This site is 100% ad supported. Please add an exception to adblock for this site.

chapter 19 physics


undefined, object
copy deck
___is a form of two dimensional Doppler?
color flow
____is coded into colors and superimposed on a two dimensional grayscale, anatomic image?
velocity information
black and white identifies_____, but color identifies ____?
anatomic structures...blood flow velocities and function
color Doppler provides___?
1. pulsed ultrasound technique
2. range resolution (range specificity)
3. subject to aliasing
color Doppler provides information regarding____?
direction of flow and semi-quantitative
Color Doppler reports___?
average velocities or mean velocities
pulse and continuous wave Doppler reports___?
peak velocities
color Doppler uses____or lookup table to convert____ into colors, with black region in the center?
dictionary...measured velocity
the two most commonly used dictionaries are called?
1. velocity mode
2. variance mode
color present information on____?
flow direction
black region in the middle of the color map indicate____?
no Doppler shift
color above the black stripe indicate cell moving toward the transducer or____?
positive Doppler shift
multiple color closer to black stripe indicate___?
lower velocity
colors higher above the black stripe indicates___?
higher velocity
the color below the black stripe indicate blood cell moving___?
away from the transducer
multiple color closer to the black stripe indicates___?
lower velocity
colors farther below the black stripe indicates__?
faster velocities
with the velocity mode map, the color change____?
up and down (no side to side)
____ mode distinguishes ____from turbulent flow?
variance...laminar flow
color in a variance and____ mode map indicates____?
velocity...flow direction
the variance mode maps display___?
different color side to side
in variance map, color from the left side indicates___?
laminar flow (normal)
in variance map, color from the right side indicate___?
turbulent flow (asso. w/ pathology)
multiple ultrasound pulses determine____?
blood cell velocities
____ or ensemble (multiple pulses) determine___ of the blood cell?
larger packets or longer ensemble lengh (large pulses) have 2 advantages___?
1. more accurate velocity measurement
2. more sensitive to low flow
packet with more pulses also have disadvantages___?
1. more time
2. reduce frame rate
3. decrease temporal resolution
color Doppler measures___?
mean velocity
spectral Doppler (pulsed and continuous wave) measures__?
peak velocity
power mode Doppler only identifies_____?
the presence of a Doppler shift
Power mode Doppler does not evaluate___?
speed or direction
Power mode Doppler is___?
non-directional color Doppler
all the vessels in the power Doppler image have the same__?
power Doppler also called?
energy mode or color angio
traditional Doppler such as pulsed, continuous, color process____?
velocity information
in power mode, _____of the reflected signal is processed regardless speed or direction?
the strenght or amplitude
_____directly related to the number of moving blood cells?
the amplitude of the reflection
three advantages in power mode?
1. increase sensitivity to low flow
2. unaffected by Doppler angles, unless 90 degree
3. no aliasing
three disadvantage in power mode?
1. no measurement of velocity or direction
2. lower frame rate than color flow Doppler
3. susceptible to motion of the transducer, burst color, flash artifact
on spectral display, low frequency Doppler shift artifact called___?
on spectral display, low frequency with color Doppler shift called___?
ghosting artifact
____is used to eliminate low frequency Doppler shifts resulting form moving anatomy rather than moving blood cells?
wall filter
wall filters exclude____ shift around the baseline of a spectral display?(but no effect on higher Doppler frequency)
low frequency Doppler
with color Doppler,_____eliminate color arising from slow velocity?
wall filters
mirror image artifact arises only with spectral Doppler, called?
crosstalk appears_______ the base line?
above and below
flow pattern in crosstalk is ___?
unidirectional, but appears bidirectional
2 things cause crosstalk
1. Doppler receiver gain too high
2. incident beam near 90 degree between sound beam and flow direction
_____is a tool that breaks the ____ into its basic building block and identifies individual velocity?
spectral analysis...complex signal
2 method of spectral analysis?
1. Fast Fourier Transform (FFT)
2. Autocorrelation
early methods of Doppler analysis include___?
zero crossing detector, Chirp-Z transform, and time interval histogram (not for computer)
_____a digital technique used to process both____ and ____ wave Doppler signal?
Fast Fourier Transform (FFT)...pulsed...continous
FFT has 2 advantages?
1. exceeding accurate
2. individual velocity that make up complex reflected signal
spectral display of the FFT distinguishes_____from____?
laminar flow, turbulent flow
with laminar flow, most cells travel at___?
similar velocities
the region between the baseline and the spectrum called___?
spectral window
with blood in chaotic, and many different direction and speed, the pulsed Doppler spectral______filled in by___?
window, turbulent flow
_____wider range of velocities and Doppler shifts within the sample volume?
spectral broadening
____is the digital to analyze____?
autocorrelation... color flow Doppler
____used with color Doppler because of lot data being processed?
_______or percentage of blood composed of red blood cell, normally 45%
Doppler spectrum displays the blood_____throughout the entire cardiac cyle
an arterial Doppler waveform is____?
____is useful in establishing the diagnosis of arterial stenosis?
resistivity index (RI)
RI and pulsatility Index (PI) have advantages?
1. mathematical measurement
2. the shape of the Doppler spectrum

Deck Info