Download - New carotid doppler ultrasound
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CAROTID DOPPLER ULTRASOUND
DR. MUHAMMAD BIN ZULFIQAR PGR 1 FCPS SHL
Part I
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Doppler US of carotid arteries
Anatomy of carotid arteries
Normal Doppler US of carotid arteries
Causes of carotid artery disease
Effect of extra-carotid diseases
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PART I
Anatomy of carotid arteries
Normal Doppler US of carotid arteries
Causes of carotid artery disease• Common Carotid Artery• Internal Carotid Artery • External carotid Artery
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Extra cranial cerebral arteries
All arteries that carry blood from heart up to base of skull
Right & left sides of extra cranial circulation not symmetrical
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Variants resulting from elongation of ICA
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Variations in extracranial circulationFew
• Left CCA & SCA share single trunk
• Left vertebral artery arising directly from aortic arch
• Right vertebral origin arising directly from aortic arch
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Vertebral artery course
V1
V0
V2
V3
V4
BA
VAs asymmetric in 75 % – Left dominant in 80 %
Posteriorly directed loop when exists C1 transverse process2 VAs units to form basilar artery: collateralization
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Doppler US of carotid arteries
Anatomy of carotid arteries
Normal Doppler US of carotid arteries
Causes of carotid artery disease
Effect of extra-carotid diseases
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All carotid artery examinations should beperformed with:
Tahmasebpour HR et al. RadioGraphics 2005 ; 25 : 1561 – 1575.
• Gray-scale US
• Color Doppler
• Power Doppler
• Spectral Doppler
Integrate gray scale, color flow, & spectral findings
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Position for scanning the carotid arteries
Patient lie down in supine or semisupine position
Head hyperextended & rotated 45° away from side being examined
Higher-frequency linear transducers (≥ 7.5 MHz)
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Doppler ultrasound of carotid arteries / Tips
• Begin each scan on same side, usually the right
• Avoid excess pressure on carotid bifurcation to avoid – Stimulate carotid sinus Bradycardia
SyncopeVentricular asystole
– Compress arteries to cause spurious high velocities
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Intima-Media complexNormal value ≤ 0.8 -0.9mm
Wall of CCA, bulb, or ICABest measured on far wall
Only intima & media included
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Normal carotid bifurcation
Gray Scale US
ICA Larger & lateral
ECA Smaller & internalNormal flow separation
Color Doppler ultrasound
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Longitudinal scan to visualize carotid arteries
Anterior
Posterior
Lateral
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Carotid bifurcation
Longitudinal B-mode image of carotid bifurcation
ICA & ECA seen in same plane
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Normal flow reversal zone in ICA
Velocities highest near flow dividerFlow reversal on opposite side
to flow divider
Flow reversal zoneOpposite to origin of ECA
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Internal & external carotid artery
2 small branches originating from ECA
Power Doppler US
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Standard Doppler spectral examination
Traces obtained from
• CCA Proximal – Distal
• Carotid Bulb
• ICA Proximal – Middle – Distal
• ECA Proximal
• Vertebral Artery V0 – V1 – V2
• SCA
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Typical normal Doppler spectra
Common carotid artery
Internal carotid artery
External carotid arteryTriphasic pattern
Dicrotic notch
PSV: 45 – 125 cm/secDifference between 2 sides < 15 cm/sec
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Dicrotic notch
Normal feature
Closure of aortic valve with temporary cessation of forward flow
Resumption of forward flow by elastic rebound of aortic wall
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Coiling of ICACongenital - Bilateral - Symmetrical
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Abnormal Doppler flow in tortuous vessel
Tortuous CCA displays color
Doppler eccentric jets of flow
High velocity due to eccentric
jet in tortuous CCA
Tortuosity can increase velocity, although there is no stenosis
Try sampling just beyond the curve
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Temporal tapping of ECA“Saw-tooth” appearance
Small regular deflections (TT)
Frequency corresponds to rate of temporal tapping
Deflections best seen during diastole
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Differentiation between ICA & ECA
Features ICA ECA
Size Usually larger Usually smaller
Temporal tap Usually negative Usually positive
