CAROTID DUPLEX PROTOCOL

Sheldon Boston, RCS, RVS

Houston Methodist Hospital

Houston, Texas

Date

No Disclosures

Houston Methodist Hospital DeBakey Heart and Vascular Center

• Houston Methodist comprises of 7 hospitals,

several emergency centers, imaging centers

and physical therapy clinics throughout

greater Houston area. Houston Methodist

Hospital has 900 licensed beds.

DeBakey Heart and Vascular Center

• 24 hour vascular ultrasound lab

• 16 full time vascular technologists

• 17,000 peripheral vascular exams in

performed 2018

• Exam modalities include carotid duplex,

transcranial Doppler (routine & intraop),

AVG/AVF, venous reflux, IVC, aorta-iliac duplex,

upper/lower venous duplex, arterial duplex,

physiologic arterial exams and vein mappings

• The combination of real-time B-mode

imaging with pulsed wave and color

Doppler to evaluate the cervical carotid

artery for disease states and/or

stenosis

• Doppler measures speed of the moving

red blood cells through the vessels

Carotid Duplex Exam

What is It?

• Cerebrovascular accident (CVA)

• Transient ischemic attacks (TIA)

• Syncope

• Visual disturbances

• Carotid bruit

• Follow up of known stenosis

• Post-op or post-intervention surveillance (Carotid

endarterectomy, stent, bypass)

• Trauma

• Pulsatile neck mass

Indications

• Patients with extensive bandages or cervical collars

• Patients with neck IV

• Uncooperative /confused patients

• Patients who cannot be adequately positioned.

• Acoustic shadowing from calcification

• Postoperative hematoma, dressing and surgical

sutures

• Poor visualization due to vessel depth (Short neck,

obesity, high bifurcation)

Contraindications/Limitations

Equipment & Supplies

• Duplex ultrasound system with appropriate pulsed

wave probe, frequencies ranging from 4-9MHz

• Ultrasound gel

• Towels for clean up

• Vital signs monitor (BP)

Patient history and physical findings

• Technologist should obtain information from

patients or medical staff about indications and

symptoms.

• Evaluate and document identification of physical

findings. (facial drooping, slurred speech)

• Obtain bilateral brachial artery blood pressures

• Review patient medical history (TIA, CVA, HTN)

• Review to prior studies if available.

Exam Preparation

Patient position: Patient should be supine with head turned slightly away

from the side being examined.

Sonographer: Operator may sit at the head of the exam table with legs

beneath the table, while the scanning arm rests on the patient’s pillow and

the opposite arm operates the ultrasound system.

Ergonomics & Patient Positioning

Limitations:

Proper patient and operator positioning

may not always be possible in ICU and IMU

setting due to several factors such as:

• Inadequate space

• Life support equipment in room

(ventilator, IABP)

• Time constraints

• Availability of power outlets!

Image Optimization

• Utilize KNOBOLOGY

- Make the machine work for you

- Learn shortcuts and functions from user manuals

• Power Doppler Imaging

Technique that displays the

strength of the Doppler signal in

color, rather than the speed and

direction information.

• B Flow

A blood flow visualization

technique that displays the

blood flow echoes in grayscale

imaging.

• Panoramic Imaging

The ability to display an entire

abnormality and show its

relationship to adjacent

structures on a single static

image.

Image Enhancing Options

Components of the Carotid

Duplex Ultrasound

• Anatomy

• B-mode

• Colorflow

• Doppler

Anatomy

Cervical Carotid Anatomy

Internal carotid artery:

• Sizeable first branch is

intracranial-Ophthalmic artery,

divides into the anterior and

middle cerebral arteries.

