Quantitative evaluation of signal integrity for magnetocardiography

Magnetocardiography (MCG) is a non-invasive diagnostic tool used to investigate the activity of the heart. For applications in an unshielded environment, in order to extract the very weak signal of interest from the much higher background noise, dedicated hardware configuration and sophisticated signal processing techniques have been developed during the last decades. Being powerful in noise rejection, the signal processing may introduce signal distortions, if not properly designed and applied. However, there is a lack of an effective tool to quantitatively evaluate the signal integrity for MCG at present. In this paper, we have introduced a very simple method by using a small coil driven by a human ECG signal to generate a simulated MCG signal. Three key performance indexes were proposed, which are correlation in time domain, relative heights of different peaks and correlation in frequency domain, to evaluate the MCG system performance quantitatively. This evaluation method was applied to a synthetic gradiometer consisting of a second-order axial gradiometer and three orthogonal reference magnetometers. The evaluation turned out to be very effective in optimizing the parameters for signal processing. In addition, the method can serve as a useful tool for hardware improvement.

[1]  S. Taulu,et al.  Applications of the signal space separation method , 2005, IEEE Transactions on Signal Processing.

[2]  R Marchesini,et al.  Monte Carlo simulation of light fluence in tissue in a cylindrical diffusing fibre geometry. , 1999, Physics in medicine and biology.

[3]  Jens Haueisen,et al.  Passive vortex currents in magneto- and electrocardiography: comparison of magnetic and electric signal strengths , 2006, Physics in medicine and biology.

[4]  U Leder,et al.  Source localization in an inhomogeneous physical thorax phantom. , 1999, Physics in medicine and biology.

[5]  Yangchao Tian,et al.  A noise feedback least-mean-square algorithm of data processing for SQUID-based magnetocardiography , 2005 .

[6]  Alex I. Braginski,et al.  Biomagnetism using SQUIDs: status and perspectives , 2006 .

[7]  R. Fenici,et al.  Magnetocardiography: ventricular arrhythmias. , 1993, European heart journal.

[8]  Yi Zhang,et al.  Adaptive frequency dependent gradiometry applied to SQUID magnetocardiography , 2003 .

[9]  Riccardo Fenici,et al.  Phantom Validation of Multichannel Magnetocardiography Source Localization , 2003, Pacing and clinical electrophysiology : PACE.

[10]  S N Erné,et al.  A novel approach for the averaging of magnetocardiographically recorded heart beats , 2005, Physics in medicine and biology.

[11]  Birgit Hailer,et al.  Magnetocardiography in coronary artery disease with a new system in an unshielded setting , 2003, Clinical cardiology.

[12]  Audrius Brazdeikis,et al.  Non-invasive assessment of the heart function in unshielded clinical environment by SQUID gradiometry , 2003 .

[13]  H.-P. Müller,et al.  Noise reduction in magnetocardiography by singular value decomposition and independent component analysis , 2006, Medical and Biological Engineering and Computing.

[14]  P. Hugenholtz,et al.  Magnetocardiography Predicts Coronary Artery Disease in Patients with Acute Chest Pain , 2005, Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc.

[15]  Ken Sakuta,et al.  Noise Reduction Process with Generalized Harmonics Analysis for High-Temperature Superconducting Quantum Interference Device Magnetocardiography , 2002 .

[16]  Vittorio Pizzella,et al.  SQUID systems for biomagnetic imaging , 2001 .

[17]  Jens Haueisen,et al.  Vortex Shaped Current Sources in a Physical Torso Phantom , 2005, Annals of Biomedical Engineering.

[18]  I Yamaguchi,et al.  Noninvasive, direct visualization of macro-reentrant circuits by using magnetocardiograms: initiation and persistence of atrial flutter. , 2003, Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology.

[19]  L Toivonen,et al.  Repolarization Abnormalities Detected by Magnetocardiography in Patients with Dilated Cardiomyopathy and Ventricular Arrhythmias , 2001, Journal of cardiovascular electrophysiology.