Toward smart utilization of two X-ray images for 2-D/3-D registration applied to abdominal aortic aneurysm interventions

Minimally invasive abdominal aortic aneurysm (AAA) stenting can be greatly facilitated by overlaying the pre-operative 3-D model of the abdominal aorta onto the intra-operative 2-D X-ray images. Accurate 2-D/3-D registration in 3-D space makes the 2-D/3-D overlay robust to the change of C-Arm angulations. Typically at least two X-ray images showing the abdominal aorta from different angles are needed for an accurate registration of the aorta in 3-D. This requires two or multiple contrast agent injections into the aorta which on the other hand needs to be minimized for patient's safety. In this paper, a novel 2-D/3-D registration technique is proposed for using only one image with contrast injection in the abdominal aorta and one native image showing the spine to achieve accurate registration of the abdominal aorta in 3-D. The proposed method utilizes the two X-ray images in an integrated but differentiable way in order to best utilize the complementary information provided by the two types of images. A hierarchical registration scheme is deployed by a sensible partition of the registration parameter space based on the image acquisition protocol and the patient's motion constraint. The proposed method was validated using both synthetic and clinical datasets, and achieved significantly improved accuracy and robustness compared to the conventional methods.