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.     

Ex vivo identification of atherosclerotic plaque calcification by a 31P solid-state magnetic resonance imaging technique.

Calcified tissue is a common component of atherosclerotic plaques, and occurs most often in mature plaques. The process of calcification is a poorly understood risk factor that may contribute to a plaque's vulnerability to sudden rupture. In this study a solid-state imaging sequence, termed single-point imaging (SPI), was used to observe calcification directly in ex vivo atherosclerotic plaques. Standards were used to validate the ability of (31)P SPI to detect and differentiate calcification from crystalline cholesterol, phospholipids, and other plaque components. After suitable experimental parameters were found, human carotid specimens obtained by endarterectomy were imaged ex vivo by (31)P solid-state imaging and standard (1)H methods. In contrast to (1)H imaging methods, (31)P imaging detected only the calcification in the plaque.     

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.     

Detection and global quantification of cardiovascular molecular calcification by fluoro18-fluoride positron emission tomography/computed tomography--a novel concept

The aim of this study was to examine the degree and prevalence of regional (aorta) and global (cardiac) fluorine-18-sodium fluoride ((18)F-NaF) uptake by positron emission tomography (PET)-computed tomography (CT) as evidence for calcification in the atherosclerotic plaques in the aorta and the heart as a function of age. Image data from 51 patients, who had undergone whole-body (18)F-NaF-PET/CT, were evaluated retrospectively. Cardiac and arterial (aorta) radiotracer uptakes were analyzed quantitatively by measuring standard uptake values (SUV). This approach involved examining the entire heart and various aortic segments as identified by CT. By combining CT and PET data, regional and global concentrations of this molecule were calculated and correlated with age over the decades. (18)F-NaF uptake in the heart and aorta increased significantly with advancing age (P<0.01). The Pearson correlation coefficient for the mean (18)F-NaF uptake of cardiac region and 5 age groups was 0.92 (P=0.003) and for aorta and 5 age groups was 0.97 (P=0.004). In conclusion, these preliminary data indicate the feasibility of (18)F-NaF-PET/CT for measurement of regional and global calcification of the heart and major arteries. The (18)F-NaF-PET/CT may provide highly relevant information about the state of calcified plaque before structural calcification is detectable by standard CT techniques. This, therefore, may allow for earlier intervention for risk reduction in cardiovascular diseases. Further studies are needed to validate the role of this promising technique in the management of patients with suspected atherosclerosis.     

Identification of different lipid phases and calcium phosphate deposits in human carotid artery plaques by MAS NMR spectroscopy

Accumulation of lipids in atherosclerotic plaques causes progressive narrowing of the arterial lumen, often followed by thrombosis and ischemia. Currently several different methods, most requiring disruption of the plaque, are used to study the physical properties of lipids accumulated in plaques, and lipid composition is typically determined by chemical analysis of completely disrupted plaques. In this study, ¹³C magic angle spinning NMR spectroscopy (MAS NMR) was used to determine in situ the lipid composition and molecular organization of all lipid phases in human carotid artery plaques (ex vivo). Protocols were developed to observe signals from one lipid phase without interference from other phases. In addition, ³¹P MAS NMR detected calcification in plaques by the signals from inorganic phosphate complexed to calcium. Together, ¹³C and ³¹P MAS NMR comprise a powerful nondisruptive approach for determining the quantity and phase state of components in arterial plaques.     

