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Vascular Technology III > Transcranial Doppler ch.23 > Flashcards

Transcranial Doppler ch.23 Flashcards

1
Q

What vessels does the transtemporal window for a TCD evaluate?

A

MCA, ACA, Terminal ICA, PCA

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2
Q

What vessels does the suboccipital/ transforamenal window for a TCD evaluate?

A

VA, BA

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3
Q

What vessels does the transorbital window for a TCD evaluate?

A

ICA and ophthalmic

carotid siphon

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4
Q

vessel: MCA

window, depth, direction, velocity, and angle

A

transtemporal, 30-60 mm, antegrade, 55 +/- 12, anterior and superior

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5
Q

vessel: terminal ICA

window, depth, direction, velocity, angle

A

transtemporal, 55-65 mm, bidirectional, 55 +/- 12, anterior and superior

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6
Q

vessel: ACA

window, depth, direction, velocity, angle

A

transtemporal, 60-80mm, retrograde, 50 +/- 11, anterior and superior

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7
Q

vessel: PCA

window, depth, direction, velocity, angle

A

transtemporal, 60-70mm, antegrade, 39 +/- 10, posterior

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8
Q

vessel: ICA

window, depth, direction, velocity, angle

A

transorbital, 60-80mm, parasellar: antegrade supraclinoid: retrograde genu: both, 47 +/- 14, varies

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9
Q

vessel: ophthalmic

window, depth, direction, velocity, angle

A

transorbital, 40-60mm, antegrade, 21 +/- 5, medial

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10
Q

vessel: VA

window, depth, direction, velocity, angle

A

transforamenal/ suboccipital, 60-90mm, retrograde, 38 +/- 10, right and left of midline

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11
Q

vessel: BA

window, depth, direction, velocity, angle

A

transformenal/ suboccipital, 80-120mm, retrograde, 41 +/- 10, midline

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12
Q

crossover collateralization

A

antegrade flow in the ipsilateral anterior cerebral artery, flow comes from the contralateral ACA via the AcomA
ipsilateral MCA flow diminishes with contralateral compression of the CCA and respond positively to contralateral oscillation maneuvers of the CCA

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13
Q

external to internal collateralization

A

retrograde flow in the ipsilateral OA, flow comes from the ECA branches, flow reduction, obliteration, or reversal of flow occurs in the OA with compression of the ipsilateral ECA branches

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14
Q

posterior to anterior collateralization

A

when flow velocities in the ipsilateral PCA exceed those in the ipsilateral MCA >125%
increased flow velocities in the PCA may occur with compression of the ipsilateral CCA confirms the patency of the PcomA

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15
Q

General considerations for TCD

A

accessibility of the ultrasonic windows within the skull that can be penetrated with the ultrasonic beam are often limited
arteries at the base of the skull vary greatly in size, course, development, and site of access
the power measured behind the skull is rarely >35% of the transmitted power, the bone of the skull absorbs the major portion of the power

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16
Q

To achieve acceptable signal to noise ratio systems utilize dopplers with

A

lower bandwidth

larger and less defined sample volume

17
Q

TCD systems use….

A

2MHz pulsed-wave doppler

18
Q

TCCS systems use

A

transcranial color-coded duplex sonography

1.8-3.6 MHz phased array sector transducer

19
Q

instrument requirements

A

transmitting powers between 10 and 100mW/cm2
adjustable doppler gate width
PRF up to 20kHz
focusing of the ultrasound beam at a depth of 40-60mm
online display of: TAMV and peak systolic velocity

20
Q

what is the submandibular approach useful for?

A

ICA dissection
chronic ICA occlusion
velocities for calculating the Lindegaard ratio

21
Q

Hyperemia

A

globally elevated mean velocities, intra- and extracranially

Lindegaard ratio <3 TAMV of MCA/ TAMV of ICA

22
Q

vasospasm and stenosis due to atherosclerosis

A

focal velocity elevation

distal turbulence

23
Q

patients with SAH and suspected vasospasm

A

initial baseline study should demonstrate relatively normal mean velocities
vasospasm due to SAH generally occur by the 5th day
most often there will be a gradual increase in mean velocity measurements, with changes noted over time

24
Q

treatment of vasospasm

A

percutaneous transluminal angioplasty

pharmacologic infusion- generally papaverine (vasodilator)

25
Q

HITS aka MES

A

high intensity transient signals aka microembolic signals

26
Q

HITS or MES commonly occur during what?

A

operative procedures: CEA or cardiopulmonary bypass

27
Q

HITS aka MES criteria

A

short in duration, <300ms
increased intensity, at least 3dB above background signal
unidirectional within doppler spectrum
sound chirp or snap

28
Q

Why and how do you do a vasomotor reactivity testing?

A

to identify patients at higher risk of stroke

testing is done using various stimuli, such as increasing or decreasing CO2 and monitoring the response.

29
Q

Normal vasomotor reactivity test

A

increased carbon dioxide: decrease in blood pH, vasodilatation of resistance vessels of the brain, increase in cerebral blood flow

decreased carbon dioxide; increase in blood pH, vasoconstriction of resistance vessels of the brain, decrease in cerebral blood flow

30
Q

vasomotor reactivity test abnormal

A

occlusive disease of extracranial internal carotid arteries and intracranial cerebral arteries-
maximal dilatation of the resistance vessels of the brain, autoregulation functions of the distal vessels are diminished, carbon dioxide testing.

31
Q

Abnormal MCA velocity waveform

A

decreased amplitude and pulsatility, increased acceleration time due to proximal occlusive disease
moyamoya disease

32
Q

Most common cause of subarachnoid hemorrhage

A

ruptured cerebrovascular aneurysm: occurs in approx. 28,000 people in north america annually with the mortality rate exceeding 50%

33
Q

other causes of SAH

A

trauma, tumor, AVM, spontaneous bleed

34
Q

What can result from a SAH?

A

possible vasospasm (delayed, sustained contraction of the cerebral arteries)

35
Q

vasospasm vs. hyperemia, lindegaard ratio

normal ?

A

mean velocity: 30-80 cm/s

36
Q

vasospasm vs. hyperemia,

degree of vasospasm: hyperemia

A

< 3.0

37
Q

vasospasm vs. hyperemia,

degree of vasospasm: moderate

A

3-6

38
Q

vasospasm vs. hyperemia

degree of vasospasm: severe

A

> 6

39
Q

triple H therapy

A

hemodilution, hypertension, hypervolemia

Vascular Technology III (7 decks)

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