2. 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
3. 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
4. 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
6. Variations in extracranial circulation
Few
• Left CCA & SCA share single trunk
• Left vertebral artery arising directly from aortic arch
• Right vertebral origin arising directly from aortic arch
7. Vertebral artery course
V1
V0
V2
V3
V4
BA
VAs asymmetric in 75 % – Left dominant in 80 %
Posteriorly directed loop when exists C1 transverse process
2 VAs units to form basilar artery: collateralization
8. 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
9. All carotid artery examinations should be
performed 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
10. 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)
11. 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
Syncope
Ventricular asystole
– Compress arteries to cause spurious high velocities
16. Normal flow reversal zone in ICA
Velocities highest near flow divider
Flow reversal on opposite side
to flow divider
Flow reversal zone
Opposite to origin of ECA
17. Internal & external carotid artery
2 small branches originating from ECA
Power Doppler US
19. Typical normal Doppler spectra
Common carotid artery
Internal carotid artery
External carotid artery
Triphasic pattern
Dicrotic notch
PSV: 45 – 125 cm/sec
Difference between 2 sides < 15 cm/sec
20. Dicrotic notch
Normal feature
Closure of aortic valve with temporary cessation of forward flow
Resumption of forward flow by elastic rebound of aortic wall
22. 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
23. Temporal tapping of ECA
“Saw-tooth” appearance
Small regular deflections (TT)
Frequency corresponds to rate of temporal tapping
Deflections best seen during diastole
24. 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
25. 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
26. 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
30. 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
31. Causes of carotid artery diseases
Arteriosclerotic disease
Non-arteriosclerotic diseases
Fibro muscular dysplasia
Dissection
Vasospasm
Aneurysm & pseudo aneurysm
Arterio-venous fistula
Arteritis: Takayasu – Horton
Carotid body tumor
Idiopathic carotidynia
Most common cause
32. 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 symptomatic
or asymptomatic patients with > 70% carotid
stenosis**
* CEA: Carotid endarterectomy
** NASCET: North American Symptomatic Carotid Endartectomy Trial
** ECST: European Carotid Surgery Trial
33. Common sites for extracranial arterial disease
Most common site at carotid bifurcation
with plaque extending into ICA
34. 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
36. 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
38. Sources of error in ulcer diagnosis
Plaque surface irregular
but not ulcerated
Adjacent plaque
simulate ulceration
Image plan does not include
the ulcer
40. 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
47. 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
48. ICA stenosis on angiogram
Diameter 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
51. Aliasing or high velocity jet
Area of highest velocity in area of stenosis
52. Adjustment of color gain
Color gain at 80%
Marked turbulence of ICA & ECA
No luminal narrowing
Anatomy of bifurcation
demonstrated more accurately
Color gain at 66%
54. Color Doppler bruit
Extensive soft tissue color Doppler bruit surrounds
carotid bifurcation with 90% ICA stenosis
Confetti sign
55. 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 signal
Flow reversal
Poor definition of spectral border
• May be only sign of carotid stenosis in calcified plaque
Spectral broadening
56. Spectral broadening
Immediately after stenosis
High amplitude & low frequency Doppler signal
Poor definition of spectral border
Flow reversal
Severe spectral broadening: > 70% diameter reduction
57. 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 Fistula
2AVM: Arterio-Venous Malformation
3FMD: Fibro-Muscular Dysplasia
59. 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
60. Tight stenosis or occlusion?
• Difficult to distinguish tight stenosis from occlusion
• Completely occluded ICA
Will not release emboli
Not corrected by surgery
• Very severe stenosis
Potential source for emboli or acute thrombosis
May require urgent surgery
61. 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
62. 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
63. High grade “string sign” stenosis
Tardus Parvus waveform
Tardus: Long rise time
Parvus: Low PSV
64. Endarterectomy without arteriography
• Arteriography Expensive
Risks: stroke (0.1 – 0.6%) – death (0.1%)
Rarely affect surgical plan
Sufficient information obtained with MRI
• Conditions Good experience of US department
Stenosis localized to carotid bifurcation
Unequivocal US findings
Symptoms ipsilateral to carotid stenosis
65. 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
66. Short & long stenosis of ICA
Short stenosis (frequent) Long stenosis (rare)
PSV lower than expected
EDV maintained at high level
Can produce very high PSV
(> 500 cm/s)
67. Long stenosis of ICA
Zwiebel WJ et al. Ultrasound Quarterly 2005 ; 21 : 113 – 122.
