Semiquantitative analysis of ultrasonic cerebral perfusion imaging

The bolus kinetic in ultrasonic cerebral perfusion imaging is the most favored data acquisition and processing technique. However, there has not yet been convincing evidence for the potential to (semi-) quantitatively describe perfusion. Aim of this study was to determine the intraindividual range of relevant perfusion parameters to describe individual physiological cutoff scores. In 20 healthy volunteers, cerebral perfusion was evaluated using the bilateral approach with phase inversion harmonic imaging and the bolus kinetic. Relevant parameters (time-to-peak intensity, TPI; peak width, PW) were derived in 14 regions-of-interest in both hemispheres. The median and quartile deviation (QD) of these values were individually calculated. Within the 20 individuals, the mean QD of TPI was 0.68 s, and there was no case in which any TPI exceeded the mean more than 2 s. With PW, the mean QD was 1.2 s, and the mean was not exceeded by more than 6 s. Intraindividual perfusion parameters, especially TPI, show a considerable small range. Thus, the bolus kinetic derives reliable semiquantitative information once intraindividual comparison can be accomplished. We therefore propose that bilateral examination with the unaffected hemisphere as referential region should be performed in acute stroke. Future studies have to evaluate the potential of this approach of discriminating ischemia and hypoperfusion in the affected hemisphere.