Multicontrast-weighted magnetic resonance imaging of atherosclerotic plaques at 3.0 and 1.5 Tesla: ex-vivo comparison with histopathologic correlation

The purpose was to analyze magnetic resonance (MR) plaque imaging at 3.0 Tesla and 1.5 Tesla in correlation with histopathology. MR imaging (MRI) of the abdominal aorta and femoral artery was performed on seven corpses using T1-weighted, T2-weighted, and PD-weighted sequences at 3.0 and 1.5 Tesla. Cross-sectional images at the branching of the inferior mesenteric artery and the profunda femoris were rated with respect to image quality. Corresponding cross sections of the imaged vessels were obtained at autopsy. The atherosclerotic plaques in the histological slides and MR images were classified according to the American Heart Association (AHA) and analyzed for differences. MRI at 3.0 Tesla offered superior depiction of arterial wall composition in all contrast weightings, rated best for T2-weighted images. Comparing for field strength, the highest differences were observed in T1-weighted and T2-weighted techniques (both P< or =0.001), with still significant differences in PD-weighted sequence (P< or =0.005). The majority of plaques were histologically classified as calcified plaques. In up to 21% of the cases, MRI at both field strengths detected signal loss characteristic of calcification although calcified plaque was absent in histology. MRI at 3.0 Tesla offers superior plaque imaging quality compared with 1.5 Tesla, but further work is necessary to determine whether this translates in superior diagnostic accuracy.     

Atherosclerosis of the carotid artery: Evaluation by magnetic resonance angiography

Carotid artery atherosclerotic plaques (APs) can lead to brain ischemia, an event shown to correlate with both the degree of stenosis and the composition of the AP. Currently, accurate estimates of stenosis can be obtained by either x-ray angiography or three-dimensional time of-flight (TOF) magnetic resonance angiography (MRA). Our purpose was to determine whether three-dimensional TOF MRA images could also provide information on plaque location, morphology, and composition. Seven pre-endarterectomy patients underwent three-dimensional TOF MRA. After endarterectomy, plaque histology was evaluated. Three-dimensional TOF MRA images contained sufficient soft tissue contrast to differentiate the plaques from the surrounding tissues in all cases. Estimation of plaque morphology had 80% correlation with histology. Finally, intraplaque hemorrhage and calcification were depicted as regions of moderately high and very low intensity, respectively. These preliminary results suggest that three-dimensional TOF MRA may be useful in studying the development and progression of carotid atherosclerosis.     

MRI与DSA对颈动脉狭窄和粥样硬化斑块评估能力的比较

目的 探讨MRI与DSA对颈动脉粥样硬化患者血管狭窄及粥样硬化斑块病变特点评估能力的差异.方法 46例缺血性脑血管疾病患者,超声发现颈动脉粥样硬化斑块后分别行颈动脉MRI及DSA检查.颈动脉MR检查序列包括三维时间飞跃法(3D TOF)、T1WI、T2WI、质子密度加权成像( PDWI)及增强T1WI;颈动脉DSA检查分别摄取颈动脉的正位像和侧位像.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、斑块内出血和钙化.计算Kappa值分析MRI和DSA对血管狭窄程度判断结果的一致性;应用配对卡方检验检测两种方法对溃疡斑块的检出差异.结果 89支血管的MR图像质量均满足诊断要求.MRI显示血管狭窄程度的M(范围)为50％(16％～78％),DSA显示为47％(7％～73％),二者具有很好的一致性(Kappa值为0.882,P＜0.01).MRI发现34支血管具有斑块纤维帽破溃,DSA发现10支血管具有溃疡斑块(x2=20.346,P＜0.01).此外,MRI发现37支血管有斑块内出血,71支血管有斑块内钙化,而DSA均不能显示.结论 MRI可以准确判断颈动脉的狭窄程度,在显示溃疡斑块、斑块内出血以及钙化方面较DSA更具优势.     

