AMPLITUDE DEMODULATION OF THE ELECTROCARDIOGRAM SIGNAL (ECG) FOR RESPIRATION MONITORING AND COMPENSATION DURING MR EXAMINATIONS

A method for respiration monitoring during MR-sequences using the elec trocardiogram signal (EGG) is presented. The basic principle is known in conventional patient monitoring and is based on tile fact that the amplitude of the EGG-signal varies with respiratory motion, A demodula tion of this ''cardiorespiratory signal'' yields a respiration curve t hat can be used for patient monitoring, triggering, or respiration com pensation of MRI sequences, Since no drift is introduced by digital de modulation, this method is superior to analog signal processing. The p roposed method was applied during MR examinations using an optically c oupled ECG sensor that has the advantage of almost negligible interfer ence due to the MR sequences (much less than 10% of the main ECG signa l), The respiration signal obtained is strongly correlated (r = 0.79 t o 0.98) with the position of the diaphragm in inferior-superior direct ion measured during breath-holding MRI.