Optimal sensor distribution for measuring the tangential field components in MCG.

We discuss the optimal arrangement of detectors for a 52-channel magnetocardiogram (MCG) system measuring tangential components of the cardiac magnetic fields. Nowadays, most MCG instruments are designed to cover the whole heart area to maximize the information available from the myocardial magnetic field in a simultaneous measurement. In such a system, detectors should be spread over a sufficiently wide area. However, an increased diameter of the cooling dewar will result in more heat-loss and higher production and maintenance costs. Therefore, we reviewed the spatial sampling theory to determine the proper interval between detectors, and we decided on the number of channels to cover the whole heart area. In order to fit the detector array on the cylindrical dewar economically, we removed the detectors at the corners of the square array. Through simulations using the confidence region method, we verified that our design of the detector array is enough to obtain adequate information from the heart. Simulations also suggested that tangential-component MCG measurement can localize deep current dipoles better than normal-component measurement with the same confidence volume; therefore, we conclude that measurement of the tangential component is more suitable to an MCG system than the normal component.