Using averaged models from 4D ultrasound strain imaging allows to significantly differentiate local wall strains in calcified regions of abdominal aortic aneurysms

Abstract

Abdominal aortic aneurysms are a degenerative disease of the aorta associated with high mortality. To date, in vivo information to characterize the individual elastic properties of the aneurysm wall in terms of rupture risk is lacking. We have used time-resolved 3D ultrasound strain imaging to calculate spatially resolved in-plane strain distributions characterized by mean and local maximum strains, as well as indices of local variations in strains. Likewise, we here present a method to generate averaged models from multiple segmentations. Strains were then calculated for single segmentations and averaged models. After registration with aneurysm geometries based on CT-A imaging, local strains were divided into two groups with and without calcifications and compared. Geometry comparison from both imaging modalities showed good agreement with a root mean squared error of 1.22 ± 0.15 mm and Hausdorff Distance of 5.45 ± 1.56 mm (mean ± sd, respectively). Using averaged models, circumferential strains in areas with calcifications were 23.2 ± 11.7% (mean ± sd) smaller and significantly distinguishable at the 5% level from areas without calcifications. For single segmentations, this was possible only in 50% of cases. The areas without calcifications showed greater heterogeneity, larger maximum strains, and smaller strain ratios when computed by use of the averaged models. Using these averaged models, reliable conclusions can be made about the local elastic properties of individual aneurysm (and long-term observations of their change), rather than just group comparisons. This is an important prerequisite for clinical application and provides qualitatively new information about the change of an abdominal aortic aneurysm in the course of disease progression compared to the diameter criterion.

The role of asymmetry and volume of thrombotic masses in the formation of local deformation of the aneurysmal-altered vascular wall: An in vivo study and mathematical modeling

“…In the numerical modeling aspect, averaged rather than personalized data on the viscoelastic characteristics of the thrombus, aorta and hemodynamic parameters were used, as well as averaged data on the strength properties of the vascular walls of the studied patients [ 24 ]. Similar approaches are currently actively used in averaged modeling of aortic hemodynamics with heterogeneous walls [ 32 ]. In reference to related research, a parallel stage of the study is discussed in [ 18 ], which examines a database of patients with aortic aneurysms and highlights the primary distinctions in the strength characteristics of aneurysm-affected aortas and those with other vascular tissue lesions in the abdominal segment.…”

Prediction of Hemodynamic-Related Hemolysis in Carotid Stenosis and Aiding in Treatment Planning and Risk Stratification Using Computational Fluid Dynamics

“…Therefore, developing prevention and early diagnosis is increasingly important to protect patients' health. Over the years, a number of methods for imaging cholesterol stenoses, such as optical coherence tomography [39][40][41][42][43], near infrared spectroscopy [44], ultrasound imaging [45][46][47][48], computed tomography [49][50][51][52][53][54][55], and magnetic resonance imaging [55][56][57][58][59][60][61], have been developed [62]. The information obtained thanks to imaging methods allowed for the visualization of stenoses and the creation of accurate CFD simulation models.…”

Correlation of four-dimensional ultrasound strain analysis with computed tomography angiography wall stress simulations in abdominal aortic aneurysms

“…4D-US strain analysis was performed based on the averaged models from five segmentation runs according to the methodology of Wittek and Hegner et al. 14 , 15 Segmentation and analysis of CTA, as well as registration with segmentation of 4D-US imaging, were performed by three independent investigators. We have not proven the interobserver variability of single examinations, 16 reliability of the segmentation process, and value of the averaged models for 4D-US, 14 , 15 , 17 as well as the reliability of the segmentation of the geometry and stress analysis for CTA 18 once again, because these processes have already been published and classified as reliable.…”

“…14 , 15 Segmentation and analysis of CTA, as well as registration with segmentation of 4D-US imaging, were performed by three independent investigators. We have not proven the interobserver variability of single examinations, 16 reliability of the segmentation process, and value of the averaged models for 4D-US, 14 , 15 , 17 as well as the reliability of the segmentation of the geometry and stress analysis for CTA 18 once again, because these processes have already been published and classified as reliable. However, we registered the conformity of AAA geometry in the 4D-US and in the gold standard CTA as the absolute prerequisite for the comparative analysis of wall strain and wall stress.…”

“…The results of five speckle tracking runs were merged into one averaged model. 14 , 15 Averaging multiple segmentations involved combining the closest points of each segmentation into one point. Because the commercial software was designed for the left cardiac ventricle, the artificial pseudo-apex was removed from the initial model at the inflection point.…”