Evaluation of a Novel Technique to Diagnose Carotid Artery Stenosis
Conditions: Carotid Artery Stenosis
Sponsor: The Cleveland Clinic

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Evaluation of a Novel Technique to Diagnose Carotid Artery Stenosis (CAS) 
 
Funding Support Provided by CVR Global 
 
Draft Date: 
January 30, 2018 
 
Principal Investigator:  
Heather Gornik, MD, MHS. 
Medical Director, Non-invasive Vascular Laboratory 
Section of Vascular Medicine 
Department of Cardiovascular Medicine 
Cleveland Clinic 
 
Co-Investigator: 
Imad Bagh, MD 
Section of Vascular Medicine 
Department of Cardiovascular Medicine 
Cleveland Clinic 
 
 
Introduction: 
Carotid atherosclerotic disease is associated with TIA, stroke and increased risk of major 
vascular events (1, 2). The prevalence of asymptomatic internal carotid artery (ICA) 
stenosis is low, but it increases with age (3). Other pathological disease states may 
involve the internal carotid arteries, such as fibromuscular dysplasia (FMD) and cervical 
artery dissection, and have distinguishing features on diagnostic imaging studies.  The 
extracranial ICAs can be evaluated by different non-invasive modalities, namely carotid 
duplex ultrasound, MRA, and CTA. Each of these modalities has characteristic 
advantages and disadvantages, and each varies with regard to requirements for 
technology and trained technical and interpretive personnel. Catheter-based angiography 
is the gold standard for diagnosis and assessment of severity of ICA stenosis due to 
atherosclerotic disease or non-atherosclerotic pathologies, but is generally reserved for 
cases of uncertain or discrepant non-invasive testing or when intervention is indicated.  
 
Screening for ICA stenosis could be used to identify patients at risk for cardiovascular 
events for whom cardiovascular risk reduction medical therapies may be considered, and 
to identify patients with significant ICA stenosis for whom additional imaging 
surveillance or revascularization (for severe ICA stenosis) may be indicated.  Currently, 
carotid duplex ultrasound must be performed by a trained and certified vascular 
technologist using advanced duplex imaging equipment and with subsequent 
interpretation by a trained physician.  It would be of value to develop an accurate, 
reliable, low cost, and easily accessible tool to screen for extra-cranial ICA disease in an 
office based setting. However, such a tool would require novel technology that allows for 
quick, accurate, reproducible, and safe evaluation.  
 
This study will evaluate a new technology called the Carotid Stenotic Scan (CSS) 
developed by CVR Global, a medical device company. The CSS device uses principles of 
cardiovascular resonance to detect low frequency pressure fluctuations associated with 

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flow disturbances in areas of significant arterial narrowing. The CSS device consists of 
three non-emitting (passive) piezoelectric sensors contained in a cushioned gel pad, 
linked through a Y-shaped collar that positions one sensor over each carotid artery and 
one sensor on anterior central chest in the area of the heart (figure).  These device pads lie 
on the skin surface and do not emit any energy into the body; they only gather data 
transmitted from within the body. The piezoelectric sensors in the device detect very low 
frequency pressure fluctuations generated by altered hemodynamics caused by narrowing  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
of the carotid artery. The CSS scan takes about 1-2 minutes to gather data for real-time 
analysis by the processor on the device cart.  
 
Description: Prospective study of evaluable patients presenting to the Cleveland Clinic 
Non-Invasive Laboratory for a clinically indicated complete carotid duplex ultrasound 
examination. We aim to enroll 300 subjects. We will enroll at least 100 patients who have 
moderate stenosis of one ICA based on prior ultrasound studies and up to 25 patients with 
known carotid FMD. Subjects who enroll in the study will undergo evaluation by both 
carotid duplex ultrasound and the CSS device.  Carotid duplex studies will be read by a 
registered physician in vascular interpretation, blinded to the CSS device result, and 
degree of ICA stenosis will be determined according to velocity criteria adopted by 
Cleveland Clinic Non-Invasive Vascular lab.  Findings from CSS device will be analyzed 
and degree of ICA stenosis will be categorized. 
 
Objectives: 
1. 
To determine agreement of degree of internal carotid artery narrowing as 
measured by the CSS device versus carotid duplex ultrasound. 
2. 
To determine the reproducibility measures of carotid artery narrowing as 
measured by the CSS device. 
3.  
To compare the degree of carotid artery narrowing as measured by the CSS 
device versus any other imaging modality used to evaluate the internal carotid 
artery (CTA, MRA or catheter based angiography) (pilot analysis) 
Right 
Left 
Chest 

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4. 
Exploratory data regarding CSS device output in the setting of carotid artery 
occlusions and fibromuscular dysplasia (FMD). 
 
Study Subjects: 
The study population will consistent of adult patients (> 18 years) presenting to the 
Cleveland Clinic Non-Invasive Vascular Laboratory for a scheduled carotid duplex 
ultrasound to evaluate for carotid artery disease or in follow-up of known ICA stenosis. 
By design, we will enroll at least 100 patients who are known to have at least moderate 
stenosis of one ICA (i.e., PSV > 125 cm/sec based upon the findings of prior imaging 
studies.  In addition, a subset of up to 25 patients enrolled will include those with 
previously documented fibromuscular dysplasia of at least one ICA.  Potentially eligible 
patients will be approached in the area where the ultrasound testing will be done by a 
qualified member of the study team prior to the ultrasound examination to explain the 
study and obtain appropriate informed consent.   
 
