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16 Cards in this Set
- Front
- Back
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What are the 3 main processes of a typical CT scanner.
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Data Acquisition, Image Reconstruction, Image display
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What is the first step in data acquisition?
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A tightly collimated beam is passed through a patient at a precise location.
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What is the second step in data acquisition?
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The remnant beam from this exposure is detected by an array of photodiode or ion chamber radiation sensors. Each one sends an analog electrical signal as data.
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What is the 3rd step in data acquisition?
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The tube detector array rotates to a new position relative to the patient. 1 and 2 are repeated for new data acquisitions.
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Typically how many views or projections are obtained for each slice?
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500
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What is the 5th step in data acquisition? How has this changed in more modern times?
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An analog to digital converter changes the analog electrical signal to a digital CT number. Instead of an analog to digital converter we use a dedicated microprocessor.
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What is the 6th step in data acquisition?
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The digital CT number is relayed to the CPU of the computer.
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What is the first part of image reconstruction?
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Application of a reconstruction Algorithm
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How is the application of a reconstruction algorithm used in 2 dimensional slice by slice imaging?
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Filtered Back Projection was used
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How is the application of a reconstruction algorithm used in 2 dimensional helical slice imaging?
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Filtered back projection is used after interpolation is performed to calculate CT numbers for individual slice locations.
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What is the first step of image display?
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Digital output of the is converted a dac, or dedicated microprocessor back to analog form for Image display.
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Turning axial or transverse sections into sagittal or coronal sections is referred to as what?
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Reformatting
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Improves contrast resolution?
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Image smoothing
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Improves spatial resolution?
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Edge Enhancement
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Improves the conspicuity of specific anatomy?
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Gray Scale Manipulation
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It may be done retrospectively, that is after the original images have been displayed, or preplanned prior to the scan?
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3 dimensional image processing
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