Sensitivity and Specificity of Quantitative Cerebral Blood Flow vs. Time from Symptom Onset as a Predictor of Cerebral Infarction
Background and Purpose: To compare the sensitivity and specificity of quantitative cerebral blood flow (qCBF) vs. time from symptom onset to the measurement of qCBF (Time) as a predictor of cerebral infarction in patients (pts.) with acute ischemic stroke. Methods: 51 pts. with acute ischemic stroke who were assessed with XeCT, CTA and CT within 24 hours of symptom onset were studied. The MCA territory was divided into anterior and posterior divisions (two divisions/pt. for a total of 102 divisions). The average qCBF for each of these divisions was calculated and initial and follow-up CT scans were read for new infarction in both divisions. 24 divisions with evidence of prior infarction on the initial CT were excluded from the analysis. This left a total of 78 divisions available for analysis. Logistic regression was used to generate receiver operating curves (ROC) for both qCBF and Time. The area under each ROC curve is reported. Results: Twenty-one of the 78 (26.9%) divisions without initial infarction on CT had evidence of new infarction on the follow-up CT. The area under the qCBF curve was 0.81 compared with an area of 0.49 under the Time curve (p=0.00025). Excluding patients receiving thrombolytic therapy, (n=11), the area under the qCBF curve was 0.799 and the area under the Time curve was 0.590 (p=0.00004). The area under the ROC curve for qCBF was significantly greater than Time in those patients studied < 180 minutes (qCBF=0.92, Time=0.51; p=0.02) and > 180 min. (qCBF=0.76, Time=0.50; p=0.01) Conclusion: Quantitative cerebral blood flow measured by XeCT is a better predictor of new infarction on follow-up CT than Time in pts. with acute ischemic stroke. This holds true for time < 180 minutes and > 180 minutes.