Carotid Imaging Modalities


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  • Carotid Imaging Modalities

    1. 1. Carotid Imaging Modalities Kyle Boyce August 3, 2007
    2. 2. Leading Causes of Death in U.S. <ul><li>1. Heart Disease </li></ul><ul><li>2. Cancer </li></ul><ul><li>3. Stroke (2 nd leading cause Worldwide) </li></ul><ul><ul><ul><li>Carotid Artery Atherosclerosis – 7% of patients presenting with initial stroke </li></ul></ul></ul>
    3. 3. Risk Factors <ul><li>Non-modifiable </li></ul><ul><li>Age </li></ul><ul><li>Race </li></ul><ul><li>Gender </li></ul><ul><li>Family History </li></ul><ul><li>Genetics </li></ul><ul><li>Modifiable </li></ul><ul><li>*HTN* </li></ul><ul><li>Hyperlipidemia </li></ul><ul><li>Diabetes </li></ul><ul><li>Smoking </li></ul><ul><li>EtOH </li></ul><ul><li>High Homocysteine </li></ul><ul><li>Low Folate </li></ul>
    4. 4. Brief Review - Pathophysiology <ul><li>Fatty streaks </li></ul><ul><ul><li>Intimal thickening </li></ul></ul><ul><li>Fibrous Plaque </li></ul><ul><ul><li>Increased Smooth muscle cells </li></ul></ul><ul><ul><li>Accumulation of connective tissue </li></ul></ul><ul><ul><li>Lipid pool </li></ul></ul><ul><li>Advanced lesions </li></ul><ul><ul><li>Re-vascularized </li></ul></ul><ul><ul><li>Necrotic lipid-rich core </li></ul></ul>
    5. 6. Carotid Atherosclerosis – Progession of Dz Plaque Formation Plaque ulceration Formation of Thrombus Further Stenosis or Occlusion Release of Emboli Plaque Enlargement Decrease Cerebral Flow Decreased or Absent Flow
    6. 7. Cerebrovascular Symptoms <ul><li>Ipsilateral Partial or Complete Blindness </li></ul><ul><li>Absent Pupillary Light Response </li></ul><ul><li>Contralateral Hemianopsia </li></ul><ul><li>Contralateral Hemiparesis </li></ul><ul><li>Contralateral Sensory Loss </li></ul><ul><li>Aphasia (Left Hemisphere Ischemia) </li></ul><ul><li>Left visuospatial Neglect (Right Hemisphere) </li></ul><ul><li>Atypical findings include Limb shaking and Syncope (not generally considered a result of carotid stenosis) </li></ul>
    7. 8. Measuring Degree of Stenosis <ul><li>Currently, three methods (NASCET, ECST and CC) predominate worldwide. </li></ul>
    8. 9. Imaging <ul><li>Carotid Duplex Ultrasound </li></ul><ul><li>CT angiography </li></ul><ul><li>MR angiography </li></ul><ul><li>Cerebral Angiography (gold standard) </li></ul>
    9. 10. Carotid Duplex U/S <ul><li>Uses B-mode ultrasound imaging and Doppler ultrasound to detect focal increases in blood flow velocity </li></ul><ul><li>The peak systolic velocity is the most frequently used measurement to gauge the severity of the stenosis </li></ul><ul><li>end-diastolic velocity, spectral configuration, and the carotid index provide additional information </li></ul>
    10. 11. Carotid Duplex U/S <ul><li>Advantages </li></ul><ul><li>Non-invasive </li></ul><ul><li>Safe </li></ul><ul><li>Inexpensive </li></ul><ul><li>High Sensitivity and Specificity for significant stenosis (70-99%) </li></ul><ul><li>Disadvantages </li></ul><ul><li>Overestimates the degree of stenosis </li></ul><ul><li>May miss hairline lumens </li></ul><ul><li>Limitations </li></ul>
    11. 12. CT Angiography <ul><li>Use of x-rays to visualize arterial and venous blood flow </li></ul><ul><li>Create cross-sectional images which then are assembled by computer into a three-dimensional picture </li></ul><ul><li>Provides an anatomic depiction of the carotid artery lumen and allows imaging of adjacent soft tissue and bony structures. </li></ul>
    12. 13. CT Angiography <ul><li>Advantages </li></ul><ul><li>anatomical detail of blood vessels more precisely than MRA or U/S </li></ul><ul><li>Disadvantages </li></ul><ul><li>CI in pt’s with renal insufficiency or severe DM </li></ul><ul><li>Risk of Allergic rxn </li></ul><ul><li>Radiation exposure </li></ul>
    13. 14. Magnetic Resonance Angiography <ul><li>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 </li></ul><ul><li>Most often used for evaluating the extracranial carotid arteries. </li></ul><ul><li>Utilize either three dimensional time-of-flight MRA or gadolinium-enhanced MRA (contrast enhanced MRA). </li></ul>
    14. 15. Magnetic Resonance Angiography <ul><li>Advantages </li></ul><ul><li>Great imaging w/o use of contrast or radiation </li></ul><ul><li>CEMRA – higher quality image with less artifact </li></ul><ul><li>No catheter in area of interest </li></ul><ul><li>May be most accurate non-invasive method </li></ul><ul><li>Disadvantages </li></ul><ul><li>May overestimate degree & length of stenosis? Use NASCET </li></ul><ul><li>CI for pt’s with metallic implants </li></ul><ul><li>CI in patients with renal insufficiency </li></ul>
    15. 16. Cerebral Angiography <ul><li>Cerebral angiography is the gold standard for imaging the carotid arteries. </li></ul><ul><li>The development of intraarterial Digital Subtraction Angiography (DSA) has largely replaced conventional angiograpy </li></ul><ul><ul><ul><li>Lower dose of contrast </li></ul></ul></ul><ul><ul><ul><li>Small catheters </li></ul></ul></ul><ul><ul><ul><li>Shorter procedure </li></ul></ul></ul>
    16. 17. Cerebral Angiography <ul><li>Advantages </li></ul><ul><li>Evaluates entire carotid a. system </li></ul><ul><li>Information about the disease process </li></ul><ul><li>Assess collaterals </li></ul><ul><li>Disadvantages </li></ul><ul><li>Invasive </li></ul><ul><li>Expensive </li></ul><ul><li>Radiation exposure </li></ul><ul><li>Potential for stroke </li></ul><ul><li>Limited views of carotid & bifurcation </li></ul>
    17. 18. <50 % > 50% CEA more beneficial for asymp men with 60-99% stenosis who are good surgical candidates
    18. 19. May be benefit with 50 to 69% symptomatic stenosis (clearly shown in men but not women)
    19. 20. References <ul><li>Up to date Online. Pathophysiology of Symptoms from Carotid Artery Atherosclerosis. Last revised May 1, 2006. </li></ul><ul><li>Up to Date Online. Evaluation of Carotid Artery Stenosis. Last revised June 22, 2006. </li></ul><ul><li>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. </li></ul><ul><li>Zwiebel, WJ. Duplex sonography of the cerebral arteries: Efficacy, limitations, and indications. AJR Am J Roentgenol 1992; 158:29. </li></ul><ul><li>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. </li></ul>
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