Application Of DWI, 3D-TOF MRA And FAIR MR Perfusion Techniques In Cerebral Ischemia

ObjectivesTo compare the diagnostic value of diffusion-weighted MR imaging(DWI), three-dimensional time-of-flight magnetic resonance angiography(3D-TOF MRA) and no-invasive flow-sensitive alternating inversion recovery(FAIR)MR perfusion techniques in cerebral ischemia of different stages,especially in the pre-infarction and acute phase,the incidence of cerebral infarction will decrease.Methods15 healthy volunteers and 108 cases with ischemia stroke included 14cases of pre-infarction stage,15 cases of super-acute stage and 79 cases of acute stage were collected.All cases were examined with T₁WI,T₂WI,FLAIR,DWI,3D -TOF MRA and FAIR MR perfusion simultaneously.FAIR MR perfusion images were obtained from a magnitude subtraction of the labeled from the unlabeled images from the FAIR sequence.Region of interest(ROI)analysis was performed in white matter and gray matter of healthy volunteers and patients with unilateral cerebral artery stenosis or occlusion.Mean ROI signal intensities for white matter of ischemic side vs. contralateral side and gray matter of ischemic side vs.contralateral side were compared using the student-test of SPSS 15.0.Results1.T₁WI,T₂WI,FLAIR,DWI,3D -TOF MRA and FAIR MR perfusion images were gained of high quality in 15 healthy volunteers and 108 cases.2.In 15 healthy volunteers,good gray/white-matter contrast observed.The mean signal intensity values were 252.18±15.35(left gray matter),251.64±16.68(right gray matter),109.47±12.05(left white matter),108.90±11.70(left white matter).The mean signal intensity values were showed stable between bilateral gray matter(P＞0.05)and bilateral white matter(P＞0.05).The mean signal intensity values were 251.91±15.75, 109.18±11.67 in the bilateral gray matter and white matter.The ratio of gray matter to white matte is 2.33±0.28.3.Only MRA and FAIR MR perfusion in six techniques of MRI(T₁WI,T₂WI, FLAIR,MRA,DWI and FAIR)can test the 14 cases with cerebral artery stenosis or occlusion and cerebral hypo-perfusion in pre-infarction period,the others can not do that.14 patients' perfusion images were successfully obtained.Mean signal intensity values of hypo-perfusion side were 98.74±7.79(white matter),188.70±16.37(gray matter).Mean signal intensity values of contra-lateral side were 111.27±8.82(white matter),251.95±18.20(gray matter).Mean signal intensity values were decreased in the white matter and gray matter of the hemisphere ipsilateral to the hypo-perfusion side,as compared with values in the white matter and gray matter of the contra-lateral side(P＜0.005)and with values in the white matter and gray matter of the control subjects(P＜0.005).4.In 15 cases of super-acute cerebral infarction,the positive diagnostic rates with DWI,T₂WI,FLAIR,3D-TOF MRA and FAIR are 100%,0%,40%,53.3%and 53.3%, respectively;the other 79 cases of acute cerebral infarction,the positive diagnostic rates with DWI,T₂WI sequence,FLAIR sequence,3D-TOF MRA and FAIR are 100%,79.7%,89.9%,30.4%and 30.4%,respectively。In the 94 cases of cerebral infarction,there 32 cases were LAA(large artery atherosclerosis).For cases of LAA, the positive diagnostic rate with FAIR is 100%whether the area of infarction is large or not.For 62 cases of SAA(small artery occlusion lacunary),the positive diagnostic rate with FAIR is 0%.Of the 32 LAA cases,there 30 cases were unilateral cerebral artery stenosis or occlusion.For the 30 unilateral cerebral artery stenosis or occlusion eases,mean signal intensity values of hypo-perfusion side were 88.95±10.39(white matter),172.83±18.14(gray matter).Mean signal intensity values of contra-lateral side were 107.55±9.54(white matter),248.51±16.88(gray matter).Mean signal intensity values were decreased in the white matter and gray matter of the hemisphere ipsilateral to the hypo-perfusion side,as compared with values in the white matter and gray matter of the contralateral side(P＜0.005)and with values in the white matter and gray matter of the control subjects(P＜0.005).5.Of the 108 cases,there were 44 LAA cases were unilateral cerebral artery stenosis or occlusion(14 pre-infarction cases,30 infarction cases).Mean signal intensity values of hypo-perfusion side were 92.06±10.60(white matter), 177.88±18.94(gray matter).Mean signal intensity values of contra-lateral side were 108.73±9.37(white matter),249.60±17.17(gray matter).Mean signal intensity values were decreased in the white matter and gray matter of the hemisphere ipsilateral to the hypo-perfusion side,as compared with values in the white matter and gray matter of the contra-lateral side(P＜0.005)and with values in the white matter and gray matter of the control subjects(P＜0.005).Conclusion1.No complications were encountered in performing FAIR MR perfusion.FAIR MR perfusion is high repeatability,not necessary to use contrast agents,non-invasive technique,and convenient instruments.2.FAIR can test the pre-infarction and infarction cases caused by large artery atherosclerosis effectively.FAIR is a better method of functional MRI at present.3.DWI is more sensitive than routine MRI and FLAIR in detecting acute ischemia stroke.4.MRA can directly demonstrate the distribution and degree of occlusive artery. The consulting images for cerebral FAIR MR perfusion imaging could be provided by method of MRA.5.MRI allows the combined use of many of imaging modalities-routine MRI, DWI,MRA,FAIR MR perfusion- to rapidly obtain comprehensive information regarding the extent of ischemic damage in stroke patients.