Quantification Of Atherosclerotic Plaques Research Articles

2126 Saphenous vein graft atherosclerotic plaque quantification utilizing magnetic resonance imaging and multidetector computed tomography: a comparison with intravascular ultrasound

Methods Sequential patients (n = 22) undergoing coronary angiography with anginal symptoms and significant saphenous vein graft lesions were enrolled. All patients had IVUS, MDCT (16-detector) and MRI using black-blood T1weighted imaging (1.5 T) performed. Cross-sectional images from IVUS and MDCT were analysed at 1 mm intervals along the entire length of the lesion. MRI images were obtained and analysed at 5 mm intervals. The sum of the plaque areas on these images gave the lesion volume. The MDCT and MRI images were analysed by two independent investigators. Spearman's correlation and BlandAltman plots were used where appropriate. Results MRI data were analysed for 18 patients (n = 19 lesions) as 3 patients were unable to finish their scans and one patient's scan was degraded by artefact. The mean age of the SVGs was 13.95 years ( ± 4.41 years). The interobserver variability as determined by coefficient of variance for assessing plaque volume for MDCT and MRI was 3.6% and 9.9% respectively. The correlation between MDCT and IVUS was better in mean luminal area (r = 0.87; p < 0.001) than mean vessel wall area (r = 0.77; p < 0.001). In contrast, MRI and IVUS correlation was better in vessel wall area (r = 0.77; p < 0.001) than luminal area (r = 0.59; p = 0.008). Spearman's correlation for plaque volume was better for MRI and IVUS (rs = 0.97; p < 0.001) compared to MDCT and IVUS (rs = 0.85; p < 0.001). However, Bland-Altman plots (Figure 1) show plaque volumes by MDCT to be closer to IVUS (differences of mean = 186.9 mm3; SD = 239.1) compared to MRI and IVUS (differences of mean = 437.5 mm3; SD = 407.9).

Volumetric Quantification of Atherosclerotic Plaque in CT Considering Partial Volume Effect

Coronary artery calcification (CAC) is quantified based on a computed tomography (CT) scan image. A calcified region is identified. Modified expectation maximization (MEM) of a statistical model for the calcified and background material is used to estimate the partial calcium content of the voxels. The algorithm limits the region over which MEM is performed. By using MEM, the statistical properties of the model are iteratively updated based on the calculated resultant calcium distribution from the previous iteration. The estimated statistical properties are used to generate a map of the partial calcium content in the calcified region. The volume of calcium in the calcified region is determined based on the map. The experimental results on a cardiac phantom, scanned 90 times using 15 different protocols, demonstrate that the proposed method is less sensitive to partial volume effect and noise, with average error of 9.5% (standard deviation (SD) of 5-7mm(3)) compared with 67% (SD of 3-20mm(3)) for conventional techniques. The high reproducibility of the proposed method for 35 patients, scanned twice using the same protocol at a minimum interval of 10 min, shows that the method provides 2-3 times lower interscan variation than conventional techniques.

Is Magnetic Resonance Image Guidance the Key to Opening Chronic Total Occlusions?

Through progressive plaque growth or fibrotic organization of occlusive thrombus, atherosclerosis may result in chronic total occlusion (CTO) of a major arterial conduit. If CTO develops slowly, collateral pathways may supply sufficient perfusion to retain tissue viability despite occlusion of the major inflow conduit. However, such collateral-mediated perfusion rarely matches that provided by an open main conduit, particularly during the peak demand of regional muscular activity. Although strategies to limit regional oxygen demand (eg, β-blockers for the treatment of angina pectoris) or to enhance collateral function (eg, a walking program for superficial femoral occlusion, experimental angiogenesis) may be of some benefit, these approaches generally offer less complete return of normal physiology and relief of ischemic symptoms than does direct revascularization of the occluded vessel. With surgical bypass, the nature of the occlusion (its length, duration, tortuosity, calcification) is less important than the presence of a suitable distal anastomotic target. On the other hand, with catheter-based techniques, success depends heavily on these lesion characteristics. In fact, crossing such occluded segments with a guidewire remains the dominant barrier to catheter-based treatments of occluded arterial segments. Once the guidewire has been passed successfully into the distal true lumen, the process of dilating and stenting the segment is usually straightforward and durable, at least with the use of drug-eluting stents in coronary CTOs.1,2 Article p 1101 Devices designed to cross CTOs should have 3 key features: an ability to distinguish a true luminal path from one created within (dissection) or through (perforation) the vessel wall of the occluded segment, an ability to change direction (steer) to correct deviations from the desired path through the occlusion, and an ability to penetrate the frequently fibrotic and focally calcific substance of the occlusion through the use of either mechanical stiffness or an alternative energy modality (laser, …

