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CT Chapter 1 Computed Tomography An Overview questions with correct answers.
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CT Chapter 1 Computed Tomography AnOverview questions with correct
answers.
Introduction ANS - Meaning of CT
Fundamental principles
History of CT
Tomography ANS - - 1920 originally termed "body section radiography"
Used to describe imaging a specific layer or section of the body
- 1935 the term was refined to tomography derived from the greek word tomos meaning section
- 1937 transverse axial tomography was the term used to refer to the imaging ability of cross-sectional
images to be acquired
Image Reconstruction from Projections ANS - -derived by mathematician Radon
-two or three-dimensional objects could be "built up" from several projections from different directions
Basic Principle of CT ANS - -Produces sharp, clear cross-sectional images by reconstructing a large
number of projections from different locations
Hounsfield ANS - -Applied reconstruction techniques to produce worlds first CT for the brain
Formation of CT Images (3 steps) ANS - 1. Data acquisition
2. Image reconstruction
3. Image display, manipulation, storage, recording, and communication
1. Data Acquisition ANS - - Collection of x-ray transmission measurements from the patient
- Electronic detectors measure the attenuation of the x-ray beam as it passes through the patient
, 1. Data Acquisition (Cont.) ANS - 1st CT scanners= x-ray tube and detectors move in a straight line
across the patients head
-left-->right, rotate 1 degree, right-->left (repeat for 180 degrees)
-Termed translate-rotate-stop-rotate or scanning
-Problematic due to length of exam time
Newer generation CT scanners acquire a volume of tissue (volume scanning) with continuous rotation of
the x-ray tube and detectors (spiral/helical)
2. Image Reconstruction ANS - - Data collected during acquisition are sent to the computer for
processing
- Computers then use mathematical techniques known as image reconstruction algorithms which are
applied to the data to produce and image
3. Image Display ANS - -Reconstructed image can be displayed for viewing or stored for later reanalysis
- Occurs on monitors
3. Image Manipulation (digital image processing) ANS - Images may be modified to make them more
diagnostic
EX:
Image reformatting
Smoothing
Edge enhancement
Gray-scale manipulation
3D processing
3. Image Storage and Recording ANS - Images can be stored and recorded in some form of archive
- x-ray film
- magnetic tapes/disks
- optical storage media (disk, tape, and card)
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