TCD Flashcards

1
Q

What is the formula for the Doppler shift (f)

A

f=2 fo v/c v=velocity of blood fo = frequency of emitted US wave c = velocity of emitted US wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the frequency of TCD probe

A

2 MHz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the avg error of MCA FV due to changes in angle of insonation?

A

Small, ~3%. The observed velocity varies between 0.87 and 1.0 of the true velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

TCD recorded velocity depends on what?

A

Cosine of the angle of insonation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the typical depth of insonation for MCA

A

5 - 6 cm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the units for FV and CBF?

A

FV = cm/s CBF = ml/100g/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is the correlation between FV and CBF? What assumptions are required?

A

Poor in absolute terms, however, they should vary in the same direction. Assumption: MCA diameter is constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the ‘normal’ range of MCA FV?

A

35 - 90 cm/sec

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What percentage of patients have poor temporal windows?

A

~5%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What arteries can be insonated through a transtemporal approach?

A

MCA, ACA, ICA bifurcation and PCA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the typical depth of the ICA bifurcation

A

60 - 65 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the approximate insonation depth of M1?

A

45 - 55 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When insonating, what anatomic structure can be confused with MCA FV?

A

PCA, but this cannot be insonated at depths less than 55 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the measured velocity parameters?

A

Peak systolic velocity (S), end-diastolic velocity (D), mean velocity (M) and pulsatility index (PI)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the pulsatility index (PI)?

A

PI = (S-D)/M

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is FVmean calculated?

17
Q

What velocity parameter is preferred?

18
Q

What leads to increased PI?

A
  1. Cerebral vasoconstriction
  2. Increased ICP
19
Q

Draw the relationship between FVmean, FVs and FVd over the range of CPP

20
Q

What will you observe with FV in the presence of intact and abnomal autoregulation?

A

Assessment of autoregulation using TCD depends on
the assumption that relative changes in FV correlate
with relative changes in CBF. Thus, if autoregulation
is intact, FV should remain constant with a changing
CPP. Conversely, if autoregulation has failed, then the
relation between CPP and FV becomes linear

21
Q

Draw the relationship between PI and CPP

22
Q

What is a better correlated with CPP, FV or PI? Why?

A

PI, because it is independent of the mechanism of CPP (ICP or decreased MAP)

23
Q

What is the relationship between FV blood flow volume and vessel diameter?

A

FV = blood flor volume / diameter

24
Q

What is the Lindegaard index or ratio?

A

MCA FV / ICA FV

1) < 3: normal
2) 3 - 6 mild - moderate
3) >6 severe