TRANSCRANIAL DOPPLER ULTRASOUND

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TRANSCRANIAL DOPPLER ULTRASOUND

• INTRODUCTION TO TCD
• Nicolet Vascular, Inc.
• A Division of
• VIASYS HEALTHCARE

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WHAT IS TCD?

• TCD (Transcranial Doppler) is a
• non-invasive assessment of cerebral blood
  flow in the basal cerebral arteries
• Utilizes low frequency Doppler ultrasound

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WHAT IS TCD?

• Uses 2 MHz pulsed Doppler ultrasound
• Passes through cranial windows
• Provides information regarding velocity and
  direction of cerebral blood flow

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Middle Cerebral Artery
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BLOOD FLOW VELOCITY

• Changes in flow velocity occur when
• There is a change in vessel caliber
• There is a change in volume flow

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TRANSCRANIAL DOPPLER

• Non-invasive
• Painless
• Inexpensive
• Can provide instantaneous and continuous
  cerebral blood flow information
• Can be used in any hospital environment
• Safe

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DEVELOPMENT OF TCD

• 1982 Dr. Rune Aaslid
• First publication Transtemporal Approach
• 1984 Dr. Merrill Spencer
• First publication Transorbital Approach
• 1986 Dr. M. Von Reutern
• First publication Suboccipital Approach
• 1983 First commercial TCD unit (EME)

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TCD APPLICATIONS

• Accepted applications (AAN)
• Detect intracranial stenosis
• Follow the time course of vasospasm
• Confirm the diagnosis of brain death
• Assist in the detection an management of AVMs

American Academy of Neurology
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TCD APPLICATIONS

• Other reported uses
• Assess of collateral pathways
• Assess autoregulation and vasomotor reactivity
• ICU monitoring (effects of ICP)
• Surgical monitoring (CEA, CABG)
• Detection of emboli (HITS)
• Aid in classification of strokes

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TCD APPLICATIONS

• Other reported uses
• Subclavian steal assessment
• Assess mechanical compression of the vertebral
  arteries
• Evaluate Sickle Cell patients
• Evaluate patients with carotid dissections

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TCD APPLICATIONS

• Assess the effects of pharmacological
  interventions
• Research applications
• Surgical monitoring

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INTRAOPERATIVE MONITORING APPLICATIONS

• Carotid Endarterectomy
• Carotid Stenting
• Coronary Artery Bypass Surgery
• Cardiac Valve Surgery
• Abdominal Aortic Aneurysm
• Liver Transplants
• Orthopedic Surgery

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TCD MONITORING

• Patent Foramen Ovale evaluation
• Implantable cardioverter defibrillator testing
• Any procedure where knowledge of the state of
  blood flow to the brain is of critical importance

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TRANSCRANIAL DOPPLER

• EXAMINATION TECHNIQUE

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TCD - APPROACHES

• Transtemporal
• Transorbital
• Suboccipital (Transforaminal)
• Submandibular

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TRANSCRANIAL DOPPLER ACCESS ROUTES
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TRANSTEMPORAL APPROACH

• Middle Cerebral Artery MCA
• Anterior Cerebral Artery ACA
• Terminal Internal Carotid Artery T-ICA
• Posterior Cerebral Artery PCA
• Communicating Arteries
• Anterior Communicating Artery ACoA
• Posterior Communicating Artery PCoA

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CRITERIA FOR VESSEL IDENTIFICATION

• Depth of the sample volume
• Direction of flow
• Traceability of the vessel
• Transducer angulation
• Spatial relationship of spectra
• Response to carotid or vertebral oscillations or
  compressions

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TRANSTEMPORAL WINDOWS
FW
AW
Frontal
MW

PW
PW
MW
AW
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Middle Cerebral Artery
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MCA / ACA
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Anterior Cerebral Artery
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Posterior Cerebral Artery P1
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TRANSORBITAL APPROACH

• Ophthalmic Artery OA
• Internal Carotid Artery Siphon
• Parasellar
• Genu
• Supraclinoid

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Ophthalmic Artery
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Carotid Siphon - Genu
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SUBOCCIPITAL APPROACH

• Vertebral Artery VA
• Basilar Artery BA

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Vertebral Artery
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Basilar Artery
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NORMAL VELOCITY RELATIONSHIPS

• MCA gt ACA gt PCA
• PCA VA and BA

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PRIMARY DIAGNOSTIC FEATURES

• Changes in velocity
• Changes in pulsatility
• Changes in systolic upstroke
• Changes in flow direction
• Side to side differences
• Embolic phenomena (HITS)

