Objective To investigate the diagnostic value of CT perfusion source images(CTPSI)in acute stroke less than 9 hours.

Methods "One-stop shop"CT examination were performed in 100 patients with symptoms of acute stroke in less than 9 hours.Patients were divided into two groups according to with and without delayed perfusion on CTPSI, and compared Alberta stroke program early CT score study(ASPECTS)scores on non-contrast CT, arterial phase CTPSI and venous phase CTPSI with follow-up imaging.The ASPECTS were analyzed on arterial phase CTPSI and venous phase CTPSI using Wilcoxon rank-sum test, then compared with the follow up imaging ASPECTS using multiple linear regressions.

Results The median(min-max)scores of ASPECTS on NCCT, arterial phase CTPSI, venous phase CTPSI and follow-up imaging were 8.0(6.0-10.0), 7.0 (1.0-8.0), 8.0(3.0-10.0)and 7.5(0-10.0)in group with delayed perfusion, respectively, and 8.0(1.0-10.0), 7.5 (1.0-10.0), 8.5(1.0-10.0)and 7.0(0-10.0)in group without delayed perfusion respectively.ASPECTS scores measured on arterial phase CTPSI did not differ with venous phase CTPSI group without delayed per-fusion (Z=-1.00, P=0.459), while there was statistic difference in group with delayed perfusion(Z=-3.08, P=0.001).There were significant correlation of ASPECTS scores measured on mon-contrast CT, arterial phase CTPSI and venous phase CTPSI to follow-up imaging ASPECTS(r=0.879, 0.902, 0.945, P < 0.01)in group without delayed perfusion; ASPECTS measured in venous phase CTPSI showed the best correlation to follow-up imaging ASPECTS (r=0.831, P=0.004)in group with delayed perfusion.Multiple linear regression showed that the correlation in only venous phase CTPSI with follow-up imaging ASPECTS was statistically significant: in group without delayed perfusion, β=0.946, P < 0.001; in group with delayed perfusion, β=0.714, P=0.003.

Conclusion Presence of delayed perfusion in CTPSI is quit important in identifying ischemic penumbra, which plays a critical role in imaging-guided thrombolytic therapy.