Pulsed Doppler Low resistance High resistance
Orientation Posterior Anterior
Branches Rarely Yes
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Protocol for VA examination
– Direction of flow– Waveform configuration– Measure PSV
Longitudinal VA between transverse processes
Caudad survey
– Follow artery cauded to its origin
Cephalad survey
– Follow artery cephalad above transverse processes
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Ultrasound of normal vertebral vessels
Cephalad flow throughout cardiac cycle Low resistance flow pattern VA origin regularly seen by experienced sonographers Size: variable & asymmetric – Mean diameter 4 mm PSV: 20 – 40 cm/sec – <10 cm/sec potentially abnormal
Vertebral artery
Vertebral vein
May occasionally be seen adjacent to VA Flow caudad & nonpulsatile
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Normal vertebral artery originV0
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Normal vertebral artery & veinV2
Vertebral artery & vein seen between vertebral processes of spine
Color Doppler Pulsed Doppler
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Subclavian artery
Mirror image below pleura
Color Doppler US Pulsed Doppler US
Normal triphasic waveform
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Doppler US of carotid arteries
Anatomy of carotid arteries
Normal Doppler US of carotid arteries
Causes of carotid artery disease
Effect of extra-carotid diseases
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Causes of carotid artery diseases
Arteriosclerotic disease
Non-arteriosclerotic diseasesFibro muscular dysplasia DissectionVasospasm Aneurysm & pseudo aneurysm
Arterio-venous fistula Arteritis: Takayasu – Horton Carotid body tumor Idiopathic carotidynia
Most common cause
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Extracranial carotid artery & stroke
• Stroke is third leading cause of death in USA
• > 500,000 new cases of CVA reported annually
• 20 – 30% of stokes due to severe carotid artery stenosis
• Stenosis involves ICA within 2 cm of bifurcation
• CEA* more beneficial than medical tm in symptomaticor asymptomatic patients with > 70% carotid stenosis**
* CEA: Carotid endarterectomy** NASCET: North American Symptomatic Carotid Endartectomy Trial
** ECST: European Carotid Surgery Trial
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Common sites for extracranial arterial disease
Most common site at carotid bifurcation
with plaque extending into ICA
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Plaque characterization
Low Lipid – Flow void
Moderate Collagen – Easy to see High with shadow Calcification – Focal or diffuse
Echogenicity
Calcification: no correlation with neurologic symptoms Focal hypoechoic zones: Hemorrhage – Necrosis – Lipid
Heterogenous plaque
Common sources of cerebral emboli: TIA – Stroke Poor US results for ulcer detection
Plaque surface features
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Appearance of atheromatous plaquesHomogeneous echolucent Homogeneous echogenic
Heterogeneous plaque Cauliflower’ calcification
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Calcified plaque
Calcific plaque with shadow
obscuring portion of the bulb
Interrogate artery beyond plaque
Shadowing segment < 1 cm No turbulent flow: insignificant stenosis Damped or turbulent flow: tight stenosis
Shadowing segment > 2 cm Degree of stenosis indeterminate Other modalities recommended
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Intraplaque hemorrhage
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Sources of error in ulcer diagnosis
Plaque surface irregular
but not ulcerated
Adjacent plaque
simulate ulceration
Image plan does not include
the ulcer
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Large plaque ulcer
Power Doppler“eddy flow”
Color DopplerPseudo-dissection
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Ulcerated plaque or twinkle artifact
Scale 86 cm/sec, color in diastole Color flow disappeared
Color artifact continues to twinkle
Hard plaque in proximal ICA
Questionable flow at plaque surface
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Estimation of carotid stenosis
Diameter reduction Surface reduction
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Relationship between diameter reduction & cross-sectional area reduction
Diameter reduction(%)
Cross-sectional area reduction(%)
30 50
50 75
70 90
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Cardinal Doppler parameter to grade stenosis
Best documented Doppler parameter for carotid stenosis
Peak Systolic Velocity (PSV)
Quite valuable for detecting high-grade carotid stenosis
End Diastolic Velocity (EDV)
Avoid errors of collateralization Avoid errors of physiological factors: BP – Pulse rate – Cardiac output – Peripheral resistance
PSV ratio
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Relationship of flow, velocity & lumen size
Spencer MP & Reid JM. Stroke 1979 ; 10 : 326 – 330.
