Spectral CT of carotid atherosclerotic plaque: comparison with histology

Objective

To distinguish components of vulnerable atherosclerotic plaque by imaging their energy response using spectral CT and comparing images with histology.

Methods

After spectroscopic calibration using phantoms of plaque surrogates, excised human carotid atherosclerotic plaques were imaged using MARS CT using a photon-processing detector with a silicon sensor layer and microfocus X-ray tube (50?kVp, 0.5?mA) at 38-μm voxel size. The plaques were imaged, sectioned and re-imaged using four threshold energies: 10, 16, 22 and 28?keV; then sequentially stained with modified Von Kossa, Perl’s Prussian blue and Oil-Red O, and photographed. Relative Hounsfield units across the energies were entered into a linear algebraic material decomposition model to identify the unknown plaque components.

Results

Lipid, calcium, iron and water-like components of plaque have distinguishable energy responses to X-ray, visible on spectral CT images. CT images of the plaque surface correlated very well with histological photographs. Calcium deposits (>1,000?μm) in plaque are larger than iron deposits (<100?μm), but could not be distinguished from each other within the same voxel using the energy range available.

Conclusions

Spectral CT displays energy information in image form at high spatial resolution, enhancing the intrinsic contrast of lipid, calcium and iron within atheroma.

Key Points

? Spectral computed tomography offers new insights into tissue characterisation. ? Components of vulnerable atherosclerotic plaque are spectrally distinct with intrinsic contrast. ? Spectral CT of excised atherosclerotic plaques can display iron, calcium and lipid. ? Calcium deposits are larger than iron deposits in atheroma. ? Spectral CT may help in the non-invasive detection of vulnerable plaques.     

颈动脉粥样硬化斑块的能谱CT检查:组织学对比

目的通过能谱CT对易损粥样硬化斑块进行能量反应分析,区分其成分,并与组织学进行对比。方法采用斑块体模对MARSCT设备进行能谱校准后对所切除的人颈动脉粥样斑块进行成像,使用具有硅传感器层的光量子探测器和体素大小为38μm的微焦点X线球管(50kV、0.5mA)。采用4个能量阈值:10、16、22和28keV对斑块进行成像,切片和再次成像,然后相继进行改良的VonKossa、Perl普鲁士蓝和红油O染色并照像。将整个能量体系中的相对CT值输入线性代数物质模型来确定未知斑块的成分。结果根据能谱CT中对X线的能量反应,确定斑块的脂质、钙化、铁质和水样成分。斑块表面的CT成像与组织学照片具有很好的相关性。斑块内的钙沉积(>1000μm)体积大于铁沉积(<100μm),但是在现有能谱范围内并不能区分同一体素内的两种成分。结论能谱CT能够以图像形式在高空间分辨力的条件下显示能量信息,提高粥样斑块中脂质、钙化与铁质的内在对比。     

Vascular calcification in ex vivo carotid specimens: precision and accuracy of measurements with multi-detector row CT

PURPOSE: To test the accuracy and precision of multi-detector row computed tomography (CT)-derived measurements of vascular calcification in ex vivo human carotid endarterectomy (CEA) specimens. MATERIALS AND METHODS: Sixteen ex vivo CEA specimens were imaged with multi-detector row CT. Multi-detector row CT-derived calcium scoring algorithms (ie, mineral mass and volume score) were compared with the mass and volume of ashed remnants of the CEA specimens. Bland-Altman analysis was performed to assess the mean (ie, bias) and SD (ie, precision) of differences between multi-detector row CT- and ashing-derived measurements. In addition, conventional Agatston score, volume score, mineral mass, and modified Agatston score were calculated for each specimen by using a number of scanning protocols. Images were obtained at a section thickness of 1.25 mm by using different tube energy settings and tube currents. Specimens were also imaged at different section thicknesses with fixed combinations of tube energy and tube current. To compare measurement variability of scoring methods, coefficients of variation for all protocols were calculated. RESULTS: Both mean multi-detector row CT-derived mineral mass and mean ashing-derived mineral mass were 0.129 g +/- 0.173 (r = 0.99, P <.001). Mean multi-detector row CT- and ashing-derived volumes were 339.94 mm3 +/- 395.4 and 39.48 mm3 +/- 55.76, respectively (r = 0.95, P <.001). Measurement bias relative to the reference ashing values was high (2,800.0%) for volume score and low (2.58%) for mineral mass. Measurement precision was 0.6% for volume score and greater than 0.0005% for mineral mass. Mean coefficients of variation for all CT protocols were 5.0% +/- 4.2 and 4.9% +/- 4.2 for mineral mass and modified Agatston score, respectively, and 16.0% +/- 9.2 and 14.5% +/- 3.9 for conventional Agatston and volume scores, respectively (P <.001). CONCLUSION: Compared with the conventional volume score, multi-detector row CT-derived mineral mass is a less biased and more precise measurement of the mineral content of nonmoving ex vivo CEA specimens. Mineral mass and modified Agatston score are more reproducible than conventional volume and Agatston scores.     

