Magnetocardiography using HTS rf SQUIDs with coplanar resonators

We have employed HTS rf washer SQUIDs with coplanar resonators for magnetocardiography measurements. The white field noise of such a magnetometer (rf washer SQUID, 3.5 mm in diameter, flip-chip mounted on a flux concentrator 13 mm in diameter) inside a 4 layer μ-metal shielding was 16 fT/√Hz. MCG measurements were performed with a magnetometer in the Berlin magnetically shielded room (BMSR) and with a first order gradiometer in a standard shielded room in Jülich (JMSR). The results are compared regarding the fragmentation score, which is supposed to be a risk marker for sudden cardiac death. Despite different environments, score values determined with the magnetometer and the gradiometer were almost identical.