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
Soft copies are viewed on ??
Cathode ray tube
LCD
Bright light/ effects cones of eye
Dim light/effects rods of eye
Photopic
Scotopic
Illuminates the pixel and is blocked or transmitted by the orientation of the liquid crystals
Backlight
A measure of image luminance or LCDs ?
Aperture ratio
A medical flat panel is ___________
Monochrome
Electroluminenscence
Or light emitting diode (LED)
A diode that is an electronic device that allows current flow in one direction
Active matrix and pixels
Is flat faced
LCD
An LEDs purpose is to not replace the LCD but rather be the
Backlight for such a monitor
LEDs have many advantages such as??
Lower power use
Thinner in size
Longer life
Preprocessing provides electronic calibration to reduce pixel to pixel.. and this is done manually or electronically??
It is automatic!!
The preprocessing calibration techniques are identified as
Flat shielding
What is ambient light??
The light we have before a light is turned on.
Makes white-black and black-white
See changes in anatomy
Removing anatomy
Image inversion
Subtraction (DSA)
Effective for small fractures and hug contrast tissues
A scanned beam
Is curved faced
Edge enhancement
Cathode ray tube (CRT)
Low frequency = contrast
High frequency = contrast
Good
Bad
RIS
Radiology info system
Patient Health records/data
The higher the frequency the greater the
Blur
