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Progressive enlargement of an aortic aneurysm of the descending aorta in a 76-year-old patient with history of prior surgical repair of the ascending aorta. Aortic enlargement is noted at all intervals, but increases in rate and extent over time. Aortic lumen area (in square millimeter) measured at a single level (black line) in the distal descending aorta was used to corroborate a focal region of enlargement in the distal descending aorta seen on the VDM map. VDM values for replaced ascending aorta are not displayed owing to artifact.
Source publication
Thoracic aortic aneurysm is a common and lethal disease that requires regular imaging surveillance to determine timing of surgical repair and prevent major complications such as rupture. Current cross-sectional imaging surveillance techniques, largely based on computed tomography angiography, are focused on measurement of maximal aortic diameter, a...
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Purpose
Heterozygous pathogenic/likely pathogenic (P/LP) variants in the ACTA2 gene confer a high risk for thoracic aortic aneurysms and aortic dissections. This retrospective multicenter study elucidates the clinical outcome of ACTA2-related vasculopathies.
Methods
Index patients and relatives with a P/LP variant in ACTA2 were included. Data were...
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Citations
... Recent papers [3][4][5][6] have proposed a Vascular deformation mapping (VDM) method for quantifying soft tissue growth using deformable image registration. Studies [4,5] have shown the success of using this method in monitoring the growth of AAA. ...
An abdominal aortic aneurysm (AAA) is a dangerous pathology that needs regular monitoring based on medical images. Currently, only visual estimates of the growth rate and methods based on the assessment of changes in the maximum diameter of the aneurysm in clinical practice are used. However, the quantitative assessment of vessel wall growth rate based on deformable image registration is gaining popularity in research. This paper presents a study of the applicability of the neural network approach of image registration for the quantitative growth assessment problem. In this study, we analyzed classical and neural network methods of image registration and used VoxelMorph and HyperMorph neural network architectures to evaluate local AAA growth based on the available dataset. Also, we compared the results of the obtained maximum local deformations of the AAA with the method of estimating the change in the maximum diameter.
... Vascular deformation mapping (VDM) is a validated medical image registration technique which allows for comprehensive assessment of the degree and extent of growth mapping of the aorta (VDM(G): VDM growth) [10][11][12] using longitudinal CTA data acquired at two different points during clinical surveillance. However, when applied to dynamic CTA data (i.e., time-resolved CTA), VDM allows for 3D assessment of the aortic deformation throughout the cardiac cycle (VDM(D): VDM dynamic). ...
... VDM employs b-spline deformable image registration techniques to quantify the 3D deformation of the aortic wall surface between two CTA images of a given subject. This approach has been previously applied to assess 3D aortic growth based on CTA images acquired at two time points spanning several years and has been validated in expert-rater and in silico phantom studies [10][11][12]. We refer to this growth assessment technique as VDM(G). ...
The aorta is in constant motion due to the combination of cyclic loading and unloading with its mechanical coupling to the contractile left ventricle (LV) myocardium. This aortic root motion has been proposed as a marker for aortic disease progression. Aortic root motion extraction techniques have been mostly based on 2D image analysis and have thus lacked a rigorous description of the different components of aortic root motion (e.g., axial versus in-plane). In this study, we utilized a novel technique termed vascular deformation mapping (VDM(D)) to extract 3D aortic root motion from dynamic computed tomography angiography images. Aortic root displacement (axial and in-plane), area ratio and distensibility, axial tilt, aortic rotation, and LV/Ao angles were extracted and compared for four different subject groups: non-aneurysmal, TAA, Marfan, and repair. The repair group showed smaller aortic root displacement, aortic rotation, and distensibility than the other groups. The repair group was also the only group that showed a larger relative in-plane displacement than relative axial displacement. The Marfan group showed the largest heterogeneity in aortic root displacement, distensibility, and age. The non-aneurysmal group showed a negative correlation between age and distensibility, consistent with previous studies. Our results revealed a strong positive correlation between LV/Ao angle and relative axial displacement and a strong negative correlation between LV/Ao angle and relative in-plane displacement. VDM(D)-derived 3D aortic root motion can be used in future studies to define improved boundary conditions for aortic wall stress analysis.
