STABLE XENON CT IN PATIENTS WITH CHRONIC CEREBROVASCULAR-DISEASE

Xenon-enhanced CT (XeCT) is a method of measuring regional cerebral bl ood flow (rCBF). Although it is used for acute and perioperative asses sment the ability of XeCT to show hypoperfused areas in vivo, as compa red with morphological imaging modalities other than noncontrast CT, i s not defined. Correlation with MRI helps to define the smallest detec t able hypoperfused area. We examined 17 patients 6 weeks after acute cerebral infarcts with CT, XeCT and MRI and the findings were compared . All examinations were performed with the same slice angulation and t hickness and the sizes of the abnormal areas were measured. XeCT showe d a high correlation with MRI, but less so with conventional CT. Lesio ns appeared significantly smaller on CT than on XeCT or MRI. No signif icant difference between MRI and XeCT changes was found. The minimal l esion on MRI correlating with a hypoperfused area on XeCT was 0.8 cm(2 ), whereas lesions measuring less than 0.5 cm(2) on MRI could not be d etected on XeCT. The good correlation between XeCT and MRI underlines the reliability of rCBF examinations with XeCT. A significant differen ce between CT and XeCT findings shows the difficulty of interpreting h ypoperfused regions only by correlation with CT. Combined XeCT and MRI gives a better estimate of the vascular state of the brain.