Stanford Advisors

All Publications

  • Influence of Thoracic Endovascular Aortic Repair on True Lumen Helical Morphology for Stanford Type B Dissections. Journal of vascular surgery Bondesson, J., Suh, G., Marks, N., Dake, M. D., Lee, J. T., Cheng, C. P. 2021


    OBJECTIVE: Thoracic endovascular aortic repair (TEVAR) can change the morphology of the flow lumen in aortic dissections, which may affect aortic hemodynamics and function. This study characterizes how helical morphology of the true lumen in type B aortic dissections is altered by TEVAR.METHODS: Patients with type B aortic dissection who underwent computed tomography angiography pre- and post-TEVAR were retrospectively reviewed. Images were used to construct 3D stereolithographic (STL) surface models of the true lumen and whole aorta using custom software. STL models were segmented and co-registered to determine helical morphology of the true lumen with respect to the whole aorta. The true lumen region covered by the endograft was defined based on fiducial markers pre- and post-TEVAR. Helical angle, average helical twist, peak helical twist, and cross-sectional eccentricity, area, and circumference were quantified in this region for pre- and post-TEVAR geometries.RESULTS: Sixteen patients (61.3±8.0 years, 12.5% female) were treated successfully for type B dissection (five acute and eleven chronic) with TEVAR and scans pre- and post-TEVAR were retrospectively obtained (follow-up interval 52±91 days). From pre- to post-TEVAR, true lumen helical angle (-70.0±71.1 to -64.9±75.4 deg, p=0.782), average helical twist (-4.1±4.0 to -3.7±3.8 deg/cm, p=0.674) and peak helical twist (-13.2±15.2 to -15.4±14.2 deg/cm, p=0.629) did not change. However, true lumen helical radius (1.4±0.5 to 1.0±0.6 cm, p<0.05) and eccentricity (0.9±0.1 to 0.7±0.1, p<0.05) decreased, and cross-sectional area (3.0±1.1 to 5.0±2.0 cm2, p<0.05) and circumference (7.1±1.0 to 8.0±1.4 cm, p<0.05) increased significantly from pre- to post-TEVAR. The distinct bimodal distribution of chiral and achiral native dissections disappeared post-TEVAR, and subgroup analyses showed that the true lumen circumference of acute dissections increased with TEVAR, while it did not for chronic dissections.CONCLUSIONS: The unchanged helical angle and average and peak helical twists as a result of TEVAR suggest that angular positions of the true lumen are constrained and that the endografts were helically conformable in the angular direction. The decrease of helical radius indicated a straightening of the "corkscrew" shape of the true lumen, and in combination with more circular and expanded lumen cross-sections, TEVAR produced luminal morphology that theoretically allows for lower flow resistance through the endografted portion. The impact of TEVAR on dissection flow lumen morphology and the interaction between endografts and aortic tissue can provide insight for improving device design, implantation technique, and long-term clinical outcomes.

    View details for DOI 10.1016/j.jvs.2021.04.029

    View details for PubMedID 33940073

  • Multiaxial pulsatile dynamics of the thoracic aorta and impact of thoracic endovascular repair. European journal of radiology open Suh, G., Bondesson, J., Zhu, Y. D., Lee, J. T., Dake, M. D., Cheng, C. P. 2021; 8: 100333


    Purpose: The thoracic aorta is a highly mobile organ whose dynamics are altered by thoracic endovascular aorta repair (TEVAR). The aim of this study was to quantify cardiac pulsatility-induced multi-axial deformation of the thoracic aorta before and after descending aortic TEVAR.Methods: Eleven TEVAR patients (8 males and 3 females, age 57-89) underwent retrospective cardiac-gated CT angiography before and after TEVAR. 3D geometric models of the thoracic aorta were constructed, and lumen centerlines, inner and outer surface curves, and cross-sections were extracted to measure aortic arclength, centerline, inner surface, and outer surface longitudinal curvatures, as well as cross-sectional effective diameter and eccentricity for the ascending and stented aortic portions.Results: From pre- to post-TEVAR, arclength deformation was increased at the ascending aorta from 5.9 ± 3.1 % to 8.8 ± 4.4 % (P < 0.05), and decreased at the stented aorta from 7.5 ± 5.1 % to 2.7 ± 2.5 % (P < 0.05). Longitudinal curvature and diametric deformations were reduced at the stented aorta. Centerline curvature, inner surface curvature, and cross-sectional eccentricity deformations were increased at the distal ascending aorta.Conclusions: Deformations were reduced in the stented thoracic aorta after TEVAR, but increased in the ascending aorta near the aortic arch, possibly as a compensatory mechanism to maintain overall thoracic compliance in the presence of reduced deformation in the stiffened stented aorta.