Inclusion Criteria: 
 Outpatients age > 18 years sent to the vascular laboratory for carotid duplex 
examination for initial carotid ultrasound study or for follow-up of known carotid 
disease.  
 Enrolled patients will include at least 100 subjects with at least moderate known 
stenosis (50-69% or greater, PSV > 125 cm/sec) or occlusion of one or both ICAs 
 Up to 25 patients with known fibromuscular dysplasia (FMD) of the internal 
carotid arteries. 
 
Exclusion criteria: 
 Age < 18 years.  
 Hospitalized inpatients. 
 Inability to provide informed consent. 
 Prior history of carotid endarterectomy or carotid artery stent. 
 Prior neck surgery 
 Known prosthetic heart valve, known critical aortic stenosis, or study indication 
“preop” open heart or aortic surgery. 
 
Study Visit Procedures: The research study will be conducted on the same day of the 
clinical carotid duplex study but may be performed prior to or after the scheduled carotid 
ultrasound (and any other vascular) examination(s), depending upon the patient schedule.  
After informed consent is obtained, limited medical history will be obtained, and self-
reported height and weight will be recorded. The patient will undergo the standard of care 
carotid duplex examination and the CSS study procedure. Each subject will have a unique 
identifier number assigned that will be used on all ensuing study documents. 
 
 
 
 
 

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Medical History:  
Data will be obtained by limited subject questionnaire and review of the electronic 
medical record, to include:  
 Age on date of the study 
 Sex 
 Race, ethnicity 
 Height and weight (self-reported) 
 Study indication (first carotid duplex in lab, surveillance of known carotid 
artery stenosis, fibromuscular dysplasia, other) 
 Treated medical conditions, including: 
 Coronary artery disease (History of myocardial infarction, angina + 
abnormal stress test, or prior coronary artery bypass grafting or 
stenting/PCI) 
 History of congestive heart failure 
 Left ventricular ejection fraction (if known and date of echocardiogram 
within the past 1 year) 
 Known peripheral artery disease (PAD) 
 History of transient ischemic attack 
 History of stroke 
 Did patient have TIA, stroke or symptoms of retinal ischemia within 30 
days of ultrasound study 
 Hypertension requiring medication therapy 
 Hyperlipidemia requiring medication therapy 
 Diabetes requiring medication therapy or diet 
 History of smoking cigarettes (> 100 in lifetime) 
 Known diagnosis of fibromuscular dysplasia 
 Known history of internal carotid artery dissection 
 History of COPD 
 Any correlative imaging studies (CTA, MRA, angiography) within 1 
month prior to the day of the carotid duplex examination 
 
Follow-up and Correlative Examinations: 
Within 3 months (+/- 7 days) following the date of the study visit, the electronic medical 
record will be queried for any interval correlative imaging studies (CTA, MRA, or 
angiography) and reports performed up to 1 month prior and 3 months after the duplex 
examination date.  Report of findings well be document (i.e., % ICA stenosis by 
CTA/MRA).  
 
Study Procedures (Appendix B) 
 
Standard Clinical Procedures: 
The subject will undergo the clinically ordered clinical carotid duplex ultrasound as part 
of standard of care. Studies are performed using a standardized scanning protocol 
(Appendix C) by a Registered Vascular Technologist and interpreted by a Registered 

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Physician in Vascular Interpretation or otherwise qualified member of the medical staff.  
The vascular technologist and interpreting physician will be blinded to the output of the 
CSS study device. 
 For purposes of this study, degree of ICA stenosis will be reported according to SRU 
consensus velocity criteria., Primary SRUCC parameter to determine % ICA stenosis 
will be peak systolic velocity, unless there is a clear indication for the use of a 
secondary parameter (ICA/CCA ratio, EDV), such as contralateral occlusion, tandem 
lesions, discrepancy between visual assessment of the plaque and PSV and others(4). 
 
SRU Consensus Criteria (4) 
 
Primary  
Parameters 
 
Secondary 
Parameters 
 
Degree of 
stenosis (%) 
ICA PSV 
(cm/sec) 
Plaque 
Estimate (%)* 
ICA/CCA PSV 
Ratio 
ICA EDV 
(cm/sec) 
Normal 
< 125 
None 
<2.0 
<40 
< 50 
< 125 
<50 
<2.0 
<40 
50-69 
125-230 
≥50 
2.0-4.0 
40-100 
≥ 70 but less 
than near 
occlusion 
>230 
≥50 
>4.0 
>100 
Near 
occlusion 
High, low, or 
undetectable 
Visible 
Variable 
Variable 
Total 
occlusion 
Undetectable 
Visible, no 
detectable 
lumen 
Not applicable 
Not 
applicable 
*Plaque estimate (diameter reduction ) with gray-scale and color Doppler US. 
 
