Fig. 1From: Transcranial Doppler ultrasonography (uses, limitations, and potentials): a review articleTranscranial insolation of anterior circulation. Power-mode multigated transcranial Doppler (TCD) employs 2 MHz ultrasound that penetrates the entire diameter of the skull (a). In an average adult skull, midline is believed to be at 75 mm. Thus, the flow signals obtained from beyond 75 mm are from contralateral arteries [6].Back to article page