Comparison of three artificial models of the magnetohydrodynamic effect on the electrocardiogram

Abstract

The Electrocardiogram (ECG) is often acquired during Magnetic Resonance Imaging (MRI) for both image acquisition synchronisation with heart activity and patient monitoring to alert for life-threatening events. Accurate ECG analysis is mandatory for cutting-edge applications, such as MRI guided interventions. Nevertheless, the majority of the clinical analysis of ECG acquired inside MRI is made difficult by the superposition of a voltage called the MagnetoHydroDynamic (MHD) effect. MHD is induced by the flow of electrically charged particles in the blood perpendicular to the static magnetic field, which creates a potential of the order of magnitude of the ECG and temporally coincident with the repolatisation period. In this study, a new MHD model is proposed which is an extension of several existing models and incorporates MRI-based blood flow measurements made across the aortic arch. The model is extended to several cardiac cycles to allow the simulation of a realistic ECG acquisition during MRI examination and the quality assessment of MHD suppression techniques. A comparison of two existing models is made with our new model and with an estimate of the MHD voltage observed during a real MRI scan. Results indicate a good agreement between our proposed model and the estimated MHD for most leads, although there are clearly some descrepencies with the observed signal which are likely to be due to remaining deficiencies in the model. However, the results demonstrate that our new model provides a closer approximation to observed MHD effects and a better depiction of the complexity of the MHD effect compared to the previously published models. The source code will be made freely available under and open source license to facilitate collaboration and allow more rapid development of more accurate models of the MHD effect.

Intra-MRI Extraction of Diagnostic Electrocardiograms Using Carotidal Magnetohydrodynamic Voltages

“…Correlation between extracted MHD from 12-lead ECGs recorded inside the MRI and each source was computed and used to determine the optimal source of intra-MRI dynamic feedback. Furthermore, average flow was quantified in the ascending aorta and the carotid artery using conventional PCMR during exercise stress testing to predict induced VMHD based on superimposing an MHD term on 12-lead ECG traces acquired outside of the MRI bore, whereas MRI derived flow (q) and a unique proportionality constant (α i ) for each lead (i = 1:12) were used to predict induced VMHD which occurs in 12-lead ECG (Equation (1)) [18].…”

“…However, results from this approach have presented difficulties in filter training for ECG real extraction. The conventional method of ECG real extraction involves the subtraction of ECGs recorded inside the MRI from those recorded outside the MRI (Figure 1b) [18]. This method is flawed because it is based on the assumption that ECG real does not vary once the subject is placed inside the MRI, which is not necessarily the case.…”

The Magnetohydrodynamic Effect and Its Associated Material Designs for Biomedical Applications: A State‐of‐the‐Art Review

“…The development of early models of the MHD effect in arterial vasculature, led to the partial validation of the hypothesis, proving that VMHD of a comparable magnitude and direction could be induced by aortic blood flow, with the primary contribution to the net signal being attributed to the aortic arch, a large diameter vasculature in the human body transverse to the MRI magnetic field and with a high volumetric flow rate [74, 79] . Similarly, a phantom in-vitro model was developed to record bipolar VMHD signals (Fig.…”

Exploring magnetohydrodynamic voltage distributions in the human body: Preliminary results

“…In addition, the correlation between V MHD observed on conventional ECG traces and cardiac blood flow was demonstrated [19]. Current modeling approaches have been able to successfully simulate the induced V MHD as a linear combination of the true ECG signal and a V MHD term (Eq 1) with an additional scaling factor which was dependent on the measurement electrode selected [20]. Induced V MHD was shown to increase with cross-sectional area and vessel diameter [20, 21].…”