Download - Computer Tomography
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COMPUTER TOMOGRAPHY
BY -: Lovnish Thakur (IBT -1ST Semester)Enrollment N o. -: ASU2014010100099From -: school of bioscience
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Computer tomography (CT), originally known as computed axial tomography (CAT or CT scan) and body section
rentenography.
It is a medical imaging method employing tomography wheredigital geometry processing is used to generate a three-dimensional image of the internals of an object from a largeseries of two-dimensional X-ray images taken around a singleaxis of rotation.
The word "tomography" is derived from the Greek tomos (slice)and graphein (to write). CT produces a volume of data whichcan be manipulated, through a process known as windowing, inorder to demonstrate various structures based on their ability toblock the X-ray beam.
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CT: The beginning
CT founded in 1970 by Sir Godfrey Hounsfield
first applications were in neuroradiology.
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CT Scanner
Used to determine
extent of trauma
location and type
of tumors
status of blood
vessels
-pre surgical planning
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Basic CT scanner components
Gantry
X-Ray Tube
Detector
Control Console
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Gantry. The CT scanner gantry is a moveable frame that
contains the x-ray tube, including: collimators and filters, detectors, data acquisition system, rotational components including slip ring systems, and all associated
electronics such as
CT scanner gantry
angulation motors
& positioning laser
lights.
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Capture energy that has not been attenuatedby the patient.
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Digital projection
AP, PA, Lat or Oblique projection
Conventional CT
-Axial
Volumetric CT
- Helical or spiral CT
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X-ray tube and detectorremain stationary
Patient table movescontinuously
Produces an imagecovering a range ofanatomy
Image used todetermine scan location
Digital Projection
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Axial CT X-ray tube and detector rotate 360°
Patient table is stationary
Produces one cross-sectional image
Once this is complete patient is moved to next position.
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X-ray tube and detector rotate 360°
Patient table moves continuously
Produces a helix of image information
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Attenuation
X-ray beam passes through patient
Each structure attenuates X-ray beam differently
According to individual densities
Radiation received by detector varies according to these densities
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Transferred from detector to CT computer(A to D converter)
Reconstructed by computer into a cross-sectional imageDisplayed on screen
Each pixel displayed on monitor has varying brightnessThe greater the attenuation, the brighter the pixel
The less attenuation, the darker the pixel
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Density values correspond to
a range of numbers
Hounsfield scale
Density information
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Window widthDetermines range of CT numbers displayed on animage
-:Values above this range = white
-:Values below this range = blackWindow level
Sets the center CT number displayed on themonitor
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CT image quality
Spatial resolution Ability to resolve small objects in an image.
Contrast resolution Ability to differentiate small density differences in an
image.
Post Processing Options• Visualization of vasculature in relation to pathology.• Show course of vessels.• Define vascular stricture.
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CT SCANNERThus provide a window into the
body.
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SOME OF IMAGE FORMED BY CT SCAN
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THANK YOU