Comparison of dynamic and xenon computed tomography in the evaluation of cerebrovascular ischemia.

Dynamic computed tomographic (DCT) scans with iodine contrast enhancement were compared with simultaneously obtained xenon CT studies of cerebral blood flow (CBF) in 15 patients with subacute or chronic cerebrovascular ischemic disease. Specifically, the width and corrected first moment (cMT1), as demonstrated by DCT, were compared with the regional CBF (rCBF) data and the rCBF map obtained with xenon CT. The DCT and rCBF images were well correlated in patients without, but poorly correlated in those with, leptomeningeal anastomotic collateral circulation. The correlation of rCBF and 1/width with 1/cMT1 was significant (r = 0.78, p less than 0.01) in the former, but not in the latter. These data were thought to reflect a difference in the tracer inflow pattern between the patients with and those without leptomeningeal anastomoses. Our series did not include patients with acute cerebral infarction or recanalization, which are thought to be associated with marked changes in cerebral blood volume in the affected region. However, the influence of cerebral blood volume should be studied in detail in our subacute or chronic series.