Factors of Carotid Arterial Enlargement in a Population Aged 59 to 71 Years

Factors of carotid arterial enlargement are not well known in general populations. The purpose of this study was to assess the cross-sectional associations of arterial wall lesions and cardiovascular risk factors with carotid lumen diameter in elderly subjects. B-mode ultrasound examinations of the carotid arteries and risk factor assessment were made in 1272 participants in the EVA (Etude sur le vieillissement artériel) Study, a longitudinal study designed to evaluate vascular and cognitive aging in men and women aged 59 to 71 years. Ultrasound examinations included measurements of intima-media thickness (IMT) and interadventitial and lumen diameters of the common carotid arteries and quantification of atherosclerotic plaques in extracranial carotid arteries. Men showed greater IMT interadventitial and lumen diameters of the common carotid arteries than did women. In both sexes, common IMT and plaque score were positively associated with common interadventitial and lumen diameters. Stepwise multiple regression analysis showed that male sex, body height and weight, common IMT, plaque score, systolic blood pressure, and alcohol consumption were positively and independently related to lumen diameter. On the other hand, an independent negative association was observed between low density lipoprotein cholesterol and lumen diameter. In 59- to 71-year-old subjects, increased IMT and atherosclerotic plaques were accompanied by an increase in lumen diameter of the common carotid arteries, indicating an overcompensation. Luminal enlargement observed with several risk factors and with high blood pressure in particular might be partially counteracted by high lipid levels.

Quantification of atherosclerotic plaques in carotid arteries by three-dimensional ultrasound

The aim of this study was to develop three-dimensional (3D) ultrasound imaging of the carotid arteries in order to reduce intraexaminer and interexaminer variabilities of volume measurements in follow-up scans of atherosclerotic plaques. The non-invasive quantification of human atherosclerosis by 3D ultrasound was performed using a three-dimensional computer based image reconstruction. The linear movements of the transducer were driven by a motor triggered by electrocardiography. The method included an option to change angle of insonation and a correction of skin contact adaptation. Repeated measurements were performed at weekly intervals in 70 patients. Variabilities and ranges of three newly developed evaluation procedures of plaque volumes (manual tracing, threshold procedure, watershed algorithm) were used. Intraexaminer variability varied between 2.8% (watershed algorithm) and 4.1% (threshold procedure). Interexaminer variability ranged from 4.2% (manual tracing) to 7.6% (threshold procedure), follow-up measurements from 5.2% (watershed algorithm) to 9.4% (threshold procedure). Pearson correlation coefficients of interexaminer agreement and also those between all three measurement procedures were highly significant (p < 0.01). We conclude that the newly developed 3D computer based image reconstruction allows repeated quantification of moderate atherosclerosis with a high reliability.

Morphometric quantification of atherosclerotic plaques by computer-assisted image-analysis of histographs

A method is described for quantifying the amount of atherosclerotic plaque in collapsible blood vessels by a computer-assisted image analysis of cross-sectional contours traced under microscopic visualization. The digitized contours are processed using a computer program that transforms the irregular image of the collapsed vessel into an ideal geometry and then calculates in vivo linear and areal parameters, variables, and ratios. The analysis is based on conventional stereologic principles and utilizes relatively inexpensive and widely available equipment: microscope with drawing tube attachment, digitizing board, microcomputer, monitor, and printer or plotter. Some of the output data include the fraction of vessel lumen occluded by plaque, average thickness of plaque, the fraction of wall surface area covered by plaque, and the ratio of the vessel bore to vessel wall volumes. The error and precision of measuring lumen occlusion and plaque surface area are assessed.