QRS filter for real time heart imaging with ECG monitoring in the magnetic field of an NMR imaging system and NMR imaging apparatus employing such filter

摘要

A pair of Butterworth 4th order filters are cascaded with an absolute value filter to filter the QRS wave of an ECG signal generated in a magnetic field of an NMR imaging system. The NMR system includes a magnet for producing a static B.sub.O field and a set of coils for producing RF pulse induced fields in which an ECG monitoring system is located. The ECG monitoring system transmits the resultant QRS waves to a receiver which processes the received signals and applies the received signals to a display via the above filters. The -3 dB point of the high pass filter is at about 10 Hertz to filter the T-wave and Bo field induced breathing artifacts and the -3 dB point of the low pass filter is about 20 Hertz to filte the high frequency components of pulsed static field gradient noise created by the NMR system.