Comparison between magnetic resonance phase contrast imaging and transcranial Doppler ultrasound with regard to blood flow velocity in intracranial arteries: Work in progress

Objective. The authors evaluate blood flow velocities in the medial cerebra l artery (MCA) and the basilar artery using magnetic resonance (MR) phase c ontrast technique in comparison with transcranial Doppler ultrasound (TCD). Eleven healthy male volunteers were studied. TCD of the MCA (n = 22) and b asilar artery (n = 11)was performed. MR phase velocity mapping was done in each vessel at the same location where the TCD signal had been acquired. A 2-dimensional FLASH sequence with retrospective cardiac gating and an avera ge temporal resolution of 45 ms was used. Resistance indices (Rls) and puls atility indices (Pls) were calculated for both modalities. The TCD insonati on angle was measured retrospectively with MR, and TCD velocities were corr ected based on these measurements. The comparison of flow velocities obtain ed with TCD and MR led to a low correlation coefficient with regard to the basilar artery and the MCA: maximum systolic velocity, r = 0.02 and r = 0.5 0, respectively; enddiastolic velocity, r = 0.47 and r = 0.65, respectively ; mean velocity, r = 0.52 and r = 0.66, respectively. The average Pls in th e basilar artery and the MCA were 0.80 and 0.81 with MR and 0.65 and 0.85 w ith TCD, respectively. The average Rls in the basilar artery and the MCA we re 0.52 and 0.54 with MR and 0.52 and 0.55 with TCD, respectively. The TCD insonation angle differed significantly from the ideal value in the basliar artery (mean value = 32.6 degrees) and the MCA (mean value = 26.5 degrees) . The authors find a low correlation between velocities measured with MRI a nd TCD but similar results with regard to the Pls and Rls. Several sources of error, such as a nonideal TCD insonation angle, were identified.