What is the usual operating frequency of handheld TCD instrumentation?

The usual operating frequency of handheld Transcranial Doppler (TCD) instrumentation is 2 MHz. This frequency is chosen because it strikes a balance between adequate penetration and resolution when performing ultrasound examinations of the cranial blood vessels. At 2 MHz, the ultrasound waves can effectively travel through the skull, allowing for the assessment of blood flow velocities in the intracranial arteries. This frequency also minimizes attenuation, which can be an issue with higher frequencies, while still providing sufficient detail for clinical diagnostics.

Lower frequencies, such as 1 MHz, may not provide the necessary resolution to differentiate between various blood flow pathways, while higher frequencies, like 3 MHz and 4 MHz, could face difficulties penetrating the bone of the skull effectively, leading to compromised imaging quality or limits in detection depth. Hence, 2 MHz is the optimal choice for handheld TCD devices, allowing clinicians to obtain reliable and accurate measurements of cerebral blood flow.