Atherosclerotic Plaque Tissue: Noninvasive Quantitative Assessment of Characteristics with Software-aided Measurements from Conventional CT Angiography

Abstract

Purpose To (a) evaluate whether plaque tissue characteristics determined with conventional computed tomographic (CT) angiography could be quantitated at higher levels of accuracy by using image processing algorithms that take characteristics of the image formation process coupled with biologic insights on tissue distributions into account by comparing in vivo results and ex vivo histologic findings and (b) assess reader variability. Materials and Methods Thirty-one consecutive patients aged 43-85 years (average age, 64 years) known to have or suspected of having atherosclerosis who underwent CT angiography and were referred for endarterectomy were enrolled. Surgical specimens were evaluated with histopathologic examination to serve as standard of reference. Two readers used lumen boundary to determine scanner blur and then optimized component densities and subvoxel boundaries to best fit the observed image by using semiautomatic software. The accuracy of the resulting in vivo quantitation of calcification, lipid-rich necrotic core (LRNC), and matrix was assessed with statistical estimates of bias and linearity relative to ex vivo histologic findings. Reader variability was assessed with statistical estimates of repeatability and reproducibility. Results A total of 239 cross sections obtained with CT angiography and histologic examination were matched. Performance on held-out data showed low levels of bias and high Pearson correlation coefficients for calcification (-0.096 mm and 0.973, respectively), LRNC (1.26 mm and 0.856), and matrix (-2.44 mm and 0.885). Intrareader variability was low (repeatability coefficient ranged from 1.50 mm to 1.83 mm among tissue characteristics), as was interreader variability (reproducibility coefficient ranged from 2.09 mm to 4.43 mm). Conclusion There was high correlation and low bias between the in vivo software image analysis and ex vivo histopathologic quantitative measures of atherosclerotic plaque tissue characteristics, as well as low reader variability. Software algorithms can mitigate the blurring and partial volume effects of routine CT angiography acquisitions to produce accurate quantification to enhance current clinical practice. Clinical trial registration no. NCT02143102 RSNA, 2017 Online supplemental material is available for this article. An earlier incorrect version of this article appeared online. This article was corrected on September 15, 2017.

Carotid Intraplaque-Hemorrhage Volume and Its Association with Cerebrovascular Events

“…21 Volume analysis was performed with dedicated software (Elucid Bioimaging, Wenham, Massachusetts) to semi-automatically quantify the subcomponent volume. 22,23 With this software, it is possible to identify attenuation values of all the voxels within a volume, and by means of applying some thresholds, it is possible to classify the tissues according to the attenuation values (Fig 1). For this analysis, we considered 5 classes: 3, as suggested by de Weert et al 24 in which voxels identifying lipid tissues were <60 HU, fibrous tissue between 60 and 130 HU, and calcium tissue >130 HU.…”

Quantitative assessment of carotid plaque morphology (geometry and tissue composition) using computed tomography angiography

“…We used an image processing software (vascuCAP, version A.1.1; Elucid Bioimaging, Wenham, Mass) 15 to outline (segment) the luminal and outer wall surfaces of the common, internal, and external carotid arteries. Fig 1 illustrates the overall workflow.…”

“…16,17 vascuCAP reduces this error by compensating for the blurring caused by the imaging system point spread function using a Gaussian-regularized multistage level-set approach. 15 The resulting plaque tissue composition measures have been histologically validated for calcium, LRNC, and matrix (composed of all stable wall elements including fibrous tissue and all other unlabeled pixels). 15 These algorithms mitigate artifacts, such as partial volume effects due to calcium, whereby calcified plaques appear larger than their actual size.…”

Carotid Plaque CTA Analysis in Symptomatic Subjects with Bilateral Intraparenchymal Hemorrhage: A Preliminary Analysis

“…11,29,30 However, other studies suggest that by using CT, it is possible to analyze, with very good detail, the volume of different plaque components. 19,31 The observation that plaque composition and IPH can be analyzed with CT has very important practical consequences in clinical practice. Unlike MR imaging, CT is routinely used in the urgent/emergent evaluation of patients with acute ischemic events, it is widely available 24/7, and is more convenient for patients, especially the elderly with acute cerebrovascular syndromes because in such cases, good quality MR images are challenging to obtain because of patient movement, discomfort, and lack of cooperation.…”

“…with 11 and 8 years of experience, respectively, in CT of the supra-aortic vessels) unaware of the patient's symptomatic side, using as window/level settings W ϭ 850 and L ϭ 300, 18 with a dedicated software (VascuCAP; Elucid Bioimaging, Wenham, Massachusetts) to semiautomatically quantify the volume of the subcomponents. 19 The inner and outer boundaries of the plaque were automatically identified by the software, but each volume was checked manually by the radiologists to avoid mistakes in the segmentations. Special care was used to exclude the presence of thrombus attached to the carotid artery plaque, which was defined according to Eesa et al 20 as "an eccentric pedunculated filling defect projecting into the lumen of the vessel."…”