Introduction to US and TCD - The American Society of Neuroimaging

Report
Introduction to Carotid Ultrasound
and Transcranial Doppler
Ultrasound
Ryan Hakimi, DO, MS
Director, Critical Care Neurology
Assistant Professor
Department of Neurology
The University of Oklahoma Health Sciences Center
January 16, 2015
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Disclosures
 Many of the slides have been adapted from slides
presented at the American Society for Neuroimaging
Annual Meetings by my mentors
Andre Alexandrov, MD


Zsolt Garami, MD
Charles Tegeler, MD
Alex Razumovsky, PhD
FINANCIAL DISCLOSURE
 Nothing to disclose
UNLABELED/UNAPPROVED USES DISCLOSURE
 Nothing to disclose
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Objectives
 Review the basic principles of carotid ultrasound (CUS)
and transcranial Doppler ultrasound (TCD)
 Illustrate the process of plaque morphology and
assignment of range of carotid stenosis
 Illustrate the process of determining vasospasm by TCD
 Discuss some of the current applications of TCD
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Principles of Ultrasound
Blood flow velocity through a cross
sectional area of a particular vessel (cm/s)
Blood flow velocity is directly related to
Doppler shift
If you measure the Doppler shift you can
derive the blood flow velocity
 Carotid ultrasound and transcranial Doppler
ultrasound can accomplish this
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Ultrasound Physics
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Carotid Ultrasound
Indications
Ischemic stroke or TIA
Assessment of carotid bruit
Assessment of carotid stenosis or occlusion
Pre-operative assessment for cardiovascular
surgery
Post carotid endarterectomy or stenting
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Principles of Carotid Duplex
 Duplex (B-mode and Doppler)
 B-mode (brightness mode)
 Grayscale, used for visualization of structures and
assessment of plaque morphology
• Hyperechoic (bright white: bone, calcium), causes a
shadow posterior to it
• Hypoechoic (black or grey: thrombus)
 Doppler velocities (peak systolic and end diastolic)
 Used to determine the direction of blood flow
 Used to estimate the range of stenosis
 Each lab should have own validated parameters of
the velocities to be used for assignment of
stenosis, not just use published values
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Assignment of Carotid Stenosis
Carotid Artery Stenosis: Gray-Scale and Doppler US Diagnosis—Society of Radiologists in
Ultrasound Consensus Conference
Grant et al., 2003
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Transverse Right ICA B-Mode
Skin surface
Fat and subcutaneous tissue
internal
jugular
vein
muscle
common
carotid
artery
(Transverse Right Proximal Common Carotid Artery)
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Longitudinal Right ICA B-mode Plaque
Focal irregular,
heterogeneous
plaque in the R Prx
ICA
(Longitudinal Right Proximal Internal Carotid Artery)
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Right ICA B-mode with Color
Doppler
+ Flow
(toward
probe)
- Flow
(away
from
probe)
Patient’s Head
Flow
(away
from
probe)
(Right Proximal Internal Carotid Artery)
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Right ICA Doppler Velocities
+ Flow
(away
from
probe)
Patient’s
Head
Cardiac
irregularity
Flow
(away
from
probe)
- Flow
(away
from
probe)
(Right Proximal Internal Carotid Artery)
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Report
 Focal plaque in the right internal carotid artery
 No hemodynamically significant stenosis demonstrated in the right internal
carotid artery.