多层螺旋CT血管成像在评价椎鄄基底动脉粥样硬化斑块稳定性中的应用价值

目的：探讨多层螺旋CT血管成像（MSCTA）在评价椎-基底动脉粥样硬化斑块的稳定性中的应用价值研究。方法120例椎-基底动脉粥样硬化斑块的患者,扫描结束后进行平扫横轴位重组图像/增强扫描横轴位重组图像（ARI/CE-ARI）后处理重建技术;计算出不同类型斑块的平均CT值,对不同类型斑块的强化程度、不同类型斑块血管壁的强化程度和对照组进行比较。结果120例椎-基底动脉粥样硬化斑块患者中,单侧38例,双侧82例,共计发现斑块316处,其中非钙化斑块85处,混合斑块103处,钙化斑块128处。统计学分析显示非钙化斑块处血管壁强化程度与对照组之间差异有统计学意义（t＝8．21,P＜0．01）,非钙化斑块的强化程度与管壁强化程度之间存在显著性相关（r＝0．97,P＜0．01）。结论 MSCTA在评价椎-基底动脉粥样硬化斑块成分、斑块稳定性等方面有着其独特的优势,可以提供可靠的影像学依据。椎-基底动脉粥样硬化斑块中,血管壁的强化程度与斑块的稳定性之间存在相关性。     

3.0T MR成像对兔腹主动脉粥样硬化斑块破裂及血栓形成模型的成像研究

目的 探讨3.0T高分辨MRI对兔腹主动脉粥样硬化模型药物诱发斑块破裂和血栓形成的成像研究.方法 20只雄性新西兰白兔,采用数字表法随机分为实验组16只,对照组4只,采用间断高脂饲料喂养结合球囊拉伤腹主动脉技术建立动脉粥样硬化模型,并在建模3个月后给予蝰蛇毒+组胺药物诱发试验,以期斑块破裂和形成血栓.在药物诱发试验前后...     

Quantification of coronary plaque by 64-slice computed tomography: a comparison with quantitative intracoronary ultrasound

BACKGROUND: Noninvasive assessment of coronary atherosclerotic plaque may be useful for risk stratification and treatment of atherosclerosis. MATERIALS AND METHODS: We studied 47 patients to investigate the accuracy of coronary plaque volume measurement acquired with 64-slice multislice computed tomography (MSCT), using newly developed quantification software, when compared with quantitative intracoronary ultrasound (QCU). Quantitative MSCT coronary angiography (QMSCT-CA) was performed to determine plaque volume for a matched region of interest (regional plaque burden) and in significant plaque defined as a plaque with > or =50% area obstruction in QCU, and compared with QCU. Dataset with image blurring and heavy calcification were excluded from analysis. RESULTS: In 100 comparable regions of interest, regional plaque burden was highly correlated (coefficient r = 0.96; P < 0.001) between QCU and QMSCT-CA, but QMSCT-CA overestimated the plaque burden by a mean difference of 7 +/- 33 mm3 (P = 0.03). In 76 significant plaques detected within the regions of interest, plaque volume determined by QMSCT-CA was highly correlated (r = 0.98; P < 0.001) with a slight underestimation of 2 +/- 17 mm3 (P = not significant) when compared with QCU. Calcified and mixed plaque volume was slightly overestimated by 4 +/- 19 mm3 (P = ns) and noncalcified plaque volume was significantly underestimated by 9 +/- 11 mm3 (P < 0.001) with QMSCT-CA. Overall, the limits of agreement for plaque burden/volume measurement between QCU and QMSCT-CA were relatively large. Reproducibility for the measurements of regional plaque burden with QMSCT-CA was good, with a mean intraobserver and interobserver variability of 0% +/- 16% and 4% +/- 24%, respectively. CONCLUSIONS: Quantification of coronary plaque within selected proximal or middle coronary segments without image blurring and heavy calcification with 64-slice CT was moderately accurate with respect to intravascular ultrasound and demonstrated good reproducibility. Further improvement in CT resolution is required for more reliable measurement of coronary plaques using quantification software.     

