TCD

Anterior circulation of brain

-cavernous internal carotid artery, ICA, MC, aca, anterior comunicating artery

segments of carotid siphon

-parasellar segment

-genu segment

-supraclinoid segments

ICA branches

-opthalamic

-PCA

Posterior circulation

-vertebral

-basilar

-pca

frequency for TCD

1-2 MHZ

Spectral doppler waveforms are obtained from blank and blank circulation

ant and post

sample volume for TCD

large

large sample volume causes

spectral broadening

what is recorded for TCD

mean velocities

waveform of vessels other than OA

low resistance with high diastolic flow

is audio signal important

yes

temporal windows

-transtemporal

-transorbital

-transoccipital

-submandibular

transtemoral approach is located over blank and superior to blank

temporal bone and zygomatic arch

temporal approach is subdivided into

posterior, middle, anterior and frontal

foramen magnum approach takes advantage of

natural opening in the skull which the spinal cord passes

foramen magnum approach the transducer is placed at

base of skull and aimed toward the nose

submandibular approach allows interrogation of the

very distal extracranial ica

Atlas loop approash is used to evaluate

extracranial vertebral artery

five criteria used to identify vessels

-approach

-sample volume depth

-direction of blood flow relative to ultrasound transducer

-spatial realtionship

-flow velocity

flow velocity

MCA>ACA>PCA=BA=VA

arteries seen in the orbital approach

opthalamic artery and cavernous carotid siphon

temporal approach arteries identified

MCA, ACA, TICA, PCA

for temporal approach transmit power is

maximum

foreamen magnum approach arteries seen

vertebral arteries

ophalamic artery transmit power

lower

For opthalamic artery set color box to blank

back of globe

opthalamic artery waveform

low velocity with high resistance

terminal ICA appears as blank and and is what color

S shape, blue and red

MCA location

slightly above and parallel to lesser wing on sephnoid bone, from TICA angle cephalad

PCA where do place color box

butterfly shaped midbrain

vertebral arteries may be

tortuous

VA spectral doopler should be obtained every blank mm

5mm

the confluence of VAs and BA looks like a

Y

lindegaard ratio

mean velocity of MCA/ mean velocity of ipsilateral extracranial ICA

retromandibular ICA obtained in patients that require calculations of the blank

Lindegaard ratio

ICA is useful for determining what

distal arterial narrowing

ICA power level can be set

low

for ICA transducer placed at an

angle of the jaw with orientation marker facing up

MCA depth and flow direction

30-60 mm, toward

MC

60-70 mm, toward and or away

MCA/ACA depth and flow direction

55-65 bidirectional

ACA 1 depth and flow direction

60-80 mm, away

PCA 1 direction and depth

60-70, toward

OA direction and depth

40-60, toward

carotid siphon depth, and direction

55-80mm, toward bidirectional and away

TICA depth and flow

55-65 mm, away

VA flow direction and depth

60-90mm, away

BA depth and direction

80-120 mm, away

no or limited temporal bone window

hyperostosis

Anatomical variations in circle of willis

-difference in orgin

-differences in size

-differences in course of vessel

TCD accuracy is blank

operator dependent

velocity calculation depends on

angle of insonation

asliasing is often present in the setting of

severe stenosis,vasospasm, collateral flow, and hyperemia.

what is primarily used for diagnosis

spectral waveform

primary diagnostic features include

-alteration in velocity

-deviations from laminar flow

-changes in pulsatility

-changes in direction of flow

with hemoynamically significant extracranial carotid artery setnosis the brain will

compensate with collateral flow and auto regulation

TCD can help blank and blank of collateral circulation

identify and assess adequacy

TCD can help predict blank of cross-clamping during carotid endarterectomy

hemodynamics consequences

Extternal carotid to internal carotid collateral

retrograde flow in OA, decreased pulsatility and increased velocity in OA, obliteration diminishment or reversal of flow in the OA with compression of the branches of the ECA

Crossover collateral through ACA

-retrograde flow in the ACA

-increased flow velocities in teh colateral ACA

-usually high velocities detected at midline in the small ACOA

Posterior to anterior collateral through the posterior communicating artery

-increased flow velocities in the ipsilateral PCA
-veclocities in PCOA are usually quite high

TCD is useful for derection of

>50% intracranial stenoses and occlusions

what is the most common cause of intracranial stenosis

atherosclerosis

conditions that produce stenosis

-atherosclerosis

-dissection

-fibromuscular dysplasia

-radiation-induced vasculopathy

-myoma disease

-inflmmatory vasculopathies

stenosis criteria for MCA

100-120

stenosis criteria for ICA

90

stenosis criteria for ACA

greater than 90

stenosis criteria for PCA

greater than 80

stenosis criteria for basilar

110

stenosis criteria for vertebral

110

what is the most common cause of occlusion beyond the circle of willis

embolism

what is preferred treatment method and for embolic stenosis and occlusion

thrombolysis

TIBI

thrombolysis in brain ischemia

transient and delayed narrowing of basal cerebral arteries following subarachnoid hemorrhage

vasospasm

SAH

subarachnoid hemorrhage

vasospasm usually begins within blank to blank after SAH

3-4 days

TCD used to detect blank that is indicative of vasospasm

elevated blood velocities

for vasospasm patients are monitored daily for what events

-onset

-location

-degree

-resolution

what is commonly monitored for vasospasm

MCA

interpretation of vasospasm is complicated by

-intracranial pressure

-blood pressure

-hematocrit

-arterial co2

-collateral flow

-autoregulation

-responses to therapeutic interventions

what procedures TCD can be used to monitor for emboli during procedures

-carotid endarterectomy

-carotid stenting

-cardiopulomary bypass surgery

-neruologic procedures

microembolic signal has what signature

HITS

why is emboli monitoring important

reduct stroke risk

How does DVT cause PFO

dvt, ra, pfo, LA, LV, AO, CCA

brain death waveform

short systolic spike followed by either a small retrograde deflection in diastoe or no flow in diasotle

sickle cell patients are prone to stroke involving blank and blank

MCA and ACA

children with sickle cell disease undergo what kind of screening

routine annual TCD

sickle cell border line measurement

170-200

sickle cell normal

<170

sickle cell abnormal

200

what can reduct rate of first stoke in sickle cell patients

early detection of MCA velocities and initaion of blood transfusions