RICA
RICA: PSV 183 cm/sec
EDV 105 cm/sec
CCA: PSV 76 cm/sec
PSV ratio: 2.4
Inconsistent data
Long stenosis of ICA > 70%
68. 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
70. 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
72. 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”
73. Occlusion of CCA
Tahmasebpour HR et al. RadioGraphics 2005 ; 25 : 1561 – 1575.
Absence of flow in distal CCA
Reversed flow in ECA
Normal flow in ICA
Internalization of ECA
Delayed systolic acceleration (Tardus)
Positive temporal tap maneuver
CCA, which has no branches, divides into the internal and external carotid arteries.Carotid artery widens at the level of the bifurcation to form the carotid bulb & degree of widening of carotid bulb is quite variable.Level of the carotid bifurcation in the neck is highly variable.Proximal branches of the ECA are the superior thyroid, lingual, facial and maxillary arteries.Vertebral artery is the first branch of the subclavian artery, arising from the highest point of the subclavian arch. At the sixth cervical vertebra, the vertebral artery runs posteriorly to travel upward through the transverse foramen of cervical vertebrae.Two vertebral arteries join, at the base of the skull, to form basilar artery, which then divides to form posterior cerebral arteries.
Tortuosity can cause apparent velocity increase even although there is no stenosis. This is due to difficulty in obtaining a correct insonating angle, non-linear or helical flow, or increased velocityon the inside of the curve. Try sampling just beyond the curve.
“Saw-tooth” appearance: مظهر أسنان المنشار
Endarterectomy decrease the risk of ipsi-lateral hemispheric stroke or death by 53 to 84% as compared to medical treatment.
Cauliflower: قرنبيط
Eddy: دوامة
A panel of experts from a variety of medical specialties was convened under the auspices of the Society of Radiologists in Ultrasound to arrive at a consensus about the performance of Doppler ultrasonography (US) to aid in diagnosis of internal carotid artery (ICA)stenosis. The panel met in San Francisco, Calif, October 22–23, 2002, and drew up a consensus statement. Although there are several facets of carotid disease that could be considered by such a panel, carotid stenosis (and by extension, carotid occlusion) is by far the most common pathologic process involving carotid arteries.The panel consisted of a moderator and 16 panelists from various medical specialties.
the method used to report the degree of narrowing from an angiogram differed between the European and North American trials.In the ECST trial, the degree of stenosis was measured by comparing the residual lumen diameter with the estimated diameter of the carotid bulb, whereas the NASCET trial compared the residual lumen diameter with the diameter of the normal distal ICA.
In the North American Symptomatic Carotid Endartectomy Trial, the narrowest portion of the vascular lumen was compared with the “normalized lumen distally”.In the European Symptomatic Carotid Trial study and studies performed prior to the NASCET study, the degree of stenosis was determined by comparing the narrowest diameter of the residual lumen to an estimate of the original lumen in the same area. Because the original lumen cannot be depicted on the angiogram, exact measurement is impossible.The panel recommended that the NASCET method of carotid stenosis measurement should be employed when angiography is used to correlate the US findings. While the NASCET method of measurement may not reflect the burden of atherosclerosis in the proximal ICA, it does minimize the amount of interobserver variability.
Stringsign stenosis(Figure 15a. Circumferential calcified plaque in the proximal ICA. (a) PW Doppler image of the right ICA obtained immediately distal to a circumferential shadowing plaque shows no sign of turbulence, and the PSV is within normal limits. Therefore, there is unlikely to be a significant stenosis behind the calcified plaque. (b) PW Doppler image of the proximal right ICA shows a tardus-parvus waveform. A severe proximal stenosis behind the shadowing plaque is suspected; therefore, evaluation with another imaging modality is required. (c) PW Doppler image of the right ICA shows spectral broadening (turbulence) with an elevated PSV. These results may be due to a high degree of stenosis immediately proximal to the point of sampling; therefore, further investigation with another imaging modality is required. )
Long stenosis: > 2 cm
It can be difficult to distinguish tight stenosis from occlusion. A completely occluded ICA cannot be corrected by surgery and will not release emboli. However, very severe stenosis can be a potential source for emboli or acute thrombosis and may require urgent surgery.
Thud: صوت مكتوم
The ECA is an important collateral pathway in patients with ipsilateral ICA occlusion and recurrent symptoms.This may influence the surgical decisions involving revascularization of the stenotic ECA.