MRI-Compatible C-Arm Imaging for Cardiac Intervention

Minimally invasive interventions limit visual access to the anatomy under treatment requiring the use of imaging technologies for guidance. Organs and vessels located deep within the body can be visualized with imaging modalities having good tissue penetration such as X-ray or magnetic resonance imaging (MRI). X-ray guidance via fluoroscopy provides real-time images of large anatomical territories with a spatial resolution of ~0.2 mm usually with the aid of contrast agents. X-ray guidance also provides excellent percutaneous device visualization. MRI provides superior soft tissue differentiation and three-dimensional (3D) localization. However, intravascular MRI guidance is still in its clinical infancy, and concerns remain over exclusive reliance on this modality (Bock M and Wacker FK, J Magn Reson Imaging 27:326–38, 2008; Hushek SG et al., J Magn Reson Imaging 27:253–66; Ratnayaka K et al., J Cardiovasc Magn Reson 10:62, 2008). MRI and X-ray catheterization imaging exhibit complementary strengths that may potentially improve percutaneous therapies. Efforts to combine these two modalities into a fully hybrid X-ray-MR (XMR) system were first proposed by Fahrig et al. (J Magn Reson Imaging 13:294–300, 2001; Acta Neurochir 145:995–7, 2003). Current approaches include (1) the use of conventional X-ray catheterization and MRI systems in adjacent rooms with the addition of a dual-modality compatible patient table and transport system, (2) “combined” or “hybrid” systems, whereby both modalities can image overlapping volumes of interest with no or minimal patient relocation. Examples of interventions that may benefit from XMR are presented, as well as the imaging requirements associated with these procedures. We describe a novel hybrid cone-beam XMR system built by introducing a rotating anode X-ray catheterization system within 140 cm of a closed-bore 1.5 T MRI. The system is used to acquire images of an MRI-compatible catheter moving inside an aorta phantom.