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Grading stenosis – PSV ratio
Proximal: 2 cm proximal to carotid bulb
At stenosis: same Doppler angle if possible
Normal value < 2.0
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17 authors:1 Moderator16 panelists
San Francisco, CalifOctober 22–23, 2002
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ICA stenosis on angiogram
ECST 2 (1998)
European Carotid Surgery Trial
(C – A / C) x 100
NASCET 1 (1991 – 1998)
North American Symptomatic Carotid Endartectomy Trial
(B – A / B) x 100
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ICA stenosis on angiogramDiameter reduction
* NASCET: North American Symptomatic Carotid Endartectomy Trial
** ECST: European Carotid Surgery Trial
30% 65%
40% 70%
50% 75%
60% 80%
70% 85%
80% 91%
90% 97%
* NASCET (B – A / B) x 100
** ECST(C – A / C) x 100
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Degree of ICA Stenosis in Doppler US*Consensus Criteria – NASCET criteria
ICA stenosis ICA PSV ICA EDV PSV ratio (%) cm/sec cm/sec ICA/CCA
Normal < 125 < 40 < 2.0< 50% < 125 < 40 < 2.0
50 – 69% 125 – 230 40 – 100 2.0 – 4.0
> 70% > 230 > 100 > 4.0Near occlusion variable variable variableTotal occlusion undetectable undetectable not applicable
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Degree of ICA Stenosis in Doppler US*Consensus Criteria – NASCET criteria
ICA stenosis ICA PSV ICA EDV PSV ratio (%) cm/sec cm/sec ICA/CCA
Normal < 125 < 40 < 2.0< 50% < 125 < 40 < 2.0
50 – 69% 125 – 230 40 – 100 2.0 – 4.0
> 70% > 230 > 100 > 4.0Near occlusion variable variable variableTotal occlusion undetectable undetectable not applicable
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Aliasing or high velocity jet
Area of highest velocity in area of stenosis
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Adjustment of color gain
Color gain at 80%
Marked turbulence of ICA & ECANo luminal narrowing
Anatomy of bifurcationdemonstrated more accurately
Color gain at 66%
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ICA stenosis
PSV 500 cm/sec
EDV 300 cm/sec
Spectral broadening
80% diameter stenosis
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Color Doppler bruit
Extensive soft tissue color Doppler bruit surrounds
carotid bifurcation with 90% ICA stenosis
Confetti sign
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Post stenotic zone/ Immediately after stenosis
• Cannot be precisely quantified (evaluated visually)Fill-in of spectral window > 50% diameter reduction
Severely disturbed flow > 70% diameter reduction High amplitude & low frequency Doppler signalFlow reversalPoor definition of spectral border
• May be only sign of carotid stenosis in calcified plaque
Spectral broadening
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Spectral broadening Immediately after stenosis
High amplitude & low frequency Doppler signalPoor definition of spectral border
Flow reversal
Severe spectral broadening: > 70% diameter reduction
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Pseudo-spectral broadening
• High gain setting
• Vessel wall motion
• Tortuous vessels
• Site of branching
• Abrupt change in vessel diameter
• ↑ velocity: athlete - high cardiac output - AVF1 - AVM2
• Aneurysm, dissection, & FMD3
1AVF: Arterio-Venous Fistula2AVM: Arterio-Venous Malformation3FMD: Fibro-Muscular Dysplasia
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Post stenotic zone / Distal to site of stenosis
Tardus-parvus waveform
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Sonographic features of severe ICA stenosis
Significant visible plaque (≥ 70% diameter reduction)
PSV > 230 cm/sec
EDV > 100 cm/sec
ICA/CCA PSV ratio ≥ 4.0
Spectral broadening
Color aliasing despite high velocity scale (100 cm/sec)
Color bruit artifact in surrounding tissue of stenosis
High-pitched sound at pulsed Doppler
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Tight stenosis or occlusion?