... We found the model parameters through an iterative search and using previously reported values [35], with the objective of maximizing the image contrast energy term while maintaining the surface regularity. In the case of the Gaussian filter, we considered a search where ∈ [2,4] . First, a common time step was defined, by setting Δt = 10 −2 . ...
... Future developments of the MISIGA may benefit from advanced numerical techniques employed in cardiovascular simulations that can reduce the computation time without compromising the accuracy [18,30]. Finally, our method does not directly estimate radial strain components, which may be of interest particularly for pathologies where the vessel wall thickness may change during disease, such as aortic dissection [4]. This limitation may be easily addressed by locally enforcing volume conservation under the assumption of an isochoric behavior of the vessel wall. ...
Abnormal deformation of blood vessels has been related to the onset and progression of prevalent cardiovascular diseases. This mechanical connection has motivated the development of computational techniques to assess strain fields in the wall of the aorta from medical images. In this work, we present the mechanics-informed snakes isogeometric analysis (MISIGA) method, which provides seamless 3D estimations of strain fields in the full aorta from magnetic resonance images. Our approach leverages image segmentation formulations with advanced curvilinear representations of irregular vessels to capture the deformation mapping between two configurations captured by image datasets. We further inform this model by describing the motion of the aortic wall based on a Kirchhoff-Love shell approach, which allows us to construct continuous circumferential and longitudinal strain fields in the full aorta. We validate the MISIGA method using synthetically generated images from aortic mechanical simulations, obtaining errors in the strain estimation of 13.2 and 9.8 for the circumferential and longitudinal components. This performance compares favorably with other approaches that are not informed by mechanical considerations. Further, we apply the MISIGA method in the strain assessment of the aorta of a normal subject, which results in longitudinal and circumferential strain values that are in the range of those found in previous studies. We envision that the MISIGA method can open the way to seamless 3D high-fidelity analysis of local strain from medical images of the aorta and other vessels.
... Comprehensive geometrical quantification of AA description involving the maximal diameter, centreline length, volume and combinations thereof has been reported to provide improved diagnostic accuracy [6,7]. Furthermore, geometric analysis has the capacity to contribute to the interpretation of aneurysm progression mechanisms and their mechanobiology, which are still poorly understood [3,8]. ...
The instrumental role of comprehensive geometrical quantification in contemporary, effective descriptions of aortic growth and disease is well established. General or specific purpose algorithms are being developed to provide automatic landmark detection and high accuracy measurements. In the present study, an objective method for automated delineation of the ascending aorta is introduced, based on geometrical properties of the aortic wall. In the proximal ascending aorta, the method identifies the sinotubular junction by tracing the mean surface curvature transition region from the origins of the coronary arteries to the location where the aorta acquires its tubular shape. In the distal ascending aorta, the brachiocephalic artery origin is defined by a split centreline cross section within the brachiocephalic artery-aortic arch bifurcation region. The method's accuracy of detection was quantified against the manual border identification performed by two experienced observers on 3D aortic reconstructions of 44 computed tomography examinations. Median (method, observer) distance and inclination measurements ranged from 0.89 [1.02] mm and 4.66 [5.07]°, respectively, in the proximal border, to 2.18 [2.39] mm and 7.13 [4.77]° in the distal. Accuracy of border detection was found to be high compared to interobserver variability and relevant automatic and manual methodology results previously reported in literature. Delineation of the ascending aorta on a three-dimensional aortic reconstruction with automated identification of the sinotubular junction (proximal border) and of the origin of the brachiocephalic artery (distal border).
... Therefore, these have not translated into clinical practice and appear unlikely to become relevant in the near future. [10][11][12][13][14] Therefore, although research into novel methods of aneurysm surveillance has been significant, maximal diameter measurements and growth in the maximal diameter have remained the default, yet suboptimal, clinical parameters. ...
