Addition computed tomography with stable xenon--special reference to ischemic cerebrovascular diseases

Stable xenon (Xes) is used as a contrast agent because it freely diffuses to cerebral tissues through the blood-brain barrier. In this study, 2 axial levels for Xes enhancement analysis were selected from a baseline series of computed tomographic (CT) scans and 6 serial CT scans were obtained every 20 seconds for each scan level during the 240 seconds inhalation period of 30% Xes in 10 volunteer controls and in 52 patients with ischemic cerebrovascular diseases (ICVD). The serial CT scans were added and averaged in each pixel. This was used to make a new CT picture (addition CT scan). The CT scans before the Xes inhalation, the scan at the end of the Xes inhalation, and the addition CT scan were compared to see whether gray matter and ischemic areas could be differentiated from white matter. The addition CT scans could differentiate the three structures very well in both the acute and chronic stages of ICVD. This technique is thought to be a very simple and useful method to detect the small infarcted areas and low perfusion areas that cannot be visualized on precontrast CT scans.