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16 Cards in this Set

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