... Although deformable image registration is rapidly being applied to neurologic and pulmonary disease processes, it has infrequently been applied to the field of vascular surgery, with no effects yet in clinical practice. 14,[16][17][18][19] A continued need exists for a more sensitive and accurate method of measuring the changes in aortic aneurysm dimensions, considering that the accurate detection of small magnitude changes has important implications for improving the understanding of aortic aneurysm progression and better informing treatment decisions. The aim of the present study was to develop a novel, semiautomated deformable image registration pipeline that can be applied to routine clinical surveillance CTA studies of patients with AAAs. ...
... Perhaps the most significant is that our process does not use custom inhouse developed scripts or software, which have been often used in prior studies. 14,[25][26][27] The proposed method uses open-source software applications with graphic user interfaces, which are inexpensive, widely accessible, and can be implemented even by those with limited background in programming. ...
Background
Assessment of regional aortic wall deformation (RAWD) may better predict abdominal aortic aneurysm (AAA) rupture than maximal aortic diameter or growth rate.
Objectives
Utilizing sequential CT angiograms (CTA), we developed a streamlined, semi-automated method of computing RAWD using deformable image registration (dirRAWD).
Methods
Paired sequential CTA’s of fifteen patients taken 1-2 years apart with AAAs of varying shape and size were selected. In patient’s initial CTA, the luminal and aortic wall surfaces were segmented both manually and semi-automatically. The patient’s follow-up CT scan was aligned with the first using automated rigid image registration; then, deformable image registration was used to calculate local aneurysm wall expansion between sequential scans (dirRAWD). To measure technique accuracy, deformable registration results were compared to local displacement of anatomic landmarks (fiducial markers) – the origin of the inferior mesenteric artery and/or aortic wall calcifications. Additionally, for each patient the maximal RAWD was manually measured for each aneurysm (manRAWD), and was compared to the dirRAWD at the same location.
Results
The technique was successful in all patients. Mean landmark displacement error was 0.59±0.93 mm with no difference between true landmark displacement and deformable registration landmark displacement by Wilcoxon rank-sum test (p = 0.39). The absolute difference between maximal manRAWD and dirRAWD was 0.27±0.23 mm, with a relative difference of 7.9%, and no difference by Wilcoxon rank-sum (p = 0.69). There was no difference in maximal dirRAWD when derived using a purely manual AAA segmentation compared to using a semi-automated AAA segmentation (p = 0.55).
Conclusions
Accurate and automated RAWD measurements are feasible with clinically insignificant error. Using semi-automated AAA segmentations for deformable image registration methods did not alter maximal dirRAWD accuracy compared to using manual AAA segmentations. Future work will compare dirRAWD with FEA-derived regional wall stress, and determine whether dirRAWD might serve as an independent predictor of rupture risk.
... The consequent need for long-term follow-up for a reliable GR assessment (15,16) hampered previous studies aimed at relating WSS and GR (12). Recently, a new technique for the semiautomatic assessment of aortic diameters and their GRs has been presented (17) and favorably compared with the reference standard (15). Based on automatic deformable registration of baseline and follow-up computed tomography angiograms (CTAs), robust maps of aortic GR can be obtained (15,17,18). ...
... Recently, a new technique for the semiautomatic assessment of aortic diameters and their GRs has been presented (17) and favorably compared with the reference standard (15). Based on automatic deformable registration of baseline and follow-up computed tomography angiograms (CTAs), robust maps of aortic GR can be obtained (15,17,18). ...
... Baseline and follow-up CTAs were automatically registered using Elastix (22). The multistep registration included a first rigid registration to align both scans, followed by 2-step, multiresolution, nonrigid registration based on mutual information metrics (17). The overall nonrigid trans- Using an in-house MATLAB code, peak systolic WSS was evaluated, and WSS axial and circumferential components were obtained as described (3,23). ...
Objectives
This study sought to assess the predictive value of wall shear stress (WSS) for colocalized ascending aorta (AAo) growth rate (GR) in patients with bicuspid aortic valve (BAV).
Background
BAV is associated with AAo dilation, but there is limited knowledge about possible predictors of aortic dilation in BAV patients with BAV. An increased WSS has been related to aortic wall damage in patients with BAV, but no previous prospective study tested its predictive value for dilation rate. Recently, a registration-based technique for the semiautomatic mapping of aortic GR has been presented and validated.
