| Objective To evaluate the middle cerebral artery?MCA?atherosclerotic plaque features in patients with intracranial atherosclerotic disease?ICAD?and their predictive value for leptomeningeal collateral?LMC?status.First,to evaluate the feasibility of using StraTegically Acquired Gradient Echo?STAGE?sequence derived magnetic resonance angiography?STAGE-MRA?in assessing LMC status by comparing to time-of-flight magnetic resonance angiography?TOF-MRA?.Second,to assess atherosclerotic plaque features in M1-2 segments using high resolution vessel wall imaging?HR-VWI?and explore their predictive power for LMC status.Methods First,55 subjects were prospectively enrolled between May 2018 and December 2018,including 47 healthy volunteers and 8 patients with atherosclerotic ischemic stroke?AIS?admitted in the Neurosurgery Department in our hospital.All subjects underwent conventional magnetic resonance imaging?MRI?,TOF-MRA and STAGE scan using Siemens MAGNETOM Prisma 3.0T superconducting magnetic resonance scanner,64-channel phased array standard head coil.STAGE-MRA thin-slice images were obtained using STAGE software.Qualitative analysis:Two observers scored image quality at internal carotid artery?ICA?terminal,proximal MCA and leptomeningeal anastomosis?LMA?on STAGE-MRA and TOF-MRA images using a3-point scale in all 55 subjects and compared the two MRA modalities with reference to digital subtraction angiography?DSA?images using a 4-point scale in 5 AIS patients.Quantitative analysis:the maximum density projection?MIP?function was used at the Siemens Syngo workstation to generate a 90 mm-thick image of both STAGE-MRA and TOF-MRA at the same head level.Displayed through the SPIN software,10 regions of interest?ROI?were manually drawn in bilateral M1-4segments and stationary tissue where vessels were carefully avoided,and the maximum signal intensity(Vmax)or the average and standard deviation of signal intensity in each ROI were recorded.The contrast to noise ratio?CNR?was calculated.Lines were drawn in bilateral MCA distal territories and numbers of LMA were counted in the line-signal intensity profiles.Comparisons of image quality,CNR and number of LMA between STAGE-MRA and TOF-MRA were conducted using Wilcoxon rank sum test.Second,61 ICAD patients undergoing HR-VWI in our hospital from September 2016 to December 2017 with symptom of AIS or transient ischemic attack?TIA?and confirmed stenosis more than 30%in M1-2 segments were retrospectively collected.Imaging examination was performed using a Siemens MAGNETOM Trio Tim 3.0T MR scanner,32-channel phased array standard head coil.All patients underwent conventional MRI,three-dimensional plain and enhanced T1 weighted Sampling Perfection with Application-optimized Contrast using different flip angle Evolutions?3D T1W-SPACE?and STAGE scan.The plaque morphology,enhancement and distribution were assessed and measured by two obsevers at 3D T1W-SPACE images.Compared with 0%,50%or 100%of contralateral LMA as a reference,LMA in the lesion side was scored using a collateral score?CS?scale of0-4 on STAGE-MRA images.According to CS,28 patients were divided into poor LMC group?CS=0-2?and 33 into good LMC group?CS=3-4?.Two independent samples t-test,Mann-Whitney U test and Kruskal-Walli test were used to compare the demographic data,plaque morphology,enhancement and distribution between the poor and good LMC groups as appropriate.Univariate logistic regression was conducted to compare demographic data,plaque morphology,enhancement and distribution,then plaque features with P<0.15 were taken into multivariate logistic regression.Independent predictive variables were found after adjusted by age,gender and risk factors for AIS.Receiver operating characteristic?ROC?curves and the area under the curve?AUC?values were calculated to assess the predictive power.Results ?1?Image quality of 55 subjects assessed by two observers showed significant difference between STAGE-MRA and TOF-MRA in the regions of ICA terminal,proximal MCA and LMA?Ps<0.05?;?2?No statistical difference was found in the CNR between left and right cerebral hemispheres?Ps>0.05?;?3?The CNR in MCA M1-4 segments at STAGE-MRA images were significantly superior to that of TOF-MRA?Ps<0.001?;?4?The number of LMA was 12.5±0.3 in STAGE-MRA and 9.5±0.3 in TOF-MRA,which indicated the former had better depiction than the latter with statistically significant difference?P<0.05?;?5?The intra-observer and inter-observer reproducibilities were excellent in the measurement of atherosclerotic plaque with intraclass correlation coefficient values more than 0.75;?6?Plaque morphology:plaques in the good LMC group had larger outer wall area,lumen area,wall area and smaller arterial stenosis compared with the poor LMC group?Ps<0.05?;?7?Plaque enhancement:plaques in the two groups had similar enhancement pattern with P>0.05;?8?Plaque distribution:plaques in the poor LMC group had a tendency to distribute along the inferior wall and distribution proportion was higher than that in the good LMC group?P<0.05?,meanwhile no specific distribution pattern was observed in the good LMC group?P>0.05?;?9?After adjusted by age,gender and AIS risk factors,arterial remodeling ratio and normalized wall index were the two factors correlated with CS?Ps=0.004 and 0.027?with AUC values of 0.635?95%CI 0.502-0.755?and 0.614?95%CI 0.480-0.736?,respectively.The multivariate model combining both variables showed an AUC of0.806?95%CI 0.685-0.896?and the Kendall's tau-b correlation coefficient of 0.626?P<0.05?,which indicated the multivariate model had improved predictive power for LMC status over the univariate models with good positive correlation with CS.Conclusion STAGE-MRA is superior to TOF-MRA in the aspects of image quality,CNR and number of LMA,therefore it has the feasibility and potential to apply in clinical setting when it comes to evaluate LMC.The atherosclerotic plaque in M1-2 segments has different morphology and distribution pattern in ICAD patients with different LMC status.Arterial remodeling ratio and normalized wall index are the independent predictors for LMC status.By combining the univariate factors,the multivariate model has good positive correlation with CS.Analyzing atherosclerotic plaque features and their predictive efficacy for LMC status provides a basis for prediction of clinical outcome and decision-making in ICAD patients. |
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