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Article Flashcards

1
Q

How has TCD evolved?

A

It has evolved as a diagnostic, monitoring, and therapeutic tool.

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2
Q

What is the only diagnostic tool that can provide real time information about cerebral hemodynamics and can detect embolization to the cerebral vessels.

A

TCD

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3
Q

What is TCD?

A

It is a noninvasive, cost-effective, and beside tool for obtaining information regrading the collateral flow across various branches of the circle of Willis in patients with cerebrovascular disorders.

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4
Q

What are some advanced applications of TCD?

A

Helps in the detection of:

  • Right-to-left shunts
  • Vasomotor reactivity
  • Diagnosis
  • Monitoring of vasospasm in subarchnoid hemorrhage
  • Supplementary test for confirmation of brain death
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5
Q

Who is Rune Aaslid?

A

Introduced the transcranial doppler for detecting blood flow in the basal intracerebral arteries.

It was a single gate spectral TCD.

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6
Q

Who is Mark Moehring?

A

He invented the transcranial power-motion Doppler (PMD) with 33 sampling gates.

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7
Q

What are the advantages that PMD or M-mode Doppler had?

A

It had the advantage of simultaneously displaying the intensity and direction of intracranial blood flow with over 6 cm or more of intracranial space.

Simplified the examination technique

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8
Q

What was TCD intially introduced for?

A

Detecting the vasospasm following a subarachnoid hemorrhage.

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9
Q

What is the TCD now used/known for?

A

TCD has emerged as a noninvasive and cost effective tool for evaulating cerebral arterial patency, detecting stenosis, collateral flow patterns, and embolization.

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10
Q

TCD is known to ______ the rates of arterial recanalization.

A

Enhance

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11
Q

What is the only diagnostic tool available that provides real-time information about the cerebral hemodynamics over extended periods of monitoring, as well as detects embolization to cerebral vessels?

A

TCD

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12
Q

What can be done in the setting of an acute ischemic stroke?

A

A combination of TCD and cervical duplex US can evaluate the cerebral hemodynamics consequences of an extracranial carotid stenosis and help in identifying the lesion amendable for interventional therapy

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13
Q

How does TCD compare to CTA?

A

TCD demonstrated 79% sensitivity and 94% specificity in detecting intracranial stenosis.

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14
Q

What are TCD findings complementary to?

A

They are complementary to CTA in:

  • Detecting real time embolization
  • Various collateral flow patterns due to prox. stenosis
  • Detecting alternating flow signals in the posterior circulation→suggestve of the steal phenomenon.
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15
Q

What does alternating flow in the posteror circulation suggest?

A

It is suggestive of the steal phenomenon.

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16
Q

What are some of the important and established applications of TCD?

A
  • Detection of right-to-left shunt
  • Cerebral vasomotor reactivity
  • Monitoring flow velocities for stroke prevention in sickle cell dis.
  • Supplementary diagnostic test for the confirmation of brain death
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17
Q

Continuous TCD monitoring during systemic thrombolysis is known to do what?

A

Enhance the rates of clot dissolution in acute ischemic stroke.

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18
Q

Current diagnostic ultrasound systems are based on what?

A

Pulse-echo technique.

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19
Q

What is the difference between the transmitted and the refected sound frequencies called?

A

Doppler shift.

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20
Q

What does the doppler shift enable?

A

It enables the detection of tissue motion and blood flow.

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21
Q

The complex signals resulting from the reflections of moving RBC are broken into indivual velocities by a method called_______.

A

Fast Fourier Transform

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22
Q

What is the angle of insonation in TCD?

A

0°

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23
Q

What is the biggest hurdle in order to obtain acoustic information from the intracranial space is what?

A

The skull bone.

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24
Q

How much does the skull bone attenuate?

A

About 90% of the ultrasound wave.

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25
Q

What is doppler sonography?

A

It is obtaining information regarding tissue motion and blood flow velcoties only, without structural imaging.

26
Q

When tissue imaging is combined with flow velocities, the process is called________.

A

Duplex sonography.

27
Q

What does TCCD stand for?

A

Transcradial color-coded doppler.

28
Q

What time of tranducer is used for TCCD?

A

a 2MHz Phased-array transducer is used

29
Q

What are the pro’s and con’s to TCCD?

