Exam 4 Flashcards
Ability to detect and display echo amplitude differences
Contrast resolution
Better contrast resolution allows for differentiation of echoes that are
Very close together in amplitude to be shown as different SOG
What is the gold standard for resolution
Ability to display fetal lip echoes at different SOG than fetal cheek echo
What is the equation of contrast resolution
Dynamic range/SOG
What are the units of contract resolution
dB/SOG
Contrast resolution is determined by
Dynamic range and number of SOG it can store/display
When echoes are further apart in amplitude and intensity they’re displayed as
Different shades
Poor resolution echoes are ____ (Far or close) and are the same _____
Close and are same SOG
Range of signals that a piece of equipment is processing
Dynamic Range
The minimum dynamic range is detected by
Piece of equipment
The maximum dynamic range can be
Processed without distoration
What are the units of dynamic range
dB
What is the equation for Nyquist criteria
PRF/2
Analog numbers have _____ & _____ values
Unlimited and continuous
What was the first type of scan converter
Analog
Analog converted has good spatial resolution because of
Continous values being read and displayed
What are the disadvantages of analog scan converter
Instability
Image flicker
Deterioration
Image fade
What causes the instability in analog scan converter
Image is influenced by other factors such as room temp
What causes the image flicker in analog scan converter
Constant need to read and write new info
What causes the deterioration in analog scan converter
The older the image the more the image degrades
What causes the image fade in analog scan converter
Electron charges dissipated and image becomes darker over time
Digital numbers have _____ & _____ values
Distinct & Discrete Values
T or F:
Digital numbers sample and store only some values
True
What are the advantages of digital scan converter
Durability
Uniformity
Stability
Accuracy
What causes the durability for the digital scan converter
Quality of image doesn’t deteriorate with age/heavy use
What causes the uniformity for the digital scan converter
Image has consistent grayscale throughout
What causes the stability for the digital scan converter
Image doesn’t fade or drift
What causes the accuracy for the digital scan converter
Image is error free
T or F:
Convert D to A first
False
Convert A to D
Smallest part of digital picture that can be controlled
Pixel
Pixel is denisty per
Inch
High pixel density improves ____ ____ and results in an image with _____ (Good or poor) detail
Spatial resolution, better detail
How many bits are in 1 byte
8
Magnification is used to
Improve visualization f ROI
Performed while data is being read in, before storage in the scan converter
Write magnification
What are the 4 steps for write magnification
Scan
Convert A to D
Identify ROI & system discards data
U/S system rescans ROI & write new data
Finish the characteristics of write magnification:
Used to -
Number of pixels in ROI -
Increased number of pixels in -
Identify ROI discarded
Greater than ROI of original image
ROI improves spatial resolution
Performed after image is stored in scan converter
Read magnification
What are the 3 steps for read magnification
Scan
Convert A to D, store data
Select ROI, system reads & displays only that info
Finish the characteristics of read magnification:
Number of pixels in magnified image -
Spatial resolution -
Can be done -
Same as in original
Does not change
On frozen image
What is Bernoulli’s equation
P + 1/2pv^2 + pgh
What does P stand for in Bernoulli’s equation and what are it’s units
Pressure
Pascals
What does p stand for in Bernoulli’s equation and what is the equation for it
Density
Mass/volume
What does v stand for in Bernoulli’s equation
Velocity
What does 1/2pv^2 stand for in Bernoulli’s equation
Kinetic energy
What does pgh stand for and when is it cut out
Potential energy
Cut out in stenosis