Echomorphologic and histopathologic characteristics of unstable carotid plaques

BACKGROUND AND PURPOSE: Our hypothesis was that the carotid plaques associated with retinal and cerebrovascular symptomatology and asymptomatic presentation may be differ from each other. The aim of this study was to identify the sonographic and histopathologic characteristics of plaques that corresponded to these three clinical manifestations. METHODS: The echo process involved duplex preoperative imaging of 71 plaques (67 patients, 21 plaques were associated with retinal, 25 with cerebrovascular symptoms, and 25 were asymptomatic), which was performed in a longitudinal fashion. Appropriate frames were captured and digitized via S-video signal in a computer and digitized sonograms were normalized by two echo-anatomic reference points: the gray scale median (GSM) of the blood and that of the adventitia. The GSM of the plaques was evaluated to distinguish dark (low-GSM) from bright (high-GSM) plaques. Subsequent to endarterectomy, the plaques were sectioned transversely, and a slice at the level of the largest plaque area was examined for the relative size of necrotic core and presence of calcification and hemorrhage. RESULTS: Retinal symptomatology was associated with a hypoechoic plaque appearance (median GSM: 0), asymptomatic status with a hyperechoic plaque appearance (median GSM: 34), and cerebrovascular symptomatology with an intermediate plaque appearance (median GSM: 16) (P = .001). The histopathologic characteristics did not disclose differences between the three clinical groups. The hypoechoic plaque appearance was associated only with the presence of hemorrhage (median GSM for the hemorrhagic plaques, 6, and for the non-hemorrhagic ones, 20 [P = .04]). The relative necrotic core size and the presence of calcification did not show any echomorphologic predilection. CONCLUSION: Our results showed that distinct echomorphologic characteristics of plaques were associated with retinal and cerebrovascular symptomatology and asymptomatic status. Histopathologically, only the presence of hemorrhage proved to have an echomorphologic predilection.     

Coronary artery calcium score: has anything changed?

Calcium deposition along the coronary artery walls is a surrogate biomarker for atherosclerosis, and its presence in the coronary arteries could reflect the severity of coronary artery disease (CAD) High coronary artery calcium score (CACS) correlates with advanced disease and a higher likelihood of coronary stenoses. Many studies have supported the role of CACS as a screening tool for CAD. Historically, CACS was introduced with electron beam computed tomography (EBCT), but in the last 30 years, many changes have occurred in CT, where the development of multidetector spiral technology has made reliable the noninvasive study of the heart and coronary arteries. Correlation studies with intravascular ultrasound (IVUS) and histology have demonstrated the capability of multidetector CT (MDCT) to provide information useful for characterising atherosclerotic plaque in a noninvasive manner. This has shifted the interest from heavily calcified deposits to plaque with a low-density core and small, superficial calcified nodules, features more frequently present in atherosclerotic plaque prone to rupture and responsible for acute coronary events (culprit lesions). The purpose of this review article is to summarise the recent evolution and revolution in the field of CT, strengthen the importance of a coronary CT study not limited to CACS evaluation and CAD grading but also used to obtain information about plaque composition, and to improve stratification of the patient at risk for acute coronary events.     

ISCHEMIA trial – Failed intervention or failed stratification?

Treatment of stable ischemic heart disease remains controversial due to lack of proper measures to identify the vulnerable patient who will suffer acute coronary events. Imaging modalities can identify rupture-prone coronary plaques but studies have found that most plaque ruptures without causing clinical events (1). High risk plaques identified by CT Angiogram (CTA) was found to be predictive of acute coronary events (ACS) in a large cohort study but the extent of atherosclerotic burden was a confounder (2). As such, numerous studies have suggested total atherosclerotic plaque burden as the main determinant of adverse patient outcomes (3,4). Coronary artery calcium (CAC) is a highly specific surrogate for coronary atherosclerosis burden and is the most predictive single cardiovascular risk marker in asymptomatic persons (5). The greater the atherosclerotic plaque burden, the more likely plaque ruptures will occur and the greater the probability that one of them triggers vascular thrombosis and a clinical event (6).     

Changes in measured size of atherosclerotic plaque calcifications in dual-energy CT of ex vivo carotid endarterectomy specimens: effect of monochromatic keV image reconstructions

Objective

The aim of this study was to compare the size of the calcifications measured on the different keV images to a histological standard.