A

PRO: Provides parenchymal imaging with a structural flow map of cerebal vessles

CONS: Fewer successful examinations can be done, especially with elderly with insufficent temporal acoustic bone windows.

30
Q

What are con’s of the single gate TCD developed by Rune Aaslid?

A
  • Could only obtain informaation from a small volume of intrancranial space.
    • this limitation led to difficulaties in evaluating the information gathered from multiple points.
      • Made it “operator-dependent”
31
Q

How did Moehring’s PMD revolutionize the application of TCD?

A

Systems simultaneously displayed flow intensity and direction, over 6 cm or more of intracranial space.

Made possible by using 33 overlapping sample gates

32
Q

What does the circle of Willis provide?

A

It provides an important communication between the anterior and posterior circulatory systems.

33
Q

Where does the ICA enter the cranial cavity?

A

Through the foramen lacerum.

It divides into the anterior and middle cerebral arteries,

34
Q

The ACA are connected to eachother by what?

A

Anterior communicating artery.

35
Q

Posteriorly, the right and left vertebrals join to form the _______

A

Basilar artery

36
Q

Where does the basilar artery run?

A

It runs along the ventral surface of the pons and terminates by dividing into the right and left posterior cerebral arteries.

37
Q

The ICA on either side if connected with the PCA’s by the_________.

A

Posterior communicating arteries.

38
Q

What is the circle of Willis?

A

It is a natural collateral conduit through which blood gets diverted in case of proximal vessel occlusion.

39
Q

In some areas on the skull, the bones are relatively thinner and permit sufficient penetration of ultrasound….what are these areas called?

A

Acoustic windows.

40
Q

What are the 4 common acoustic windows?

A
  1. Temporal
  2. Orbital
  3. Suboccipital
  4. Submandibular
41
Q

What flow velocities can be obtained through the transtemporal window?

A
  • MCA
  • ACA
  • PCA
  • PCOM
42
Q

What can be insonated throught the transorbital window?

A
  • Opthamalic artery
  • ICA
43
Q

What can be insonated in the in the suboccipital window?

A
  • VA
  • BA
44
Q

Where can the BA be insonated?

A

The subocciptal and transforaminal

45
Q

The submandibular approach approach is emplyed to evaluate the what?

A

The distal ICA in order to evaulate vasospasm in patients with subarachnoid hemorrhage.

46
Q

How are intracranial arteries indentified?

A

Depth, direction of blood flow, and the Doppler spectra.

47
Q

What does a red color signal indicate?

A

Flow towards the probe.

48
Q

Red signal between 40 and 65 mm represents the flow in the ______

A

Ipsilateral MCA

49
Q

What does blue signal indicates what?

A

Flow away from the probe.

50
Q

What does a blue signal between 65 and 80 mm represents?

A

It represents the flow from the ipsilateral ACA

51
Q

In favorable patients, a red signal may be noted beyond ______ which represents_______.

A
  • 80 mm
  • Represents flow in the contralateral A1 ACA
52
Q

The power output is reduced to_____ when the transorbital acoustic window is employed.

A

10%

53
Q

Flow signals at a depth of less than 60 mm, with a high resistance pattern and towards the probe represents what?

A

Opthamalic artery

54
Q

In order to obtain the ICA siphon, how should you move?

A

Sample volume has to be moved beyond a 60 mm depth.

55
Q

How is flow in the ICA Siphon?

A

The flow signals may be directed towards or away form the probe since its a curved artery

56
Q

How does the sample volume compare to the diameter of the intracranial arteries?

A

The SV is usually large in reference to the diameter of the intracranial arteries

57
Q

What does a normal spectral waveform look like?

A

It shows a sharp systolic upstroke and stepwise deceleration with positive end-diastolic.

58
Q

What is the PSV?

A

This is the first peak on the TCD waveform from each cardiac cycle.

A rapid upstroke represents the absence of a severe stentoic lesion between the insonated intracranial arterial segments.

59
Q

What is the EDV?

A

EDV lies between 20 and 50% of the PSV values, indicating a low resistance intracranial arterial flow pattern.

60
Q

How is the MFV calculated?

A

It is claculated as EDV plus 1/3 of the difference between PSV and EDV.

61
Q

Who should have the highest MFV?

A

The MCA should have the highest MFV among all major intracranial arteries.

62
Q

the spectrum is commonly seen where?

A

distal steno-occlusive lesion,

TCD (5 decks)

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