Comparison of ECG derived respiratory signals and pneumatic bellows for respiratory motion tracking

The respiratory motion of the heart causes inaccuracies in the cardiac emission tomography reconstructions, which can mislead diagnosis. Various motion-tracking methods using specialized instruments have been developed to compensate for the cardiac respiratory motion. However, most of these methods tend to be time consuming, costly and require additional effort both from patients and technicians. In this study, we investigated the performance of a tool which derives a signal related to respiration from the patient´s ECG. The method is called ECG/EMG derived respiration (EDR) and with it the respiratory signal is obtained from the ECG signals already being acquired during a cardiac study, without needing any additional instrument or set-up. We compared the EDR with pneumatic bellows placed on chest and abdomen to determine if the signal from EDR may be used as a surrogate for the bellows for respiratory motion correction. Preliminary results show that the EDR had better amplitude and phase correlation with the abdominal bellow than that between the bellows or between the EDR and chest bellow. The EDR is also affected by volunteer motion like other external surrogate devices. However, this can be used to our advantage as a source of information about the timing of changes in patient motion states for use in data-driven motion correction.