External carotid artery and

Branches:

1. Superior thyroid

2. Facial artery

3. Lingual artery

4. Superficial temporal artery

5. Maxillary artery

6. Occipital artery

7. Posterior auricular

8. Ascending pharyngeal

Common Carotid Artery:

• large elastic artery which provides

the main blood supply to the head

and neck

Aortic Arch & Carotid Arteries

ECA

Vertebral A

ICA

Intracranial Arteries

ECA Vertebral A

ICA

Vert A

ICA

ICA

Vert A

Known as 2D

or Grayscale

B-Mode

•B mode

B-Mode Ultrasound

B-mode image is a cross-sectional

image representing tissues and organ

boundaries within the body:

• Obtain images

• Identify anatomy in real time

• Abnormal anatomy

• Intimal thickening

• Plaque

• Plaque morphology

• Surface characteristics

What it B-Mode

Creating B-Mode Image Longitudinal View

Linear array probe position

Plaque Morphology

Echogenicity - Anechoic, hypoechoic and hyperechoic

• Calcified -Very bright, highly reflective echoes. Acoustic shadowing is often present, preventing thorough evaluation of the vessel.

Texture

• Homogenous plaque - consists of uniformly high to medium level echoes.

• Heterogeneous plaque - Complex plaque, contains mixed high, medium and low level echoes.

Surface• Irregular Plaque - plaque surface is discontinuous, may have multiple

echoes present.

• Ulcerated plaque- characterized by deterioration of the normally smooth fibrous cap. Important -may give off debris that can embolize distally—stroke!

• Intraplaque hemorrhage- an anechoic area within a plaque. Important-High risk for rupture resulting in a distal embolization.

Plaque Classification

Homogenous plaque

Heterogeneous plaque

Calcified plaque-acoustic shadowing

Color Flow

Color flow

Ultrasound scanners use the Doppler effect to form a color map of

blood flow superimposed onto the anatomical map provided by

pulse echo imaging.

Use of color flow

• To identify presence or absence of blood flow

• To identify direction of flow

• To identify areas of stenosis or color flow disturbance

Color demonstrate flow

direction in tortuous vessels

oppler

Doppler

The Doppler effect provides an ultrasonic method for the

detection of echoes from moving structures, particularly flowing

blood

Doppler Waveforms

• Spectral Doppler waveform

analysis is used in conjunction

with color imaging

• Confirms presence or absence

of flow

• Diagnosis of percent stenosis

by amount of velocity increase

(PSV, EDV, ICA/CCA ratio)

• Detects vascular vs non-

vascular structures

CCA

ICA

ECA

Waveform Characteristics

Laminar Flow• When all blood flow velocities measured

in a sample volume are the same or

nearly so a narrow velocity spectrum

results.

Spectral Broadening• Increased spectral broadening may indicate

the presence of disease.

Stenotic Waveforms

Velocity increases as the blood flows through a stenosis

Protocol: Image sequence

Acquisition • Transverse gray scale and color flow sweep of the entire CCA, bulb, and

bifurcation for anatomy and orientation.

• Longitudinal gray scale still images of the proximal, mid and distal CCA.

• Longitudinal color flow and spectral Doppler of the proximal, mid and distal

CCA.

• Gray scale clips of plaque or any pathology needing additional images in real-

time.

• Longitudinal gray scale still images of the proximal ECA.

• Color flow and spectral Doppler of the proximal ECA.

• Longitudinal gray scale still images of the proximal, mid and distal ICA.

• Longitudinal color flow and spectral Doppler of the proximal, mid and distal ICA.

• Longitudinal color common carotid artery/ vertebral artery clip compare.

• Long color/Doppler still image at vertebral artery, measure PSV/ED.

• Long gray scale image of subclavian artery demonstrating plaque if present in

the lumen.

• Still color flow and spectral Doppler of the subclavian artery.

Image Acquisition Sequence

Vert A/CCA Color Compare

• The proximal subclavian artery is evaluated during all

carotid duplex exams, additional images are obtained

whenever stenosis is present.

• The following signs and symptoms may increase

suspicion for hemodynamically significant subclavian

artery disease:

– Increased velocities in the proximal subclavian artery

– ≥20 mmHg difference between the right and left arm may

indicate pathology.

– Abnormal or retrograde flow in the extracranial vertebral

artery

Subclavian Artery Evaluation

• At the conclusion of the exam, the study data is automatically sent to the

PACS server.

