3 research outputs found
Variation of longitudinal strain along the arterial wall adjacent to the asymptomatic carotid plaque
The motion, and resulting strain, of the arterial wall nearby an
atheromatous plaque is believed to be affected by the plaque and
therefore may carry important information about disease status. Strain
of the arterial wall in the longitudinal direction, i.e. along its
length, has recently gained attention as determinant of cardiovascular
risk. In this work, longitudinal strain (LS) was estimated along the
wall proximal to asymptomatic carotid plaque, in an attempt to highlight
the significance of arterial wall kinematics in atherosclerotic subjects
without cerebrovascular events. Twenty five atheromatous carotid
arteries of elderly male adults (59-81 y.o., 50-100% stenosis) were
imaged in longitudinal sections, and videos of B-mode images were
analysed using a previously developed method based on optical flow. The
analysis consisted in the estimation of the longitudinal positions of
three regions of interest (ROIs) on the posterior wall. LS was
subsequently defined as the normalised difference of the longitudinal
positions between two ROIs, and was assessed at two locations along the
wall. A longitudinal strain index (LSI) was then calculated as the
average of the amplitudes of the LS curves over 2-3 cardiac cycles. LSIs
at location 1 (closer to the plaque) were significantly higher than at
location 2 (4.74 +/- 1.66 vs. 2.54 +/- 1.08, p-value= 1.25E-06). This
indicates that the wall closer to the plaque undergoes higher strain
than the wall farther from it, which may be due to the effect of the
presence and motion of the nearby lesion; an effect, which seems to be
extended to the area around it. These findings show promise toward
better understanding the complex mechanical phenomena taking place not
only within the plaque but also in the neighbouring tissues
Ultrasound-image-based texture variability along the carotid artery wall in asymptomatic subjects with low and high stenosis degrees: unveiling morphological phenomena of the vulnerable tissue
Valid identification of the vulnerable asymptomatic carotid
atherosclerosis remains a crucial clinical issue. In this study, texture
differences were estimated along the atherosclerotic arterial wall,
namely at the plaque, the wall adjacent to it and the plaque shoulder,
i.e. the boundary between wall and plaque, in an attempt to reveal
morphological phenomena, representative of the high stenosis (considered
vulnerable) cases. A total of 25 arteries were interrogated, 11 with low
(50-69%) and 14 with high (70-100%) degrees of stenosis. The two
groups had similar ages. Texture features were estimated from B-mode
ultrasound images, and included four second-order statistical parameters
(contrast, correlation, energy and homogeneity), each calculated at four
different image directions (0 degrees, 45 degrees, 90 degrees, 135
degrees), yielding a total of 16 features. Texture differences between
(a) wall and plaque and (b) wall and plaque shoulder were quantified as
the differences in texture feature values for each tissue area
normalised by the texture feature value of the wall, which was
considered as reference, as illustrated in the following equation:
dTF(i) = (TFi,W - TFi,P/S)/TFi,W, where dTF(i) the estimated texture
difference, TFi,W the texture of the wall, and TFi,P/S the texture of
the plaque (P) or the shoulder (S). Significant differences in texture
variability of wall vs. shoulder were observed between high and low
stenosis cases for 3 features at diastole and 7 features at systole. No
differences were observed for wall vs plaque, although wall texture was
significantly different than plaque texture, in absolute values. These
findings suggest that texture variability along the atherosclerotic
wall, which is indicative of tissue discontinuities, and proneness to
rupture, can be quantitatively described with texture indices and reveal
valuable morphological phenomena of the vulnerable tissue. (C) 2015 The
Authors. Published by Elsevier B.V