Quantification of

Internal Carotid Artery Stenosis

with Duplex US

2011. 03. 31

Hye seon Jeong

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

B-mode imaging of carotid plaques

• Intima-media

thickness (IMT)

• Fatty streak or

soft plaques

• Small non-

stenotic plaque

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

Composition of carotid plaque

HeterogenousComplicated atherosclerotic

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

Composition of carotid plaque

Homogenous

Purely cellular in nature

No calcification

Significant cholesterol

deposition or hemorrhage

Commonly associated with

intimal hyperplasia

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

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

Power mode

• Used for same

purpose of CDFI

• display regardless

of flow direction and

velocity value

Color-coded flow imaging of carotid

stenosis

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

• 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

Angle corrected Doppler velocimetry

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

US grading

of carotid stenosis

Highest PSV

Color flow definition of the residual

lumen

ICA/CCA ratio

B-mode finding

Tabulated duplex US criteria used to quantify ICA stenosis according to

NASCET angiographic grades.

Society of Radiologists in Ultrasound consensus criteria for

carotid stenosis measurements with duplex

NASCET vs ECST Methods

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

Ann Vasc Surg. (2002) Filis et al.

J Endovasc Surg (1996) Nicolaides et al.

Radiology (2003) NACC.