Assessment of three-dimensional stent-graft dynamics by using fluoroscopic roentgenographic stereophotogrammetric analysis

ObjectiveTo validate the use of fluoroscopic roentgenographic stereophotogrammetric analysis (FRSA) for its feasibility and accuracy for measuring the three-dimensional dynamic motion of stent grafts.MethodsA digital biplane fluoroscopy setup was calibrated (Siemens Axiom Artis dBc). Stereo images were acquired of a static aortic model with a stent graft in different axial positions, imposed by a micromanipulator. The three-dimensional measurement error of FRSA was determined by comparing FRSA measurements with the micromanipulator. An aortic model with a stent graft was constructed and connected to an artificial circulation with a physiological flow and pressure profile. Markers were added to the spine (tantalum spherical markers; diameter 1 mm) and stent (welding tin; diameter 1 mm). The three-dimensional measurement precision was determined by measuring the position of a single (stable) spine marker during two pulsatile cycles. Finally, three-dimensional stent marker motion was analyzed with a frame rate of 30 images per second, including three-dimensional marker position (change), diameter change, and center of circle position change.ResultsThe mean error of FRSA measurement of displacement was 0.003 mm (SD, 0.019 mm; maximum error, 0.058 mm). A very high precision of position measurement was found (SD, 0.009-0.015 mm). During pulsatile motion, the position (changes) of the markers could be assessed in the x, y, and z directions, as well as the stent diameter change and center of circle position change.ConclusionsFRSA has proven to be a method with very high accuracy and temporal resolution to measure three-dimensional stent-graft motion in a pulsatile environment. This technique has the potential to contribute significantly to the knowledge of stent-graft behavior after endovascular aneurysm repair and improvements in stent-graft design. The technique is ready for clinical testing.

Clinical RelevanceUntil now, three-dimensional stent-graft motion due to the cardiac cycle could not be quantified in vivo. Fluoroscopic roentgenographic stereophotogrammetric analysis (FRSA) uses a new combination of two techniques: digital biplane fluoroscopy and roentgenographic stereo photogrammetric analysis. This in vitro study describes the validation and feasibility of FRSA. With FRSA it becomes possible to measure three-dimensional motion of stent-graft markers with a very high accuracy and precision. Using this technique, clinical studies can be performed to better understand stent-graft motion and the repetitive forces acting on the graft. Knowledge of three-dimensional motion can have a significant effect on stent-graft design and outcome.