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Us Patents
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
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.