Objective: To study the calculation of cerebral blood flow loss ratio after cerebral artery stenosis using the data obtained from transcranial Doppler sonography (TCD), by deducing regional cerebral blood flow loss index (rCBFLI).
Methods and results: The data of TCD performed in 31 cases of unilateral stenosis in the middle cerebral artery (MCA) were collected and analyzed for deducing the formula for calculating the MCA stenosis index (STI): STI=1 (Vm(0)/Vm(1)) x (PI(1)/PI(0)), where Vm(0) is the mean normal velocity of MCA blood flow (derived from the measurements in 908 normal subjects at varied ages receiving TCD) and Vm(1) the mean velocity at the stenosed MCA, and PI(0) and PI(1) stand for the pulsatility index before and after stenosis. The ratio of PI(1) to PI(0) is likely to be equivalent to the ratio of Q(1) to Q(0) (Q(0) and Q(1) represent the volume of blood flow in the MCA in normal condition and after stenosis, respectively), thus the equivalence can be extended as rCBFLI=(1 Q(1)/Q(0)) x 100%=(1 PI(1)/PI(0)) x 100%. rCBFLI after MCA stenosis was calculated in 31 cases accordingly, and by means of correlation analysis, we found positive correlation between rCBFLI and Vm(1) (r=0.76, P < 0.001) and between Vm(1) and STI (r=0.85, P < 0.001). In the same way, rCBFLI of 55 sides with MCA stenosis in 43 cases were analyzed, and positive correlation between rCBFLI and Vm (r=0.76, P < 0.001) and between rCBFLI and STI (r=0.83, P < 0.001) was found.
Conclusion: rCBFLI can be used to evaluate the degree of regional cerebral blood flow loss due to artery stenosis, and the combination of rCBFLI and STI may provide an insight into the changes of cerebral hemodynamics in this pathologic condition.