Alterations in human ECG due to the MagnetoHydroDynamic effect: A method for accurate R peak detection in the presence of high MHD artifacts

Abstract

Blood flow in high static magnetic fields induces elevated voltages that contaminate the ECG signal which is recorded simultaneously during MRI scans for synchronization purposes. This is known as the magnetohydrodynamic (MHD) effect, it increases the amplitude of the T wave, thus hindering correct R peak detection. In this paper, we inspect the MHD induced alterations of human ECG signals recorded in a 1.5 Tesla steady magnetic field and establish a primary characterization of the induced changes using time and frequency domain analysis. We also reexamine our previously developed real time algorithm for MRI cardiac gating and determine that, with a minor modification, this algorithm is capable of achieving perfect detection even in the presence of strong MHD artifacts.

Detailing the use of magnetohydrodynamic effects for synchronization of MRI with the cardiac cycle: A feasibility study

“…It has been eloquently demonstrated that MHD effects can be successfully eliminated from ECG signal trace in real time (18). However, the run time of blood together with the delay in blood pulsation and vessel motion between the heart and the target territory remains a concern when using ECG triggering/ gating.…”

“…Various approaches have been proposed to assess, cancel, correct for, bypass, or extract MHD blood flow potential induced artifacts from the surface ECG. These efforts include the assessment of MHDinduced ECG distortions in the fringe field of an MR magnet (12), optimization of ECG electrode placement (13), R-wave detection algorithms based on the vector cardiogram (14), alternative triggering/gating techniques that are less sensitive or even immune to interference with EMF, including self-gating techniques (11,15,16), and sophisticated ECG signal processing (17,18).…”

“…Contrary to the notion (5,8,18,19) that considers MHD effects as adverse concomitants of traditional ECG acquired in a magnetic field environment, this feasibility study explores the merits of MHD effects for cardiac-gated MRI. We propose that the MHD effect being inherently sensitive to magnetic flux density, flow orientation with respect to the magnetic field lines, and velocity of an electrical charge carrier such as blood can be put to use as an alternative approach for registration of cardiac activity and for cardiac gating/triggering.…”

Influence of the trigger technique on ventricular function measurements using 3-Tesla magnetic resonance imaging: comparison of ECG versus pulse wave triggering

“…This phenomenon is called 'magnetohydrodynamic effect'. The magnitude of the voltages produced by the magnetohydrodynamic effect is determined by the velocity of flow of the fluid, the diameter of the tube through which the fluid is flowing, and the strength of the magnetic field (5,25,26). CMR typically relies on the use of an ECG signal to synchronize segmented data acquisition to the cardiac cycle (18).…”

Effects of static magnetic field exposure on blood flow

“…More recently, Abi Abdallah et al [12] characterized temporal and spectral alterations of human ECG, measuring T wave amplitudes, and showing a signal energy increase and a spectral shift toward low frequencies. Jehenson et al [13] observed variations of heart frequency at 2T and indicated that the sinus node might be affected.…”