Methods

Five ex vivo carotid endarterectomy (CEA) specimens were imaged with a dual-energy CT. CT images were reconstructed at different monochromatic spectral energies (40, 60, 77, 80, 100, 120, 140 keV). Cross-sectional area of the plaque calcifications present on each CT image was measured. The histological calcium areas on each corresponding CEA specimen were traced manually on digitised images of Toluidine Blue/Basic Fuchsin stained plastic sections. The CT images and corresponding histology sections were matched. The CT-derived calcium areas on each keV image were compared to the calcified area measurements by histology.

Results

A total of 107 histology sections were matched to corresponding CT images. The average calcified area per section by histology was 7.6?±?7 mm² (range 0–26.4 mm²). There was no significant difference between the calcified areas measured by histology and those measured on CT–virtual monochromatic spectral (VMS) reconstructed images at 77 keV (P?=?0.08), 80 keV (P?=?0.20) and 100 keV (P?=?0.14).

Conclusions

Calcium area measured on the 80 keV image set was most comparable to the amount of calcium measured by histology.

Key Points

? Dual-energy computed tomography allows reconstruction of virtual monochromatic images. ? Virtual monochromatic images reconstructed at different keVs reveal different atherosclerotic calcification quantification. ? Virtual monochromatic images allows better evaluation of calcified atherosclerotic plaques.     

Intraplaque Hemorrhage and the Plaque Surface in Carotid Atherosclerosis: The Plaque At RISK Study (PARISK)

BACKGROUND AND PURPOSE:An important characteristic of vulnerable plaque, intraplaque hemorrhage, may predict plaque rupture. Plaque rupture can be visible on noninvasive imaging as a disruption of the plaque surface. We investigated the association between intraplaque hemorrhage and disruption of the plaque surface.MATERIALS AND METHODS:We selected the first 100 patients of the Plaque At RISK study, an ongoing prospective noninvasive plaque imaging study in patients with mild-to-moderate atherosclerotic lesions in the carotid artery. In carotid artery plaques, disruption of the plaque surface (defined as ulcerated plaques and/or fissured fibrous cap) and intraplaque hemorrhage were assessed by using MDCTA and 3T MR imaging, respectively. We used a χ² test and multivariable logistic regression to assess the association between intraplaque hemorrhage and disrupted plaque surface.RESULTS:One hundred forty-nine carotid arteries in 78 patients could be used for the current analyses. Intraplaque hemorrhage and plaque ulcerations were more prevalent in symptomatic compared with contralateral vessels (hemorrhage, 38% versus 11%; P < .001; and ulcerations, 27% versus 7%; P = .001). Fissured fibrous cap was more prevalent in symptomatic compared with contralateral vessels (13% versus 4%; P = .06). After adjustment for age, sex, diabetes mellitus, and degree of stenosis, intraplaque hemorrhage was associated with disrupted plaque surface (OR, 3.13; 95% CI, 1.25–7.84) in all vessels.CONCLUSIONS:Intraplaque hemorrhage is associated with disruption of the plaque surface in patients with a carotid artery stenosis of <70%. Serial studies are needed to investigate whether intraplaque hemorrhage indeed increases the risk of plaque rupture and subsequent ischemic stroke during follow-up.

