Transcranial Doppler

Question 1

What is a transcranial doppler and what is evaluated?

Answer 1

• Noninvasive method for assessing cerebral hemodynamics

- Evaluating intracranial cerebrovascular diseases

Question 2

what is used in a transcranial doppler?

Answer 2

• power doppler
• duplex sonography
• contrast agents

Question 3

TCD applications require?

• signal to noise?
• bandwidth?
• sample volume?

Answer 3

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

Question 4

TCD transmitting power?

Answer 4

10 and 100 mW/cm/sec

Question 5

TCD focusing of beam?

Answer 5

40-60mm from probe

Question 6

Indications for TCD? (7)

Answer 6

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

Question 7

Nomenclature?

Answer 7

• developed for describing the segments of the intracranial cerebral arteries

Question 8

Nomenclature: ACA?

Answer 8

• 2 segments

- A1 and A2

Question 9

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

Answer 9

• has 3 segments

- C1, C2 and C3

Question 10

Nomenclature opthalmic artery

Answer 10

Ophthalmic artery branches at the junction of C2 and C3

Question 11

Nomenclature: MCA?

Answer 11

2 segments: M1 andM2

Question 12

Nomenclature: PCA?

Answer 12

2 segments: P1 and P2

Question 13

Segments labelled 1 are closest to?

Answer 13

midline of the brain

Question 14

4 Ultrasonic Windows?

Answer 14

Temporal approach
Orbital
Submandibular
Suboccipital

Question 15

Submandibular Approach?

- where is the probe directed?

Answer 15

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

Question 16

Suboccipital Approach?

Answer 16

• 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

Question 17

Transorbital Approach?

Answer 17

• Carotid siphon and Opthalmic artery

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

Question 18

Transtemporal Approach?

Answer 18

• 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

Question 19

Transtemporal Approach?

Answer 19

• 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

Question 20

Transtemporal approach: anterior orientation?

Answer 20

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

Question 21

Transtemporal approach: Posteriorly angulated beam?

Answer 21

• insonates-P1 and P2 segments of PCA

- Top of the basilar artery and the posterior communicating arteries

Question 22

Suboccipital-transforaminal approach essential for screening?

Answer 22

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

Question 23

Suboccipital-transforaminal approach probe and patient location?

Answer 23

• 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

Question 24

Transorbital approach?

Answer 24

• 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

Question 25

Submandibular approach?

Answer 25

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

Question 26

Typical TCD Depths (mm) transtemporal approach? - MCA - ACA - carotid siphon - PCA - Basilar

Answer 26

``` MCA- 50mm ACA-70 Carotid siphon-65 PCA-65-70 Basilar- 75 ```

Question 27

Typical TCD velocities trastemporal approach? - MCA - ACA - Carotid siphon - PCA - Basilar

Answer 27

``` MCA-55 ACA-50 Carotid siphon-39 PCA-40 Basilar-40 ```

Question 28

How to identify cerebral arteries?

Answer 28

- 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

Question 29

How to start TCD exam?

Answer 29

- 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

Question 30

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

Answer 30

50-55mm

Question 31

What does traceability refer to?

Answer 31

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)

Question 31

What does traceability refer to?

Answer 31

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)

Question 32

MCA flow direction?

Answer 32

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

Question 33

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

Answer 33

Insonation of A1 segment

Question 34

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

Answer 34

- carotid siphon at its junction with MCA

Question 34

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

Answer 34

- carotid siphon at its junction with MCA

Question 35

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

Answer 35

P1 segment of the PCA