• Comparison is made with any prior exam from the VUL lab

• The comparison statement will be the last finding in the both the

preliminary and final reports.

• A preliminary report is generated describing gray scale, color and

Doppler findings using the VUL diagnostic criteria

• The interpreting physician will read the exam and a final report will be

available within two business days of the day the exam was performed.

• In the event of critical findings, ICA stenosis of >80%, any stenosis

related to new onset of lateralizing symptoms or the presence of

thrombus, the referring physician will be contacted at the conclusion of

the exam.

Report Generating

• It is important to document any variation from the

normal protocol to be able to recreate the study at

a later date or to have the study interpreted

adequately by someone other than the examiner

Special Note

When carotid stents are present, additional gray

scale images of the entire stent should be captured.

• Note the proximal and distal stent in relation to the

anatomy of the carotid arteries.

• Note should be made of any colorflow noted

between the stent and wall of the artery, any gaps

between stents.

• If the stent is narrowed or misshapen in any way.

Carotid Stent Assessment

Carotid Ultrasound Interpretive Criteria

• Normal ICA PSV <125 cm/sec, Ratio <2, No plaque

• <50% ICA PSV <125 cm/sec, Ratio <2

• 50-69% ICA PSV 125-230 cm/sec, EDV 40-100, Ratio 2-4

• 70-99% ICA PSV >230 cm/sec, EDV >100, Ratio >4

• *80-99% Asymptomatic special consideration for intervention: EDV

>140 cm/sec

• 100% (Occluded) Flow to zero or reversed

• CCA stenosis: Doubling of velocities is 50% stenosis

Tripling Doubling of velocities is 70% stenosis

• ECA stenosis PSV >150 cm/sec

• SCA stenosis PSV >200 cm/sec

Interpretive Criteria

Society of Radiologists in Ultrasound Carotid Consensus

Non-vascular abnormalities or abnormalities not related to the

carotid artery should be documented under duplex findings

and in the preliminary report.

• The interpreting physician will also report these findings

and their significance.

• Any further recommendations, such as additional imaging,

may also be made by the interpreting physician.

• Examples of incidental findings:

– Enlarged lymph nodes, Enlarged thyroid lobes, Thyroid nodules or

cysts, Internal jugular thrombosis (acute or chronic)

– Any other mass noted in the neck or supraclavicular space –

describe as to location, size and echogenicity

Incidental Findings

• Every carotid duplex exam performed will be entered into the VUL

database.

• Under the direction of the Manager or technical director attempts to

correlate every exam with either arteriogram, CTA and/or surgical

findings, will be made on a monthly basis.

• Correlations dated three months prior to the exam or three months after

the exam will be used.

• Any exams not positively correlating will be examined in the monthly

vascular lab meetings to determine factors influencing negative

correlations.

• In the month following the end of each quarter, correlation findings will

be discussed in the monthly vascular lab meetings.

Quality Assurance

Carotid Body Tumor

Carotid Body Tumor

Carotid Body Tumor

LT ICA Stenosis

RT CCA Disection

LT CCA Thrombus

Vert Retrograde Flow

LT ICA Thrombus

RT CCA TO LT CCA BPG

Right Thyroid Mass

• Follow department standardized protocol that meet

the requirements of IAC and SVU

• Optimize images by adjusting B-mode, color and

Doppler settings

• Utilize advanced image enhancing options

• Adhere to standard interpretive criteria

• Review and compare to prior studies

• Review cases during Quality Assurance meetings

Conclusion

• Inside Ultrasound Vascular reference guide

– Gail P Size BS, RVT, RVS FSVU, RPHS; Laurie Lozanski BS, RVT; Troy Russo RDCS,

RDMS, RCS, RVT

• Medical gallery of Blausen Medical 2014,

--- Blausen.com staff

• Introduction to B-mode imaging, Kevin Martin

• Vascular Technology, An illustrated review 4th Edition

– Claudia Rumwell, Michalene McPharlin

References