In vivo 3D modeling of the femoropopliteal artery in human subjects based on x-ray angiography: Methodology and validation

Endovascular revascularization of the femoropopliteal (FP) artery has been limited by high rates of restenosis and stent fracture. The unique physical forces that are applied to the FP artery during leg movement have been implicated in these phenomena. The foundation for measuring the effects of physical forces on the FP artery in a clinically relevant environment is based on the ability to develop 3D models of this vessel in different leg positions in vivo in patients with peripheral arterial disease (PAD). By acquiring paired angiographic images of the FP artery, and using angiography-based 3D modeling algorithms previously validated in the coronary arteries, the authors generated 3D models of ten FP arteries in nine patients with PAD with the lower extremity in straight leg (SL) and crossed leg (CL) positions. Due to the length of the FP artery, overlapping paired angiographic images of the entire FP artery were required to image the entire vessel, which necessitated the development of a novel fusion process in order to generate a 3D model of the entire FP artery. The methodology of angiographic acquisition and 3D model generation of the FP artery is described. In a subset of patients, a third angiographic view (i.e., validation view) was acquired in addition to the standard paired views for the purpose of validating the 3D modeling process. The mean root-mean-square (rms) error of the point-to-point distances between the centerline of the main FP artery from the 2D validation view and the centerline from the 3D model placed in the validation view for the SL and CL positions were 0.93 +/- 0.19 mm and 1.12 +/- 0.25 mm, respectively. Similarly, the mean rms error of the same comparison for the main FP artery and sidebranches for the SL and CL positions were 1.09 +/- 0.38 mm and 1.21 +/- 0.25 mm, respectively. A separate validation of the novel fusion process was performed by comparing the 3D model of the FP artery derived from fusion of 3D models of adjacent FP segments with the 2D validation view incorporating the region of fusion. The mean rms error of vessel centerline points of the main FP artery, the main FP artery plus directly connected sidebranches, and the mean rms error of upstream, downstream, and sidebranch directional vectors at bifurcation points in the overlap region were 1.41 +/- 0.79 mm, 2.13 +/- 1.12 mm, 3.16 +/- 3.72 degrees, 3.60 +/- 5.39 degrees, and 8.68 +/- 8.42 degrees in the SL position, respectively, and 1.29 +/- 0.35 mm, 1.61 +/- 0.78 mm, 4.68 +/- 4.08 degrees, 3.41 +/- 2.23 degrees, and 5.52 +/- 4.41 degrees in the CL position, respectively. Inter- and intraobserver variability in the generation of 3D models of individual FP segments and the fusion of overlapping FP segments were assessed. The mean rms errors between the centerlines of nine 3D models of individual FP segments generated by two independent observers, and repeated measurement by the same observer were 2.78 +/- 1.26 mm and 3.50 +/- 1.15 mm, respectively. The mean rms errors between the centerline of four 3D models of fused overlapping FP segments generated by two independent observers, and repeated measurement by the same observer were 4.99 +/- 0.99 mm and 5.98 +/- 1.22 mm, respectively. This study documents the ability to generate 3D models of the entire FP artery in vivo in patients with PAD in both SL and CL positions using routine angiography, and validates the methodologies used.