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Computed Tomography questions and 100% correct answers.
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Computed Tomography questions and100% correct answers.
Fundamentals of CT ANS - -Creating a cross-sectional tomographic place of any body part
-A patient is scanned by an x-ray tube rotating around the body
-A detector assembly measures the radiation exiting the patient.
Radiographic Tomosynthesis ANS - Uses an x-ray beam to produce multiple digital images.
What does Tomo mean? ANS - image// to long axis of the body
What does CT mean? ANS - Image is transverse to the body
-Computed Tomography
*The CT image is a transaxial or transverse image that is perpendicular to the long axis of the body.
CT Imaging System ANS - CT imaging system consists of a finely collimated x-ray beam and a single
detector; both moving synchronously in a translate rotate mode.
Translation ANS - One rotation of source and detector around the body
Projection ANS - Attenuation pattern and intensity profile is formed for that translation.
When was CT first demonstrated? ANS - in 1970, dedicated to head CT only; Dr. Godfrey Hounsfield,
Allan Macleod Cormack
When was the first full-scale commercial unit installed? ANS - 1971; Physicians recognized its value for
providing diagnostic neurologic information; these early units were also dedicated head CT scanners
When was the first whole-body scanner developed? ANS - 1974; Dr. Robert S Ledley
, First Generation Scanners ANS - -Translation/Rotation
-Tube produced a finely collimated beam or pencil beam
-1 to 3 detectors were placed opposite the tube for radiation detection
-Tube required 180 translations with 1 degree rotation
What is the downfall to first generation scanners? ANS - It takes 5 minutes to gather enough
information for one image
Second Generation Scanners ANS - -Fan shaped x-ray beam
-5 to 30 detectors
-20 seconds per slice or 10 minutes for a 40 slice exam
-10 degree rotation increments, 18 translations for 180 degree image acquisition
-Long data reconstruction time
Disadvantage of the Fan beam in a second generation scanner ANS - Increased radiation intensity that
occurs towards the edges of the beam because of body shape
-Compensated for by using a "bowtie" filter
Third Generation Scanner ANS - *Fan beam
*Multiple detectors along an arc
*The tube/detector assembley rotates around the patient
*Total scan time faster than 1 second per image
*Uses a curvilinear detector
Disadvantage of the Third Generation Scanner ANS - Ring artifacts from detector malfunction
Fourth Generation Scanner ANS - -Fixed ring of as many as 4,000 detectors, completely surrounding the
patient, rotate only movement
-Rotating x-ray tube provides short burst of radiation
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