Assessment of calcified carotid plaque volume: comparison of contrast-enhanced dual-energy CT angiography and native single-energy CT

OBJECTIVE: The purpose of this study was to compare estimates of calcified plaque volume in the carotid arteries based on contrast-enhanced dual-energy CT angiograms with volume estimates based on native CT scans. CONCLUSION: Detection of hard plaque in the carotid arteries with dual-energy CT angiography was successful in all patients. Estimates of calcified plaque volume based on dual-energy CT angiograms correlated well with those based on native single-energy CT scans but at a lower attenuation threshold (130 HU as opposed to 180 HU) were underestimates compared with those on the native CT scans.     

心脏双源多层CT评估仿人类心脏运动模具的血管钙化斑块标本

目的评估心脏双源多层CT及其图像后处理技术是否可以比单源多层CT能更准确地对钙化斑块进行定量评估,以光学相干断层成像(optical coherence tomography,OCT)     

Direct quantitative in vivo comparison of calcified atherosclerotic plaque on vascular MRI and CT by multimodality image registration

PURPOSE: To investigate direct volumetric in vivo correspondence of calcified atherosclerotic plaque lesions in MRI and CT images of the thoracic aorta by multimodality image registration and fusion. MATERIALS AND METHODS: Twelve CT (11 noncontrast and one contrast) and MRI (TruFISP, contrast T1-weighted volumetric interpolated breath-hold examination (VIBE)) data sets were co-registered by approximate segmentation of the aorta and subsequent automatic co-registration by maximization of mutual information (MI). We quantitatively assessed 22 co-registered calcified plaque lesions on CT and MRI. RESULTS: The three-dimensional registration consistency and accuracy were 1.74 +/- 1.3 mm, and 2.42 +/- 1.65 mm, respectively. The ratio of CT/MRI calcified plaque volume decreased asymptotically with MRI volume, and correlated with average CT lesion density (r = 0.72) for small lesions (<25 mm(3)). The average calcified plaque volume, circumferential extent, and maximal radial width by MRI were significantly smaller compared to CT (35%, 68%, and 53%, respectively; P < 0.05). CONCLUSION: Software co-registration allowed precise, direct, and voxel-based comparison of calcified atherosclerotic plaque lesions imaged by MRI and CT. In comparison with co-registered MRI, overestimation of calcified plaque in aortic CT due to "blooming" correlates with the average lesion density for small plaques, and is greater for small plaques.     