• Difficult to distinguish tight stenosis from occlusion
• Completely occluded ICA Will not release emboliNot corrected by surgery
• Very severe stenosis Potential source for emboli or acute thrombosisMay require urgent surgery
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Optimization of low flow velocities
• Decreased color velocity scale
• Increase color, power & pulsed Doppler gain
• Decreased wall filter
• Focal zone at level of diseased segment
• Doppler angle as low as possible (60° or less)
• Increased persistence
• Increase sample volume gate
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Subtotal occlusion of ICA
“string sign” or “trickle flow ”
Narrow channel of low-velocity in subtotal ICA occlusion
Low PRF & low filter required to detect low-velocity flow
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High grade “string sign” stenosis
Tardus Parvus waveform
Tardus: Long rise time
Parvus: Low PSV
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Endarterectomy without arteriography
• Arteriography ExpensiveRisks: stroke (0.1 – 0.6%) – death (0.1%)Rarely affect surgical planSufficient information obtained with MRI
• Conditions Good experience of US departmentStenosis localized to carotid bifurcationUnequivocal US findingsSymptoms ipsilateral to carotid stenosis
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Causes of image/Doppler mismatch
• Cardiac arrhythmia• Severe aortic stenosis• Hypotension or hypertension• Tortuous vessels• Hypoechoic, anechoic or calcified plaques • Long segment high grade stenosis• Pre-occlusive lesion• Tandem lesion• Contra-lateral carotid stenosis• Carotid dissection
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Short & long stenosis of ICAShort stenosis (frequent) Long stenosis (rare)
PSV lower than expected
EDV maintained at high level
Can produce very high PSV
(> 500 cm/s)
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Long stenosis of ICA
Zwiebel WJ et al. Ultrasound Quarterly 2005 ; 21 : 113 – 122.
RICA
RICA: PSV 183 cm/secEDV 105 cm/sec
CCA: PSV 76 cm/sec PSV ratio: 2.4
Inconsistent data
Long stenosis of ICA > 70%
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Occlusion of ICA
• Absence of flow by color, power & pulsed Doppler
• “Internalization” of ipsilateral ECA waveform
• Reversed flow in ICA or CCA proximal to occlusion
• Thrombus or plaque completely fills lumen of ICA
• Externalization of ipsilateral CCA or proximal ICA
• Higher velocities in contralateral CCA vs. ipsilateral CCA
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Occlusion of ICA
ICA
ECA
CCA
Retrograde flow in stump of ICA
Absence of flow in ICA beyond
Doppler spectrum from CCA
Externalization of CCA
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Occlusion of ICA“to-and-fro” flow or thud flow
Tahmasebpour HR et al. RadioGraphics 2005 ; 25 : 1561 – 1575.
Damped systolic flow
Reversed flow in early diastole
Pulsed Doppler of CCA
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Internalization of ECA
Patient with complete occlusion of left ICA
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Occlusion of CCA
Robbin ML et al. Ultrasound Clin 2006 ; 1 : 111 – 131.
Reversed flow from ECA
to supply ICA & brain
“ECA-to-ICA collateralization”
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Occlusion of CCA
Tahmasebpour HR et al. RadioGraphics 2005 ; 25 : 1561 – 1575.
Absence of flow in distal CCAReversed flow in ECANormal flow in ICA
Internalization of ECADelayed systolic acceleration (Tardus)
Positive temporal tap maneuver
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Stenosis of ECA
• PSV of ECA stenosis Minimal < 200 cm/sec
Moderate 200 – 300 cm/sec Severe > 300 cm/sec
• ECA/CCA systolic ratio* < 2 ≤ 50% Ø stenosis ≥ 2 ≥ 70% Ø stenosis
Isolated ECA stenosis not clinically significant
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Ectatic CCA
Ectatic CCA as it arises from innominate artery
Responsible for pulsatile right supra clavicular mass
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Thank You