chapter 19 physics
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- ___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?
- packet...velocity
- 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__?
- color
- 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___?
- clutter
- 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
- 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?
- autocorrelation
- _______or percentage of blood composed of red blood cell, normally 45%
- hematocrit
- Doppler spectrum displays the blood_____throughout the entire cardiac cyle
- velocities
- an arterial Doppler waveform is____?
- pulsatile
- ____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