 Degree of stenosis per the Cleveland Clinic Non-invasive Vascular Laboratory will 
also be recorded (ECST based): 
o 0-19% stenosis PSV < 105 cm/sec no plaque 
o 20-39% stenosis PSV < 105 cm/sec plaque visualized 
o 40-59% stenosis PSV 105 – 150 cm/sec 
o 60-79% stenosis PSV > 150 cm/sec but EDV ≤ 135 cm/sec 
o 80-99% stenosis PSV > 240 cm/sec and EDV > 135 cm/sec 
o Occlusion – absent flown on extensive Doppler interrogation 
o Ultrasound features of carotid FMD (increased velocity and turbulent flow mid 
to distal ICA). 
 
The following ultrasound parameters will be recorded for each side: 
 Distal CCA peak systolic velocity 
 Highest origin/proximal to mid ICA peak systolic velocity (PSV) 
 Associated end diastolic velocity (EDV) for highest PSV 
 ICA/CCA PSV Ratio 
 Presence of plaque in the ICA (defined as wall thickness > 1.5 mm) 
 Presence of distal ICA waveform dampening (qualitative) 

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 Presence of post-stenotic spectral and/or color Doppler turbulence 
 SRU Consensus Criteria % ICA Stenosis 
 Cleveland Clinic Criteria % ICA Stenosis 
 
For FMD subset: highest ICA mid/distal PSV and associated EDV 
 
CSS Study Procedures: 
Subjects will have a noninvasive CSS assessment as described below before or after the 
carotid duplex ultrasound. It is expected that the entire CSS evaluation will take 
approximately ten minutes. See Appendix A for the CSS Study Procedure. 
 
Study Data Collection 
Each subject will have a hard copy file with case report information and source 
documents, medical history questionnaire, CSS output, and the ultrasound reports. These 
individual files will be maintained with identifiers, including the signed consent form, 
and maintained in a locked filing cabinet accessible to the study coordinator and the 
authorized investigators. A Redcap database will be developed and maintained for 
clinical data entry and this will be housed on a password-protected network. All data that 
the sponsor receives will either be aggregate data or de-identified case report files. 
Deidentified ultrasound images and de-identified correlation study images and report may 
be requested by the sponsor for cases in which CSS results and duplex findings were 
discrepant.    
 
Statistical Analysis Plan and Power Calculation: Primary analysis % agreement CSS 
and carotid duplex ultrasound (SRUCC interpretation) for ICA stenosis. Agreement will 
be assessed using the intraclass kappa coefficient (and corresponding 95% confidence 
intervals) for categorical data.  Percent stenosis from both the CSS measurement and the 
duplex ultrasound will be categorized as follows: 
 
Carotid Duplex by 
SRU Consensus 
Simplified Duplex 
Category by SRU 
Consensus 
CSS Device 
Normal 
<50% 
<50% 
<50% 
<50% 
<50% 
50-69% 
50-69% 
50-69% 
>70% 
>70% 
>70% 
Occlusion 
Occlusion 
Exploratory data 
U/S Features of 
FMD 
FMD 
Exploratory data 
 
It is anticipated that approximately 40% of total patients will have an ICA stenosis of 
50% or greater.  A sample of at least 300 patients (up to 500 carotid arteries) will have 
90% power to detect an intraclass correlation coefficient of 0.80, assuming a null 
hypothesis of 0.65, with a 2-sided alpha of 0.05. 
 

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The secondary endpoint of reproducibility of the CSS measurement will be analyzed 
using the continuous stenosis measurement.  Each CSS measurement will be repeated and 
the Intraclass Correlation Coefficient (ICC) will be calculated.  The ICC in an index of 
the reliability of measurements from the same operator. Pearson and/or Spearman 
correlation coefficients and plots may also be produced. 
 
Separate exploratory analyses will address the following: 
 
1) Correlation of CSS results to duplex ultrasound results in those with ICA by 
duplex occlusion  
2) Correlation of severity of stenosis from CTA, MRA, or catheter based 
angiography (when available) to CSS results. 
3) Correlation of CSS stenosis results to duplex ultrasound results in those with 
known ICA FMD (approximately 25 patients) 
 
 
Data and Safety Monitoring 
This protocol poses no physical risk and the need for a formal Data Safety and 
Monitoring Board (DSMB) is not anticipated. However, reporting of any adverse events 
will follow the standard procedures of Cleveland Clinic.  The only risk to the subject is 
loss of confidentiality and this will be protected to the best of the sponsor’s ability.  
 
Potential Risks: This is a low risk protocol.  The CSS devise is non-invasive and passive 
and does not cause any discomfort. The only risks relate to confidentiality and the study 
team will minimize these risks as discussed above. In the unlikely event of a study-
related adverse event, the Principal Investigator, IRB and CVR Global will be notified.                 
 
 
Potential Benefits 
There will be no direct benefit to the subject for participation, though study participants 
will receive a parking pass. There may be benefit to society as a whole when the accuracy 
and efficacy of the device as a rapid, noninvasive means to diagnose carotid artery 
disease has been shown.   
 

