High Resonlution Magnetic Resonance Imaging Clinical Study On Carotid Atherosclerotic Plaques

Part Ⅰ MRI features of carotid atherosclerotic plaques with ischemic storkeObjectiveThis study sought to analysis of plaque composition, determine plaque stability, quantitative evaluation of plaque burden, then evaluate the differences in plaque composition, plaque burden and clinical risk factors between patients with vulnerable plaques and patients with stable plaques by3.0T MRI multi-contrast imaging study in carotid plaques on patients who with ischemic stroke.Materials and Methods1. SubjectsBetween2012and2013,65consecutive patients underwent a carotid artery MRI examination, who meet the three inclusion criterias in our hospital department of neurology, Arteries were include if there was:1)adult patients who had TIA or stroke,2) a recent history of TIA or stroke(symptoms occur within≤14days),3) duplex carotid ultrasound prompted presence AS plaque or intima-media thickness(IMT)≥1.5mm. The study procedures and consent forms were reviewed and approved by institutional review board before study initiation. All patients have been checking the ethics committee agreed and signed informed consent.2. MR Imaging equipment, scanning sequence and parametersPatients were imaged with a using a8-channel phased-array carotid coil (Shanghai chengguang medical technologies Co.,LTD.) in a3.0T MRI scanner (Achieva3.0T,Holland Philips).Carotid dedicated8-channel phased-array carotid coil fixed patients’ jaw and neck. When scanning the patients is asked to remain stationary and minimize swallowing. At first patients with carotid artery2D-TOF scan, MIP method reconstruction MRA images to obtain the exact location of the carotid bifurcation, expert cross-sectional carotid MR images to obtain5different contrast-weighted images(3D-T0F, T1WI, T2WI, MP-RAGE,3D MERGE) of the carotid arteries2cm proximal and2cm distal to the bifurcation. The main parameters of each sequence:(1) three-dimensional time of flight (3D TOF), TR/TE20ms/4.9ms, flip angle20°, FOV140mm×140mm, thickness2mm;(2) quadruple inversion-recovery, T1WI sequence, two-dimensional TSE, TR/TE800ms/10ms, FOV140mmx140mm, thickness2mm;(3) multi-slice double inversion recovery T2WI sequence, TR/TE4800ms/50ms, FOV140mmx140mm, thickness2mm;(4)3D magnetization-prepared rapid acquisition gradient-echo sequence (MP-RAGE),3D FFE, TR/TE10ms/4.8ms, FOV140mmx140mm, thickness2mm;(5)3D MERGE,3D FFE, TR/TE10ms/4.8ms, FOV250mm×160mmx70mm, thickness2mm.3. Carotid imaging evaluationEach scan was interpreted by2reviewers reaching a consensus opinion. Reviewers were blinded to subject information and clinical information. Image quality was reted per axial location on a four-point scale(1, poor;2, marginal;3, good;4, excellent) dependent on the overall signal-to-noise ratio and clarity of the vessel wall boundaries. Slices with image quality<2were excluded form the study.4. Carotid plaque image analysis and processingCarotid MR images were interpreted by two fully trained reviewers with consensus agreement using customdesigned software(CASCADE, Seattle, WA, USA). Reviewers were blinded to subject information and clinical information. Carotid MRI analysis including:1) presence or absence of carotid plaque components, such as calcificarion, lipid-rich necrotic core, plaque hemorrhage.The volumes of each plaque component were also calculated;2) carotid atherosclerotic plaques morphological measurements:total vessel area (TVA), lumen area (LA), wall thickness (WT), wall area (WA) and normalized wall index (NWI).3) the surface of carotid artery plaque fibrous cap status determination:incomplete or broken.Statistical MethodSPSS13.0software package was applied to deal with the data of the study. Measurement data were expressed as mean±standard deviation (x±s) representation. Compare carotid plaque burden, clinical risk factors between the vulnerable group and stable group using two independent samples t test, Fisher’s exact probability analysis, Wilcoxon rank sum test and so on. Statistical tests were two-tailed test method using side, a significant level of statistical significance test P <0.05. The results of quantitative data measured by taking the average of the two raters for the analysis of qualitative data inconsistencies when negotiating consensus for analysis.Results1、59/65cases were involved in this study due to with excellent image quality(except1cases with carotid artery dissection,3cases of poor image quality,2cases with unilateral carotid artery data loss). Of the remaining59subjects,39were male, and age range from43-83years, and the mean age was62.27±9.99years,44patients with hypertension, diabetes mellitus in21cases,20patients with smoking.TC4.86±1.23mmol/L, TG1.73±1.18mmol/L, HDL1.25±0.29mmol/L, LDL3.09±1.12mmol/L. Carotid plaque stability divided by two groups:the vulnerable plaque group of10cases, stable plaque group of49cases.2、Comparison of plaque components between vulnerable plaque group and stable plaque group:there are obvious differences between the vulnerable plaque group and stable plaque group in CA, LRNC, IPH volume and their corresponding area ratio(P <0.05).3、To evaluate the differences in plaque burden between vulnerable plaque group and stable plaque group:the difference of two group in average total vessel area (TVA) was not statistically significant (P>0.05), while the average lumen area (LA) and minimal lumen area (min LA) of vulnerable plaque group were less than stable plaque group, the differences were statistically significant (P<0.05); the average size of vulnerable plaque wall area (WA), the average wall thickness (WT), the average normalized wall index (NWI) and the maximum wall area (max WA), the maximum wall thickness (max WT), the maximum normalized wall Index (max NWI) larger than stable group, the differences were statistically significant (P<0.05).Conclusions1、The MRI "black blood","white blood" technology combined with observations of plaque, more comprehensive and more accurate