Damper Design for Improving S/N Ratio of the Seismocardiogram Monitoring in the OpenMRI-guided Operating Theater

The final goal of this study is to establish a method of measuring precisely the seismocardiogram (SCG) of a patient who lying in an open magnetic resonance imaging (openMRI) machine for myocardial ischemia monitoring during surgery. Vibration isolation from the gantry vibration during MRI scan is essential for clinical use. Authors previously reported the comparison between the SCG and the gantry vibration. A damper to decrease vibration below 30 Hz should be designed. In this paper, authors fabricated a damper model to check the feasibility of the damping effect, and compared with the patient bed mat. Experiment using a vibrator showed 1) the viscosity damping coefficient of the current damper was 2 kN s/m, 2) owing to the damper, peak ratio between input and output amplitude decreased from 2.5 to 1.2, and 3) natural frequency decreased from 12 Hz to 5 Hz. Damping below 30 Hz was successfully achieved. The maximum S/N ratio was calculated 6, improving from 1.8. Simulation showed that the maximum S/N would be 75 under the viscosity damping coefficient of 1 N s/m.