Diagnostic ultrasound ( PDFDrive )

CHAPTER 47 Doppler Sonography of the Brain in Children 1593
A
B
Left MCA
C
FIG. 47.1 Temporal Window. (A) Transtemporal transcranial
Doppler (TCD) sonogram with normal landmarks. Note the heartshaped
cerebral peduncles with the echogenic suprasellar cistern.
Anteriorly and laterally from this basilar cistern is the echogenic
issure for the middle cerebral artery (MCA, arrow). (B) Transtemporal
color low Doppler sonogram shows the circle of Willis
anterior to the landmark of the heart-shaped cerebral peduncles.
Flow directed toward the transducer (red) is the MCA in the
middle cerebral issure just anterior to the cerebral peduncles.
Flow in the anterior cerebral artery (ACA) on that side (blue) is
away from the transducer. Flow is also seen in the MCA on the
opposite side (blue) as it courses away from the transducer. (C)
Normal spectral Doppler ultrasound waveform in the right MCA
with low directed toward transducer. The posterior cerebral arteries
(PCAs) are coursing around the cerebral peduncles.
low toward the transducer is coded red and above the baseline,
whereas low away from the transducer is coded blue and below
the baseline). A large sample volume (4-6 mm) allows for good
signal to noise ratio. Velocities, such as peak systolic velocity
(PSV), end diastolic velocity (EDV), and mean low velocity,
and indices relecting vascular resistance including pulsatility
index and resistive index are evaluated.
On spectral analysis of the waveform, the maximum, minimum,
and mean velocities can be measured in centimeters per second.
It is important to remember which velocity measures are used
for various applications. For the STOP study assessing stroke
risk in the sickle cell population, the time-averaged mean of
the maximum (TAMM) velocity is followed, and is sometimes
called the time-averaged peak velocity. his is not the same
value as the mean velocity. PSV is the value followed for vasospasm.
Terminology of the various mean and TAMM velocities
can be vendor speciic and need to be clariied dependent on
the application TCD is being used for. At least two tracings
should be made for each vessel. he highest velocity obtained
is likely the most accurate, because it is believed to be the velocity
obtained at the best insonating angle to the vessel. 19
Angle correction cannot be performed with the nonimaging
technique, and a 0-degree angle is assumed. Although angle
correction is possible with the imaging technique because of
visualization of the vessel course, published velocities typically
have not been angle-corrected. In clinical applications such as