    View details for DOI 10.1016/j.ejro.2021.100333

    View details for PubMedID 33748348

  • Thoracic aortic geometry correlates with endograft bird-beaking severity. Journal of vascular surgery Frohlich, M. M., Suh, G., Bondesson, J., Leineweber, M., Lee, J. T., Dake, M. D., Cheng, C. P. 2020


    OBJECTIVE: Aortic geometry has been shown to influence the development of endograft malapposition (bird-beaking) in thoracic endovascular aortic repair (TEVAR), but the extent of this relationship lacks clarity. The aim of this study was to develop a reproducible method of measuring bird-beak severity and to investigate preoperative geometry associated with bird-beaking.METHODS: The study retrospectively analyzed 20 patients with thoracic aortic aneurysms or type B dissections treated with TEVAR. Computed tomography scans were used to construct three-dimensional geometric models of the preoperative and postoperative aorta and endograft. Postoperative bird-beaking was quantified with length, height, and angle; categorized into a bird-beak group (BBG; n= 10) and no bird-beak group (NBBG; n= 10) using bird-beak height ≥5mm as a threshold; and correlated to preoperative metrics including aortic cross-sectional area, inner curvature, diameter, and inner curvature*diameter as well as graft diameter and oversizing at the proximal landing zone.RESULTS: Aortic area (1002± 118mm2 vs 834± 248mm2), inner curvature (0.040± 0.014mm-1 vs 0.031± 0.012mm-1), and diameter (35.7± 2.1mm vs 32.2± 4.9mm) were not significantly different between BBG and NBBG; however, inner curvature*diameter was significantly higher in BBG (1.4± 0.5 vs 1.0± 0.3; P= .030). Inner curvature and curvature*diameter were significantly correlated with bird-beak height (R= 0.462, P= .041; R= 0.592, P= .006) and bird-beak angle (R= 0.680, P< .001; R= 0.712, P< .001).CONCLUSIONS: TEVAR bird-beak severity can be quantified and predicted with geometric modeling techniques, and the combination of high preoperative aortic inner curvature and diameter increases the risk for development of TEVAR bird-beaking.

    View details for DOI 10.1016/j.jvs.2019.11.045

    View details for PubMedID 32035770

  • Quantification of True Lumen Helical Morphology and Chirality in Type B Aortic Dissections. American journal of physiology. Heart and circulatory physiology Bondesson, J. n., Suh, G. Y., Lundh, T. n., Dake, M. D., Lee, J. T., Cheng, C. P. 2020


    Chirality is a fundamental property in many biologic systems. Motivated by previous observations of helical aortic blood flow, aortic tissue fibers, and propagation of aortic dissections, we introduce methods to characterize helical morphology of aortic dissections. After validation on computer generated phantoms, the methods were applied to patients with type B dissection. For this cohort, there was a distinct bimodal distribution of helical propagation of the dissection with either achiral or exclusively right-handed chirality, with no intermediate cases or left-handed cases. This clear grouping indicates that dissection propagation favors these two modes, potentially due to the right-handedness of helical aortic blood flow and cell orientation. The characterization of dissection chirality and quantification of helical morphology advances our understanding of dissection pathology and lays a foundation for applications in clinical research and treatment practice. For example, the chirality and magnitude of helical metrics of dissections may indicate risk of dissection progression, help define treatment and surveillance strategies, and enable development of novel devices that account for various helical morphologies.

    View details for DOI 10.1152/ajpheart.00778.2020

    View details for PubMedID 33382638

  • Automated Quantification of Diseased Thoracic Aortic Longitudinal Centerline and Surface Curvatures. Journal of biomechanical engineering Bondesson, J. H., Suh, G., Lundh, T., Lee, J. T., Dake, M. D., Cheng, C. 2019


    Precise description of vascular morphometry is crucial to support medical device manufacturers and clinicians for improving device development and interventional outcomes. A compact and intuitive method is presented to automatically characterize the surface geometry of tubular anatomic structures and quantify surface curvatures starting from generic stereolithographic surfaces. The method was validated with software phantoms and used to quantify the longitudinal surface curvatures of 37 human thoracic aortas with aneurysm or dissection. The quantification of surface curvatures showed good agreement with analytic solutions from the software phantoms, and demonstrated better agreement as compared to estimation methods using only centerline geometry and cross-sectional radii. For the human thoracic aortas, longitudinal inner surface curvature was significantly higher than centerline curvature (0.33±0.06 vs. 0.16±0.02 cm-1 for mean; 1.38±0.48 vs. 0.45±0.11 cm-1 for peak; both p<0.001). These findings show the importance of quantifying surface curvatures in order to better describe the geometry and biomechanical behavior of the thoracic aorta, which can assist in treatment planning and supplying device manufactures with more precise boundary conditions for mechanical evaluation.

    View details for DOI 10.1115/1.4045271

    View details for PubMedID 31633168