Project Abstract 1.4 million people in the US (2021) have implanted cardioverter-defibrillators (ICDs) of which ~50% will require an MRI scan in their lifetime. All ICDs generate large artifacts in MRI such as signal-voids in cardiac MR (cMR) images, which frequently occur in important pathological (infarcted) regions. Reliable diagnosis of ventricular tachycardia, premature ventricular contraction and myocarditis using cMR is therefore prevented, as well as MR-guided therapy of these potentially life-threatening diseases. The scanner’s own shim coils cannot correct these large inhomogeneities, so powerful dedicated resistive shim coils are required. It is proposed that a Cardiac Shim System (CSS), consisting of a mechanical frame for accurate shim-coil placement, a shim coil, a programmable power supply, electromagnetic filtering circuits, shim-coil placement optimization software, and system-use protocols can be used to precisely reduce artifacts in a user-determined region of the heart. The innovative CSS design does not interact with, and is not acted upon by, the rf coils and the gradient coils of the scanner, maintaining the scanner’s specified performance. Furthermore, the magnetic forces acting upon the CSS are balanced, permitting the shim coil to be moved freely within the MRI scanner bore and maximizing patient safety. Aim 1 of this Phase I STTR project is to develop a commercial prototype (V2), based upon the initial proof- of-concept system (V1), to be used on a Siemens 1.5T MRI scanner at JHU. This includes refinements in shim coil design, software reconstruction, protocol development, and the development of a motorized positioning system. In Aim 2, it is proposed, to test this novel system quantitatively using 5 infarcted swine and 6 human volunteers to demonstrate CSS effectiveness in performing cMR safely using standard cardiac MRI protocols such as LGE and cine. Future Phase 2 efforts will pursue clinical testing to prepare for submission to the FDA for regulatory clearance.