The need to identify patients with mild-to-moderate carotid artery stenosis and an increased stroke risk who might benefit from surgical treatment has shifted research interest from assessment of the degree of carotid stenosis to assessment of vulnerable plaque characteristics.¹ Vulnerable plaques are atherosclerotic plaques more prone to rupture and are associated with a higher risk for thromboembolism and ischemic stroke.^2,3 Intraplaque hemorrhage is an important characteristic of the vulnerable plaque.⁴ Prevalence of intraplaque hemorrhage has been shown to be higher in symptomatic than in asymptomatic lesions.⁵ Moreover, the presence of intraplaque hemorrhage in carotid artery disease is associated with an increased risk of cerebral ischemic events.^6–8The pathophysiologic mechanism leading to intraplaque hemorrhage is a topic of debate. However, a common viewpoint is that small leaky neovessels in the atherosclerotic plaques are a likely source of intraplaque hemorrhage.^5,9,10 The presence of intraplaque hemorrhage is thought to initiate several biologic processes like phagocytosis and local inflammation, leading to the release of proteolytic enzymes, deposition of free cholesterol and subsequently plaque growth, plaque destabilization, and possible plaque rupture.^5,9–12 Plaque rupture can be visible on imaging as a disruption of the atherosclerotic plaque surface (plaque ulceration and/or a fissured fibrous cap).^13,14 A previous study reported that plaque ulceration on CTA was useful for the prediction of intraplaque hemorrhage on MR imaging in a broad group of symptomatic patients referred for carotid artery imaging.¹⁵ Ulcerated plaques themselves are independently associated with an increased risk of ipsilateral ischemic events as well.^16,17The aim of the current study was to investigate the association between intraplaque hemorrhage, as assessed on MR imaging, and disruption of the plaque surface, assessed on MDCTA, in symptomatic patients with a carotid artery stenosis of <70%.     

18F-FDG accumulation in atherosclerosis: use of CT and MR co-registration of thoracic and carotid arteries

Purpose The purpose of this study was to depict ¹⁸F-fluoro-2-deoxy-D-glucose (FDG) accumulation in atherosclerotic lesions of the thoracic and carotid arteries on CT and MR images by means of automatic co-registration software. Methods Fifteen hospitalised men suffering cerebral infarction or severe carotid stenosis requiring surgical treatment participated in this study. Automatic co-registration of neck MR images and FDG-PET images and of contrast-enhanced CT images and FDG-PET images was achieved with co-registration software. We calculated the count ratio, which was standardised to the blood pool count of the superior vena cava, for three arteries that branch from the aorta, i.e. the brachial artery, the left common carotid artery and the subclavian artery (n=15), for atherosclerotic plaques in the thoracic aorta (n=10) and for internal carotid arteries with and without plaque (n=13). Results FDG accumulated to a significantly higher level in the brachial artery, left common carotid artery and left subclavian artery at their sites of origin than in the superior vena cava (p=0.000, p=0.000 and p=0.002, respectively). Chest CT showed no atherosclerotic plaque at these sites. Furthermore, the average count ratio of thoracic aortic atherosclerotic plaques was not higher than that of the superior vena cava. The maximum count ratio of carotid atherosclerotic plaques was significantly higher than that of the superior vena cava but was not significantly different from that of the carotid artery without plaque. Conclusion The results of our study suggest that not all atherosclerotic plaques show high FDG accumulation. FDG-PET studies of plaques with the use of fused images can potentially provide detailed information about atherosclerosis.     

Asbestos-related pleural disease: value of dedicated magnetic resonance imaging techniques

OBJECTIVES: We sought to compare respiratory-gated high-spatial resolution magnetic resonance imaging (MRI) and radial MRI with ultra-short echo times with computed tomography (CT) in the diagnosis of asbestos-related pleural disease. METHODS: Twenty-one patients with confirmed long-term asbestos exposure were examined with a CT and a 1.5-T MR unit. High-resolution respiratory-gated T2w turbo-spin-echo (TSE), breath-hold T1w TSE, and contrast-enhanced fat-suppressed breath-hold T1w TSE images with an inplane resolution of less than 1 mm were acquired. To visualize pleural plaques with a short T2* time, a pulse sequence with radial k-space-sampling was used (TE = 0.5 milliseconds) before and after administration of Gd-DTPA. CT and MR images were assessed by 4 readers for the number and calcification of plaques, extension of pleural fibrosis, extrapleural fat, detection of mesothelioma and its infiltration into adjacent tissues, and detection of pleural effusion. Observer agreement was studied with the use of kappa statistics. RESULTS: The MRI protocol allowed for differentiation between normal pleura and pleura with plaques. Interobserver agreement was comparable for MRI and CT in detecting pleural plaques (median kappa = 0.72 for MRI and 0.73 for CT) and significantly higher with CT than with MRI for detection of plaque calcification (median kappa 0.86 for CT and 0.72 for MRI; P = 0.03). Median sensitivity of MRI was 88% for detection of plaque calcification compared with CT. For assessment of pleural thickening, pleural effusion, and extrapleural fat, interobserver agreement with MRI was significantly higher than with CT (median kappa 0.71 and 0.23 for pleural thickening, 0.87 and 0.62 for pleural effusion, and 0.7 and 0.56 for extrapleural fat, respectively; P < 0.05). For detection of mesothelioma, median kappa was 0.63 for MRI and 0.58 for CT. CONCLUSION: High-resolution MR sequences and radial MRI achieve a comparable interobserver agreement in detecting pleural plaques and even a higher interobserver agreement in assessing pleural thickening, pleural effusion, and extrapleural fat when compared with CT.     

