Patient Monitoring During Magnetic Resonance Imaging Exams by Means of Ballistocardiography

Magnetic resonance imaging (MRI) has become indispensable in modern medicine. In many cases, it is necessary to monitor the vital signs of the patient during an MRI exam, particularly the heart rate. The MRI’s environment often makes it difficult to acquire reliable physiological signals, especially the electrocardiogram (ECG). In addition, applying the monitoring hardware requires additional patient preparation time. In order to avoid these drawbacks, this work makes use of the ballistocardiographic (BCG) effect for obtaining a heart rate estimate.To measure body motions caused by the BCG effect, an inflated air cushion was integrated into the MRI’s patient table. An external pressure sensor detected the pressure changes caused by the BCG effect. A synchronously acquired ECG was used as a reference. Five subjects were included in this preliminary study. The measurements were performed inside a 3 T MRI scanner.Taking the ECG as reference or gold-standard, heart beats in the BCG were detected with sensitivity of 91.7 % and a positive predictive value of 93.9 %.This preliminary study showed the feasibility of using BCG signals for patient monitoring during MRI exams. In conclusion, this approach enables patient monitoring during MRI exams and eliminates the time-consuming patient preparation.