Carotid Duplex/Color Flow Imaging Flashcards
Accelerated flow mistakenly attributed to stenosis instead of what?
- Cardiac output
- Tortuous vessel
- Compensatory flow
- Inappropriate Doppler angle
Disease process could be under-estimated if accelerated flow not present or detected such as?
- Jet of accelerated flow missed
- Long, smooth plaque formation
- Stenosis at area of dilatation
- inappropriate Doppler angle
Individual frequencies/velocities displayed with time on horizontal axis and various frequency shifts/velocities on vertical axis
Fast Fourier TRansform (FFT) method
What displays true frequency/velocity shifts and utilizes the FFT method?
spectral analysis
Two piezo-electric crystals, one constantly sending and one constantly receiving reflected waves. No range resolution and fixed sample size?
Continuous wave Doppler
Crystals send then receive the reflected ultrasound. Has range resolution, variable sample size, and well-defined spectrum?
pulsed Doppler
Spectral window is filled in with what type of Doppler?
CW Doppler
Assigns color to display average frequencies and direction of moving blood?
color Doppler
With color Doppler, pulse doppler beams evaluate multiple samples sites throughout a specific area. Scan rates are _____ because of multiple transmit/received pulse cycles in each color line of site.
slower
Normal ICA Doppler signals?
More high-pitched and continuous than ECA
Rapid upstroke and down stroke with a high diastolic component
ECA normal Doppler signals?
Signal more pulsatile, vary similar to peripheral vessels
Rapid upstroke and down stroke with low flow in diastole
How can a stenosis be characterized by abnormal Doppler signals?
Higher pitched sound and waveform with higher velocity. Spectral broadening evident and loss of spectral window.
Distal to a stenosis has what type of flow patterns?
turbulent, bi-directional, can be dampened and monophasic/continuous
Consider disease at carotid siphon when high resistant flow patterns evident in?
ICA
DIminished velocities in what vessel bilaterally may indicate poor cardiac output or stroke volume?
CCA
Diminished velocities unilaterally suggests prox disease where?
innominate or common carotid artery
Criteria that is critical in determining an occlusion?
- CCA may have a ver low or absent diastolic component
- Evidence of collateralization when ECA may exhibit high flow in end diastole
- Absent ICA Doppler signal or pre-occlusive thump
Misrepresentation of Doppler signal due to limitations of the equipment being used is called what?
aliasing
wave firm has flat, crew-cut appearance
Maximum frequency is 1/2 PRF. Flow information greater than 1/2 PRF cannot be displayed is called what?
Nyquist limit
What are methods of increasing the PRF/Nyquist limit?
Decrease the baseline, increase Doppler scale, change frequency, alter angle of insonation, decrease depth, or use continuous wave Doppler
Doppler shifts above and below the baseline, displaying a duplicating spectrum or color-flow Doppler. What type of artifact if from strong reflectors or too much gain?
Mirror imaging
What occurs when flow moves into a wider portion of the vessel?
helical flow
common in the carotid bulb
Characteristics of helical flow?
- Doppler shifts above and below the baseline
- Spectral waveforms are different
- Doppler angle constantly changing
- Flow is not laminar ; spectral broadening present
