Test 6 Ch 17-18 Flashcards
Spatial frequency is measured in
Line pairs
2 very important image properties!! ?
Spatial resolution
Contrast resolution
The ability to render small objects on an image
Spatial resolution/MTF
Are soft tissues like liver high or low frequencies??
Are bones, breast, vessels high or low frequencies??
Low spatial frequencies
Easy to image
High spatial frequencies
More difficult to image
No digital imaging system can image an object smaller than?
1 pixel
What is MTF?
Modulation transfer function
MTF curve graphs show- low spatial frequency=large objects
Single screen and smaller focal spot result in better spatial resolution in?
Mammography
Th ability to distinguish many shades of gray from white to black
Contrast resolution
Dynamic range is ??
Gray scale
Viewers can only visualize dynamic range up to??
30 shades of grey
Digital systems have different dynamic range such as
MRI n CT-
DR-
DM-
12 bit
14 bit
16 bit
Image contrast change
Human eye sees 30 shades of grey
Post processing (Window and level)
Radiographers strive for ______ SNR
High
Signal noise ratio -
mAs increased than SNR is increased =higher patient dose
Image detail (spatial resolution is determined by ?
MTF
Contrast resolution is improved with ________ mAs
Higher
What modality is the best contrast resolution system??
CT
Bcuz of collimation and scatter reduction
Technique creep should replace dose creep meaning ??
Lower mAs an increase KvP on certain body parts
A measure of X-ray absorption efficiency
DQE
Detective quantum efficiency
The basic photo metric unit
Lumen
The fundamental quantity of photometry ___________
This is the total intensity of light from a source
Luminous flux
One lumen of luminous flux incident on a single square foot is a ??
Foot candle (ft)
A property of a source of light
Measured in ??
Luminance intensity
Candela
Two fundamental square laws associated with photometry ?
Inverse square law
Cosine law
A measure of brightness
Measured in ?
Luminance
A nit
