Neurovascular Ultrasound Course

Transcription

1 Neurovascular Ultrasound Course William M. McKinney (6/6/30-10/24/03) Father of Neurosonology Founder, Neurosonology Course, WFUSM Welcome to Winston-Salem, NC, Wake Forest School of Medicine, and the Program for Medical Ultrasound Course Overview Schedule for the week Sign slips for CME Introductions Textbooks Food, restrooms, bookstore, phones Applications for ASN, NSRG, AIUM Special needs Carotid Interpretation Charles H. Tegeler, MD McKinney-Avant Professor of Neurology Director, Comprehensive Stroke Center Director, Ward A. Riley Ultrasound Center Medical Director, Neurosonology Lab WFUSM Carotid Interpretation CEA Specimen: ICA Plaque Review clinical imperative Doppler velocity B-mode imaging Duplex and color flow imaging Select ancillary testing 1

2 Carotid Ultrasound Clinical Imperatives Carotid/Vertebral disease is the most commonly identified stroke mechanism Carotid/Vertebral atherosclerosis/stenosis is marker of increased stroke risk Established surgical benefit for tight symptomatic carotid stenosis (NASCET) and tight asymptomatic stenosis (ACAS, ACST) Carotid Ultrasound Clinical Imperatives Results influence use of additional testing Influences choice of medical Rx Marker of increased risk for other atherosclerotic events (MI and PAD) Carotid Ultrasound Clinical Decision-Making First decide if any testing is needed Will it help with Dx or influence management decisions? If so, use safe, non-invasive, low risk, less costly methods initially, saving more costly, risky, invasive methods for specific needs If not, don t do it. Carotid/Vertebral Ultrasound Clinical Decision-Making Carotid ultrasound now part of initial vascular evaluation for patients with Stroke or TIA, or at risk for the same. Safe, accurate, portable, relatively less expensive, and readily available. If CUS negative, usually don t pursue Ideal for serial follow up for progression Carotid/Vertebral Ultrasound Clinical Questions to Answer Is any carotid stenosis present? If so, where, what is the distribution, how bad is it, and is it accessible? Most Rx decisions still made based on hemodynamic effect (% stenosis) Plaque features can influence decision Carotid Ultrasound Indications Stroke, TIA, Cerebral ischemia Bruit evaluation (Sx or Asx) Serial follow up of CVD Serial follow up of CVD Pre-op study, or perioperative in CEA Pulsatile neck masses/abnormal structures High risk groups for CS or stroke/screening? 2

3 Doppler Spectral Analysis Normal vessels have laminar flow Multiple speeds & directions of flow in any sample volume Doppler Spectral Analysis At any point in time, there is a spectrum of different speeds and directions i of flows (frequency shifts or velocities) Doppler Spectral Analysis FFT Spectral Display Vascular Doppler Spectral Analysis Parameters Flow direction Peak systolic velocity End-diastolic velocity Spectral pattern (vessel fingerprint) Spectral broadening Doppler Spectral Analysis Parameters Doppler Spectral Analysis Spectral Fingerprints 3

4 Doppler Velocity Spectrum: ICA Doppler Velocity Spectrum: ECA CCA/BIF ECA CCA/BIF ICA Doppler sample volume CCA Doppler Spectral Analysis Sampling Across Vessel Velocity scale PSV Doppler velocity spectrum: CCA EDV Hemodynamic Principles Key Factors Affecting Flow Hemodynamic Effect Of Stenosis Pressure difference Resistance Tube/stenosis length Fluid viscosity Radius (residual lumen) Brain tries to maintain flow 4

5 Hemodynamic Effect of Stenosis Doppler Velocity Spectral Analysis Normal ICA Velocity Doppler Spectral Analysis Changes with Moderate Stenosis Doppler Spectral Analysis Moderate Stenosis ICA BIF Increased systolic velocity shows 50-75% ICA stenosis Doppler Spectral Analysis Severe Stenosis Doppler Spectral Analysis Severe Stenosis/Near Occlusion 5

