Application Of 3D-ASL Perfusion-weighted Imaging And MRA In Study Of Transient Ischemic Attack

Objective:To investigate the value of three dimension-arterial spin labeling(3D-ASL)combined with magnetic resonance angiography(MRA)in transient ischemic attack(TIA).Materials and Methods:1.From November 2016 to August 2017,we collect twenty TIA patients in our hospital,including 11 male and 9 female,age from 40 to 72,mean age(56.4±9.5);and twenty age-matched healthy volunteers including 10 male and 10 female,age from 37 to 70,mean age(53.8±10.1),as control group.2.MRI scans were performed on a GE 3.0T(DISCOVERY MR 750)machine and a 8 channel phased array head and neck joint coils(GE Medical System).3.Transfer all 3D-ASL raw images of the subject to GE AW 4.6 workstation using Functool software.Adjust threshold to put brain tissue all in calculation field,get cerebral blood flow(CBF)images by3D-ASL post-processing software in GE Function Tool.Put region of interest(ROI)in fields including right frontal lobe,parietal lobe,temporal lobe,occipital lobe,cerebellar hemisphere gray area for images of test group and control group.Use brain midline as axis of symmetry,measure 3 times and avoid blood vessel and CSF,then record mean CBF.Then calculate the rCBF ratio,which was equal to the right rCBF value/the left rCBF value,and the rCBF ratio was 0.8-1.2 with normal perfusion,and>1.2 was high perfusion,<0.8 was low perfusion.For patients with abnormal perfusion,the rCBF ratio was equal to the ipsilateral rCBF/native rCBF.Transport the 3D TOF-MRA data of all subjects to work station and get vessel images using 3D MIP for evaluation of narrow cranial carotid artery.For the TIA group,it is also necessary to evaluate the consistency of narrow blood supply area and low perfusion area.Two MRI diagnostics were judged by double blind analysis and reached a consensus.4.SPSS 19.0 statistical software was used for analysis.Compare the rCBF values of the left and right sides of the healthy control groupaccording to pared-samples t test.Compare the rCBF ratio between the healthy control group and the TIA group according to independent-samples t test.Compare the number of perfusion reduction in TIA group and the number of patients in the control group by using Chi-square test.The clinical diagnosis of TIA was considered as the“gold standard”,compute the sensitivity,specificity,positive predictive value and negative predictive value of 3D-ASL,MRA,and the combined application,and draw ROC curve to compare the diagnostic efficacy of the three methods.The relationship between the frequency of TIA attack and low perfusion and vascular stenosis was analyzed by Fisher accuracy test.Results:1.There was no significant difference in the rCBF values between the left and right sides of each lobe of the normal control group,the average cerebral blood flow of brain tissue was(47.62±5.88)ml/(min·100g).2.In group TIA,3D-ASL positive+MRA was positive in 8 cases,3D-ASL positive+MRA negative in 5cases,3D-ASL negative+MRA positive in 3 cases,and 3D-ASL negative+MRA negative in 4 cases.In the control group,1 cases of 3D-ASL positive+MRA were positive,0 cases with 3D-ASL positive+MRA negative,1 cases of 3D-ASL negative+MRA positive,and 18 cases with negative+MRA negative 3D-ASL.3.The low perfusion in group TIA was significantly more than that of the control group(c~2=13.30,P<0.05).The average rCBF ratio of TIA patients(0.76±0.13)was lower than that of healthy controls(0.97±0.09)(t=-5.98,P<0.05).4.The sensitivity of 3D-ASL in the diagnosis of TIA was 65.0%and the specificity was 95.0%;the sensitivity of MRA in the diagnosis of TIA was 55.0%and the specificity was 90.0%;The combined use of the two techniques for the diagnosis of TIA has a sensitivity of 80.0%and a specificity of 90.0%.And the combination of 3D-ASL and MRA in the diagnosis of TIA was associated with a significantly higher sensitivity and negative predictive value for the diagnosis of TIA than either the single MRA technique or the 3D-ASL technique.5.8 cases of TIA patients had both vascular stenosis and local perfusion reduction,of which 7 cases(87.5%)were matched with the location of MRA arterial stenosis.6.Patients with 3D-ASL perfusion reduction and vascular stenosis were more susceptible to TIA frequent episodes(100%)compared to the other three groups.Conclusions:1.3D-ASL can detect lesions that can not be found in routine MRI scan of TIA patients.It is of great value for TIA diagnosis and prognosis evaluation.It can be used as a routine scan sequence for diagnosing TIA.2.MRA can evaluate the vascular condition of TIA patients,and the narrow blood supply area of MRA has good consistency with 3D-ASL hypoperfusion area.MRA can help analyze and determine the cause of TIA.3.3D-ASL low perfusion and vascular stenosis is one of the most frequent risk factors for TIA patients.The combined application of two technologies of 3D-ASL and MRA can improve the efficiency of TIA diagnosis,and provide better evidence for the formulation of clinical treatment plan,so as to prevent TIA repeated attack and the occurrence of ischemic stroke.