8 
 
REFERENCES 
1. 
Norris JW, Zhu CZ, Bornstein NM, Chambers BR. Vascular risks of 
asymptomatic carotid stenosis. Stroke. 1991;22(12):1485-90. 
2. 
Goessens BM, Visseren FL, Kappelle LJ, Algra A, van der Graaf Y. 
Asymptomatic carotid artery stenosis and the risk of new vascular events in patients with 
manifest arterial disease: the SMART study. Stroke. 2007;38(5):1470-5. 
3. 
de Weerd M, Greving JP, Hedblad B, Lorenz MW, Mathiesen EB, O'Leary DH, 
et al. Prevalence of asymptomatic carotid artery stenosis in the general population: an 
individual participant data meta-analysis. Stroke. 2010;41(6):1294-7. 
4. 
Grant EG, Benson CB, Moneta GL, Alexandrov AV, Baker JD, Bluth EI, et al. 
Carotid artery stenosis: gray-scale and Doppler US diagnosis--Society of Radiologists in 
Ultrasound Consensus Conference. Radiology. 2003;229(2):340-6. 
 
 
 

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APPENDIX A 
CSS STUDY PROCEDURE 
Study is performed with patient in a seated position (chair) 
 
1. 
Prior to placement on the subject’s neck, wipe the device clean and place clean 
unused gel packs over the piezoelectric sensors. Have the subject sit upright and 
straight in a comfortable chair. 
 
2. 
Open a new subject file in the CSS device program and enter the assigned subject 
number. 
 
3. 
Place the device on the subject assuring good contact over each carotid artery 
 
(just at or above the bifurcation) and the anterior chest wall. 
 
4. 
Verify on the display that the device is sensing the signals. 
 
5. 
Instruct the subject to sit very still and breathe quietly while holding the collar 
 
component of the device. 
 
6. 
Select the “Start” button on the display touch screen for signal verification to 
 
begin; once the device notes signal verification select the “Start” button again.  
 
7. 
After 30 seconds of uninterrupted recording, stop the scan and have the subject 
release the collar device.  
 
8. 
To test for reproducibility, repeat steps (1) through (7) one more time.  
 
Typical output display at end of CSS test (subject to change as software is developed) 
 
 
 
 

10 
 
 
APPENDIX B: 
CSS STUDY VISIT CHECKLIST 
 
Inclusion (all must be answered “YES”/checked off):  
□ Patient at least 18 years old  
□ Seen as an outpatient 
□ Scheduled for a carotid duplex ultrasound examination for initial or follow-up 
evaluation of known carotid disease  
□ Able to give informed consent in English 
  
 
Patient known to qualify for subgroup?: 
□ At least moderate stenosis (PSV > 125 cm/sec) or occlusion of one or both ICAs on a 
prior CCF duplex study 
□ Known fibromuscular dysplasia of one or both ICAs 
 
□Exclusion criteria checked (confirm none of the following are true):  
• 
Prior history of carotid endarterectomy or carotid artery stent  
• 
Prior history of prosthetic heart valve 
• 
Known critical severe aortic stenosis (AVA < 1 cm/sec)  
• 
Indication for carotid duplex ultrasound is “pre-op” for open heart surgery or 
aortic surgery 
• 
Prior neck surgery 
 
Study Procedures:  
□ Informed consent complete and copy given to patient  
□ Generate subject ID number 
□ Medical history form, height and weight 
□ Carotid duplex ultrasound study completed (can be done before or after consent or CSS 
exam) 
□ 5 minute rest period  
□ 1st CSS measurement  
□ 2nd CSS measurement  
□ Validate parking  
□ Code database form  
 
 
_______________________________________ 
 
 
_____________ 
Research Coordinator/ Investigator Signature  
  
 
 
Date  
 
 
 
 
 

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APPENDIX C: Cleveland Clinic Non-Invasive Laboratory Carotid Duplex 
Examination Protocol (Native Carotid Arteries) 
 
EXTRACRANIAL CAROTID DUPLEX ULTRASOUND 
 
I.  PURPOSE 
Duplex scanning permits accurate localization of disease in the extracranial carotid and 
vertebral arteries.  Spectral analysis of velocity waveform permits accurate classification 
of disease in the internal carotid artery into categories based on the extent of diameter 
reduction. 
 
II.  INDICATIONS 
A. Transient ischemic attack (TIA) 
B. Asymptomatic cervical bruit 
C. Stroke/cerebrovascular accident (CVA) 
D. Suspected subclavian steal 
E. Screening of patients prior to cardiac or vascular surgery with asymptomatic 
bruit or high risk for carotid artery stenosis 
F. Post carotid intervention patients (endarterectomy, stent, etc.) 
G. Pulsatile mass in either the carotid or subclavian region 
H. Follow up studies on patients with known carotid disease 
I. Suspected carotid artery dissection 
 
III.  LIMITATIONS 
A. Recent neck surgery (i.e., endarterectomy) 
B. Patients who are unable to lie flat or still may prove difficult to scan 
C. Patients with very thick, muscular necks are a challenge.  Note:  Asking the 
patient to reach for his/her hips may help to bring the shoulders down and out 
of the way 
D. Patients with mental status issues unable to cooperate with the  
Examination 
E.  Bedside exams which may limit access to the patient or his/her anatomy   
 
IV.  PATIENT PREPARATION 
A. Review report and/or images of any prior examinations in the vascular lab. 
B. Explain the examination to the patient and why it is being performed.   
C. Patient history is obtained for relevant vascular information (e.g., prior 
endarterectomy or stenting). 
D. Answer any questions or concerns the patient may have before proceeding.                    
E. Patient should be positioned in a manner that allows for maximum access to 
the vessels being examined.  
 