 High resistance with focal plaque in the right internal carotid artery
 Cardiac irregularity was noted
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Longitudinal Left CCA B-mode Plaque
Plaque with
fibrous cap and
lipid rich core
(Longitudinal Left Mid Common Carotid Artery)
Hyperechoic
plaque with
posterior
acoustic
shadowing
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Longitudinal Left CCA B-mode Plaque
Heterogeneous
plaque with
posterior
acoustic
shadowing
(Longitudinal Left Distal Common Carotid Artery)
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Longitudinal Left ICA Color Doppler
Noise
(sample volume
picking up
multiple velocity
jets)
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Carotid US vs Transcranial Doppler US
Carotid Ultrasound
Directly visualize the vessel
Stenosis determined by peak systolic velocity
TCD
Blind insonation
Uses mean velocity
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Transcranial Doppler Ultrasound
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TCD Wave
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TCD Spectra
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Pulsatility Indices
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Pulsatility Indices
Low PI
AVM
low ejection fraction
aortic regurgitation
High PI: intracranial atherosclerosis
increased intracranial pressure
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Insonation of Brain
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TCD use in Carotid Occlusive Disease
Allows for evaluation of:
Collateral flow
Cerebral embolism
Poor vasomotor reserve i.e. progression of
carotid stenosis
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TCD use in Carotid Occlusive Disease
Slide courtesy Z. Garami, MD
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Risk of Ipsilateral Stroke: Number of
Activated Collaterals (ACA, PCOM, OA)
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Subarachnoid Hemorrhage
 Detection of vasospasm
 Clinical exam (usually somnolence or non-focal
symptoms), not very sensitive
 Daily TCD (non-invasive, 90% sensitivity, often
precedes clinical vasospasm)
 TCD or CTA can be used to screen for “plasty-able”
lesions
Images from 1. http://www.spencertechnologies.com/products.html#thumb 2. www.viswiki.com/en/Transcranial_doppler,
3. http://depts.washington.edu/uwtcdlab/images/tcd/tcd3_lg.gif all accessed on 1/24/2010 4. Cerebrovascular Ultrasound in Stroke
Prevention and Treatment
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Thresholds for Anterior Circulation Vasospasm
Should be validated at the given center
Mild vasospasm 120-140 cm/s,
Lindegaard Ratio (MCA velocity/extracranial ICA) 3-4
Moderate vasospasm 140-180 cm/s,
Lindegaard Ratio (MCA velocity/extracranial ICA) 4-6
Severe vasospasm >200 cm/s, Lindegaard
Ratio (MCA velocity/extracranial ICA) >6
Less reliable in posterior circulation (due
to greater anatomic variance)
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Data on TCD Monitoring
Courtesy Mauro Oddo, MD
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Subarachnoid Hemorrhage
 Triple-H therapy (hypertension, hypervolemia,
hemodilution)
 Introduced in 1970’s to prevent delayed cerebral
ischemia from vasospasm
 Prophylactic triple-H (in absence of vasospasm) does
not prevent vasospasm (Treggiari et al. J. Neurosurg 2008)
 Double-H therapy (hypertension and
hypervolemia as hemodilution is consequence of
hypervolemia)
 Must be individualized and titrated to clinical exam
and TCD
 Can result in pulmonary edema, hyponatremia, MI,
etc.
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Brain Death
Uniform Determination of Death Act
Legally acknowledged brain death as a
mechanism of death
Defined death as:
 Irreversible cessation of circulatory and respiratory
functions OR
 Irreversible cessation of all functions of the entire
brain, including the brain stem
1. Guidelines for the determination of death: report of the medical consultants on the diagnosis of death to the
President’s commission on the ethical problems in medicine and biochemical and behavioral research. JAMA
1981;246:2184-2186.
2. Uniform Determination of Death Act, 12 uniform laws annotated 589 (West 1993 West suppl 1997)
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AAN recommendations on use of
ancillary testing
AAN Clinician Guideline Supplement: Ancillary Testing;
Update: Determining Brain Death in Adults. 2010.
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Diagnosis of Patent Foramen Ovale
(PFO)
Slide courtesy Alex Razumovsky, PhD
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Diagnosis of Patent Foramen Ovale (PFO)
PFO is a residual channel between the
right and left atrium which originally
allowed oxygenated placental blood to
pass from the right to left atrium bypassing
the fetal lungs
Usually closes by age 2, but can persist in
25-30% of the general population
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Diagnosis of PFO by TCD
Agitated saline study
Monitor the MCA
Slide courtesy Z. Garami, MD
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Diagnosing subclavian steal by TCD
Image the vertebral artery
Ischemic cuff test
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Subclavian Steal Syndrome
Slide courtesy Z. Garami, MD
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Questions
Thank you
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