leaf system. The Task Group TG-142 Report by the American Association of Physicists in Medicine recommends the coincidence of the radiation and mechanical isocenter to be within ±1 mm. The Winston-Lutz test is commonly used to verify the linac isocenter position: it has the advantages of being a simple method that uses a film or electronic portal imaging device (EPID). However, the film method requires a higher radiation dose, which makes it more time-consuming than the EPID method, and the results are highly dependent on the skills of the observer. The EPID method has certain advantages over the film method, but it has low resolution and can only be used for a few combinations of gantry and couch angles. This prompted us to develop an in-house-designed radiation receptor system based on digital radiography, using a photostimulable storage phosphor and automated analysis algorithm for Winston-Lutz test images using a template-matching technique based on cross-correlation coefficients. Our proposed method shows a maximum average absolute error of 0.222 mm (less than 2 pixels) for 0.5 mm and 1.0 mm displacement from the isocenter toward the inline and crossline directions. Our proposed method is thus potentially useful for verifying the Linac isocenter position with a small error and good reproducibility, as demonstrated by improved accuracy of evaluation.
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  • Optimization of Black Blood CINE for Mobile Plaque
    Kenichi Nakagawa, Shinsuke Komaki
    2013 Volume 69 Issue 11 Pages 1274-1280
    Published: November 20, 2013
    Released on J-STAGE: November 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.11.1274
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    For examining carotid plaque, black blood (BB) magnetic resonance (MR) imaging can diagnose plaque components based on MR signals. Dynamic images for evaluating the mobility of carotid plaque may also be useful as an adjunct to the diagnosis of carotid plaque. The aim of this study was to find optimal parameters for dynamic images using the black blood technique (BB CINE). All experiments were acquired using electrocardiographically (ECG)-gated T1 turbo field echo (T1 TFE) combined with the regional saturation technique (REST) and improved motion-sensitized driven equilibrium (iMSDE) at 1.5 tesla (T). The following parameters were investigated. (1) Four fat suppression techniques: spectral presaturation with IR (SPIR), the principle of selective excitation technique (PROSET) with a binomial excitation of 1-1 (PROSET1-1), PROSET1-2-1 and PROSET1-3-3-1; (2) TFE factors 1 and 2; and (3) flow velocity encoding (venc) of 1, 3, 5, 10 and 15 cm/s for iMSDE. The results showed the optimal parameters for BB CINE to be PROSET1-2-1, TFE factor 2, and flow venc of 3–5 cm/s for iMSDE.
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Work in Progress
Lecture for JSRT Members
Educational Lecture—Statistical Methods for Radiologic Research
Science Exchanges Committee Report
JIRA Topics
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