6 Doppler Spectral Analysis Severe Stenosis/Near Occlusion Vascular Doppler Correlating with Stenosis Use velocity and spectral pattern to determine presence/severity of stenosis Many sets of criteria in literature All only estimate range of stenosis Criteria chosen depend on equipment/goals Must be validated for your laboratory Velocity Criteria at WFUSM PRIMARY CRITERIA Standard angle peak systolic velocity End-diastolic diastolic velocity SECONDARY PARAMETERS Spectral broadening/turbulence, ICA:CCA ratio, resistive pattern in CCA, side differences, extensive plaque on B-mode Criteria for Carotid Stenosis WFUBMC % Stenosis PSV EDV ICA:CCA < 50% < 140 cm/s < 40 cm/s < % > 140 cm/s < 110 cm/s % > 140 cm/s > 110 cm/s > % Variable Variable Variable Probable Occlusion N/A N/A N/A Consensus Panel ICA Stenosis Criteria % Stenosis ICA PSV (cm/s) Primary Parameters Secondary Parameters Plaque % estimate ICA/CCA PSV Ratio ICA EDV (cm/s) Normal <125 None <2.0 <40 <50 <125 <50 <2.0 < >50% >230 >50 >4.0 > High, low, Visible Variable Variable or none seen Total occlusion Undetectable Visible, no lumen N/A N/A Velocity Criteria Ratios Relationship between velocity at stenotic site and proximal or distal segments Higher stenosis higher ratio Higher stenosis, higher ratio Remains constant even if bad heart so can t generate velocity to make stenotic criteria ICA:CCA, ICA:Distal ICA validated Ratio can be systolic or diastolic velocity Grant et al,

7 Carotid Stenosis Identifying Significance Many use systolic velocity for 70% stenosis 200, 230, 270 cm/s suggested as cut points Use severe/tight grouping (75-99%) Velocity ratios ICA:CCA, ICA:Distal ICA Volume flow may help confirm hemodynamic significance Carotid Interpetation Suggestions/Biases Larger Doppler sample volume helps avoid missing off center high velocity jet, and covers entire width of vessel easier Sample with ends of vessel segment open (like a stove pipe) so more confident of flow direction and angle of insonation If aliasing, move baseline down, or increase PRF Doppler Sampling Ends of Vessel Open Doppler Sampling Ends of Vessel Closed Vascular Doppler Suggestions/Biases Watch out for internalization of the ECA Use indirect changes from proximal or distal disease High resistance wave form implies distal tight stenosis or occlusion, stiff pipes, heart problem Rule of 10 : < 10 cm/s diastolic in CCA or >10 diastolic in the ECA Post-stenotic wave form (low pulsatility) Doppler Spectral Analysis Disturbed Flow at BIF/ICA 7

8 Doppler Spectral Analysis Disturbed Flow at BIF/ICA Carotid Interpretation Suggestions/Biases May need to sample from transverse to better identify vessel (but can t tell angle) Try transverse image with color/power Doppler imaging to better see string/trickle flow if longitudinal sampling difficult If heart irregular, use cardiac cycle with highest velocity Transverse Duplex Sampling Transverse Duplex Sampling Carotid Protocol & Techniques Suggestions/Biases ECA Doppler Identification Temporal Tap/Oscillation Tapping of superficial temporal artery can help identify ECA Adjust baseline/scale so velocity spectrum fills 2/3-3/4 of screen If signal sounds abnormal, but can t capture, try higher velocity scale 8

9 Indirect Changes Right ICA String Sign Right ICA String Sign ICA String Sign Distal Turbulence Right ICA String Sign Intracranial Effects Effect of Cardiac Disease Aortic Insufficiency Indirect Changes Distal Occlusion Right CCA waveform Left CCA waveform 9

