Chapter 20 - Carotid duplex and color flow Flashcards
Duplex overestimates disease in these situations
1) artifact mistaken for plaque 2) accelerated flow due to increase CO, vessel tortuosity, compensatory flow for controlateral disease, hyperemia, hypoplastic vessel 3) inappropriate Doppler angle
Duplex underestimates disease in these situations
1) low level echoes of soft plaque missed 2) missed accelerated flow in short segment of disease 3) long smooth plaque does not have accelerated, turbulent flow pattern 4) high bifurcation 5) inappropriate Doppler angle
Continuous wave vs pulsed wave doppler and spectral analysis
Spectral analysis can only be done with pulsed wave Continuous wave will have spectral broadening even in laminar flow
Sample volume of the pulsed doppler
1-1.5 mm
Normal intima-media thickness in age > 60
< 0.9 mm
Surface characteristics of plaque description
1) smooth 2) slightly irregular 3) grossly irregular 4) crater like
Types of atherosclerotic lesions
1) fatty streaks 2) fibrous plaque (Soft) 3) complex plaque 4) calcification 5) thrombosis
Define spectral window
Blank area under systole in a pulse doppler signal indicating laminar flow
Type of flow at the carotid bulb
Helical or nonaxial flow due to changes in geometry Corkscrew like
Power doppler define
Doppler energy Enhanced doppler processing produce solid color within flow channel vs no color at all for occlusion
Duplex criteria based on consensus 2003
Aliasing
Misrepresentation of doppler signal due to low pulse repetition frequency
Nyquist limit
one half of the pulse repetition frequency
Crosstalk
Mirror imaging
Artifact due to strong reflectors
Duplicated above and below baseline
Doppler probe for intraoperative monitoring
High frequency transducer 12-15 MHz