V.  PROCEDURE:  GENERAL CONSIDERATIONS 
A. Technique:  Reproducible and constant velocity measurements require that 
the data be obtained in the same manner at each site and time.  Since the 
criteria for the disease states are based on spectral velocity waveforms, it is of 
the utmost 

12 
 
importance that the protocol be adhered to as closely as possible.  Bilateral 
studies are critical for a complete exam.  A limited study should be performed 
only in very special circumstances (e.g., intra-operative carotid examination). 
B. Angle:  A constant angle measurement should be maintained between the 
ultrasound beam and the axis of the vessel and/or direction of flow.  The axis 
of the vessel is defined as an imaginary line drawn parallel to the vessel wall.  
The angle cursor should be placed in this position before recording a spectral 
waveform.  The classifications for disease used in this protocol were validated 
using a constant angle of 60 degrees.  In tortuous vessels where obtaining a 60 
degree angle may be difficult, take the most favorable angle close to 60 degrees 
and always document it for future studies.  Never take spectral waveforms at 
angles above 60 degrees, as the cosine value changes rapidly, and small errors 
in angle measurements cause large errors in the peak velocity calculations. 
C. Sample volume size:  Keep the sample volume as small as possible to obtain 
the most discrete spectral information.  In the case of an occlusion or a very 
tight lesion, the sample volume may be increased to help locate the flow 
channel. 
D. Sample volume placement:  Place the sample volume in the center of the 
vessel or the flow channel. 
E. Scan planes:  The examination should include multiple views (anterior, 
lateral, postero-lateral) of the vessels in  both the  longitudinal and transverse 
planes.   Doppler velocity waveforms should be generated from the 
longitudinal plane, which provides the most favorable angles between the 
Doppler ultrasound beam and the axis of the vessels. 
F. Documenting stenosis:  The classifications of disease are based on locating 
the highest peak systolic and end-diastolic velocities.  It is essential that the 
sample volume be moved throughout the area of stenosis. Stenotic segments 
should be documented with spectral waveforms for three locations. 
1. Pre-stenotic waveform (it may be a dampened signal) 
2. Stenotic waveform (taken at the point of maximum velocity) 
3. A post stenotic waveform (demonstrates post stenotic turbulence) 
This waveform should be identified with every high-grade stenosis to 
verify a true velocity increase attributable to a stenosis. 
 
VI. 
PROCEDURE:  TEST PROTOCOL 
A. Patient setup:  The test is performed with the patient supine with a small  
towel placed under the neck for support.  The technologist is seated at the 
head of the bed.  The patient’s head is slightly hyperextended and turned 
toward the contralateral side.  The head position can be changed to 
optimize visualization of the vessel. 
B. Scan technique:  A study of the carotid system should be evaluated with 
grayscale and color and spectral Doppler analysis.  In grayscale, plaque 
should be described by echo characteristics (e.g., homogeneous, 
heterogeneous) as well as by surface characteristics (e.g., smooth, 
irregular).  With color Doppler waveform and spectral analysis, areas of 
narrowing within the lumen, color disturbances or absence of color flow 
should be noted.  The sample volume of the Doppler should be moved 
continuously throughout the length of the vessel searching for regions of 

13 
 
increased velocity or flow disturbance.  It is important to note that a 
stenosis may be very focal and the flow distal to it may normalize over a 
short distance.  The sample volume must not be skipped around but rather 
moved methodically through the vessel.  Spot recordings of velocity 
waveforms may overlook a significant lesion.  Color flow imaging 
facilitates the identification of anatomy, areas of interest, and the area of 
greatest stenosis. 
C. Transducers:  Selected based on vessel depth while allowing for the best 
display of both grayscale and color and spectral Doppler imaging.   
D. Common carotid artery:  The artery is evaluated throughout its length for 
the presence of visible plaque, tortuosity, and changes in the velocity.  A 
spectral waveform should be taken from the most proximal segment of the 
vessel, mid, and distal segments.  The characteristic of the waveform is 
that of a low-resistance vessel.  The end-diastolic velocity should be above 
the baseline. In the proximal common carotid artery waveform, a higher 
resistive or hybrid type signal may be seen, but the distal common carotid 
artery waveform should have a low-resistance pattern. Important 
hemodynamic information from the common carotid artery may indicate 
proximal or distal disease.  If there is a high-grade stenosis of the internal 
carotid artery or a total occlusion, the blood will be shunted through the 
external carotid artery.  The common carotid will take on the 
characteristics of the external carotid artery with flow of zero or very close 
to zero in end-diastole.  In the presence of a significant stenosis at the 
origin of the common carotid artery, the ipsilateral common carotid artery 
may be dampened with low velocity and a slower slope to peak systole 
compared with the contralateral common carotid waveform.  The 
ipsilateral common carotid waveform may also appear post-stenotic in 
character.   
E. External carotid artery:  The external carotid supplies the structure of the 
face, neck, and scalp.  The waveform has a sharp upstroke to systole, 
followed by a prominent dicrotic wave, which may reverse at end-
systole/early diastole, and velocities reaching zero in end-diastole 
(waveforms rest on the baseline).  The peak systolic velocity of the 
external carotid is normally higher than that of the internal carotid artery.  
Branches may be visualized near the origin, which may help distinguish 
the external carotid from the internal carotid, which has no branches in the 
neck.  The use of superficial temporal oscillation (“temporal tap” 
maneuver) can help distinguish the external carotid artery from the 
internal carotid artery by causing a disturbance in the spectral Doppler 
waveform.  The external carotid artery normally will lie in an anterior 
medial plane. 
F. Carotid bulb:  The bulb is usually located in the proximal portion of the 
internal carotid artery; however, the location is variable.  The normal flow 
patterns become complicated as the blood moves through the dilation and 
the angled branches of the bifurcation.  These normal anatomic features 
cause a flow separation and reversal of flow at the outer walls.  The profile 
of waveforms taken across the bulb usually demonstrates unidirectional 
flow along the divider of the bifurcation, and a transient reversal of flow at 

