Cerebral arteriovenous transit time (CTT): A sonographic assessment of cerebral microcirculation using ultrasound contrast agents

Transcranial color-coded sonography (TCCS) has been used to investigate maj or brain-supplying arteries, draining veins and brain parenchyma. Here, we describe a contrast-enhanced TCCS analysis of cerebral arteriovenous transi t time (cTT) as a measure of cerebral microcirculation. We evaluate its rep roducibility and its correlation with clinical impairment of brain function and neuropsychological tests. A total of 27 patients with cerebral microan giopathy and 30 healthy controls were examined. CTT is defined by the time an ultrasound contrast agent requires to pass from the P2-segment of the po sterior cerebral artery to the vein of Galen, This was measured by comparis on of power Doppler intensity in two off-line defined regions of interest. Serial intraindividual cTT measurements within several min showed a good re producibility of this parameter. cTT was significantly longer in patients w ith cerebral microangiopathy than in controls (Mann-Whitney U test, p < 0.0 01) and related to cognitive impairment measured by the Mini-Mental-State e xamination. We conclude that it is a quick and reliable parameter related t o increased vascular resistance of the microcirculation or a rarefaction of microvessels. Further studies are needed to show the sensitivity and speci ficity of cTT in the diagnosis of small vessel disease and the interference of important circulation factors, such as heart failure or blood viscosity . (C) 1999 World Federation for Ultrasound in Medicine & Biology.