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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 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
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.