14 
 
peak systole near center stream, and at the outer wall opposite the flow 
divider. 
G. Proximal to mid internal carotid artery:  The characteristic Doppler 
waveform is that of a low-resistance vessel.  The normal flow disturbances 
of the carotid bulb may extend into the mid segment and be reflected in 
the waveform.  The mid internal carotid artery waveform is generally 
taken distal to the normally placed bulb in an area where the vessel is no 
longer dilated.  The carotid artery normally will lie in a posterior/lateral 
plane. 
H. Distal internal carotid artery:  The distal internal carotid artery is that 
segment of the vessel beginning at least three (3) cm above the 
bifurcation.  Atherosclerosis will usually develop in the first two (2) cm of 
the internal carotid artery and rarely will be seen in the distal internal 
carotid artery.  The distal internal carotid artery typically will dive away 
from the transducer or will be tortuous and difficult to visualize.  Caution 
should be used in this area because of inaccurate angle measurements, 
which may lead to overestimation of velocity increases and hence 
misdiagnosis of stenosis.  There are cases where true increases in velocity 
are detected in the distal internal carotid artery.  Fibromuscular dysplasia, 
(which causes the typical string of beads appearance of the vessel) 
develops in this region.  To fully evaluate for fibromuscular dysplasia, a 
lower-frequency curved array transducer should be used to scan high in 
the neck. 
A high resistance waveform suggests a change in resistance of the 
distal vascular bed.  It may suggest the presence of a significant siphon 
lesion, intracranial stenosis, or distal carotid dissection. 
The internal carotid waveform may also be found to have markedly 
elevated end-diastolic velocities in comparison with the contralateral 
internal carotid artery.  The elevation in overall flow rate will be noted 
throughout the common carotid as well.  This pattern of flow may 
indirectly suggest a decrease in the resistance of the distal vascular bed as 
in the presence of a distal arteriovenous malformation. 
I. Vertebral artery:  The origin of these vessels from the subclavian artery 
lie deep under the clavicle and are difficult to scan.  The vertebrals can be 
small, tortuous, and asymmetric in size. 
The scanhead is initially placed low in the neck, and the common 
carotid artery is identified as a landmark.  The scanhead is then moved out 
laterally and tipped inferiorly.  The vertebral artery may then be seen lying 
deep to the common carotid.  Color Doppler helps to readily locate the 
vertebral arteries, followed by a confirmation with the spectral waveform.  
The typical spectral waveform from a vertebral artery is that of a low-
resistance vessel similar to the internal carotid artery.  The vertebral artery 
is assessed for its flow direction (antegrade or retrograde).  Subclavian 
stenosis or occlusion at its origin may cause the vertebral artery flow to 
reverse direction to supply the arm (subclavian steal).  Proper 
identification of the direction of flow is important. A blunted, post-stenotic 
waveform in the vertebral artery should prompt investigation for more 
proximal stenosis. 

15 
 
J. Subclavian artery:  The subclavian artery is located under the clavicle and 
is difficult to access with some transducers.  The flow velocity in the 
subclavian artery is classically peripheral in its character.  It should have 
the typical triphasic character, a forward systolic component, a reversal 
component in late systole/early diastole, and a second forward component 
in late diastole. 
K.  Innominate artery:  The innominate artery is the first branch that 
arises from the aortic arch.  The distal portion of the artery can be 
accessed from above the clavicle.  The proximal and mid portions of the 
vessel cannot typically be visualized due to bony structures.  The 
transducer can be angled transversely down into the sternoclavicular notch 
giving sight to the distal portion of the vessel.    The Doppler spectral 
appearance is triphasic in character.    
 
 
VII: 
PLAQUE CHARACTERISTICS 
Sonographic images of atheromatous carotid plaques should be carefully evaluated to 
determine plaque extent and location, severity, surface contour, and texture.  Most 
importantly, the plaque texture should be classified as appearing either homogeneous or 
heterogeneous.  A diagnosis of ulcerative plaque cannot be made accurately by merely 
identifying that the plaque surface is irregular. 
 
Homogeneous plaque usually has a smooth surface, and its uniform acoustic texture 
corresponds pathologically to dense fibrous connective tissue.  Heterogenous plaque may 
have either a smooth or irregular surface and its complex acoustic appearance can be 
associated pathologically with the presence of intraplaque hemorrhage. 
 
