Abstract
Angioplasty is an interventional treatment for blood vessel stenosis, that uses a catheter navigated to obstructed vasculature under fluoroscopy to force open the blockage with a balloon or permanent wire stent. Accurate stent placement is critical to avoid stent shifting and enabling new blockages. Unfortunately, background structures such as bone and tissue interfere with stent visualization during angioplasty, making it difficult for physicians to visualize stents during placement and post-operative checkups. This contributes to the 25% restenosis rate in patients with permanent stents<sup>1</sup>. Multi-energy subtraction angiography (ESA) with fast kV switching may enhance nickel-stent visualization by suppressing background structures. The objective of this work was to develop an ESA protocol to enhance the visualization of nickel wire stents. The signal-to-noise ratio of nickel for a given radiation exposure was simulated using MATLAB® and validated against images of a deployed nitinol stent overlaid on a chest phantom. The stent was isolated from bone or soft tissue by applying a calculated weighting factor to the low energy image. We found that by manipulating the weighting factor, it is possible to selectively remove anatomical structures obstructing the view of the stent.
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