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

This method can help answer key questions in the field of inter-procedural image-based guidance, about the limited anatomical information available from x-ray fluoroscopy, with respect to a patient's 3D anatomy. The main advantage of this technique is that it represents a further incremental advancement in real-time navigation of complex interventions that will ultimately lead to increased efficacy and safety of the procedures. The number of TAVR procedures is continuously increasing in Germany, and with that, in some cases, the complexity is also very high.

To treat those patients properly, we do need image solution, especially in the field of cerebral embolic protection. Although this procedure has been demonstrated for a specific system, it can easily be transferred to other systems as long as a similar software is available. To segment the computer tomography, or CT, aorta and left ventricle images, drag the CT data into the patient's view within the image fusion software and deselect the other tissues until only the aorta and left ventricle remain.

Verify that the edges of the tissues are correctly detected in each slice, using the edit button to modify the automatic segmentation in the tissue window as necessary. To perform manual segmentation of any additional structures, click Add and use the editing tools to fill the structure, drag the edges of the structure in the 2D view, or remove structure parts in the 3D view. Then perform manual segmentation of the main trunks of the left and right coronary arteries, main artery branches, left and right iliofemoral arteries, hip bones, and hip joints as just demonstrated.

After merging the selected patient's data with the current patient's data in the x-ray system, place three reference markers at the aortic valve cusps in the Live Work setting by clicking Add New Tack Point in the Tack Points window. Next, open the Registration Workstep to acquire the x-ray runs. Click Copy to Reference View 1 to copy the angiographic projection of the appropriate puncture, and approximately 20-30 degrees in the left anterior oblique orientation, or approximately 20-30 degrees in the right anterior oblique orientation, depending on the initial puncture side, into the Reference View 1.

Click Copy to Reference View 2 to copy the x-ray projection acquired in approximately the anterior/posterior orientation during visualization of the transition from the contralateral a. iliaca communis to the a. femoralis communis into Reference View 2.

Use the Registration Pan, Registration Rotate, and Registration Roll interaction tools to manually align the model of the iliofemoral arteries with the acquired x-ray projections. Use the initial course co-registration to guide the puncture of the common femoral artery on the sheath side, and click Copy to Reference View to record an angiographic projection of the device sheath femoral artery in the right anterior oblique 20-30 degree orientation. Then finalize the image co-registration in the iliofemoral region.

To use these data for further overlay realignment, copy any additional acquired projections to the reference view during the transition from the iliofemoral to the thoracic region, as well as any catheterization of the brachiocephalic trunk via the right radial artery. After placing the pigtail catheter into the aortic arch, acquire two fluoroscopic projections without a contrast agent in the left anterior oblique 30-40 degree and right anterior oblique 20-30 degree orientations, and copy the projections into Reference Views 1 and 2 as demonstrated. Use the interaction tools to manually adjust the registration in the thoracic region, and guide the placement of the protection device based entirely on the anatomic overlay.

Then use the interaction tools to manually correct the overlay position on each acquired x-ray projection over the entire course of the intervention as necessary to ensure an accurate overlay at each time point, using the positions of the pigtail catheter, the double filter cerebral embolic protection system, and the aortogram as landmarks. Technical difficulties can arise from the static nature of the anatomic models, caused by overlay misalignment in instances of cardiac and respiratory motion, the formation of the structures during device manipulation, or inconsistent patient positioning between the settee and catheterization tables. Several interventional steps will benefit from the image fusion.

For example, the guidance of a common femoral artery puncture above the femoral bifurcation on the sheath side, the accurate placement of the cerebral embolic protection device, even in very torturous anatomies, based solely on the anatomic overlay, the visualization of the model in an arbitrary c-arm angulation without x-ray exposure or contrast agent administration, as well as identification of the optimal view before the valve deployment, and the alignment of the valve prosthesis in even very complex anatomies. Once mastered, the manual segmentation of all of the related anatomic structures can be completed in 20-30 minutes, depending on the quality of the CT images. While attempting this procedure, it's important to consider that the more projections that are available for the co-registration, the higher the accuracy of the overlay will be.

The demonstrated protocol is applicable to a wide variety of transcatheter interventions, from the clinically established, such as atrial and ventricular ablations, to procedures on the verge of clinical implementations, such as percutaneous treatment of the tricuspid valve.