TCD Flashcards
Normal order of mean flow velocities in TCD?
MCA > ACA > siphon > PCA > BA > VA
If CHF, anemia, circulatory conditions, how do you determine MCA stenosis?
Use focal MFV difference of >30% between stenosis and adjacent arterial segments.
Criteria for indirect flow disturbance in MCA?
- turbulence distal
- compensatory flow diversion via ACA
- low frequency noise
- distal MCA microembolic signals
According to Alexandrov, a proximal MCA stenosis of >70% will produce a stenotic/prestenotic PSV ratio of ??
3:1 or greater.
blunting
slow systolic upstroke, slow diastolic downstroke, low velocities, reduction of MCA MFV less than ACA or any other intracranial arteries.
MCA stenosis/near occlusion is often accompanied by what?
flow diversion to ACA.
For DOPPLER, sample volume corresponds to what?
the “time that the machine is listening” to the blood. Tegeler says it corresponds to the “gate”.
Alexandrov: when should you suspect intracranial stenosis?
- normal hierarchy of flow velocity is DISRUPTED by MFV > 20% between arteries; 2. focal velocity increase
Lindegaard ratio?
MFV (MCA) / MFV (ICA) (ipsilateral)
> 80 cm/s and LR 3-4?
Hyperemia + possible mild spasm
> 120 cm/s and LR 3-4?
Hyperemia + mild spasm
> 120 cm/s and LR 4-5?
Hyperemia + moderate spasm
> 120 cm/s and LR 5-6?
Moderate spasm
> 180 cm/s and LR =6
mod-severe spasm
> 200 cm/s and LR>6
severe spasm
> 200 cm/s and LR 4-6?
Hyperemia + moderate spasm
> 200 cm/s and LR 3-4?
Hyperemia + mild spasm
> 200 cm/s and LR
Hyperemia
PI formula + meaning
PI = (PSV-EDV) / MFV
Means the velocity change as proportion of mean velocity.
OA angle of insonation
15 degrees.
How do you reduce aliasing?
“drop the baseline”; reduce sample volume; increase scale (scale = 1/2 * PRF); decrease the depth (increase PRF and therefore the Nyquist limit)
M2 depth, direction, velocity?
30-45 mm;
M1 depth, direction, velocity?
45-65 mm; towards;
A1 depth, direction, velocity?
62-75 mm; away;
A2 depth, direction, velocity?
45-65 mm; TOWARDS;
ICA siphon depth, direction, velocity?
60-64 mm; BIDIRECTIONAL;
OA depth, direction, velocity?
50-62 mm; towards; variable velocity
PCA depth, direction, velocity?
60-68 mm; BIDIRECTIONAL;
BA depth, direction, velocity?
80-100+mm; away;
VA depth, direction, velocity?
45-80 mm; away;
Manual MFV calculation?
MFV = (PSV + 2*EDV) / 3
STOP criteria?
TAMM (time-averaged mean of maximum) velocity > 200 cm/s in MCA and/or ICA. Child w 2 or more TAMM>200 exams should be offered exchange transfusion.
typical findings in Doppler for subclavian steal?
Systolic flow reversal in VA + low-resistance flow in SCA.
