Carotid imaging modalities
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Carotid Imaging Modalities. Kyle Boyce August 3, 2007. Leading Causes of Death in U.S. 1. Heart Disease 2. Cancer 3. Stroke (2 nd leading cause Worldwide) Carotid Artery Atherosclerosis – 7% of patients presenting with initial stroke. Non-modifiable Age Race Gender Family History

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Carotid Imaging Modalities

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Carotid Imaging Modalities

Kyle Boyce

August 3, 2007


Leading Causes of Death in U.S.

  • 1. Heart Disease

  • 2. Cancer

  • 3. Stroke (2nd leading cause Worldwide)

    • Carotid Artery Atherosclerosis – 7% of patients presenting with initial stroke


Non-modifiable

Age

Race

Gender

Family History

Genetics

Modifiable

*HTN*

Hyperlipidemia

Diabetes

Smoking

EtOH

High Homocysteine

Low Folate

Risk Factors


Brief Review - Pathophysiology

  • Fatty streaks

    • Intimal thickening

  • Fibrous Plaque

    • Increased Smooth muscle cells

    • Accumulation of connective tissue

    • Lipid pool

  • Advanced lesions

    • Re-vascularized

    • Necrotic lipid-rich core


Carotid Atherosclerosis – Progession of Dz


Cerebrovascular Symptoms

  • Ipsilateral Partial or Complete Blindness

  • Absent Pupillary Light Response

  • Contralateral Hemianopsia

  • Contralateral Hemiparesis

  • Contralateral Sensory Loss

  • Aphasia (Left Hemisphere Ischemia)

  • Left visuospatial Neglect (Right Hemisphere)

  • Atypical findings include Limb shaking and Syncope (not generally considered a result of carotid stenosis)


Measuring Degree of Stenosis

Currently, three methods (NASCET, ECST and CC) predominate worldwide.


Imaging

  • Carotid Duplex Ultrasound

  • CT angiography

  • MR angiography

  • Cerebral Angiography (gold standard)


Carotid Duplex U/S

  • Uses B-mode ultrasound imaging and Doppler ultrasound to detect focal increases in blood flow velocity

  • The peak systolic velocity is the most frequently used measurement to gauge the severity of the stenosis

  • end-diastolic velocity, spectral configuration, and the carotid index provide additional information


Advantages

Non-invasive

Safe

Inexpensive

High Sensitivity and Specificity for significant stenosis (70-99%)

Disadvantages

Overestimates the degree of stenosis

May miss hairline lumens

Limitations

Carotid Duplex U/S


CT Angiography

  • Use of x-rays to visualize arterial and venous blood flow

  • Create cross-sectional images which then are assembled by computer into a three-dimensionalpicture

  • Provides an anatomic depiction of the carotid artery lumen and allows imaging of adjacent soft tissue and bony structures.


Advantages

anatomical detail of blood vessels more precisely than MRA or U/S

Disadvantages

CI in pt’s with renal insufficiency or severe DM

Risk of Allergic rxn

Radiation exposure

CT Angiography


Magnetic Resonance Angiography

The electromagnetic energy that is released when exposing a patient to radiofrequency waves in a strong magnetic field is measured and analyzed by a computer

Most often used for evaluating the extracranial carotid arteries.

Utilize either three dimensional time-of-flight MRA or gadolinium-enhanced MRA (contrast enhanced MRA).


Advantages

Great imaging w/o use of contrast or radiation

CEMRA – higher quality image with less artifact

No catheter in area of interest

May be most accurate non-invasive method

Disadvantages

May overestimate degree & length of stenosis? Use NASCET

CI for pt’s with metallic implants

CI in patients with renal insufficiency

Magnetic Resonance Angiography


Cerebral Angiography

  • Cerebral angiography is the gold standard for imaging the carotid arteries.

  • The development of intraarterial Digital Subtraction Angiography (DSA) has largely replaced conventional angiograpy

    • Lower dose of contrast

    • Small catheters

    • Shorter procedure


Advantages

Evaluates entire carotid a. system

Information about the disease process

Assess collaterals

Disadvantages

Invasive

Expensive

Radiation exposure

Potential for stroke

Limited views of carotid & bifurcation

Cerebral Angiography


<50 %

> 50%

CEA more beneficial for asymp men

with 60-99% stenosis who are

good surgical candidates


May be benefit with 50 to 69% symptomatic stenosis (clearly shown in men but not women)


References

  • Up to date Online. Pathophysiology of Symptoms from Carotid Artery Atherosclerosis. Last revised May 1, 2006.

  • Up to Date Online. Evaluation of Carotid Artery Stenosis. Last revised June 22, 2006.

  • Rothwell, PM, Gibson, RJ, Slattery, J, et al. Equivalence of measurements of carotid stenosis. A comparison of three methods on 1001 angiograms. Stroke 1994; 25:2435.

  • Zwiebel, WJ. Duplex sonography of the cerebral arteries: Efficacy, limitations, and indications. AJR Am J Roentgenol 1992; 158:29.

  • Bowen, BC, Quencer, RM, Margosian, P, Pattany, PM. MR angiography of occlusive disease of the arteries in the head and neck: Current concepts. AJR Am J Roentgenol 1994; 162:9.


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