Geometric variability of the abdominal aorta and its major peripheral branches.

Vessel geometry determines blood flow dynamics and plays a crucial role in the pathogenesis of vascular disease. In vivo assessment of three-dimensional (3D) vessel anatomy is vital to improve the realism of arterial flow model geometries and investigate factors associated with the localisation of atherosclerosis. The quantification of vascular geometry is also particularly important for the proper design and preclinical testing of endovascular devices used to treat peripheral arterial disease. The purpose of this study was to quantitatively evaluate the intersubject variability of 3D branching and curvature of the abdominal aorta and its major peripheral arteries. Contrast-enhanced renal MRA scans of healthy abdominal vessels obtained in 12 subjects (8 men, 4 women mean age 49 years, range 27-84 years) were segmented, and smoothed centerlines were determined as descriptors of arterial geometry. Robust techniques were employed to characterise non-planar vessel curvature, arterial taper, and 3D branching parameters. Noticeable 3D curvature and tapering were quantified for the proximal anterior visceral and renal branches. Mean 3D branching angles of 63.5+/-10.1 degrees and 73.1+/-6.8 degrees were established for the right and left renal arteries, respectively. Angles describing the ostial position and initial trajectory of the renal arteries confirmed the antero-lateral origin and direction of the right and the more lateral orientation of the left. The anterior visceral branches emerged predominantly from the left side of the anterior aortic wall. Branching parameters determined at the aortic bifurcation demonstrated mild asymmetry and non-planarity at this location. In summary, the results from this study address the scarcity of available in vivo 3D quantitative geometric data relating to the abdominal vasculature and reflect the geometric variability in living subjects.

Methods for three-dimensional geometric characterization of the arterial vasculature.

Complex vascular anatomy often affects endovascular procedural outcome. Accurate quantitative assessment of three-dimensional (3D) in-vivo arterial morphology is therefore vital for endovascular device design, and preoperative planning of percutaneous interventions. The aim of this work was to establish geometric parameters describing arterial branch origin, trajectory, and vessel curvature in 3D space that eliminate the errors implicit in planar measurements. 3D branching parameters at visceral and aortic bifurcation sites, as well as arterial tortuosity were determined from vessel centerlines derived from magnetic resonance angiography data for three subjects. Errors in coronal measurements of 3D branching angles for the right and left renal arteries were 3.1 +/- 3.4 degrees and 7.5 +/- 3.7 degrees , respectively. Distortion of the anterior visceral branching angles from sagittal measurements was less pronounced. Asymmetry in branching and planarity of the common iliac arteries was observed at aortic bifurcations. The renal arteries possessed considerably greater 3D curvature than the abdominal aorta and common iliac vessels with mean average values of 0.114 +/- 0.015 and 0.070 +/- 0.019 mm(-1) for the left and right, respectively. In conclusion, planar projections misrepresented branch trajectory, vessel length, and tortuosity proving the importance of 3D geometric characterization for possible applications in planning of endovascular interventional procedures and providing parameters for endovascular device design.

Generating an ex vivo vascular model.

Realistic ex vivo anthropometric vascular environments are required for endovascular device optimization and for preclinical evaluation of interventional procedures. The objective of this research is to build an anthropomorphic model of the human carotid artery. The combination of magnetic resonance angiography image processing and computer-aided design and manufacturing techniques allowed fabrication of multicomponent morphologically precise casts of the carotid artery. The lost core technique was used to produce a hollow vessel prototype incorporating polyvinyl alcohol cryogel (PVA-C) as a tissue-mimicking vessel wall material. PVA-C was mechanically characterized by uniaxial tensile testing after different numbers of freeze/thaw cycles. The novel model construction approach outlined in this study accounts for the morphologic complexities of the human vasculature, and proved successful for the production of realistic compliant ex vivo arterial model.