Medical Imaging Technology
Online ISSN : 2185-3193
Print ISSN : 0288-450X
ISSN-L : 0288-450X
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Volume 32, Issue 4
MEDICAL IMAGING TECHNOLOGY
Displaying 1-12 of 12 articles from this issue
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Reducing Radiation Exposure of CT Scans
  • Reducing Radiation Exposure of CT Scans: Introduction
    Shigeru NAWANO
    2014 Volume 32 Issue 4 Pages 237-238
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.237
    JOURNAL FREE ACCESS
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  • Image Reconstruction Methods in Low-Dose CT
    Fundamentals of Statistical Image Reconstruction, Iterative Image Reconstruction, and Compressed Sensing
    Hiroyuki KUDO
    2014 Volume 32 Issue 4 Pages 239-248
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.239
    JOURNAL FREE ACCESS
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    Recently, three new designs of CT scanners called low-dose CT, sparse-view CT, and interior CT are attracting much attention in CT community. Consequently, development of corresponding image reconstruction methods has become an area of active research. The low-dose CT refers to CT in which projection data is measured with low-dose irradiation, and the sparse-view CT refers to CT in which a number of measured projection data is reduced to decrease patient dose. This paper consists of the following two major parts. In the first part, we review fundamentals of statistical image reconstruction methods (also called as iterative reconstruction methods), which have been already incorporated into commercial CT scanners as reconstruction methods for low-dose imaging protocols. In the second part, we review fundamentals of compressed sensing including total variation regularization, which is attracting much attention as major tools to develop reconstruction methods for sparse-view CT.
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  • Low Dose Technologies on Computed Tomography
    Yotaro ISHIHARA
    2014 Volume 32 Issue 4 Pages 249-254
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.249
    JOURNAL FREE ACCESS
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    Diagnostics with X-ray Computed Tomography is very useful, but the harmfulness from X-ray dosage is inevitable. In this paper, two technologies to realize low dose CT are detailed. One is "Organ Dose Modulation (ODM)" that can reduce surface dose where X-ray sensitivity is relatively high. This function is one of the Auto Exposure Control (AEC) technology realized by reducing tube current on surface area indicated by user. The other is "Snapshot Assist" that is a guidance technique in case of cardiac scanning. This technique uses Body Mass Index (BMI) and heart rates as input information, and suggests the appropriate scan and reconstruction technique for the patient. This technique can reduce radiation dose by adjusting X-ray tube voltage and current in case of the small BMI patient.
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  • CT Dose Management by Dose Index Registry
    Yoshihisa MURAMATSU, Rikuta ISHIGAKI, Masafumi SHINOZAKI, Kozo HANAI
    2014 Volume 32 Issue 4 Pages 255-260
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.255
    JOURNAL FREE ACCESS
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    This paper described the outline of ACR-DIR (American College of Radiology-Dose Index Registry) currently performed in the U.S. as dose management of CT. And, the effective practical use method and problem were clarified based on trial experience of ACR-DIR software about the present condition of DIR in Japan. Moreover, the CADI (Combined Application Dose Index) system under present development was explained. The CADI system has not only a dose management function but the image quality management function. Through the Great East Japan Earthquake, many people are afraid of radiation and radioactivity, and are increasing uneasiness. The analysis of big data is effectively utilized in various scenes. However, if there is no history of big data, i.e., medical radiation dose, nothing will start. We would like to align with the framework of international community and to hope establishment of the DIR system in Japan, and also NRDR (National Radiology Data Registry)
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  • AIDR 3D Settings for Decreasing CT Radiation Exposure
    Hitoshi NISHIMURA, Masashi KANEKO, Haruki HIROTO, Takashi TANAKA, Shig ...
    2014 Volume 32 Issue 4 Pages 261-266
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.261
    JOURNAL FREE ACCESS
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    AIDR 3D (Adaptive Iterative Dose Reduction 3D) is expected to be a useful method for reducing X-ray exposure. However, the effect of AIDR used in practice differs by institution. In this report, the CT value, MTF, SD, NPS, and CNR were evaluated by FBP (filtered back projection) and AIDR 3D using 320-row CT and phantom. The experimental results revealed that AIDR 3D MILD-specified SD 15 was the limit value. Ultimately, SD 14 was adopted for operation, allowing for extended image quality. Under this protocol, X-ray exposure was reduced by 50% in terms of CTDIvol.
