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Transcranial Doppler Ultrasonography

Identifying Patients at Risk for Stroke

Regular transfusion therapy can prevent stroke in children with sickle cell disease (SCD). Thus, identifying patients most likely to experience a stroke is an important aspect of care. The increased risk of stroke in children with SCD is due primarily to the progressive occlusion of large intracranial arteries.1,2

What is Transcranial Doppler Ultrasonography?

Transcranial Doppler (TCD) ultrasonography is a non-invasive diagnostic tool that allows for indirect real-time evaluation of intracranial cerebral circulation.1,2 It is used to measure abnormal blood flow velocity in large intracranial arteries, which can help to predict stroke risk in children (Table).3,4

Table. Stroke risk and blood flow velocity in children with SCD

TAMMV, cm/s Stroke risk
< 170 Normal
170-199 Borderline
≥ 200 Abnormal

TAMMV = time-averaged mean of the maximum velocity.

Advantages of TCD Ultrasonography

TCD ultrasonography is safe, inexpensive, and reliable compared with other techniques. It can be repeated multiple times and can be used for continuous monitoring if needed.3

How TCD Ultrasonography Works

TCD ultrasonography uses an ultrasonic beam (2 MHz frequency) produced from piezo-electric crystals that have been stimulated electrically.1,2 The ultrasonic beam bounces off erythrocytes within an artery. The reflected signal is received by a transducer and converted to an electric signal. This information is subtracted from the transmitted signal and processed to obtain a waveform (Figure).3

TC Ultrasonography Recording from the Middle Cerebral Artery

Figure. Typical TCD ultrasonography recording from the middle cerebral artery (MCA).6

The velocity scale is shown on the left.

Reproduced from McCarville MB, et al. AJR. 2004;183:1117-22 © American Roentgen Ray Society.

The waveform allows accurate determination of blood flow velocities, flow direction, and addition of calculated parameters, such as pulsatility index (PI). PI is a reliable marker of resistance distal to the site being evaluated. The calculated blood flow velocities can be used to predict stroke risk.3

Predictive Value of TCD Ultrasonography

The predictive value of TCD ultrasonography correlates well with findings from magnetic resonance angiography (MRA), which is often used to study blood flow in children with SCD.6,7

Color TCD ultrasonography adds further information, allowing visualization of arteries and angle-corrected blood velocity measurement.8

Guidelines for Screening with TCD Ultrasonography

Regular screening with TCD ultrasonography is recommended in the USA and UK for patients aged > 2 years.1,9

For further information about TCD:

Learn more about TCD ultrasonography >


  1. National Institutes of Health (NIH). NIH publication 02-2117. 2002. Available at: Accessed April 2014.
  2. Schnog JB, et al. Neth J Med. 2004;62:364-74.
  3. Kassab MY, et al. J Am Board Fam Med. 2007;20:65-71.
  4. Adams RJ, et al. Ann Neurol. 1997;42:699-704.
  5. McCarville MB, et al. AJR Am J Roentgenol. 2004;183:1117-22.
  6. Adams R, et al. N Engl J Med. 1992;326:605-10.
  7. Sickle Cell Society. Standards for the Clinical Care of Adults with Sickle Cell Disease in the UK. 2008.
  8. Krejza J, et al. AJR;174 :1297-1303.
  9. National Health Service (NHS). Transcranial Doppler Scanning for Children with Sickle Cell Disease. 2009.

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