Improved Registration of 3D CT Angiography with X-ray Fluoroscopy for Image Fusion During Transcatheter Aortic Valve Implantation

Summary

The aim of this study was to improve the co-registration for image fusion (IF) of pre-interventional CT data with real-time x-ray (XR) fluoroscopy during transfemoral transcatheter aortic valve implantation (TAVI).

Abstract

The fusion of 3D anatomical models derived from high-fidelity pre-interventional computed tomography angiography (CTA), and x-ray (XR) fluoroscopy to facilitate anatomical guidance is of huge interest for complex cardiac interventions like TAVI procedures with cerebral protection. Co-registration of CTA and XR has been introduced either based on additional intraoperative non-/contrast-enhanced cone-beam computed tomography (CBCT) or two separate aortograms. With the related increase of radiation exposure and/or contrast agent (CA) dose, a potential additional risk for the patient is introduced. Here, we propose a modified co-registration approach making use of arteriograms of the iliofemoral arteries, routinely performed during the femoral puncture and sheath introduction. On-the-fly refinement of the co-registration during the on-going procedure enables accurate co-registration without any additional angiograms, thus reducing CA, XR dose and procedure time, while simultaneously improving operator confidence and procedure safety.

Introduction

Image fusion (IF) is the process of superimposing datasets acquired at the different time- and viewpoints on different modalities into a single-frame of reference¹. XR is the most frequently used imaging modality for intervention guidance. Even though, providing high temporal and spatial resolution, XR has low dimensionality (2D projections) and lacks anatomical details. 3D organ shape models derived from e.g. high-quality pre-interventional CTA data superimposed onto the live fluoroscopy image can augment XR by relevant anatomic soft-tissue structures. Prerequisite step for IF is the co-registration of the different imaging modalities....

Protocol

The study protocol is in compliance with the ethical guidelines of the 1975 Declaration of Helsinki as reflected in a priori approval by the institution's ethics committee. Written informed consent was obtained from all individual participants included in the study (CSI-Ulm, clinicaltrials.gov NCT02162069).

1. CT Examination

1. Perform cardiac CT angiography with retrospective ECG-gating using 80 mL of iodinated contrast media injected at a flow rate of 4.0 mL/s followed by a flushing bolus of 70 mL 0.9% saline solution.
2. Acquire data cranio-caudally extending from the femoral arteries to the subclavian arteri....

Results

We introduced a novel co-registration approach for image fusion during TAVI, which allows overlaying the patient-specific anatomic model onto the live XR images during the entire TAVI procedure without the need for any additional aortograms.

Several interventional steps will benefit from the IF: (1) guidance of the puncture of the common femoral artery above the femoral bifurcation on the sheath side (Figure.......

Discussion

The main focus of this study was to investigate the feasibility of IF without modifying the clinically established TAVI workflow. Whereas the gold standard for the co-registration of the pre-interventional CTA data and XR fluoroscopy uses dedicated aortograms⁸, we propose using multiple approximate registrations with on-the-fly refinements to provide accurate 3D model overlay during the entire course of the intervention.

The continuous manual registration refinement req.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Philips Allura FD10	Philips Healthcare		x-ray system
EP Navigator Release 5.2.10	Philips Healthcare		image segmentation and fusion SW
Iomeron 350	Bracco Imaging Deutschland GmbH		x-ray contrast agent
Sentinel  double-filter cerebral protection system	Claret Medical, Inc.		double-filter cerebral protection system
Matlab R2013	MathWorks		statistical analysis