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  • Iterative Reconstruction Techniques for Radiation Dose Reduction
    Masaki KATSURA, Kuni OHTOMO
    2014 Volume 32 Issue 4 Pages 267-271
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.267
    JOURNAL FREE ACCESS
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    Several iterative reconstruction techniques have been released for clinical use. They significantly improve image noise and streak artifacts over conventional filtered back projection, and show potential for providing diagnostically acceptable low-dose CT images.
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Papers
  • Automatic Detection of Electrical Stimulation Positions in Videos of Cortical Mapping in Awake Surgery
    Masanori SUGANUMA, Tomoharu NAGAO , Manabu TAMURA, Yoshihiro MURAGAKI, ...
    2014 Volume 32 Issue 4 Pages 272-281
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.272
    JOURNAL FREE ACCESS
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    Surgical workflow analysis based on videos used in the operating room is an important topic for comprehension of the surgical process, assessment of surgical skills and safety. In this paper, we study with videos of cortical mapping process in awake surgery. Cortical mapping has an impact on survival rates and avoidance of postoperative morbidity of patients and it is the most important process of awake surgery. Therefore it is valuable to extract meaningful information from videos for analysis of cortical mapping process but manual work is time-consuming. In this paper, we propose automatic detection method of electrical stimulation position that is important information for analysis of cortical mapping. The proposed method consists of two phases: detection of a probe tip position and detection of electrical stimulation timings. We evaluated our proposed method with six videos.
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  • Development of Ultrasound Diagnosis System for Carotid Artery Using Probe Pose Estimation and Three-dimensional Structure Reconstruction Techniques
    Satoshi KONDO, Jun OHMIYA, Tadamasa TOMA, Yuki MATSUMOTO, Keisuke HAYA ...
    2014 Volume 32 Issue 4 Pages 282-301
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.282
    JOURNAL FREE ACCESS
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    In this paper, we propose an ultrasound diagnosis system which reconstructs three-dimensional structure of carotid artery from volumetric ultrasound images captured by manual scanning using one-dimensional transducer. In this system, an optical marker is attached to the ultrasound transducer, and the three-dimensional pose of the transducer is estimated by using markers in images which are captured with a camera. A three-dimensional structure of the carotid artery is reconstructed by using the estimated pose of the transducer and the contours of the carotid artery extracted from the ultrasound images. Experimental results show that estimated errors for the three-dimensional poses of the transducer are less than 1 mm. We also confirm that estimated errors for the extracted outer contours and the center lines of the outer contours are less than 1 mm. Furthermore, we introduce an IMT (intima-media thickness) measurement navigation system which helps examiners perform the IMT measurement.
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Tutorial
  • The Present and Future of Autopsy Imaging (2) Procedures of the Postmortem Imaging (autopsy imaging: Ai) in Japan
    Kunihiro INAI, Sakon NORIKI, Akihiko NISHIJIMA
    2014 Volume 32 Issue 4 Pages 302-306
    Published: 2014
    Released on J-STAGE: September 18, 2014
    DOIhttps://doi.org/10.11409/mit.32.302
    JOURNAL FREE ACCESS
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    Detailed observation of the bodies was first reported in the Nara period in Japan. Recent advances of the postmortem inspections are involved in not only traditional autopsies but also the establishment of postmortem imaging called "Autopsy imaging (Ai)". In contrast to the decrease in autopsy rates in several decades, the frequency of postmortem imaging is dramatically increasing during this century in Japan and Western countries. However, the standard protocol has not established in our country yet. The three different procedures of Ai are performed in each facility as follows: i) the Ai inspections followed by autopsies in the limited cases without clarifying the cause of death by Ai, ii) the Ai as a supplement to the traditional autopsies, iii) the Ai in the rejected cases of hospital autopsies. Because many physicians worldwide are concerned about decreased autopsy rates, further postmortem inspection systems such as the minimally invasive autopsy in combination with Ai would be seek in a near future.
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