Blood flow velocity using transcranial Doppler velocimetry in the middle and anterior cerebral arteries: correlation with sample volume depth.

The baseline transcranial Doppler studies of the middle (MCA) and anterior cerebral (ACA) arteries of 135 patients were retrospectively reviewed. 3312 data points were classified according to gender, vessel, mean blood flow velocity (MBFV), systolic blood flow velocity (SBFV), diastolic blood flow velocity (DBFV) and sample volume depth (SVD). The flow velocities at each depth were averaged, and plotted against acquisition depth. The male MCA yielded a correlation coefficient (r), between MBFV and SVD of 0.999. For the female MCA, r = 0.986. For the ACA, male, r = 0.911, and female, r = 0.894. All other data showed r values >/= 0.563, with 11 of 12 r values >/= 0.808. These data suggest that BFV reduces with SVD in a highly predictable way for the MCA and ACA, from which expected BFV values may be estimated at any given SVD.