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Alla Shorokhova, "COMPUTED TOMOGRAPHY"
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
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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
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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
