A system for in-vivo cardiac defibrillation current density imaging in a pig

Current density imaging (CDI), based on magnetic resonance imaging (MRI), has been used in past studies to measure electrical current pathways associated with external defibrillation electrodes placed on a post-mortem pig. We are preparing to make the same measurements in a living pig. This abstract describes a fast low frequency CDI (FLFCDI) cardiac sequence for this purpose. This sequence is based on a commercial fast gradient recalled echo (FGRE) MRI sequence with cardiac triggering. This sequence can produce phase images of the heart of sufficient quality to be used for CDI. A CDI system appropriate for a living animal is described and solutions are proposed for all of the artifacts and design issues. The CDI system can apply current pulses of 150 mA zero-to-peak amplitude and 5 ms duration. Phantom images, measurements of electrode impedance, and CDI signal-to-noise ratio (SNR) for this sequence are presented.