In-vivo quantitative T2 mapping of carotid arteries in atherosclerotic patients: segmentation and T2 measurement of plaque components.
In-vivo quantitative T2 mapping of carotid arteries in atherosclerotic patients: segmentation and T2 measurement of plaque components.
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DOI：
10.1186/1532-429x-15-69
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发表时间：
2013-08-16
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影响因子：
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通讯作者：
Robson MD
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作者：
Biasiolli L;Lindsay AC;Chai JT;Choudhury RP;Robson MD
颈动脉粥样硬化斑块可以通过多层对比心血管磁共振（CMR）在体内进行表征，这已经得到了组织学的彻底验证。然而，多层对比CMR的非定量性质和需要广泛的采集后解释限制了体内CMR斑块表征的广泛临床应用。定量T2制图是一种很有前途的替代方法，因为它可以提供斑块成分的绝对物理测量，可以在不同的CMR系统中标准化，并广泛用于多中心研究。本研究的目的是通过进行美国心脏协会（AHA）斑块类型分类、分割颈动脉T2图和测量斑块成分的体内T2值，研究体内T2制图在动脉粥样硬化斑块表征中的应用。对15例动脉粥样硬化患者（男性11例，71±10岁）采用常规多层造影和多旋回波（multi - spin - echo, Multi-SE）在3t下对颈动脉进行成像。利用非线性最小二乘回归对Multi-SE获取的一系列图像进行单指数拟合，生成颈动脉T2图。两位研究者独立地对颈动脉斑块类型进行了分类，其中一位使用了多层对比CMR，另一位使用了T2图和飞行时间（TOF）血管造影。基于Bayes分类器的半自动化方法将颈动脉T2图谱分为钙化、富脂坏死核心（LRNC）、纤维组织和近期IPH 4类。计算LRNC、纤维组织和近期IPH分类体素T2值的平均值±标准差。在15例患者的37张颈动脉图像中，通过多层对比CMR和T2图（+ TOF）分类的AHA斑块类型显示出良好的一致性（76%的匹配分类和Cohen’s κ = 0.68）。用14条正常动脉的T2图测量膜内膜和中膜的T2 （T2 = 54±13 ms）。从15例晚期动脉粥样硬化的11865个体素中，2394个体素被分割为LRNC （T2 = 37±5 ms）和7511个体素为纤维组织（T2 = 56±9 ms）；钙化192个体素，近期IPH 1个（236个体素，T2 = 107±25 ms）， T2图上检测到，多对比CMR证实。这项颈动脉CMR研究显示了体内T2定位对动脉粥样硬化斑块表征的潜力。T2图谱（+TOF）分类的AHA斑块类型与传统的多重对比CMR之间的一致性很好，在LRNC、纤维组织和近期IPH中体内测量的T2显示了在T2图谱上区分斑块成分的能力。
Atherosclerotic plaques in carotid arteries can be characterized in-vivo by multicontrast cardiovascular magnetic resonance (CMR), which has been thoroughly validated with histology. However, the non-quantitative nature of multicontrast CMR and the need for extensive post-acquisition interpretation limit the widespread clinical application of in-vivo CMR plaque characterization. Quantitative T2 mapping is a promising alternative since it can provide absolute physical measurements of plaque components that can be standardized among different CMR systems and widely adopted in multi-centre studies. The purpose of this study was to investigate the use of in-vivo T2 mapping for atherosclerotic plaque characterization by performing American Heart Association (AHA) plaque type classification, segmenting carotid T2 maps and measuring in-vivo T2 values of plaque components. The carotid arteries of 15 atherosclerotic patients (11 males, 71 ± 10 years) were imaged at 3 T using the conventional multicontrast protocol and Multiple-Spin-Echo (Multi-SE). T2 maps of carotid arteries were generated by mono-exponential fitting to the series of images acquired by Multi-SE using nonlinear least-squares regression. Two reviewers independently classified carotid plaque types following the CMR-modified AHA scheme, one using multicontrast CMR and the other using T2 maps and time-of-flight (TOF) angiography. A semi-automated method based on Bayes classifiers segmented the T2 maps of carotid arteries into 4 classes: calcification, lipid-rich necrotic core (LRNC), fibrous tissue and recent IPH. Mean ± SD of the T2 values of voxels classified as LRNC, fibrous tissue and recent IPH were calculated. In 37 images of carotid arteries from 15 patients, AHA plaque type classified by multicontrast CMR and by T2 maps (+ TOF) showed good agreement (76% of matching classifications and Cohen’s κ = 0.68). The T2 maps of 14 normal arteries were used to measure T2 of tunica intima and media (T2 = 54 ± 13 ms). From 11865 voxels in the T2 maps of 15 arteries with advanced atherosclerosis, 2394 voxels were classified by the segmentation algorithm as LRNC (T2 = 37 ± 5 ms) and 7511 voxels as fibrous tissue (T2 = 56 ± 9 ms); 192 voxels were identified as calcification and one recent IPH (236 voxels, T2 = 107 ± 25 ms) was detected on T2 maps and confirmed by multicontrast CMR. This carotid CMR study shows the potential of in-vivo T2 mapping for atherosclerotic plaque characterization. Agreement between AHA plaque types classified by T2 maps (+TOF) and by conventional multicontrast CMR was good, and T2 measured in-vivo in LRNC, fibrous tissue and recent IPH demonstrated the ability to discriminate plaque components on T2 maps.