Cerebrovascular insufficiency as the criterion for revascularization procedures in selected patients: a correlation study of xenon contrast-enhanced CT and PWI

Neurosurg Rev. 2009 Jan;32(1):29-35; discussion 35-6. doi: 10.1007/s10143-008-0159-z. Epub 2008 Sep 13.


In order to identify patients who suffer from hemodynamic cerebral insufficiency and can benefit from cerebral revascularization procedures, xenon-CT scanning has been established to reliably measure the critical cerebrovascular reserve capacity. As a need for alternative quantification methods arises, this study aims to characterize the significance of both time-to-peak (TTP) and mean transit time (MTT) in perfusion-weighted imaging (PWI) in this particular subset of patients. Ten patients in routine preoperative work-up for cerebral revascularization were prospectively enrolled and underwent both XeCT scanning and PWI. Cerebrovascular reserve capacity (CVRC) was calculated for each region of interest (ROI, n = 504) after administration of a vasoactive stimulus. ROIs were anatomically matched with those of PWI after TTP and MTT were calculated. Highly significant negative correlation was found for TTP and CVRC for all ROIs (r = -0.3954, p < 0.0001; symptomatic ROIs: r = -0.4867, p < 0.0001). Correlation was weak for MTT and CVCR (r = -0.1287; p < 0.01). The optimum threshold for TTP to detect impaired cerebrovascular reactivity in our patient group was 4 s (specificity 90.8%, sensitivity 44.4%) for all ROIs (TTP > 4.4 s for symptomatic ROIs, specificity 88.4%, sensitivity 62.7%). An approximative equation to calculate the probability of pathological findings could be derived from the data. The positive predictive value (PPV) was 0.76 (symptomatic 0.78) with a negative predictive value (NPV) of 0.71 (symptomatic 0.78). While PWI currently is not able to replace XeCT in the direct quantification of CVRC, it may serve as a readily available follow-up tool. A TTP threshold of greater than 4 s allows to confirm a cerebrovascular compromise in a selected high-risk subgroup of patients.

MeSH terms

  • Adult
  • Brain / diagnostic imaging
  • Brain / pathology
  • Carotid Stenosis / diagnostic imaging
  • Carotid Stenosis / pathology
  • Carotid Stenosis / surgery
  • Cerebral Revascularization*
  • Cerebrovascular Circulation / physiology
  • Cerebrovascular Disorders / diagnostic imaging
  • Cerebrovascular Disorders / pathology*
  • Cerebrovascular Disorders / surgery*
  • Constriction, Pathologic
  • Female
  • Humans
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging
  • Male
  • Middle Aged
  • Middle Cerebral Artery / diagnostic imaging
  • Middle Cerebral Artery / pathology
  • Moyamoya Disease / diagnostic imaging
  • Moyamoya Disease / pathology
  • Moyamoya Disease / surgery
  • ROC Curve
  • Tomography, X-Ray Computed