observation wall structure, composition and volume of plaque.2、Vulnerable plaque imaging as intraplaque hemorrhage and/or rupture of fibrous cap. The composition is more complex than the stable plaque.3、There are significant differences between the vulnerable plaque group and stable plaque group in plaque burden index like NWI, WA, WT; therefore, those can be used in the evaluation of plaque burden.4、There was no significant difference in clinical risk factors between vulnerable plaque group and stable plaque group except age. Part II Association of carotid atherosclerotic plaque features with ischemic strokeObjectiveThis study sought to determine the difference of plaque burden, plaque composition between index side and non-index side by quantitative analysis using resolution MR imaging to, to determine the associations of carotid plaque burden, component volume and ipsilateral acute cerebral infarct(ACI) sizes on diffusion weighted imaging(DWI).Materials and Methods1. Subjects The research object are same with the first part. Grouped into two groups, index side:the ipsilateral cerebral hemisphere carotid artery territory ischemic stroke on that side arteries, a total of89vessels, including34occurred in the acute cerebral infarction. Non-index side:the ipsilateral cerebral hemisphere carotid artery territory ischemic stroke is not obvious that the arterial side, a total of31vessels.2. MR Imaging equipment, scanning sequence and parametersEquipment and carotid artery MRI scans of the same with the first part. Head using a standard8-channel head coil receiver. The main imaging sequences for the horizontal position T1WI T2WI, T2WI FLAIR, DWI and3D TOF MRA. The main parameters of each sequence:(1) T1WI, TR/TE2000ms/20ms, thickness=6mm, interval=lmm, FOV=24cmx24cm, Matrix=256x256;(2) T2W, TR/TE3000ms/80ms, thickness=6mm, interval=1mm, FOV=24cmx24cm, Matrix=256×256;(3) T2WI FLAIR, TR/TE11000ms/125ms, thickness=6mm, interval=1mm, FOV=24cmx24cm, Matrix=256x256;(4) DWI, TR/TE1910ms/44.4ms, thickness=6mm, interval=lmm, FOV=24cmx24cm;(5)3D TOF MRA, TR/TE20ms/4.9ms.3. Carotid imaging evaluationEach scan was interpreted by2reviewers reaching a consensus opinion. Reviewers were blinded to subject information and clinical information. Image quality was reted per axial location on a four-point scale(1, poor;2, marginal;3, good;4, excellent) dependent on the overall signal-to-noise ratio and clarity of the vessel wall boundaries. Slices with image quality<2were excluded form thestudy.4. Brain imaging analysis and processingTwo with more than5years experience of MR diagnosis of the radiologist for image analysis. Reviewers were blinded to subject clinical information and carotid imaging information. Brain MRI analysis includes:1) with/without T2WI FLAIR hyperintensity and sizes;2) with/without DWI hyperintensity and sizes. The carotid plaque imaging analysis same with the first part.5. Data analysis.SPSS13.0software package was applied to deal with the data of the study. Measurement data were expressed as mean±standard deviation (x±s) representation. Compare carotid plaque burden, compositional differences between the index side and non-index siede using two independent samples t test, Fisher’s exact probability analysis, Wilconxon rank sum test and so on.The relationship between carotid artery plaque burden, the composition of plaque volume and ipsilateral cerebral DWI hyperintense lesion volume using Spearman correlation analysis. Statistical tests were two-tailed test method using side, a significant level of statistical significance test P <0.05.Results1、The difference between the index side and non-index side1.1There was no significant difference in stroke/TIA patients with bilateral carotid artery indicators(P>0.05).1.2The index side plaque wall area (WA), the average wall thickness (WT), the average normalized wall index (NWI) and the maximum wall area (max WA), the maximum wall thickness (max WT), the maximum normalized wall Index (max NWI) large than non-index side, the differences were statistically significant (P<0.05). The total vessel area (TVA), lumen area (LA) in the index side and non-index side there was no statistical difference (P>0.05).1.3The occurrence rate of LRNC, IPH between index side and non-index side, there were significant differences, while the occurrence rate of calcification and FCR had no statistical significance. In predicting the clinical symptoms found in plaque LRNC, FCR odds ratios were8.578,2.125, IPH occurred in the index side. Calcification, LRNC, IPH volume was significantly different in two group, LRNC and IPH are more obviously.2、There was a positive relationship between the index side plaque burden of WT, NWI and ipsilateral cerebral hemisphere of acute cerebral infarction volume, the most obvious in mean NWI, has relatively correlation r=0.625. Mean LA and the ipsilateral hemisphere of acute cerebral infarction volume was negative correlation, but the degree of correlation in general r=-0.461.3、Carotid artery plaque calcification volume, LRNC volume, IPH volume with the ipsilateral cerebral hemisphere of acute cerebral infarction volume was positively correlated, but the extent of the general, the R values were0.533,0.436,0.461.Conclusions1、There is a difference of plaque burden between index side and non-index side,but atherosclerosis of the human carotid arteries is generally a bilaterally symmetrical disease.2、The index side than non-index side have more complex components. LRNC and IPH are associated with clinical ischemic events, the occurrence of FCR to some extent suggesting that stroke.3、The carotid artery plaque load WT、NWI value is more bigger, that means the plaque burden is heavier, the ipsilateral cerebral hemisphere of acute cerebral infarction volume is more larger. While mean LA value is small, it means that vascular is more narrow, ipsilateral cerebral hemisphere of acute cerebral infarction volume is more larger.4、Plaque composition is more complex, the possibility of more acute ischemic events.