Relationship between refill-kinetics of ultrasound perfusion imaging and vascular obstruction in acute middle cerebral artery stroke

Background

Ultrasound perfusion imaging (UPI) with bolus kinetic has been shown to be feasible at bedside for evaluation of perfusion deficits in stroke patients. Recent technical advances allow perfusion imaging with refill kinetics using a low mechanical index.

Methods

We examined 31 acute middle cerebral artery (MCA) stroke patients with transcranial color-coded duplex ultrasound (TCCD) and UPI. The refill of microbubbles was calculated from regions of interest in the ischemic area and the contralateral MCA territory by using the exponential function y = A(1 − e^βt); A = acoustic intensity of the plateau (dB), β = slope (1/s).

Results

We found significantly lower values of β in the ischemic area compared with the contralateral MCA territory (0.75 vs. 1.05 1/s, p < 0.05); particularly in patients with a pathological MCA flow pattern on TCCD (0.61 vs. 1.01, p < 0.01). There was a high interindividual variance without significant difference of the plateau of acoustic intensity (A) in any subgroup of patients.

Discussion

The slope parameter β of refill kinetics is useful for assessing brain perfusion in patients with acute stroke and pathological flow pattern of the ipsilateral MCA. The parameter A, however, seems more dependent from the quality of the temporal bone window.