Carotid Imaging Modalities
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Carotid Imaging Modalities

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Carotid Imaging Modalities Carotid Imaging Modalities Presentation Transcript

  • 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
  • Risk Factors
    • Non-modifiable
    • Age
    • Race
    • Gender
    • Family History
    • Genetics
    • Modifiable
    • *HTN*
    • Hyperlipidemia
    • Diabetes
    • Smoking
    • EtOH
    • High Homocysteine
    • Low Folate
  • 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 Plaque Formation Plaque ulceration Formation of Thrombus Further Stenosis or Occlusion Release of Emboli Plaque Enlargement Decrease Cerebral Flow Decreased or Absent Flow
  • 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
  • Carotid Duplex U/S
    • 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
  • 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-dimensional picture
    • Provides an anatomic depiction of the carotid artery lumen and allows imaging of adjacent soft tissue and bony structures.
  • CT Angiography
    • 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
  • 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).
  • Magnetic Resonance Angiography
    • 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
  • 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
  • Cerebral Angiography
    • 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
  • <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.