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TRANSCRANIAL DOPPLER

• COLLATERAL CIRCULATION

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Effects of Extracranial Carotid Stenosis /
Occlusion

• Factors affecting cerebral blood flow
• Degree of proximal stenosis
• Size and extent of collateral channels

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EFFECTS OF CAROTID STENOSIS

• Mild to Moderate Stenosis (lt /- 75)
• TCD exam Essentially normal
• Severe Stenosis (gt /- 75)
• TCD exam Abnormal
• Changes in Doppler spectral waveform shape
• Changes in flow patterns (Collateral)

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WAVEFORM CHANGES

• Decreased velocity
• Delayed systolic upstroke
• Decreased pulsatility

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DOPPLER WAVEFORM CHANGES
Normal MCA
Abnormal MCA
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COLLATERAL SOURCES

• Collateral detectable by TCD include
• Circle of Willis, including the vertebrobasilar
  system
• ECA to ICA collateral via the ophthalmic artery

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COLLATERAL SOURCES

• Collateral not detectable by TCD include
• Branches of the ECA connecting to branches of the
  vertebral artery
• Leptomeningeal anastomoses

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INTRACRANIAL STENOSIS

• Focal elevated velocities above adjacent segments
• Side to side differences exceeding normal
  variation (usually gt 15 or 30 cm/sec
  between right and left MCA)
• Downstream effects
• Turbulence
• Delayed systolic upstroke
• Decreased velocity

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TCD WAVEFORMS WITH INTRACRANIAL STENOSIS
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INTRACRANIAL STENOSISCauses

• Atherosclerosis
• Intraluminal thromboembolism
• Arterial dissection
• Moyamoya disease
• Vasculitis
• Vasospasm
• Extrinsic vessel compression

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TRANSCRANIAL DOPPLER

• EMBOLI DETECTION
• (HITS)

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EMBOLIC EVENTS

• Foreign solids and / or gaseous materials within
  the blood stream
• Reflect sound waves more intensely than
  surrounding red blood cells
• Characterized by an audible chirp and
  simultaneous visual HIT on the screen

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TCD - EMBOLI DETECTION

• Can detect the presence of embolic signals caused
  by the presence of a variety of materials, both
  gaseous and solid
• Cannot determine the size of an embolus
• Cannot determine the composition of an embolus
• Can detect particles as small as 50 microns

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EMBOLI RECOGNITION International Consensus
Committee

• Short lt 0.1 second, 3-60 dB transients
• Unidirectional in spectra
• Occur randomly in cardiac cycles
• Change frequency within spectrum
• Audible sound chirps, clicks, plunks
• Solid vs. air emboli distinguished by
  circumstance (solid designated when there is no
  invasion of vasculature)

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EMBOLI DETECTION

• Carotid artery stenosis
• Arterial dissection
• Post endarterectomy
• Heart valve replacement

• Patent foramen ovale
• Atrial fibrillation
• Significant CHF
• Endocarditis
• Acute MI

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MCA Microembolic Signal (MES)
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Transcranial Doppler

• Paradoxical Stroke
• and
• PFO Evaluation

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Ischemic Stroke

• Represents the third greatest cause of death in
  the western word
• Is the greatest cause of functional incapacity
• Origin is undetermined in 40 of cases according
  to conventional etiological criteria

Sacco R.L.,et al, Infarcts of undetermined cause
the NINCDS Stroke Data Bank. Ann. Neurol.
198925382-390
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Cryptogenic Stroke

• Stroke of unknown etiology
• Suspicion of paradoxical brain emboli arising
  from the venous circulation
• Emboli from the venous system can pass to the
  arterial circulation through
• a PFO (Patent foramen ovale)

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Paradoxical Brain Emboli (PBE)

• Emboli whose source is not from an identifiable
  source in the arterial system
• Also referred to as venous-to-arterial emboli

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Positive TCD Bubble Test Shower Type HITS with
Valsalva Maneuver
R MCA
L MCA
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TRANSCRANIAL DOPPLER

• Cerebral Circulatory Arrest

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TCD - BRAIN DEATH

• Brain death is a clinical diagnosis
• TCD is a confirmatory test
• TCD can detect cerebral circulatory arrest

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Transcranial Doppler

• Can aid in timing of other necessary tests
• Helpful in following potential organ donors
• Useful when patients are being treated with
  barbiturates which affect EEG

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CEREBRAL CIRCULATORY ARRESTTCD Evaluation

• Bilateral study including posterior circulation
• Oscillating flow pattern persists over time (20
  30 minutes minimum)

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CEREBRAL CIRCULATORY ARREST