Using a Kalman Filter to Compensate for Photoplethysmogram Artifacts when Monitoring CT Examinations

Computed tomography (CT) is a powerful clinical tool for generating clinically useful images. Iodinated contrast medium (ICM) is normally used to enhance the image intensity and tissue contrast, and it can induce a variety of adverse reactions. The goal of this study was to develop a method for monitoring the pathophysiologic condition of the patient during a CT examination. A photoplethysmography (PPG) waveform was used to detect changes in the heart rate (HR), which were considered to represent clinical responses to the ICM. To enhance the PPG waveform in the presence of artifacts, a Kalman filter algorithm was used to compensate artifact signals in order to extracting a more robust beat-to-beat HR. The study collected data from 82 patients who received a standard CT examination in a hospital. The results showed that patients felt more discomfort when the change in HR lasted for longer or was larger: the response times and HR change were 149plusmn49.5 seconds (meanplusmnSD) and 26plusmn12.6 beats/minute, respectively, in the group that did not experience discomfort, and 123plusmn39.1 seconds (p<0.05) and 19plusmn11.1 beats/minute (p<0.05) in the group that experienced discomfort.