Abstract： Objective To investigate the evolution of monkey brain isehemic penumbra(IP)area.Methods Seyen monkeys were used to make middle cerebral artery occlusion(MCAO)model by interventional methods.CT perfnsion imaging,MR diffusion weighted-imaging (DWI),perfusion weighted imaging(PWI)and T2W1 were performed at 1,5,10;15,20 and 24 h after MCAO respectively.Four regions of interest of infarct lesion were measured.Point 1 was at the infarct core.point 3 was at the infamt margin,and point 2 was at the midpoint between point 1 and 3.Point 4 demonstrated normal signal intensity adjacent to high signal intensity.Parameters measured included cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), apparent diffusion coefficient (ADC) and negative enhancement integral (NEI).The relative ratios between infarct lesions and the corresponding contralateral normal brain were calculated(rCBF, rCBV, rMTY, rADC and rNEI).The IP areas were calculated by two methods: IP thresholds combined with self-made computer software, and PWI( MrlT)-DWI mismatch.ANOVA and ROC analysis were used. Results Five of 7 monkey MCAO models were made successfuUy. There were signitlcanfly difference of rCBF and rNEI within 20 h, of rCBV within 15 h, of rADC within 10 h, of rMTT at24 h (P＜0.05).ROI 1,2 and 3 values as following: rCBF: 1 h(0.160 ±0.034, 0.310 ±0.037,0.540±0.107), 5 h(0.098±0.029, 0.157 ± 0.052, 0.427 ±0.116), 10 h(0.072 ±0.023, 0.097 ±0.028, 0.209 ± 0.070), 15 h(0.054 ± 0.017, 0.069 ± 0.015, 0.166 ± 0.049), 20 h(0.038 ± 0.011,0.026± 0.007, 0.092±0.013); rNEI: 1 h(0.219 ± 0.085, 0.303 ± 0.099, 0.463 ± 0.132), 5 h (0.143±0.057, 0.195± 0.055, 0.348±0.127), 10 h(0.127 ± 0.029, 0.171 ± 0.058, 0.259 ±0.079), 15 h(0.128 ±0.024, 0.164 ±0.031, 0.217 ±0.030), 20 h(0.075±0.019, 0.147±0.058,0.129 ±0.045) ; rCBV: 1 h(0.594 ± 0.199, 0.804 ± 0.099, 1.021 ±0.169), 5 h(0.457±0.103,0.462±0.145, 0.815±0.201), 10 h(0.222 ±0.046, 0.249±0.065, 0.529 ±0.135), 15 h(0.201 ±0.047, 0.187 ±0.055, 0.361 ±0.083) ; rADC: 1 h(0.515 ±0.115, 0.667±0.097, 0.761 ±0.106),5 h(0.488 ±0.100, 0.539 ±0.107, 0.674 ±0.099), 10 h(0.456 ±0.057, 0.549 ±0.049, 0.590 ±0.081 ) ; 24 h rMTT(4.163 ± 1.179, 4.192± 1.607, 2.397±0.909).The thresholds of IP were 0.203 of rCBF, 0.483 of rCBV, 0.571 of rADC and 0.250 of rNEI respectively.The values measured using the method of IP thresholds combined with software were larger than PWI(MTr)-DWI mismatch region before 15 hours, but were smaller at 20 h and 24 h. The area of IP was 20%-38% of infarct area at 1 h,15%-35% at 5-10 h, 13%-25% at 15 h, 9%-15% at 20 h, and 3%-12% at 24 h.Conclusion The time window of IP in monkey MCAO model was 15%-20 hours.At the early phase of infarction, IP was present within the region of high signal intensity on DWI.PWI-DWI mismatch method could not estimate IP areas accurately.Areas evaluated with CT perfusion (MrIT) and DWI mismatch were much closer to the actual IP areas.