Quantification of

Internal Carotid Artery

Stenosis

with Duplex US

2011. 03. 31Hye 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. length3. Composition – assessed for its;

1. echogenicity (brightness)2. texture3. extent4. edge

4. surface of the lesion: smooth or irregular

Composition of carotid plaque

Heteroge-nous

Complicated atherosclerotic process

neovascularity; calcifica-tion; intraplaque hemorrhage; Ulceration; Thrombosis

Without acoustic shadowing Fibro-fatty lesionAcoustic shadowing(+) calcification

Anechoic or hypoechoic re-gions : hemorrhage, lipid deposits or necrotic regions

Composition of carotid plaque

Homogenous

Purely cellular in nature

No calcification

Significant cholesterol

deposition or hemor-

rhage

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 scat-

tering– 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 com-pared to angle-corrected ve-locimetry

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 regard-

less of flow direc-tion and velocity value

Color-coded flow imaging of carotid stenosis

Angle corrected Doppler velocime-try

of carotid stenosis • The velocity is in-

versely proportion-ate to the radius of the residual lumen, stenosis length, blood viscosity and peripheral resistance

• The Peak systolic ve-locity (PSV) Spencer and Reid, 1979

The relationship between arte-rial stenosis, flow and velocity

• The Peak systolic ve-locity (PSV)

: Mainly a function of the radius of the resid-ual lumen, length of stenosis, and cardiac output

• Influenced by vari-ous circulatory con-ditions ICA/CCA PSV ratio

Angle corrected Doppler velocime-try

Angle corrected Doppler velocime-try

• Advantages– Direct physiologic measurement of flow ac-

celeration at the stenosis site– Widespread use– Availability of validated diagnostic crite-

ria

• Disadvantages– Operator dependency– Velocity changes due to cardiac output, bilat-

eral stenosis, flow volume reduction– Equipment dependency

US grading of carotid stenosis

Highest PSV

Color flow def-inition of the

residual lumen

ICA/CCA ratioB-mode

finding

Tabulated duplex US criteria used to quantify ICA stenosis ac-cording to NASCET angiographic grades.

Society of Radiologists in Ultrasound consensus cri-teria 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 ra-

tio or Peak Systolic Velocity Ratio (PSVR)(c)peak systolic ICA to end-diastolic CCA ra-

tio= St. Mary’s Ratio

Ann Vasc Surg. (2002) Filis et al.

J Endovasc Surg (1996) Nicolaides et al.

Radiology (2003) NACC.