Methods
Forty-seven patients with BAV free from valvular dysfunction prospectively underwent 4-dimensional flow cardiac magnetic resonance to compute WSS and subsequent follow-up with 2 electrocardiogram-gated high-resolution contrast-enhanced computed tomography angiograms for GR assessment.
Results
During a median follow-up duration of 43 months, mid AAo GR was 0.24 mm/year. WSS and its circumferential component showed statistically significant association with mid AAo GR in bivariate (P = 0.049 and P = 0.014, respectively) and in multivariate analysis corrected for stroke volume and either baseline AAo diameter (P = 0.046 and P = 0.014, respectively) or z-score (P = 0.036 and P = 0.012, respectively). GR mapping further detailed that GR was heterogeneous in the AAo and that circumferential WSS, but not WSS magnitude, showed statistically significant positive associations with GR in the regions with the fastest growth.
Conclusions
4D flow cardiac magnetic resonance–derived WSS and, in particular, its circumferential component predict progressive dilation of the ascending aorta in patients with BAV. Thus, the assessment of WSS may be considered in the follow-up of these patients.
... Advanced computational methods in the fields of computer vision and machine learning may be ideal solutions. Preliminary studies have shown that automated segmentation and classification of aortic aneurysms as well as three-dimensional deformation analysis of aortic growth are both possible, and suggest the possibility that the future of aortic imaging surveillance may evolve from the hands of human readers to the servers of medical imaging software companies (Fig. 6) [45,46]. a b Fig. 6 Future Directions to Improve Aortic Measurements and Imaging Surveillance: Software exists that permits tabulation and graphical representation of aortic measurements along the length of the aorta at each surveillance imaging study allowing for improved depiction of long-term growth trends. ...
Patients with aortic dissection and other acute aortic diseases are subject to long-term imaging surveillance to monitor aortic growth and detect complications. This chapter will focus on practical aspects of long-term aortic imaging, including the selection of imaging surveillance intervals, choice of imaging modality (echocardiography vs. CT vs. MRI) and highlight advantages and weaknesses of various imaging techniques for assessment of aortic disease progression. We will first review published data and recommendations for long-term imaging of acute aortic disease, highlight a variety of modality and patient-specific factors to guide selection of an imaging surveillance strategy, and discuss considerations for imaging surveillance after endovascular aortic repair. Furthermore, we will outline common measurement techniques for assessing disease progression with specific attention on pitfalls and sources of measurement variability, and lastly briefly highlight several emerging image analysis techniques that may improve the accuracy and efficiency of imaging surveillance.
... Three-dimensional (3D) imaging with CT angiography (CTA) and MR angiography plays an important role in the management of TAAs, including diagnosis, long-term surveillance of aneurysm size and growth, and treatment planning and follow-up (2). Although the incidence of aortic aneurysms is increasing in the U.S. population and the more widespread use of thoracic cross-sectional surveillance imaging for nonaortic indications has led to more incidental findings of dilated aortas, the natural history and mechanisms of TAA progression remain poorly understood (3) and, while rare, aortic dissection and rupture can occur in otherwise asymptomatic patients with presurgical aneurysm sizes. Current U.S. (4) and European (5) guidelines for the care of patients with TAAs recommend tracking changes in aneurysm anatomy through measurement of the maximum aortic diameter, which has been shown to correlate with future risk of aneurysm rupture (6), and the use of standard measurement locations. ...
... The consequent need for long-term follow-up for a reliable GR assessment (15,16) hampered previous studies aimed at relating WSS and growth rate (12). Recently, a new technique for the semi-automatic assessment of aortic diameters and their growth rate has been presented (17) and favorably compared with reference standard (15). Based on automatic deformable registration of baseline and follow-up computed tomography angiograms (CTA), robust maps of aortic growth rate can be obtained (15,17,18). ...
... Recently, a new technique for the semi-automatic assessment of aortic diameters and their growth rate has been presented (17) and favorably compared with reference standard (15). Based on automatic deformable registration of baseline and follow-up computed tomography angiograms (CTA), robust maps of aortic growth rate can be obtained (15,17,18). ...
