Surface-Based CT–TEE Registration of the Aortic Root

Transcatheter aortic valve implantation (TAVI) is a minimally invasive alternative to conventional aortic valve replacement for severe aortic stenosis in high-risk patients in which a stent-based bioprosthetic valve is delivered into the heart via a catheter. TAVI relies largely on single-plane fluoroscopy for intraoperative navigation and guidance, which provides only gross imaging of anatomical structures. Inadequate imaging leading to suboptimal valve positioning contributes to many of the early complications experienced by TAVI patients, including valve embolism, coronary ostia obstruction, paravalvular leak, heart block, and secondary nephrotoxicity from excessive contrast use. Improved visualization can be provided using intraoperative registration of a CT-derived surface to transesophageal echo (TEE) images. In this study, the accuracy and robustness of a surface-based registration method suitable for intraoperative use are evaluated, and the performances of different TEE surface extraction methods are compared. The use of cross-plane TEE contours demonstrated the best accuracy, with registration errors of less than 5 mm. This guidance system uses minimal intraoperative interaction and workflow modification, does not require tool calibration or additional intraoperative hardware, and can be implemented at all cardiac centers at extremely low cost.

I. Introduction

Aortic valve disease affects 3% of the general population, making it the most common acquired heart valve disease in developed countries [1]. an aging population and a lack of effective medical therapies lead to a greater burden from this condition. in the U.S. alone, more than 50 000 surgical aortic valve replacements are performed every year [2]. an increase in the number of high-risk surgical patients with multiple comorbidities and a reluctance of patients to undergo conventional open heart surgery have been driving the development of transcatheter techniques.