Development of a 6-Channel High- $T_{\rm C}$ SQUID Magnetocardiograph System

We have developed a new type of magnetocardiograph (MCG) system employing 6 high-T
_C
SQUID magnetometers. We have fabricated high performance YBCO SQUID devices for the system. The lightweight MCG system, requiring liquid nitrogen as a coolant, consists of 6-channel SQUID sensors and an adjustable patient bed with sliding motion. The MCG system showed stable operation in a room with moderate magnetic shielding. In normal operation with a moving subject, we could obtain 36-point and 48-point MCG mappings with high enough signal qualities for clinical trials.