Surface characteristics 
Smooth:  
Intimal surface appearance is continuous and shows no 
irregularities 
 
 
Irregular: 
Intimal surface is discontinuous and is not completely smooth 
 
Ulcerated: 
Ulcer cavity with blood flow within a plaque seen on multiple 
planes of view 
 
Plaque textures 
Homogeneous:  Homogeneous plaques usually produce a uniform echo pattern. 
The surface of homogeneous plaques is usually smooth. 
 
Heterogeneous:  Heterogeneous plaque has a complex echo pattern that contains 
at least one focal sonolucent area.  The intimal surface may be either smooth or 
irregular.  Acute hemorrhage can, at times, be identified by a pattern of plaque 
containing a large sonolucent area.  A false diagnosis of intraplaque hemorrhage 
may occasionally be made if there are large deposits of lipids within the plaque. 
 
Calcified: Heterogeneous (dense) plaque with very bright and highly reflective 
echoes.  This plaque contains areas of calcium that produces acoustic shadowing.  

16 
 
This shadowing causes an interruption in the color and spectral Doppler 
waveform signal which may result in an erroneous calculation in the percentage 
of stenosis.    
 
VIII: VERTEBRAL ARTERIES 
The characteristics of the Doppler spectrum obtained from the vertebral artery are those 
of a scaled-down internal carotid artery (see pp. 3-4 for examples).  The intracranial 
circulation is a low-resistance flow bed: consequently, the flow waveform has a sharp 
well-defined systolic peak followed by a gradual fall off in flow velocity through 
diastole.  In normal circumstances, antegrade flow is maintained throughout the cardiac 
cycle. 
 
1. If no flow is detected when the Doppler sample volume is placed in the mid point 
of the artery, this is diagnostic for vertebral artery occlusion. 
2. If retrograde flow is present, this is diagnostic of subclavian steal. 
3. Bi-directional flow can be indicative of a stenosis in the proximal subclavian 
artery.  This is consistent with an incomplete subclavian steal. 
4. In the setting of a more proximal subclavian or vertebral artery stenosis, there can 
be a blunted vertebral artery waveform (parvus-et-tardus) or a “bunny rabbit” pre-
steal waveform which can be seen prior to bi-directional flow.   
5. High velocities can occur when the vertebral artery is providing compensatory 
flow for an occlusive lesion elsewhere in the cerebral vascular system. 
6. Loss of diastolic flow in a vertebral artery (“high resistive” waveform) may 
indicate distal vertebral artery or basilar artery (if bilateral) stenosis or occlusion. 
 
 
 

17 
 
EXTRACRANIAL CAROTID DUPLEX ULTRASOUND 
 
DIAGNOSTIC CRITERIA 
I.  Internal Carotid Artery (ICA) Interpretation: 
 
Classifications of Internal Carotid Artery Stenosis 
 
Diameter 
 
Peak  
 
End 
 
Flow Character 
Reduction 
 
Systole  
Diastole 
and Grayscale 
 
0 – 19% 
    <105 cm/sec 
 
    * 
 
Mild spectral  
broadening during the 
deceleration phase of systole 
 
 
20 – 39% 
    <105 cm/sec 
 
    * 
 
Plaque present 
Spectral broadening present  
 
 
 
 
 
 
 
 
 
 
40 – 59% 
    105-150 cm/sec 
 
    * 
 
Plaque present  
Increased spectral broadening 
 
 
 
 
 
 
 
 
 
 
 
60 – 79% 
   >150 cm/sec        
    
 * 
 
Plaque present  
Marked spectral 
 
 
 
 
 
 
 
 
broadening present 
 
80 – 99% 
   >240 cm/sec    
    and >135 cm/sec 
Plaque present  
Marked spectral  
broadening present 
 
 
 
 
 
 
 
 
  
 
Occluded 
        N/A 
 
 
N/A 
 
No flow signal.  A  
 
 
 
 
 
 
 
 
characteristic “thump” may  
 
 
 
 
 
 
 
 
be noted at the stump or 
 
 
 
 
origin of the occlusion.    
Common carotid artery 
diastolic component low or 
reversed flow 
 
 
 
 
 
 
 
 
 
 
*End-diastolic velocity values are only used as stenosis classification for 80-99% 
diameter reduction lesions.  A lesion associated with PSV > 240 cm/sec but EDV < 135 
cm/sec is generally a 60-79% stenosis. 
 
Note:  This classification is only accurate for predicting the amount of diameter reduction 
in the first 3 cm of the internal carotid artery.  It is not reliable for accurately 
predicting disease in the external carotid artery or in the setting of fibromuscular 
dysplasia. The statement “ultrasound features consistent with fibromuscular 

18 
 
dysplasia” will be used when turbulent flow and a velocity shift are noted in mid or 
distal ICA and/or beading is present.  
 
Note:  When a patient does not have plaque present, but has elevated velocities 
throughout the ICA and the CCA (i.e., normal ICA/CCA ratio <2) the statement 
“elevated velocities, no plaque seen. Likely normal study” will be used in place of 
calling a category of stenosis.   
 
Note:  Although our criteria are based upon PSV and EDV, ICA/CCA ratios are included 
on our reports.  These criteria are added for use in interpretation of cases in which PSV 
may not accurately reflect the degree of stenosis (e.g., tandem lesions in innominate or 
CCA, contralateral occlusion, and elevated velocities in all vessels due to underlying 
cardiac disorder).  In general, an ICA/CCA ratio of > 4 is suggestive of a > 70% stenosis 
(NASCET criteria). 
 
