What angle is typically assumed during a transcranial Doppler exam?

During a transcranial Doppler (TCD) exam, the angle that is typically assumed is 0 degrees. This angle refers to the alignment of the ultrasound beam parallel to the direction of blood flow. Achieving a 0-degree angle is crucial because it allows for the most accurate measurements of blood flow velocities. Doppler ultrasound relies on the angle of incidence between the ultrasound beam and the flow of blood to provide precise velocity calculations; a 0-degree angle maximizes the Doppler effect, ensuring that the measured velocities reflect true blood flow rates without distortion that can occur at other angles.

In this context, other angles such as 30 degrees, 45 degrees, or 90 degrees would not provide the same accuracy due to the geometric relationships affecting the Doppler signal and the potential for underestimating or overestimating blood flow velocities.