Article

Question 1

How has TCD evolved?

Answer 1

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

Question 2

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

Answer 2

TCD

Question 3

What is TCD?

Answer 3

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.

Question 4

What are some advanced applications of TCD?

Answer 4

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

Question 5

Who is Rune Aaslid?

Answer 5

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

It was a single gate spectral TCD.

Question 6

Who is Mark Moehring?

Answer 6

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

Question 7

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

Answer 7

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

Question 8

What was TCD intially introduced for?

Answer 8

Detecting the vasospasm following a subarachnoid hemorrhage.

Question 9

What is the TCD now used/known for?

Answer 9

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

Question 10

TCD is known to ______ the rates of arterial recanalization.

Answer 10

Enhance

Question 11

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?

Answer 11

TCD

Question 12

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

Answer 12

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

Question 13

How does TCD compare to CTA?

Answer 13

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

Question 14

What are TCD findings complementary to?

Answer 14

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.

Question 15

What does alternating flow in the posteror circulation suggest?

Answer 15

It is suggestive of the steal phenomenon.

Question 16

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

Answer 16

• 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

Question 17

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

Answer 17

Enhance the rates of clot dissolution in acute ischemic stroke.

Question 18

Current diagnostic ultrasound systems are based on what?

Answer 18

Pulse-echo technique.

Question 19

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

Answer 19

Doppler shift.

Question 20

What does the doppler shift enable?

Answer 20

It enables the detection of tissue motion and blood flow.

Question 21

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

Answer 21

Fast Fourier Transform

Question 22

What is the angle of insonation in TCD?

Answer 22

0°

Question 23

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

Answer 23

The skull bone.

Question 24

How much does the skull bone attenuate?

Answer 24

About 90% of the ultrasound wave.

Question 25

What is doppler sonography?

Answer 25

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

Question 26

When tissue imaging is combined with flow velocities, the process is called\_\_\_\_\_\_\_\_.

Answer 26

Duplex sonography.

Question 27

What does TCCD stand for?

Answer 27

Transcradial color-coded doppler.

Question 28

What time of tranducer is used for TCCD?

Answer 28

a 2MHz Phased-array transducer is used

Question 29

What are the pro's and con's to TCCD?

Answer 29

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.

Question 30

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

Answer 30

* 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"

Question 31

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

Answer 31

Systems simultaneously displayed flow intensity and direction, over 6 cm or more of intracranial space. ## Footnote **Made possible by using 33 overlapping sample gates**

Question 32

What does the circle of Willis provide?

Answer 32

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

Question 33

Where does the ICA enter the cranial cavity?

Answer 33

Through the foramen lacerum. ## Footnote **It divides into the anterior and middle cerebral arteries,**

Question 34

The ACA are connected to eachother by what?

Answer 34

Anterior communicating artery.

Question 35

Posteriorly, the right and left vertebrals join to form the \_\_\_\_\_\_\_

Answer 35

Basilar artery

Question 36

Where does the basilar artery run?

Answer 36

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

Question 37

The ICA on either side if connected with the PCA's by the\_\_\_\_\_\_\_\_\_.

Answer 37

Posterior communicating arteries.

Question 38

What is the circle of Willis?

Answer 38

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

Question 39

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

Answer 39

Acoustic windows.

Question 40

What are the 4 common acoustic windows?

Answer 40

1. Temporal 2. Orbital 3. Suboccipital 4. Submandibular

Question 41

What flow velocities can be obtained through the transtemporal window?

Answer 41

* MCA * ACA * PCA * PCOM

Question 42

What can be insonated throught the transorbital window?

Answer 42

* Opthamalic artery * ICA

Question 43

What can be insonated in the in the suboccipital window?

Answer 43

* VA * BA

Question 44

Where can the BA be insonated?

Answer 44

The subocciptal and transforaminal

Question 45

The submandibular approach approach is emplyed to evaluate the what?

Answer 45

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

Question 46

How are intracranial arteries indentified?

Answer 46

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

Question 47

What does a red color signal indicate?

Answer 47

Flow towards the probe.

Question 48

Red signal between 40 and 65 mm represents the flow in the \_\_\_\_\_\_

Answer 48

Ipsilateral MCA

Question 49

What does blue signal indicates what?

Answer 49

Flow away from the probe.

Question 50

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

Answer 50

It represents the flow from the ipsilateral ACA

Question 51

In favorable patients, a red signal may be noted beyond ______ which represents\_\_\_\_\_\_\_.

Answer 51

* 80 mm * Represents flow in the contralateral A1 ACA

Question 52

The power output is reduced to\_\_\_\_\_ when the transorbital acoustic window is employed.

Answer 52

10%

Question 53

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

Answer 53

Opthamalic artery

Question 54

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

Answer 54

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

Question 55

How is flow in the ICA Siphon?

Answer 55

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

Question 56

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

Answer 56

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

Question 57

What does a normal spectral waveform look like?

Answer 57

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

Question 58

What is the PSV?

Answer 58

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.

Question 59

What is the EDV?

Answer 59

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

Question 60

How is the MFV calculated?

Answer 60

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

Question 61

Who should have the highest MFV?

Answer 61

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

Question 62

the spectrum is commonly seen where?

Answer 62

distal steno-occlusive lesion,