Patient-specific registration of 3D CT angiography (CTA) with X-ray fluoroscopy for image fusion during transcatheter aortic valve implantation (TAVI) increases performance of the procedure.

OBJECTIVES: The aim of this study was to adapt patient-specifically a co-registration procedure for image fusion (IF) of a pre-interventional CT dataset with real-time X-ray (XR) fluoroscopy during transfemoral transcatheter aortic valve implantation (TAVI), enabling improved performance of the procedure. BACKGROUND: The ability to use 3D models of the respective anatomies to complement the anatomic information obtained by XR fluoroscopy and provide a greater degree of real-time anatomical guidance holds great potential for complex cardiac interventions, especially for TAVI procedures with cerebral protection. METHODS: Initial registration of two datasets was performed during the femoral puncture and sheath introduction using routinely acquired arteriographies. On-time refinement of the co-registration was then performed during the on-going procedure avoiding additional angiograms for the co-registration. Performance of the method was evaluated quantitatively in terms of procedural characteristics and clinical events. RESULTS: Significant reduction of the radiation dose [51 (42-55) vs. 64 (49-81) Gy cm2, p = 0.032] and contrast agent (CA) volume [80 (50-95) vs. 100 (80-110) ml, p = 0.010] was achieved with the optimized approach as compared to the control group without IF, with simultaneous decrease of procedural [48 (41-58) vs. 61 (53-67) min, p = 0.002] and fluoroscopy times [14.8 (12.7-18.5) vs. 17.8 (14.3-19.4), p = 0.108]. CONCLUSIONS: In this proof-of-concept study we have demonstrated a novel co-registration approach for IF during TAVI not requiring any additional CA or XR scan. We have evaluated its potential benefit with the strong focus on guiding the femoral puncture, placement of the double-filter cerebral embolic protection device, and deployment of the valve prosthesis. We achieved improved performance and safety of the procedure with the introduced approach.

Image-guidance for transcatheter aortic valve implantation (TAVI) and cerebral embolic protection.

The study was aimed at evaluation of the feasibility and potential benefit of image fusion (IF) of pre-procedural CT angiography (CTA) and x-ray (XR) fluoroscopy for image-guided navigation in transfemoral transcatheter aortic valve implantation (TAVI) with the strong focus on guiding the double-filter cerebral embolic protection device and valve prosthesis placement. METHODS: In 31 patients undergoing TAVI, image registration of CTA-derived 3D anatomical models of the relevant cardiac anatomy and vasculature, and live XR was performed applying a commercially available navigation tool. The approach was evaluated in terms of the accuracy of the overlay. In 27 TAVI patients with IF receiving double-filter cerebral embolic protection device overall procedure time, fluoroscopy time, radiation dose, and total volume of intra-procedural iodinated contrast agent (CA) were registered and compared to those of a control group of prospectively enrolled during the same period of time N=27 patients receiving the same protection system but without IF. RESULTS AND CONCLUSIONS: Image co-registration and model-based guidance is feasible in TAVI procedures. The overlay facilitates placement of the embolic protection device, placement of the guide wire in the left ventricle and initial alignment of the valve prosthesis prior to final deployment, thus improving the confidence level of the operators during the procedure without compromising CA or XR dose.

Iron-loaded PLLA nanoparticles as highly efficient intracellular markers for visualization of mesenchymal stromal cells by MRI.

Monitoring of the fate of cells after injection appears paramount for the further development of cell therapies. In this context magnetic resonance imaging (MRI) is increasing in relevance owing to its unique tissue visualization properties. For assessment of cell trafficking and homing, the cells have to be labeled to become MR visible. The rather low sensitivity of MRI demands dedicated intracellular markers with high payloads of MR contrast agents for ensuring sensitive detection of local cell aggregations. In the presented work the application of custom-designed nanometer-sized iron oxide loaded poly-(l-lactide) (iPLLA) nanoparticles was investigated. The particles were synthesized by the mini-emulsion process and evaluated for labeling of mesenchymal stromal cells (MSCs). The efficient cellular uptake and long intracellular retention times of the particles as well as their nontoxicity are demonstrated. The average cellular iron content was 55 pg iron per cell. Further incorporation of, for example, fluorescent dye enables the generation of multireporter particles, providing the great potential for multimodal imaging. The efficiency of these nanoparticles as MRI contrast agent was evaluated in vitro using relaxation rate mapping, yielding relaxivities r2 = 273.3, r2 (*) = 545.1 mm(-1) s(-1) at 3 T and r2 = 415.7, r2 (*) = 872.3 mm(-1) s(-1) at 11.7 T. The high r2 (*) relaxivity of the iPLLA nanoparticles enabled visualization of a single labeled cell in vitro at 50-µm spatial resolution. In vivo evaluation in a rat injury model revealed the potential of the iPLLA particles to efficiently label MSCs for MRI monitoring of ~20 000-40 000 injected cells at 11.7 T. In conclusion the presented work demonstrates the applicability of iPLLA particles as efficient intracellular marker for MSC labeling for monitoring the fate of the cells by MRI.