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20 Cards in this Set
- Front
- Back
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The first step in generating a digital image of an object is to ______________.
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divide the object into a grid of small regions
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What is another name for a picture element?
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a pixel
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The grid of pixels comprises the ______________.
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image matrix
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The display hardware assigns a ______________ to the region of a CT image from which the attenuation information was detected.
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specific gray level
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A ______________ is a view of the anatomical cross-section from a particular vantage point.
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projection
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The digitizing process assigns an ______________ to each amplified electrical signal. The value of the ______________ is determined by the signal strength. The stronger the signal, the larger the ______________. This affects the gray level of the structure.
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integer
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CT uses ______________ to obtain images where as radiography uses only one projection.
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multiple projections
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What are the 3 scanning methods?
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Localizer
Conventional, or serial, CT helical CT |
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The ______________ scan is obtained with a stationary x-ray tube and the patient table in motion.
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localizer
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CT localizer images tend to have better ______________ compared to conventional radiography due to the reduction in scatter radiation as a result of ______________.
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tissue contrast
pre-patient and post-patient collimation |
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______________ yields the best image quality, which is free from helical artifacts.
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conventional CT
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When performing a ______________ on a single-row detector scanner, the raw data from only one cross-sectional slice location is collected during a ______________.
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conventional scan
single rotation of the gantry |
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Detectors X projections(360 degrees) X Rows of detectors = ______________
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attenuation measurements for one slice
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When performing a conventional scan on a ______________, the raw data from several cross-sectional slice locations are collected during a ______________.
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multi-row detector scanner
single rotation of the gantry |
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Spiral method scanning and volumetric scanning are both the same as a _________________.
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helical scan
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What are the 6 advantages of helical scanning?
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faster studies
more coverage in a breath-hold no missed anatomy less contrast agent used arbitrary slice positioning ideal data for post-processing |
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During a _________________ the patient table is moving while the tube rotates around the patient.
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helical scan
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Because the tube is constantly rotating and scanning during a helical scan, the measurements have to receive an extra step in reconstruction to images. This step is called _________________.
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interpolation
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What does interpolation do?
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This calculation is used to divide the helical data into raw data files for individual slices. Once these individual slices are obtained, that raw data is then reconstructed like a conventional scan would be.
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_________________ is a calculation used for reconstructing the final CT images from the raw data by adding together the attenuation information collected from all of the projections.
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back projection
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