This document discusses various methods for quantifying internal carotid artery stenosis using duplex ultrasound. It describes using B-mode imaging to visualize carotid plaques and color flow imaging to identify the residual lumen and adjust the Doppler angle. Angle-corrected Doppler velocimetry measures peak systolic velocity, which is inversely related to the residual lumen radius and stenosis length. Ratios of internal to common carotid artery velocities are also used, with different standards from NASCET versus ECST angiographic studies. The recommendations are to measure peak systolic velocity in the internal carotid artery and velocity ratios of internal to common carotid arteries.

1. Quantification of
Internal Carotid Artery Stenosis
with Duplex US
2011. 03. 31
Hye seon Jeong

2. Carotid stenosis measured by
ultrasound
• B-mode imaging of carotid plaques
• Color-coded flow imaging of carotid
stenosis
• Angle corrected Doppler velocimetry of
carotid stenosis

3. B-mode imaging of carotid plaques
• Intima-media
thickness (IMT)
• Fatty streak or
soft plaques
• Small non-
stenotic plaque

4. Plaque description
1. location
2. length
3. Composition – assessed for its;
1. echogenicity (brightness)
2. texture
3. extent
4. edge
4. surface of the lesion: smooth or irregular

5. Composition of carotid plaque
Complicated atherosclerotic
Heterogenous process
neovascularity; calcification;
intraplaque hemorrhage;
Ulceration; Thrombosis
Without acoustic shadowing
 Fibro-fatty lesion
Acoustic shadowing(+)
 calcification
Anechoic or hypoechoic
regions : hemorrhage, lipid
deposits or necrotic regions

6. Composition of carotid plaque
Homogenous
Purely cellular in nature
No calcification
Significant cholesterol
deposition or hemorrhage
Commonly associated with
intimal hyperplasia

7. Advantages of B-mode grading of the
carotid stenosis
• Quantification of early atherosclerotic changes
• Visualization of plaque structure and extent
• The possibility of ‘on-site’ diameter reduction
measurements
• Disadvantages
– common imaging artifact
• inappropriate gain setting
• shadowing due to calcium deposition and scattering
– Inability to differentiate fresh clot from moving blood

8. Color-coded flow imaging of carotid
stenosis
CDFI alone should not be used
for grading of stenosis
: aliasing with inappropriate
velocity scale setting compared
to angle-corrected velocimetry
Use
• Identify vascular structures
and the tightest residual lumen
• Adjust the Doppler angle for
pulse-wave velocimetry

9. Color-coded flow imaging of carotid
stenosis
Power mode
• Used for same
purpose of CDFI
• display regardless
of flow direction and
velocity value

10. Angle corrected Doppler velocimetry
of carotid stenosis
• The velocity is
inversely proportionate
to the radius of the
residual lumen,
stenosis length, blood
viscosity and
peripheral resistance
• The Peak systolic
velocity (PSV)
Spencer and Reid, 1979
The relationship between arterial
stenosis, flow and velocity

11. Angle corrected Doppler velocimetry
• The Peak systolic
velocity (PSV)
: Mainly a function of
the radius of the
residual lumen, length
of stenosis, and
cardiac output
• Influenced by
various circulatory
conditions 
ICA/CCA PSV ratio

12. Angle corrected Doppler velocimetry
• Advantages
– Direct physiologic measurement of flow
acceleration at the stenosis site
– Widespread use
– Availability of validated diagnostic criteria
• Disadvantages
– Operator dependency
– Velocity changes due to cardiac output, bilateral
stenosis, flow volume reduction
– Equipment dependency

13. Color flow
definition of ICA/CCA ratio
the residual
lumen
B-mode
Highest PSV
US finding
grading
of carotid
stenosis

14. Tabulated duplex US criteria used to quantify ICA stenosis according to
NASCET angiographic grades.

16. Society of Radiologists in Ultrasound consensus criteria for
carotid stenosis measurements with duplex

18. NASCET vs ECST Methods

19. Working Group Recommendations
(a) peak systolic velocity in the ICA (ICA-PSV)
(b) peak systolic ICA to peak systolic CCA ratio or
Peak Systolic Velocity Ratio (PSVR)
(c) peak systolic ICA to end-diastolic CCA ratio= St.
Mary’s Ratio

21. Radiology (2003) NACC.
Ann Vasc Surg. (2002) Filis et al.
J Endovasc Surg (1996) Nicolaides et al.