Truly Hybrid Interventional MR/X-Ray System: Investigation of in Vivo Applications

Abstract

Rationale and Objectives The purpose of this study was to provide in vivo demonstrations of the functionality of a truly hybrid interventional x-ray/magnetic resonance (MR) system. Materials and Methods A digital flat-panel x-ray system (1,024 2 array of 200 μm pixels, 30 frames per second) was integrated into an interventional 0.5-T magnet. The hybrid system is capable of MR and x-ray imaging of the same field of view without patient movement. Two intravascular procedures were performed in a 22-kg porcine model: placement of a transjugular intrahepatic portosystemic shunt (TIPS) (x-ray–guided catheterization of the hepatic vein, MR fluoroscopy–guided portal puncture, and x-ray–guided stent placement) and mock chemoembolization (x-ray–guided subselective catheterization of a renal artery branch and MR evaluation of perfused volume). Results The resolution and frame rate of the x-ray fluoroscopy images were sufficient to visualize and place devices, including nitinol guidewires (0.016–0.035-inch diameter) and stents and a 2.3-F catheter. Fifth-order branches of the renal artery could be seen. The quality of both real-time (3.5 frames per second) and standard MR images was not affected by the x-ray system. During MR-guided TIPS placement, the trocar and the portal vein could be easily visualized, allowing successful puncture from hepatic to portal vein. Conclusion Switching back and forth between x-ray and MR imaging modalities without requiring movement of the patient was demonstrated. The integrated nature of the system could be especially beneficial when x-ray and MR image guidance are used iteratively.