Week 10 - Photographic Properties Flashcards
Defined by brightness and density, visible result of an IRs response to an exposure
Brightness
Differences between brightness levels and densities, differentiates anatomic tissue
Contrast
What two factors affect radiographic visibility?
Brightness and contrast
T/F
Brightness is not related to IR exposure
True
Digital post process that produces changes in brightness
Window level
What is brightness controlled by?
The look up table (LUT)
Term used to reflect exposure to the radiographic film - the viewable result of a films response to exposure
Density
What term is interchangeable with density?
IR exposure
What is shown by an area of increased brightness on a monitor?
Decreased density on image
What is shown by an area of decreased brightness on a monitor?
Increased density on the image
ROI
Anatomic structures of interest
T/F
mAs is directly proportional to IR exposure
True
Numerical value that compares data from many images (accurately exposed images)
EXI values (exposure index)
Intensity is inversely proportional to the square of the distance
Inverse square law
T/F
For every 4-5cm of thickness, mAs should be adjusted by a factor of 2
True
*4-5cm attenuate 50%
How do grids affect exposure?
Use of a grid will reduce scatter reaching the IR, thereby reducing density/exposure
A photographic property that affects the visibility of recorded detail
Radiographic contrast
T/F
Any change that affects density will affect contrast
True
Fewer discernible shades of gray
High contrast
More discernible shades of grey
Low contrast
Fewer shades of grey levels wity greater differences between them
High contrast
Many shades of grey levels with few differences between them
Low contrast
What controlling factor Results in fewer density differences in the anatomic tissue (low/long scale contrast)
High kVp
What controlling factor results in greater density differences in the tissue (high/short scale contrast)
Low kvp
T/F
The possibility of the focal spot size altering contrast enough to be visible is extremely unlikely
True
Contrast with high atomic number; appear more radiopaque
Positive contrast agent
Contrast gases with low density appearing radiolucent
Negative contrast agent
Tool to help focus on contrast in selected area, by eliminating adjacent information
Contrast mask
Allows for adjustments to image brightness and contrast. This process involves the creation of a histogram and the application of the look-up table and windowing
Grayscale processing
Insufficient number of incoming xray photons reaching the image receptor
Quantum noise
T/F
The fewer the photons reaching the IR to form the image, the greater the quantum noise visible on the digital image
True
T/F
Increased noise decreases image contrast
True
Artifacts greater in density than the surrounding area immediately surrounding them
Plus density artifacts
Artifacts lower in density than the area immediately surrounding them
Minus density artifacts
