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CNIH > Transcranial Doppler > Flashcards

Transcranial Doppler Flashcards

1
Q

What is a transcranial doppler and what is evaluated?

A
  • Noninvasive method for assessing cerebral hemodynamics

- Evaluating intracranial cerebrovascular diseases

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2
Q

what is used in a transcranial doppler?

A
  • power doppler
  • duplex sonography
  • contrast agents
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3
Q

TCD applications require?

  • signal to noise?
  • bandwidth?
  • sample volume?
A
  • large signal- to - noise ratio
  • lower bandwidth
  • larger less defined sample volume
  • 2MHz
  • adjustable doppler gate depth
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4
Q

TCD transmitting power?

A

10 and 100 mW/cm/sec

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5
Q

TCD focusing of beam?

A

40-60mm from probe

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6
Q

Indications for TCD? (7)

A
  1. Detection of intracranial stenosis and occlusions in the major arteries
  2. Evaluation of intracranial hemodynamics and collateral flow where there is extracranial disease
  3. Monitoring of intracranial vessel recanalization in acute stroke
  4. Monitoring intracranial hemodynamics after:
    - Hemorrhage
    - Endarterectomy/angioplasty
  5. Detection of right to left shunts
  6. Detection of cerebral microemboli
  7. During functional tests:
    - Stimulation with vasoconstrictive drugs
    - External stimulation of visual cortex
    - Before neurosurgery
    - During open heart surgery
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7
Q

Nomenclature?

A
  • developed for describing the segments of the intracranial cerebral arteries
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8
Q

Nomenclature: ACA?

A
  • 2 segments

- A1 and A2

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9
Q

Nomenclature: Carotid siphon (just proximal to ICA intracranial branches)

A
  • has 3 segments

- C1, C2 and C3

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10
Q

Nomenclature opthalmic artery

A

Ophthalmic artery branches at the junction of C2 and C3

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11
Q

Nomenclature: MCA?

A

2 segments: M1 andM2

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12
Q

Nomenclature: PCA?

A

2 segments: P1 and P2

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13
Q

Segments labelled 1 are closest to?

A

midline of the brain

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14
Q

4 Ultrasonic Windows?

A

Temporal approach
Orbital
Submandibular
Suboccipital

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15
Q

Submandibular Approach?

- where is the probe directed?

A
  • The probe is directed upward toward the proximal intracranial ICA
  • Window is located below the mandible at the angle-using the carotid triangle
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16
Q

Suboccipital Approach?

A
  • Patient is positioned lying on their left side , with back toward you
  • Head must be tucked in at the chin toward the chest
  • Probe is placed at the base of the skull and directed upward into the foramen
17
Q

Transorbital Approach?

A
  • Carotid siphon and Opthalmic artery

- Probe is directed toward the orb to locate the OA, then followed to the carotid siphon-distal intracranial ICA

18
Q

Transtemporal Approach?

A
  • Probe is placed on temporal aspect of head with patient in supine position
  • Cephalad to zygomatic arch
  • Immediately anterior and slightly superior to tragus of ear
  • Position 1 of the image is most often adequate as a window
  • Position 2 and 3,less often available as windows
19
Q

Transtemporal Approach?

A
  • Probe is placed on temporal aspect of head with patient in supine position
  • Cephalad to zygomatic arch
  • Immediately anterior and slightly superior to tragus of ear
  • Position 1 of the image is most often adequate as a window
  • Position 2 and 3,less often available as windows
20
Q

Transtemporal approach: anterior orientation?

A
  • visualizes- M1and M2 segments of MCAS
  • C1 segment of carotid siphon(CS)
  • A1 segment of ACA & anterior communicating artery
21
Q

Transtemporal approach: Posteriorly angulated beam?

A
  • insonates-P1 and P2 segments of PCA

- Top of the basilar artery and the posterior communicating arteries

22
Q

Suboccipital-transforaminal approach essential for screening?

A

Essential for screening distal vertebral arteries (V4 segment) and the Basilar artery throughout its entire length

23
Q

Suboccipital-transforaminal approach probe and patient location?

A
  • Probe is placed between the posterior margin of the foramen magnum and the spinous process of C1 vertebra
  • Patient is lying on their side with the head tucked into the chest
  • This opens up the window through the foramen magnum
  • The beam is aimed at the bridge of the nose
  • Elderly individuals or arthritic necks pose a difficulty
24
Q

Transorbital approach?

A
  • The opthalmic artery can be insonated as well as components of the anterior cerebral circulation
  • Not used as much as the transtemporal and suboccipital approach
25
Q

Submandibular approach?

A
  • Useful compliment to extracranial studies
  • Probe is placed in the retromandibular area
  • Useful for detecting carotid dissection-and chronic ICA occlusion with collaterals
26
Q

Typical TCD Depths (mm) transtemporal approach?

  • MCA
  • ACA
  • carotid siphon
  • PCA
  • Basilar
A 
MCA- 50mm 
ACA-70
Carotid siphon-65
PCA-65-70
Basilar- 75
27
Q

Typical TCD velocities trastemporal approach?

  • MCA
  • ACA
  • Carotid siphon
  • PCA
  • Basilar
A 
MCA-55
ACA-50 
Carotid siphon-39
PCA-40
Basilar-40
28
Q

How to identify cerebral arteries?

A
  • Insonation depth
  • Direction of flow at insonation depth
  • Flow velocity (mean flow velocity and systolic or diastolic peak flow velocity)
  • Probe position ie- what window is being used
  • Direction of the ultrasonic beam ie-posterior,anterior,sub-occipital,submandibular
  • Traceability of vessels
  • Low resistant flow spectrum similar to ICA flow
29
Q

How to start TCD exam?

A
  • Start with the transtemporal approach
  • Identify the midline of the brain
  • If the midline is not visible, then the exam may be futile
  • Once it is identified, turn on the color
  • The MCA is identified on either side of the midline at a depth of 50-55 mm
  • Track the ipsilateral arterial network,by angling he probe anteriorly toward the ACA and then posteriorly toward the PCA
30
Q

The MCA is identified on either side of the midline at what depth?

A

50-55mm

31
Q

What does traceability refer to?

A

the fact the MCA and the other arteries can be tracked in incremental steps from a more shallow insonation depth (35mm) to deeper sites (55mm)

31
Q

What does traceability refer to?

A

the fact the MCA and the other arteries can be tracked in incremental steps from a more shallow insonation depth (35mm) to deeper sites (55mm)

32
Q

MCA flow direction?

A

Flow is normally toward the probe as the MCA flows out toward the cerebrum

33
Q

When tracking the MCA medially (65-70mm depth), an abrupt change in flow direction away from the probe indicates?

A

Insonation of A1 segment

34
Q

Flow signals toward the probe at this depth usually emanate from the?

A
  • carotid siphon at its junction with MCA
34
Q

Flow signals toward the probe at this depth usually emanate from the?

A
  • carotid siphon at its junction with MCA
35
Q

By angling the beam more posteriorly from this transtemporal approach what can be picked up at 65-70mm?

A

P1 segment of the PCA

CNIH (69 decks)

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