DSCTA对颈动脉斑块特征与急性缺血性脑卒中的相关性研究

目的 探讨双源CT血管成像（DSCTA）对颈动脉斑块的诊断价值,评估颈动脉狭窄<50%的斑块特征与急性缺血性脑卒中的关系。方法 选取符合纳入标准患者64例,回顾性分析颈动脉分叉处斑块特征,急性脑卒中侧为实验组,无急性脑卒中侧为对照组。分析内容包括斑块类型、斑块表面形态、钙化分布、钙化数目,对两组颈动脉斑块特征进行统计学分析。结果 实验组颈动脉斑块较对照组更容易出现以下特征且差异有统计学意义,包括非钙化性和混合性斑块出现率更高（Z=-2.39,P=0.02）,斑块表面不规则和溃疡出现率更高（Z=-6.04,P<0.01）,浅层钙化（Z=-2.06,P=0.04）和多发钙化出现率更高（Z=-2.52,P=0.01）。结论 DSCTA可更好的显示斑块特征,颈动脉非钙化性和混合性斑块、斑块表面不规则或溃疡形成、浅层钙化和多发钙化可能为急性缺血性脑卒中的危险因素。     

Atherosclerotic plaque at the carotid bifurcation: CT angiographic appearance with histopathologic correlation.

BACKGROUND AND PURPOSE: The likelihood that carotid plaque will give rise to cerebral ischemia probably relates to the degree of arterial stenosis and to plaque morphology. The aim of this study was to assess whether features seen at CT angiography might be used to predict carotid plaque stability by comparing CT angiograms with histopathologic examinations of the carotid artery bifurcation. METHODS: Nine patients with symptomatic severe carotid stenosis at intraarterial angiography had CT angiography of the carotid bifurcation before carotid endarterectomy. After endarterectomy, multiple sections of the specimens through the carotid bifurcation were examined histologically. Plaque characteristics recorded included the proportion of necrotic/lipid core, presence of hemorrhage, extent of fibrosis, ulceration, calcification, inflammatory cell infiltrate, and fibrous cap thickness. Corresponding CT angiograms were assessed for plaque size, distribution, and radiodensity as well as presence of calcific density and ulceration. Histologic findings and CT angiograms were compared. RESULTS: Plaque with a large necrotic/lipid core, which was often hemorrhagic, was found in 16 of 23 sections, and in 15 of these this histologic appearance corresponded with patchy or homogeneous low density on CT angiograms. Six of seven predominantly fibrous plaques were of soft-tissue density on CT angiograms. High density consistent with calcification was seen more frequently on CT angiograms than it was detected histologically, but CT angiography depicted plaque ulceration poorly (four ulcers at histology; two false-positive and two false-negative findings at CT angiography). CONCLUSION: CT angiography is a promising method for assessing the lumen and wall of the carotid artery. The apparent correlation between histologic appearance and plaque density on CT angiograms has important implications for the prediction of plaque stability, even though ulceration is shown inconsistently.