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
What does capacitance look at
Change in volume
What is the equation for capacitance
Change in volume/Change in time
What is the equation for compliance
Change in volume/Change in pressure
The greek letter n or ____ is used to represent _____
Aeta
Viscosity
Define viscosity
Resistence to flow
What is the resistance expression
R = 8nl/pie x r^4
What is RN
Reynolds number
What does the Reynolds number 2,000 or 3,000 indicate
Turbulence
In a series you will have a larger
Final sum
In parallel you will always have a smaller
Final sum
Is pressure higher in your legs than in your arm?
Yes
CRT stands for
Also known as
Cathode Ray Tube
Electron gun
CRT’s important component is the
Anode/focusing coil
What do focusing coils do
Eliminate stray electrons
Sweeping coils are ____ that do what to the electron beam
Magents that move electron beam to different regions across the screen
Draw the CRT diagram
Electron gun
Focusing coil
Sweeping coil
Electron beam
Phosphorus
RGB used to produce
All colors of rainbow
Substance that glows when activated by electron gun
Phosphorus
Define rastering
Sweeping of the beam across the display
What are the 4 characteristics of imaging
Normal incidence
High f improves resolution
PW only
Min 1 crystal
What are the characteristics of Doppler
0-180
Low f, avoid aliasing
PW & CW
Min of 1 for PW, 2 for CW
What does BART represent
Blue away, red towards
CW has the ____ (Highest or Lowest) velocity anywhere along ____ of beam
Highest
Length
What are the 4 characteristics of CW Doppler:
R
M
G
N
Range ambiguity
Most sensitive
Good temporal resolution
No aliasing
Why does CW Doppler have 2 elements
Transmitting always busy so necessary to have one for receiving
CW Doppler is produced by continuous application of
Alternating electrical current
CW Doppler is determined by
Frequency of alternating current
CW alternates current by
Flipping positive and negative charge
PW Doppler is good on
Location of flow
What are 4 characteristics of PW Doppler:
R
M
G
A
Range resolution
Moderate sensitivity
Good temporal resolution
Aliasing
What do CW and PW Doppler measure
Peak velocity
What is on the X-Axis and Y-Axis for PW Doppler
X-Axis - Time
Y-Axis - Frequency/Velocity
PW is produced by short
Repeated pulses with pauses between
Where are the positive and negative shifts shown on PW Doppler
Positive is above baseline
Negative is below baseline
What are the 3 ways of increasing aliasing
Faster blood flow velocity
High f transducer
Deeper gates/Low PRF
What are the 5 ways to clean up aliasing
Adjust max scale
Select new window with shallow simple volume
Use low f transducer
Use baseline shift
Use CW Doppler
How does adjusting max scale affect Nyquist limit
Increase
How does selecting a new window with shallow simple volume affect Nyquist limit
Increase
How does using low f transducer affect Doppler shift
Decrease
How does using baseline shift affect display
Display looks better
Using CW Doppler may avoid ____ but then you deal with ____ ____
Aliasing
Range ambiguity
With deep Doppler smaple gate and high velocity flow operator must choose between
Aliasing and range ambiguity
Deep ultrasound reflectors requires ____ (Long or Short) PRP and ____ (High or Low) PRF
Long, low
High velocity blood has high Doppler shifts requires ____ (high or low) PRF to avoid ____
High PRF
Avoid aliasing
Info from number of pulses required to estimate velocity of blood flow
Pulse packet
I iii I iii I
The i’s represent
Echoes going and returning
Which return first shallow or deep
Shallow
The heart has __mm of mercury
0
What is the equation of continuity
Q = avg velocity x area
If you have a narrow region how does that affect your velocity
Faster velocity
If you have high velocity you will have a ____ (Small or big) area
Small
What are the 4 devices used for storage
Paper
Magnetic Media
Chemical Derived Photos
Optical media
What are the 5 order of receiver operations
Amplitfication
Compensation
Compression
Demodulation
Reject
What is the equation for parallel series
1/Reffective = 1/R1 + 1/R2
What does amplification do
Each signal returning from trip is larger
What does compensation do
Correct for attenuation
What does compression do
Keeps grayscale in content in regions of viewable shades
What does demodulation do
Electrical signal from receiver is made into suitable image
What does reject do
Suppresses spurious signals
How much is 1 byte of info
2^8 (256)
If you increase your length how will that affect your resistence
Increase
If you decrease your viscosity how will that affect your resistance
Increase
If your radius decreases how will that affect your resistance
Increase (To the 4th power)
If you radius is decrease of 1/16 then your resistence will be
Increase by 16
Blood flow is due to change in
Pressure
In CRT which do you sweep first, odds or evens?
Odds
If you have 0 compliance what will it do
Not change anything
Finite can increase
Volume
T or F:
Infinite does exist
False
Doesn’t exist
What is the Hemo Law Equation
Change in pressure = Q (fluid flow) x Resistance
If you have a fixed change in pressure and your fluid flow (Q) is increased how will that affect your resistance
Decrease