10 ICA Occlusion Doppler Scale Too High Carotid B-Mode Imaging Carotid Protocol & Techniques Key Elements of Protocol B-mode B-mode imaging gives 2-D gray scale image of vessel, wall, plaque, & soft tissue Location, size, course of vessels Information on plaque features including surface (smooth, irregular, ulcer), texture (homogeneous/heterogeneous), echodensity, and movements (pulsation pattern) B-Mode Landmarks B-Mode Imaging Plaque Characteristics Assessed Location / Distribution Plaque thickness Surface features Surface features Texture / Heterogeneity Echodensity / Calcification Real-time pulsation pattern 10

11 Carotid Plaque Criteria WFUBMC Plaque Category Normal Minimal / Mild Moderate Large / Severe Measurement < 1.1 mm mm mm > 4.0 mm Plaque Features Location Surface Features Texture / Composition Echodensity Plaque Motion Plaque Features WFUBMC Descriptors / Parameters Specific vessel segment Smooth, Irregular, Crater/Ulcer/Niche /Ni Homogeneous, Heterogeneous /mixed, Possible intraplaque hemorrhage Hypechoic, Echogenic, Hyperechoic/dense, +/- shadowing Radial (normal), longitudinal CCA Tortuosity Short/Absent CCA Superior Thyroid Artery Branch Off ECA Carotid Protocol & Techniques Key Elements of Protocol B-mode Measurements made on B-mode image of plaque thickness and residual lumen Measurements from view with optimal or best image of lesion When possible document location relative to internal landmark (flow divider) 11

12 Smooth Carotid Plaque Plaque Features: Smooth and Homogeneous Surface Features: Irregular Plaque Irregular Plaque Surface Features: Crater/Ulcer Surface Features: Crater/Ulcer 12

13 Surface Features: Crater/Ulcer Plaque Features: Crater filled with thrombus Calcification and Shadowing Plaque Features: Calcification/Shadowing Plaque Features: Calcification/Shadowing Homgeneous Plaque 13

14 Plaque Features: Smooth; Heterogeneous Large hypoechoic ICA plaque CCA ICA Residual lumen BIF Plaque Features: Hypoechoic (Lusby I) Plaque Features: Hypoechoic region/? IPH Plaque Features: Complex Plaque Thrombosis/Occlusion of ICA 14

15 Thrombus in Wall (Dissection) ICA Dissection Transverse View Thrombus in CCA Mobile Component Thrombus in CCA Post-Angio Study Plaque Characteristics Suffered from lack of standardized nomenclature and scheme Many suggested systems, but pathologic correlations mixed More emphasis on hemodynamics, color flow, technical challenges, and time Plaque Features Clinical Implications Lusby (%/location of hypoechoic regions predict risk) Johnson (depth of crater predicts risk) Johnson (depth of crater predicts risk) Leahy (heterogeneity predicts risk) NASCET (ulcer high risk in nonsurgical pt) Crater/ulcer less critical independent risk Role in stroke risk, esp in less % stenosis 15

16 Plaque Features Lusby Criteria Carotid Protocol & Techniques B-mode suggestions Transverse image if unclear or large plaque ICA usually post/lat; ECA ant/medial Quick interrogation of internal jugular vein with B-mode and/or color flow imaging Note appearance of thyroid on transverse view, and report cyst/lesions > 1 cm dia. Carotid Protocol & Techniques Suggestions/Biases Adjust monitors for light in the room Adjust instrument settings; don t just cookbook the study with high contrast B/W images Learn to recognize artifacts Look for color voids to suggest unsuspected hypoechoic plaque Prior CEA Suture Line Carotid Bypass Graft Vein Wall Harmonic Artifact 16

17 Carotid Duplex Sonography Duplex Doppler ICA Tight Stenosis Combines PW Doppler & B-mode imaging Image guided placement of sample gate Angle correction Option for color flow imaging Overcomes pitfalls of stand alone tests Expect 90% sens/spec for tight stenosis Color Flow Imaging CCA Color Flow Imaging Quick ID presence/direction of flow Road map for spectral Doppler More accurate angle of insonation Improved data on surface features ID of hypoechoic plaque (color void) ID string sign/near occlusions Speed up examination Color Flow: Tortuosity ICA ICA Tortuosity 360 degree loop/coil 17

