Multichannel MCG Systems with Optimum Combinations of Pickup Coils and Shielded Rooms

In order to provide optimum signal-to-noise ratios depending on the shielding conditions, we fabricated several multichannel magnetocardiogram systems with different types of pickup coils, magnetometer, first-order gradiometers and second-order gradiometers. The magnetocardiogram (MCG) systems were operated inside different magnetically shielded rooms, and signal-to-noise ratios were compared. The MCG systems have numbers of sensors in the range of 61-64, whose coverage diameters are large enough to measure the MCG maps in a single position setting. Considering the high cost of Permalloy needed in the shielded room, combination of a second-order gradiometer system and a thin magnetically shielded room seems best choice for the detection of ischemia in noisy hospital environment, like emergency department.