... Baseline and follow-up CTA were automatically registered using Elastix (22). The multi-step registration included a first rigid registration, to align both scans, followed by 2-step multi-resolution non-rigid registration based on mutual information metrics (17). The overall non-rigid transformation was applied to the baseline aortic surface and the reference anatomical ...
Background
Bicuspid aortic valve (BAV), a congenital heart defect, is associated with ascending aorta (AAo) dilation. Whether the high prevalence of dilation in BAV patients is related to alteration of aortic blood flow and thus in wall shear stress (WSS) [1,2], which have been associated with aortic wall degeneration [3], or intrinsic abnormalities of the aortic wall, such as altered aortic stiffness [4], has not been established. Recently, a technique for the semi-automatic quantification of progressive aortic dilation maps via image registration has been introduced [5].
Purpose
To test whether ascending aorta WSS predicts co-localized progressive dilation in BAV patients.
Methods
Forty BAV patients free from moderate and severe aortic valve regurgitation (regurgitant fraction <16%) and stenosis (maximum velocity at the aortic valve <3m/s), with no previous aortic or aortic valve surgery or replacement and included in a double-blind clinical trial (BICATOR, NCT02679261) were enrolled. All patients underwent a baseline 4D flow CMR study to assess aortic hemodynamics, followed by two contrast-enhanced computed tomography angiographies to quantify progressive dilation. WSS was computed at 64 pre-specified standardized ascending aortic regions, automatically obtained dividing the ascending aorta into 8 equidistant longitudinal sections which were further divided along the circumference into 8 equal regions (I = inner, L = left, O = outer and R = right) [2]. WSS was also projected into axial and circumferential directions, as previously described [1,2]. Progressive dilation was assessed in terms of growth rate (GR), i.e. increase in diameter divided by follow-up duration [mm/year], following a previously described methodology [5], at the same 64 pre-specified ascending aortic locations. A two-tailed p-value <0.05 was considered statistically significant.
Results
Demographic and clinical characteristics of the patients are shown in Table 1. WSS and growth rate maps are shown in Figure 1. Follow-up duration was 44.8±2.6 months. Growth rate (Figure 1A) was heterogeneously distributed, being highest (up to 0.26 mm/year) in the outer region of the mid AAo and in the inner region of the proximal-mid AAo. Circumferential WSS showed highest values in the outer region of the mid AAo (Figure 1C) while WSS (magnitude) and its axial component (Figure 1B and D) presented maximum values in the right region of the mid AAo. Maps of statistically significant association between GR and WSS values showed circumferential WSS to be correlated with GR in regions where progressive dilation was fastest, while WSS magnitude and its axial component resulted in limited associations with GR maps.
Conclusions
Circumferential wall shear stress predicts location-matched progressive dilation in bicuspid aortic valve patients.
FUNDunding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This study has received funding from the Instituto de Salud Carlos III (PI17/00381). Guala A. has received funding from Spanish Ministry of Science, Innovation and Universities (IJC2018-037349-I). Table 1. Demographics Figure 1. GR and WSS maps and correlations
... Computational fluid dynamic simulations require depicting the complex interplay between physiological deformation, flow, pressure, and wall shear stress, as shown in the work of Bäumler et al. [BVS * 20]. Burris et al. [BHKR17] introduced vascular deformation mapping to assess changes in aortic dimensions to quantify 3D changes in the aortic wall geometry. The results are superimposed on a 3D model using 3D color printing. ...
Current blood vessel rendering usually depicts solely the surface of vascular structures and does not visualize any interior structures. While this approach is suitable for most applications, certain cardiovascular diseases, such as aortic dissection would benefit from a more comprehensive visualization. In this work, we investigate different shading styles for the visualization of the aortic inner and outer wall, including the dissection flap. Finding suitable shading algorithms, techniques, and appropriate parameters is time-consuming when practitioners fine-tune them manually. Therefore, we build a shading pipeline using well-known shading algorithms such as Blinn-Phong, Oren-Nayar, Cook-Torrance, Toon, and extended Lit-Sphere shading with techniques such as the Fresnel effect and screen space ambient occlusion. We interviewed six experts from various domains to find the best combination of shadings for preset combinations that maximize user experience and the applicability in clinical settings.