Note:  In the setting of a contralateral ICA occlusion, there is potential for overestimation 
of stenosis due to compensatory flow.  This should be noted in the interpretive report 
when appropriate (e.g., velocities in 80-99% category contralateral to occlusion). 
 
II. Common carotid artery interpretation: 
50-99% stenosis    
Velocity shift with doubling of PSV across an area of plaque 
 
III. External carotid artery interpretation: 
Elevated velocities, plaque noted    
PSV > 200 cm/sec with significant plaque 
visualized 
 
IV.  Subclavian artery interpretation: 
50-99% stenosis   
Velocity shift with doubling of PSV across an area of plaque  
or PSV > 275 cm/sec in proximal subclavian artery with turbulent 
flow and plaque noted 
If turbulent flow is present but no plaque is visualized, findings may suggest more 
proximal subclavian artery stenosis 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

19 
 
REFERENCES 
Cleveland Clinic internal validation studies of carotid ultrasound examinations 
and angiograms. 
 
Kim E.S., Thompson M, Nacion KM, Celestin C, Perez A, Gornik HL.  Radiologic 
importance of a high-resistive vertebral artery Doppler waveform on carotid 
duplex ultrasonography. J Ultrasound Med 2010;29:1161-1165. 
 
Lal, B.K., Beach, K.W., Roubin, G.S., Lutsep, H.L., Moore, W.S., Malas, 
M.B.,…CREST Investigators. (2012) Restenosis after carotid artery stenting and 
endarterectomy: a secondary analysis of CREST, a randomized controlled trial. 
The Lancet Neurology, 11(9), 755-763. 
 
Neumyer, M., Thiele, B. L., & Weidner, W. A. (1987). Prospective validation of pre-
screening with duplex scanning of symptomatic patients with cerebrovascular 
disease. Journal of Vascular Technology, 11, 29-32. 
Olin,  J. W., Fonseca, C., Childs, M. B., Piedmonte, M. R., Hertzer, N. R., & Young, J. R. 
(1998). The natural history of asymptomatic moderate internal carotid artery 
stenosis by duplex ultrasound. Vascular Medicine, 3(2), 01-08. 
Rohren, E. M., Kliewer, M. A., Carroll, B. A., & Hertzberg, B. S. (2003). A spectrum of 
Doppler waveforms in the carotid and vertebral arteries. American Journal of 
Roentgenology, 181(6), 1695-1704. 
 
Society for Vascular Ultrasound. (2011). Vascular technology profession performance 
guidelines. Extracranial cerebrovascular duplex ultrasound evaluation. Retrieved 
from 
http://www.svunet.org/files/positions/SVU%20Guideline%20Carotid%202011.pd
f 
 
Taylor, D. C., & Strandness Jr, D. E. (1987). Carotid artery duplex scanning. Journal of 
Clinical Ultrasound, 15(9), 635-644. 
 
Zuerker, R. E.  (1987). The use of duplex scanning for detecting progression of carotid 
artery disease in asymptomatic patients.  Journal for Vascular Technology, 13, 
93-100. 
 
Zwiebel, W. (1992). Introduction to vascular ultrasonography.  (3rd ed.). Philadelphia, 
PA: W.B. Saunders. 
 
 
 

20 
 
EXTRACRANIAL CAROTID DUPLEX ULTRASOUND 
 
DOCUMENTATION 
 
DOPPLER: 
 
Common: 
Right origin, proximal, mid, and distal vessel 
 
 
 
Left proximal, mid, and distal (origin if possible) vessel 
 
Internal: 
Origin, proximal, mid, and distal (as far distal as possible) vessel 
 
External: 
Origin  
 
Vertebral: 
Mid vessel  
 
Subclavian: 
Right origin, left proximal 
 
Innominate:  Distal (if possible) 
 
Grafts: Proximal, mid, distal and anastomotic sites 
 
GRAYSCALE: 
 Common 
 External 
 Internal 
 Grafts: anastomosis sites and body 
 
COLOR POWER ANGIOGRAPHY (CPA): 
 Suspected occlusion 
 
 
 
ADDITIONAL NOTES 
**ANY TIME A VELOCITY SHIFT IS IDENTIFIED IN ANY VESSEL, THE 
AREAS PROXIMAL TO THE SHIFT, AT THE SHIFT, AND DISTAL TO THE SHIFT 
SHOULD BE DOCUMENTED 
 
***For incidental finding of thyroid nodule: report maximal diameter of nodule and use 
standard reporting language to suggest dedicated thyroid ultrasound. 
 
 
URGENT VALUE NOTIFICATION 
The following urgent values require direct verbal communication with the ordering 
provider or service: 
1. 80 – 99% ICA stenosis 
2. 60 – 79% ICA stenosis with PSV >300 cm/sec or ICA/CCA ratio >4.0  
3. 100% ICA occlusion not previously documented at the Cleveland Clinic 
4. Carotid artery dissection not previously documented at the Cleveland Clinic 
 
*Notification: The name and pager number of the person who was notified must be 
documented on the report along with the date and time of notification.