Ch. 29 Flashcards
This is all corrections made to the “raw” digital image data to compensate for physical flaws in image acquisition inherent in the xray beam, elements and circuitry or the IR, and the Physical elements and circuitry of the processor.
Pre-processing
This is all adjustments whether by default settings in the processor or by the user at the console made after acquisition corrections have been made, targeted at refinement of the image.
Post Processing
These are variations in field uniformity due to flaws in electronics, optics, and the xray beam.
Uniformity
These suffer from various electronic faults not found in the reading process for CR plates.
Direct Capture
Which type of system typically undergoes more preprocessing?
DR
This evens out the signal brightness across the area of the image field. It is tested by low exposure with no object comparing 4 corners and center of field.
Flat Field Uniformity Corrections
Flat panel detectors are sensitive to what?
Anode Heel Effect
This is an average of SUM 8 surrounding pixels, an average of these values, and inserts results into a centered pixel.
Interpolation
What is another term for Partitioned Pattern Recognition?
Segmentation
When a histogram is first constructed the CR will read what? DR?
CR- reads entire plate but will remove background
DR- reads the collimated area only
The y-axis on a histogram represents what?
number of pixels
The x-axis on a histogram represents what?
the value of the pixels/ shade of gray
This is what is recorded from left to right on a histogram.
Metals/Contrast Bone Soft tissues- near center of graph Fat Gas/AIr
If there is a high spike to the right on a histogram this represents what?
Background brightness value in the exposure field.
Why will background brightness be the darkest value on a histogram?
Because the IR is exposed to primary beam such as in an extremity image.
