Application Of SWI In Assessment Of Ischemic Penumbra And Cerebral Blood Flow Information In Hyperacute Ischemic Stroke

Objective:To compare the utility of susceptibility weighted imaging(SWI)and perfusion-weighted imaging(PWI)sequences for the evaluation of the ischemic penumbra in hyperacute cerebral stroke,and to explore the feasibility of SWI-DWI mismatch based on ASPETS score as a neuroimaging marker for assessing hyperacute ischemic penumbra.To analyze the correlation between prominent hypointense vessel sign(PHVS)and cerebral blood flow(CBF)and cerebral blood volume(CBV),and to discuss the value of SWI in evaluating cerebral hemodynamics in patients with acute ischemic stroke.Materials and Methods:1.Clinical data:A total of 49 patients with acute ischemic stroke within 4.5 hours of onset were analyzed for thrombolytic therapy with intravenous recombinant tissue plasminogen activator(rt-PA).All patients were examined by DWI,FLAIR,MRA,PWI,SWI and the National Institutes of Health Stroke Scale(NHISS)scores before and after intravenous thrombolysis.2.MRI examination:All the patients were conducted with SIEMENS Magnetom Verio 3.0T MR imaging system scanner,with the standard 8 channel head coil,routine scanning patient in supine position,advanced head.The scan sequence includes:horizontal axis DWI,FLAIR,MRA,SWI,and PWI.The SWI automatically reconstructs the min IP image,and the PWI obtains a series of images of MTT,TTP,CBF,and CBV through post-processing.3.Image analysis:DWI,FLAIR,MRA,SWI and PWI images were analyzed by two senior neuroimaging diagnosticians.According to the abnormal signal area of DWI before and after thrombolysis,the abnormal blood perfusion area on PWI image and the PHVS display on SWI post-processing image,ASPECTS scores were performed respectively.The PHVS observed on SWI images were graded as follows:grade 1(ASPECTS score is 0-3):large number of vessels;grade 2(ASPECTS score is 4-6):more vessels;grade 3(ASPECTS score is 7-10):small amount of vessels.CBF and CBV maps obtained from PWI post-processing were quantitatively measured on the healthy side and the affected side,and then the mean values of the corresponding parameters on the lesion side and the healthy side were calculated.The r CBF ratio and the r CBV ratio were defined as the ratio of the affected side to the healthy side.MRA vessel display after thrombolysis was divided into recanalization group and uncanalization group.The correlation between PHVS display and r CBF ratio and r CBV ratio was analyzed.4.Statistical analysis:All statistical analysis was performed using SPSS 22.0.Independent sample t test was used for comparison of measurement data,andχ~2 test was used for comparison of counting data.Continuous variables are expressed as mean±standard deviation and categorized variables are expressed as numbers(frequency).For correlation analysis,Spearman correlation is applied to ordinal variables and Pearson correlation is applied to continuous variables.The difference was statistically significant with P<0.05.Results:1.The baseline data of 49 AIS patients who met the inclusion criteria were a nalyzed.The mean age was(64.10±11.92)years,including 37 male patients(75.5%)and 38 patients with hypertension(77.6%);15 patients with diabetes(30.6%);23 pati-ents with hyperlipidemia(46.9%);17 patients with atrial fibrillation(34.7%),and 34 patients with revascularization after thrombolysis(69.4%).The average NIHSS sco-re before thrombolysis was(10.80±3.05).2.The range of mismatch between SWI-DWI and MTT-DWI before thrombolysis was approximately the same.There was a good correlation between SWI-ASPECTS and MTT-ASPECTS before thrombolysis.The Pearson coefficient is 0.676(P<0.001).There was no statistically significant difference in the evaluation of ischemic penumbra between the two groups(P=0.133).3.There was a significant correlation between the change of PHVS level before thrombolysis and the change of r CBV ratio on the affected side(r=0.678,P<0.001).4.In the recanalization group,there was a significant correlation between the change ofΔPHVS level before and after thrombolysis and the ratio ofΔr CBV on the affected side(r=0.777,P<0.001).There was no significant difference between PHVS grade change and r CBF or r CBV in the group without vascular access(P>0.05).Conclusions:1.SWI-DWI mismatch can be used as a reliable index for evaluating ischemic penumbra.2.PHVS before thrombolysis can evaluate the cerebral blood volume of ischemic brain tissue.Less angiography may lead to higher relative cerebral blood volume ratio of the affected side,which may indicate the establishment of collateral circulation in the affected side of brain tissue.3.In the group of revascularization,the decrease of PHVS after thrombolysis can reflect the increase of cerebral blood volume on the affected side,suggesting that the ischemic penumbra can be rescued in time and ischemic brain tissue reperfusion.