Middle cerebral artery blood flows by combining TCD velocities and MRA diameters: in vitro and in vivo validations.

Non-invasive transcranial Doppler (TCD) is widely used for blood velocity (BV, cm/sec) measurements in the human middle cerebral artery (MCA). MCABV measurements are accepted as linear with MCA blood flow (MCABF). Magnetic resonance angiography (MRA) provides measurements of MCA lumen diameters that can be combined with TCD MCABV to calculate MCABF (mL/min). We tested the precision and accuracy of this method against a flow phantom and in vivo proximal internal carotid artery blood flow (ICABF). In vitro precision (repeated measures) and accuracy (vs. time collection) gave correlations coefficients of 0.97 and 0.98, respectively (both p < 0.05). In vivo precision (repeated measures) and accuracy (vs. ICABF) gave correlation coefficients of 0.90 (left and right), 0.94 (left) and 0.93 (right) (all p < 0.05). Bilateral MCABF in 35 adults were similar (left, 168 ± 72 mL/min; right, 180 ± 69 mL/min; p > 0.05). Results suggest that blood velocity by TCD and lumen diameter by MRA can be combined to estimate absolute values of MCABF.

Middle cerebral artery resistivity and pulsatility indices in systemic lupus erythematosus: evidence for hyperperfusion.

BACKGROUND AND PURPOSE: Systemic lupus erythematosus (SLE) is associated with significant cerebrovascular and neuropsychiatric disease for which multiple pathogeneses have been proposed. Although global cerebral hypoperfusion has been proposed, there are limited data about intracerebral arterial hemodynamics. Transcranial Doppler (TCD) allows portable, high temporal and spatial resolution, noninvasive blood velocity measurements in the middle cerebral arteries, and calculations of standard resistivity (RI) and pulsatility (PI) indices. RI and PI correlate with cerebral hemispheric arteriolar tone, blood flow resistances, and impedances. Accordingly, we hypothesized that there would be significant differences (p < 0.05) in RI and PI between SLE patients and healthy, age and gender matched controls. METHODS: TCD was used to measure RI and PI bilaterally on 34 stable SLE patients (35 ± 11 years) and 15 control subjects (34 ± 10 years). Patients and controls had similar, normal blood pressures and were examined in the supine position during normal, resting respiration. RI and PI were determined by a blinded, experienced observer. RESULTS: There were no significant differences in RI and PI bilaterally within each cohort. However, SLE patients had significantly lower average RI and PI values compared with controls: 0.45 ± 0.10 versus 0.52 ± 0.05 (p < 0.05); and 0.65 ± 0.19 versus 0.77 ± 0.12, (p < 0.05); respectively. CONCLUSIONS: These preliminary data suggest that RI and PI values in the human middle cerebral artery are significantly lower in SLE compared with controls. These indices indicate that middle cerebral arterial resistances and impedances are decreased in SLE. Under normotensive conditions, the results are consistent with hyperperfusion in SLE with increased arteriolar dilation and increased cerebral blood flow.