能谱CT重建模式与64层CT重建模式对于颈动脉粥样硬化斑块评估能力的对比分析

目的 对比分析能谱CT与64层CT后处理技术对颈动脉粥样硬化斑块病变评估能力的差异.方法 回顾性分析38例46个颈动脉斑块的能谱CT检查资料.颈动脉CT采用能谱扫描模式,重建方式分为能谱模式重建及非能谱模式重建(传统64层CT重建).通过能谱曲线、碘基图、脂基图分析颈动脉增强扫描期斑块的成分,并与病理或大体标本对照;观察颈动脉分叉处管腔的狭窄程度和斑块的病变特征,包括纤维帽的状况、斑块内出血和脂质.计算Kappa值分析能谱CT和64层CT对血管狭窄程度判断结果的一致性;应用独立样本t检验、确切概率法检验检测两种方法对颈动脉斑块成分及溃疡斑块的检出差异.结果 能谱CT重建模式显示血管狭窄程度为(63.3±3.1)％,64层CT重建模式显示为(61.6±3.8)％,二者具有很好的一致性(Kappa值为0.993,P＜0.01).颈动脉能谱CT重建模式显示12个颈动脉斑块有纤维帽破溃,64层CT重建模式显示11个颈动脉斑块有纤维帽破溃,两者间差异无统计学意义(P＞0.05).颈动脉能谱CT通过能谱曲线、碘基、脂基图分析显示11个颈动脉斑块内有出血,而64层CT重建模式未能显示,两者间差异有统计学意义(P＜0.05);斑块内出血碘浓度为(6.365±1.937) mg/cm3,无斑块内 出 血的斑块碘浓度为(1.573±0.776) mg/cm3,两者比较差异有统计学意义(t=16.39,P＜0.05).能谱CT重建模式显示9个颈动脉斑块内富含脂质成分,64层CT重建模式仅显示2个,两者间差异有统计学意义(P＜0.05);能谱CT显示28个颈动脉斑块内有钙化,64层CT显示27例,两者间差异无统计学意义(P＞0.05).结论 能谱CT重建模式在显示斑块内出血、脂肪成分较64层CT重建模式更具优势.     

Comparison of lipid-rich necrotic core size in symptomatic and asymptomatic carotid atherosclerotic plaque: Initial results

PURPOSE: To investigate the potential difference in the size of the lipid-rich necrotic core (LRNC) in carotid plaques of symptomatic patients versus asymptomatic patients. Pathological studies established that a large LRNC is an important feature of vulnerable atherosclerotic plaque. Previously, we have demonstrated a high correlation between semiquantitative analysis of the LRNC size in T1-weighted (w) turbo field echo (TFE) MR images and histology. MATERIALS AND METHODS: Thirty-seven patients with carotid stenosis >70% with (n = 26) or without (n = 11) symptoms were included. Three independent MR readers quantified the amount of LRNC with a T1w TFE pulse sequence. The relative amount of LRNC (LRNC score) was defined as sum of cross-sectional area percentages LRNC per carotid plaque. RESULTS: Interreader agreement for the three MR readers was good, with an intraclass correlation coefficient (ICC, 95% confidence interval [CI]) of 0.72 (0.57-0.83). All three MR readers on average found a larger LRNC in the symptomatic group of patients, although this was not statistically significant. The mean LRNC score was 116 +/- 129 and 59 +/- 62 for symptomatic and asymptomatic patients, respectively (P = 0.13). Symptomatic patients showed wide ranges in LRNC scores (0-424), while the range was much lower in the asymptomatic group (0-170). CONCLUSION: Single-sequence T1w TFE may be a promising technique to study atherosclerotic plaque at risk of stroke. Larger studies are warranted to confirm these promising results.     

辛伐他汀与二甲双胍联合应用对颈动脉粥样硬化斑块形态学的影响

目的:探讨辛伐他汀与二甲双胍联合应用对糖尿病并发动脉粥样硬化(atherosclerosis,AS)患者颈部AS斑块的影响及其作用。方法:选取糖尿病并发AS患者120例,将其随机分为辛伐他汀组、二甲双胍组、联合治疗组(辛伐他汀和二甲双胍)、空白对照组,疗程6个月。分别于治疗前后行颈动脉超声,观察治疗前后颈动脉内中膜厚度(intima-media thickness,IMT)变化,计算斑块面积、斑块Crouse积分。结果:治疗6个月后,各药物治疗组的IMT、斑块面积及Crouse积分较治疗前明显减小(P0.05或0.01),联合治疗组治疗后IMT、斑块面积及Crouse积分显著小于辛伐他汀组、二甲双胍组(P0.05)。结论:辛伐他汀联合二甲双胍具有抗AS的作用,能明显减轻颈部AS病变程度,疗效优于单独使用辛伐他汀或二甲双胍。     

