Abstract Number ‐ 130: Comparison of the Stents Length by Virtual Stent Simulation with the Actual Stent Length
Authors: Yuzawa Kazuya , Ishibashi Toshihiro , Takao Hiroyuki , Fujimura Soichiro , Sunami Shota , Kasai Tomoki , Uchikawa Hayato , Fukudome Koji , Yamamoto Makoto , Murayama Yuichi 
Published: April 2023

Introduction
The selection of the size of a braided stent, such as the flow diverter stent, currently depends on the surgeon’s experience. However, the suitable selection is difficult even for experienced surgeons due to shortening during the deployment. The unsuitable choice of the stent size may result in poor stent apposition or dislodgement of the stent, which may lead to inadequate treatment and increase the risk of complications. To overcome the selection problem, we developed a virtual stent simulation that virtually reproduces the stent geometry preoperatively. However, the lengths of the deployed stents in the virtual stent simulation have not been compared with those in the actual stents. In this study, we evaluated the error between the length of the virtual stent and the actual stent to investigate the clinical usefulness of the virtual stent simulation.

Methods
We identified 48 internal carotid artery cerebral aneurysms treated with a single flow diverter stent (PipelineTM) between October 2016 and March 2022. The vessel geometries were reconstructed from the preoperative angiographic images, and the virtual stent geometries were reproduced using virtual stent simulation with our in‐house code. The actual stent geometries were reconstructed from the postoperative angiographic images and overlaid on the preoperative vessel geometries using affine transformation. The lengths of the virtual and actual stents were measured, respectively. The differences between the lengths of the virtual and actual stents were calculated by subtracting the actual stent length from the virtual stent length. The errors between the virtual and actual stents were estimated to validate the virtual stent simulation.

Results
The average maximum diameter in the 48 aneurysms was 16.4±5.91 mm. The average difference in length between the virtual stents and the actual stents was +1.70 ± 4.01 mm, with the average error based on virtual stent length of +3.24 ± 11.3%. The virtual stents of 16 aneurysms were shorter than the actual stents, and the average difference in length was ‐2.97 ± 1.82 mm. On the other hand, the virtual stents of the other 32 aneurysms were longer than the actual stents, with the average difference in length of +4.04 ± 2.47 mm. One possible cause of these differences is that the actual stent may slightly change the geometry of the parent vessel due to the restoring force of the stent. Another reason is that the actual length of the stent may change slightly as the surgeon pushes and pulls the catheter during the procedure.

Conclusions
Comparing the lengths of virtual and actual stents, it was confirmed that there was some error between the stent length reproduced by the virtual stent simulation and the actual stent length. In particular, the virtual stents tend to be slightly longer than the actual stents. Although our virtual stent may be useful for identifying the appropriate size, it is necessary to investigate the causes of such errors and to realize virtual stent simulations with fewer errors.