Chapter 10 Flashcards
Fidelity of anatomical structures by the image.
Image quality
What are the 4 factors that most affect image quality?
Spatial resolution
Contrast resolution
Noise
Artifacts
Random variation in useful data or signal
Noise
Example of audio noise
Static
Random variation in optical density
Visual noise
Which type of scatter is a primary determinant of noise?
Compton scatter
Finite size of individual silver halide crystals on the film; will contribute to noise
Film grain
Finite size of individual phosphor crystals of intensifiying screen will contribute to noise
Structure mottle
Increased speed =
___ noise + ___ resolution
Increased noise
Decreased resolution
Higher spatial and contrast resolution requires what?
Low noise and slower image receptors
Higher speed =
____ patient dose
____ resolution and more noise
Decreased patient dose
Decreased resolution and more noise
Slower speed =
___ resolution and image quality
___ patient dose
Better resolution and image quality
More patient dose
For analog systems - A response curve for xray films that demonstrates density, contrast, speed, latitude
Characteristics curve
aka Hunter & Driffield Curve
aka H&D curve
Range of exposures that will result in optical densities within useful range to human eye
Latitude
More latitude (_____ slope) = ___ change in exposure on optical density scale and ___ change in contrast
Shallower slope
Less change in exposure
Less change in contrast
Less latitude (___ slope) = ___ change in contrast
Steeper slope
Larger change in contrast
What does SID stand for?
Source image distance
What does SOD stand for?
Source object distance
What does OID stand for?
Object image distance
Uneven magnification
Distortion
What are the contributing factors of distortion?
Object size, shape, position/orientation
1/2 shadow
Penumbra
Move the object closer to the source and further from the image receptor, the shadow looks ____
Bigger
What does a decrease in KVp do to the contrast?
Increases contrast with shorter scale (less steps between dark and light)
What does and increase in KvP do to contrast?
Decreases contrast image with longer scale (more steps between dark and light)