影响冠状动脉非钙化性斑块CT值准确性因素的尸体标本研究

目的 探讨管腔密度、扫描层厚和窗设置对非钙化性斑块CT值测量准确性的影响.方法 选用20个心脏标本,配制1:50、1:40、1:30、1:20和1:200的5种浓度对比剂(300 mg I/ml的碘海醇),注入血管内行CT扫描.1:200浓度对比剂用作斑块基准状态CT值测量,其余4种浓度对比剂模拟不同管腔密度.采用兴趣区法分别测量4种管腔密度、2种扫描层厚(0.625 mm和1.250 mm)和2种窗设置(窗宽1000 HU、窗位150 HU和窗宽500 HU、窗位200 HU)下的斑块CT值.对管腔密度、层厚和窗设置对斑块CT值测量影响的比较采用析因设计的方差分析,对斑块CT值与3个因素之间的相关关系进行偏相关分析.结果 符合纳入标准的斑块24个.2种窗设置下斑块基准状态CT值分别为(23.90±6.87)HU和(29.00±7.26)HU.管腔密度和窗设置对斑块CT值测量的影响有统计学意义(F值分别为45.674和79.094,P值均＜0.01),而2种层厚的影响无统计学意义(F=1.033,P＞0.05).斑块的CT值随管腔密度的增加而升高.结论 管腔密度和窗设置影响斑块CT值测量,而0.625 mm层厚和1.250 mm层厚的影响不显著.斑块CT值随管腔密度增加而升高.     

Accuracy and uniqueness of three in vivo measurements of atherosclerotic carotid plaque morphology with black blood MRI.

High-resolution MRI provides unique information about morphology of atherosclerotic carotid plaque. In this study, the accuracy and precision of measurements of carotid plaque burden and lumen narrowing were determined for in vivo black blood MRI assessment with respect to ex vivo MRI in a group of 37 atherosclerosis patients who underwent carotid endarterectomy (CEA). Three different plaque measures were compared between paired in vivo and ex vivo MR images: maximum wall area (MWA), minimum lumen area (mLA), and wall volume (WV). MWA and WV are measures of plaque burden, while mLA is a measure of lumen narrowing. The matched in vivo and ex vivo measurements showed good agreement (the correlation coefficients for in/ex vivo WV, MWA, and mLA were 0.92, 0.91, 0.90, respectively) with predictable bias. This study indicates that in vivo black blood MRI can be used to directly estimate the morphology of the plaque. Comparison of the three plaque measures showed that mLA and MWA or WV provide different information regarding the atherosclerotic lesions (the correlation coefficients between mLA and MWA or WV were less than 0.3). Black blood MRI technique is a potentially powerful clinical tool to characterize the severity of atherosclerotic plaque. It can provide accurate measurements on different aspects of the plaque, from plaque burden to lumen narrowing.     

单能和双能CT成像降低金属伪影:不同厂家和不同脊柱水平椎后融合置入物的系统性体外评价

目的评价和优化单能和双能CT成像对于不同厂家和不同脊柱水平椎后融合置入物降低金属伪影的最佳参数设置。方法采用单能(120kV)和双能(140/100kV)CT对5个厂家的颈、胸、腰椎后融合置入物进行体外扫描。双能CT产生的单能影像能量设定值分别为64、69、88、105keV并单独调整以达最佳影像质量(OPTkeV)。两名医师分别对不同厂家和脊柱水平置入物扫描所得的影像质量参数进行定量和定性评价。结果影像的定量和定性参数,在不同观察者间的一致性较好(ICC=0.81～1.00,κ=0.54～0.77)。椎体融合置入物的CT值在不同厂家(P<0.001),不同脊柱水平(P<0.01),以及单能CT与双能CT的64、69、88、105keV和OPTkeV能量值(P<0.01)之间均存在显著差异。影像质量的差异存在统计学意义(P<0.001),双能CT的较高能量设定优于单能CT(V=0.58,P<0.001)。较高能量设定时金属伪影较小(V=0.51,P<0.001)。优化的OPTkeV值位于123～141keV之间。OPTkeV根据不同厂家和脊柱水平的置入物而变化。结论与单能CT相比,双能CT能提高影像质量,减轻置入物的金属伪影。建议对不同厂家和不同脊柱水平的置入物选择个体化的keV值。