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Alla Shorokhova, "COMPUTED TOMOGRAPHY"

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  • 1. COMPUTED TOMOGRAPHY
    Saint Petersburg Electrotechnical University “LETI”
    Student Alla Shorokhova
    5104 group
    Head Professor Alexander Mikerov
  • 2. Introduction
    The term "tomography“comes from two Greek words: τομοσ - section and γραφοσ– write
    (layer-by-layer study of the structure of variousobjects)
    Typesof imaging
    Essence: on the summary information it is necessary to define the local information (the matter density at each section)
    Application
    The first and most famous application of imaging is computerized X-ray reconstructive tomography (CT)
    Shorokhova Alla, 5104
    2
  • 3. History
    Shorokhova Alla, 5104
    3
    • 1917, Johann Radon, created a mathematical foundation
    tomography
    • 1963, Allan Cormack
    • 4. 1969, GodfreyHounsfield
    EMI-scanner
    a
    b
    • 1979, Cormack and
    Hounsfield were
    awarded
    the Nobel Prize
    "for the development
    of computed
    tomography"
    The first CT scanner (a) and the first tomography
    of the brain (b)
  • 5. Schemes of imaging
    Shorokhova Alla, 5104
    4
    2 generation
    Several
    detectors;
    Imaging –
    20 sec.
    1 generation
    1973;
    incremental;
    1 image –
    4 minutes.
    3 generation
    Spiral CT
    4 generation
    1,088 fluorescent
    sensors;
    Rotates only
    X-ray tube;
    0.7 seconds
    4 generations of CT scanners
  • 6. Construction
    Shorokhova Alla, 5104
    5
    1. X-ray tube and
    a collimator
    2. Detectors and data
    acquisition system
    3. Tube controller
    4. High-frequency
    generator
    5. Built-in microcomputer
    6. Computer
    that provides data
    exchange with
    the console
  • 7. Construction (2)
    X-ray tube with the collimation system creates a narrow fan-shaped light beam, whose divergence angle is 30 ° -50 °
    Attenuation of X-ray beam -> recorded by detectors -> electrical signals. These analog signals ->converted into digital pulses
    In the CT ceramic, fluorescent and gas detectors are used
    Extensive software package
    Shorokhova Alla, 5104
    6
  • 8. Scan Modes
    Shorokhova Alla, 5104
    7
    Conventional (incremental) CT
    (short pause , several minutes)
    Spiral (helical) CT
    (helical motion of X-ray tube,
    reducing time and radiation exposure)
  • 9. Multiple-Row Detector Spiral CT
    MDCT, 1992: two or more series of detectors located around the circumference gantry
    width of the detector
    increases from center
    to edge
    1998: 4-row unit
    2004-2005:
    32-, 64-,128-row units
    Shorokhova Alla, 5104
    8
  • 10. Image reconstruction
    Shorokhova Alla, 5104
    9
    The HU of common substances:
    • The pixel itself is displayed according to the mean attenuation
    of the tissue(s) that it corresponds to on a scale from +3071
    (most attenuating) to -1024 (least attenuating) on the Hounsfield scale
    • Voxel is a volumetric pixel
  • Three-dimensional reconstruction
    Maximal Intensity Projection, MIP
    (consists of voxels having the maximum density)
    Multiplanar Reconstruction, MPR
    (makes it possible to reconstruct
    images in any projection)
    Surface Shaded Display, SSD
    (threshold value in units of HU)
    Volume Rendering
    (combination)
    Shorokhova Alla, 5104
    10
    Figure: Typical screen layout for
    diagnostic software, showing
    one 3D and three MPR views
  • 11. Example of Volume Rendering (1)
    Some slices of a cranial CT scan are shown below
    A volume rendering of this volume clearly shows the high density bones.
    Shorokhova Alla, 5104
    11
    Figures:
    Computed tomography
    of human brain,
    from base of the skull
    to top. Taken with
    intravenous
    contrast medium.
  • 12. Example of Volume Rendering (2)
    After using a segmentation tool to remove the bone, the previously concealed vessels can now be demonstrated.
    Shorokhova Alla, 5104
    12
    Bone reconstructed in 3D
    Brain vessels reconstructed in 3D after
    bone has been removed by segmentation
  • 13. Conclusions
    CT - an important component of inpatient and outpatient care.
    The result of CT - a combination of powerful computer processing with the knowledge and skills of a trained human operator.
    Modern CT scanners are able to emit and collect data about the 1400 positions of the detector tube on the circle 360 °, or about 4 positions in degrees.
    Technical merits of the spiral CT and volumetric reconstruction open up new prospects for medical imaging.
    In 2010, so-called 4-dimensional electron tomography was created - visualization techniquesof the dynamics of 3-dimensional objects in time.
    Shorokhova Alla, 5104
    13
  • 14. Thank you for your attention!

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