Comparability of measurement results obtained with multi-SQUID-systems of different sensor configurations

Currently several brands of multichannel SQUID-systems for application in biomagnetism are commercially available. However, these devices are widely differing in SQUID specifications, gradiometer construction, sensor configuration and other parameters. The distortion of temporal recordings of the magnetic field due to varying sensor constructions has been evaluated. Examples of cardiac measurements show clearly that such data differ from each other. Therefore, these data cannot directly be compared in multicentric clinical studies. This contribution presents a method for comparison of signals recorded with different sensor systems. This method transforms the recorded signals into signals of a reference system. The recorded signals are modeled by means of a multipole virtual generator, which is then used to compute the signals in the reference system. The efficiency of the algorithm is demonstrated for measurements of the heart magnetic field.