A Low-Cost System for Seismocardiography-Based Cardiac Triggering: A Practical Solution for Cardiovascular Magnetic Resonance Imaging at 3 Tesla

Abstract

This study describes a pilot clinical validation of a new low-cost system for the continuous monitoring of the human body's cardiorespiratory activities within the magnetic resonance examination area. This study primarily focuses on monitoring cardiac activity and the related cardiac triggering. The patented system tested by the authors is based on seismocardiography (SCG). The study was conducted on 18 subjects on a Siemens Prisma 3T MR scanner. Standard anatomical and diffusion sequences were used to test cardiac activity monitoring. A wide range of commonly used diagnostic sequences were used to test imaging of the heart by means of cardiac triggering. System functionality was verified against a commercially available electrocardiography (ECG) system. Monitoring of cardiac activity (detection of the R-R interval in ECG and the AO-AO interval in SCG) was objectively evaluated by determining the overall probability of correct detection (ACC), sensitivity (SE), positive predictive value (PPV), and harmonic mean between SE and PPV, i.e. F1. Imaging quality control using Cardiac Triggering was performed by subjective evaluation of images by the physicians. The study conducted clearly confirmed the functionality of the system in terms of continuous cardiac activity monitoring. In all 18 subjects, a mean PPV > 99 % was achieved; F1 > 99 %; SE > 99 %; ACC > 98 %; 1.96σ < 3.5 bpm. Also, Cardiac Triggering functionality was confirmed by the physicians on the basis of analyzing cardiac images using the T1/T2 balanced echo sequences and the T1 flash sequence measured natively. INDEX TERMS Seismocardiography-based cardiac triggering, seismocardiography (SCG), siemens prisma 3T, monitor patient vital signs during MRI, cardiac magnetic resonance imaging (CMRI).

A Comparison Between Novel FPGA-Based Pad Monitoring System Using Ballistocardiography and the Conventional Systems for Synchronization and Gating of CMRI at 3 Tesla: A Pilot Study

“…In addition to the delay of the BCG signal in comparison with the reference ECG signal, it is also necessary to take into account the delay in transmission caused the propagation of the pressure change through the tube. The issue of delays between the ECG and the BCG, or the SCG, is discussed in detail in study [36]. In general, any pressure sensor can be used to measure the pressure inside the pneumatic system.…”

“…The application displays the BCG waveform measured, the peaks detected and the triggers generated in real-time and allows the user to configure the peak detection algorithm and the triggering delay defined. The hardware and software setup utilized was identical with the ones used in our previous research [36]. A complete block diagram of the system with the detailed description of the peak detection and the trigger generation logic implemented in FPGA is shown in Fig.…”

“…The delay length depends on the patient's (patho)physiology as well as the design of the sensor itself. However, the total delay of the triggering signal (indicated by dotted lines) can be much longer due to the propagation of the signal by the medium to the control unit, the influence of filtering or the electronics controlling the state, and conversion of the signal [35], [36]. Such a delayed triggering signal then results in image acquisition in the wrong phase of the cardiac cycle, which leads to a reduced likelihood of proper diagnosis and often to the need for repeating the image acquisition, thereby extending the examination time.…”

“…The authors of the study have already developed a hybrid acoustic sensor for triggering MR acquisition based on seismocardiography (SCG) [36], which refers to monitoring of human body surface vibrations due to cardiac wall movement commonly sensed by accelerometers. In the past, the SCG signal was used to detect heart rate [37] and also to measure cardiac activity in the MR environment [38].…”

Synthesis of Dynamic Errors Correcting Algorithm for Auto–Balancing Bridge Methods

“…It would also be good to combine bioelectrical impedance spectroscopy with other measurement methods such as ECG or EEG [40]- [42]. Except measuring body structure, it would be also possible to detect stress or some serious conditions [10], [41].…”