Medical Imaging and Information Sciences
Online ISSN : 1880-4977
Print ISSN : 0910-1543
ISSN-L : 0910-1543
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Volume 29, Issue 4
Displaying 1-10 of 10 articles from this issue
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Original Article
  • Isosurface compression using regularity of Marching cubes table
    Chikara YAMASHITA, Koji NISHIO, Ken-ichi KOBORI
    2012 Volume 29 Issue 4 Pages 90-96
    Published: 2012
    Released on J-STAGE: December 28, 2012
    DOIhttps://doi.org/10.11318/mii.29.90
    JOURNAL FREE ACCESS
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    In this paper, we propose an information entropy coding method for isosurfaces. In general, isosurfaces are generated from volume data using Marching cubes. Isosurfaces are used in the medicine domain to render CT or MRI dataset. However with increase of volume data, isosurface's data size increases too. Our method uses 3D differential chain code to compress the information of 3D chain and Marching cubes type. Our method reduces entropy to 0.837-1.068 bit/faces.
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Note
  • Examination of imaging parameters using multi and single-stack on brain and neck MRA
    Ryujiro YOKOYAMA, Kimihiro KAJITA, Satoshi GOSHIMA, Hiroaki HOSHI
    2012 Volume 29 Issue 4 Pages 97-100
    Published: 2012
    Released on J-STAGE: December 28, 2012
    DOIhttps://doi.org/10.11318/mii.29.97
    JOURNAL FREE ACCESS
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    Time of flight (TOF) is one of the non-contrast MR angiography (MRA) technique which depicts the inflowing vessels non-invasively without using the contrast agent. High spatial resolution TOF image data that covers head and aortic arch by a single scan is suitable for cerebral arteries diagnosis but the examination method requires a long scan time that is not desired in clinical setting. Conversely, lower spatial resolution data can be used for carotid arteries and aortic arch diagnosis and the scan time also can be reduced, but the spatial resolution may not be good enough for the diagnosis of cerebral arteries. In this study, we optimized the spatial resolution for cerebral arteries, and compared the image quality of carotid arteries acquired with and without fat suppression and subclavian artery/aortic arch acquired with and without ECG gating. These optimized MRA images were also compared to the MRA images acquired with a conventional single-stack (SS) method. Twenty clinical MRA images acquired with both multi-stack (MS) and SS methods were visually assessed. Our study showed that higher image quality and better vessel visualization could be achieved with equal scan time to the conventional SS method by using the optimized MS method.
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Work in Progress
  • Preliminary study of MAGAT polymer gel dosimeter with MRI
    Masayuki KANAMOTO, Tosiaki MIYATI, Yusuke TSUNEI, Kei KATAHIRA, Ryoji ...
    2012 Volume 29 Issue 4 Pages 101-104
    Published: 2012
    Released on J-STAGE: December 28, 2012
    DOIhttps://doi.org/10.11318/mii.29.101
    JOURNAL FREE ACCESS
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    We devised a polymer gel (methacrylic acid gelatin tetrakis phosphonium chloride: MAGAT) dosimeter with which we attempted to measure ion beams using magnetic resonance imaging (MRI) . We irradiated X-ray, proton beam, and carbon ion beam to MAGAT and measured the relaxation rate (r1=1/T1, r2=1/T2) , apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR) . We evaluated changes in these values as time elapsed following irradiation. A strong positive correlation was found between relaxation rate and exposure dose. Relationship ADC and exposure dose were not significantly different. Relationship MTR and exposure dose were not significantly different. Relaxation time using MAGAT analyses make it possible to evaluate exposure dose of the ion beams.
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  • Effect of Air gap on slice profile in MRI
    — Evaluation of the effect of numerical simulation with Bloch equations —
    Chiemi YAMAUCHI, Kojiro YAMAGUCHI
    2012 Volume 29 Issue 4 Pages 105-108
    Published: 2012
    Released on J-STAGE: December 28, 2012
    DOIhttps://doi.org/10.11318/mii.29.105
    JOURNAL FREE ACCESS
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    In magnetic resonance imaging (MRI) , signal intensity is dependent on the substances in a voxel. The signal is decayed when Air gap is present. In addition to that, the presence of Air gap creates a local inhomogeneity in a magnetic field, causing artifact on MR images.
    Consequently, it is said that the influence of Air gap is less in fast spin-echo (FSE) sequences than spinecho (SE) sequences. We analyzed the effect of air on slice profiles of both SE sequences and FSE sequences in numerical simulation with Bloch equations. As a result, we confirmed that slice profile is more distorted in FSE sequences compared to SE sequences.
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