18 Color Changes Direction of Flow Relative to Transducer Color Changes Direction vs Aliasing Color Change Distal to Plaque Color Flow ICA Stenosis Color Duplex of ICA Stenosis Color Imaging ID of hypoechoic plaque: color void 18

19 Color Flow Imaging Color void of hypoechoic plaque Color Flow Imaging Surface features Color Flow Suggests Occlusion Duplex Doppler in ICA Stump Doppler Signal Proximal to Occlusion High resistance waveform Color Flow Imaging ICA Occlusion 19

20 Low Velocity, High Resistance Doppler Signals ICA Subtotal Occlusion Low Velocity, High Resistance Doppler Signals ICA Subtotal Occlusion ICA Subtotal Occlusion Color flashes suggest patency Indirect Changes High Resistance Pattern Distal Occlusion Indirect Changes Distal Occlusion Color Flow ICA Occlusion 20

21 Indirect Changes Intracranial Effect ACA Reversal Color Flow Imaging Distal flow confirms patency Angiogram: Near occlusion ICA Carotid Dissection B-mode appearance Carotid Dissection Color Flow shows double lumen Internal Jugular Spontaneous Echo Contrast 21

22 Internal Jugular Spontaneous Echo Contrast Internal Jugular Transverse Spontaneous Echo Contrast Internal Jugular Thrombosis Internal Jugular Thombosis Internal Jugular Thrombosis B-mode Imaging Internal Jugular Thrombus 22

23 Color Flow of IJV Thrombus Power Doppler Imaging Power Imaging ICA Stenosis and Shadowing B-Flow Imaging Cerebrovascular Anatomy Color Duplex Subclavian Artery 23

24 Color Flow Vertebral Origin Vertebral Artery Interosseous/Intertransverse Segment Duplex Interosseous Vertebral Vertebral/Subclavian Steal Carotid Protocol & Techniques Ancillary Methods Cuff Test If vertebral waveform abnormal (from systolic decceleration to frank reversal), do cuff test to check for latent steal BP cuff to 5-10 mm over systolic on ipsilateral arm for 3 minutes to provoke increased metabolic demand in arm Causes flow reversal or worsening if SSS 24

25 Vertebral Duplex Complete reversal after cuff test Vertebral Duplex Cuff test shows latent SSS Carotid Protocol & Techniques Ancillary Methods Positional Testing Occasionally symptoms with certain positional changes (as with kinks, arthritis) Monitoring of carotid or vertebrals through range of neck flexion/extension, turning can show functional blockages only present with positional changes Carotid Protocol & Techniques Ancillary Methods Volume Flow Velocities alone can be deceiving Volume flow key to hemodynamic view Extensive experience with Color Velocity Imaging Quantification, Philips Ultrasound Time domain processing, m-mode display of velocities across vessel, and flow lumen, over time. Doppler now available on most instruments CCA VFR with CVI-Q Carotid Protocol & Techniques Ancillary Methods Volume Flow Best access and accuracy for CCA, less for ICA, and even less for vertebral Predictable changes with both ipsilateral and contralateral stenosis/occlusion. VFR drops with severe ipsilateral distal disease, increases contralateral (if disease not bilateral), if intracranial collaterals normal 25

26 Carotid Stenosis & VFR Volume Flow Measurments Use at WFUSM CCA VFR if 75% or greater stenosis If spectral changes of distal/prox sten/occl Bilateral high or low velocities Waveform suggesting AVM Assess collateral function; avoid error contralaterally Follow progression of stenosis Carotid Protocol & Techniques Ancillary Methods- Ophthalmics Ophthalmic flow direction helps understand collateral flow; sources and adequacy Ophthalmics reversed when collateral from ECA through orbit to ICA siphon Suggests that carotid lesion tight Suggests relative inadequacy of A-Com and P-Com arteries Ophthalmic Collateral Flow Orbital Color Flow Helpful for Hemodynamic Picture 26

27 Orbital Color Flow Reversed Ophthalmic Artery Orbital Color Flow 27