MCG System Research Articles

Visualization of Cardiac Vectors using Electrocardiography and Magnetocardiography

In this paper, an attempt is made to simulate and compare spatio-temporal VCG and VMCG derived from epicardial potentials. Electric (EHV) and Magnetic heart vectors (MHV) are computed from the ECG and MCG at various time instants and their orientations with respect to time are found to show a reasonable tilt of 90 to 100 degrees. The complimentary information with reference to the orientation of cardiac vector offered by MHV could be attributed to its sensitivity to intracellular myocardial currents, while EHV exhibits the orientation associated with only the extracellular currents owing to volume conduction. By comparing the orientations of EHV and MHV generated from a simulated equivalent current dipole model, the present work demonstrates the usefulness of these spatiotemporal vectors in tracing the cardiac current flow inside the thorax for a healthy heart. It could be thus expected that clinically relevant information could be obtained if the present analysis is extended to highly complex and irregular cardiac activation sequences that could be seen in arrhythmia and myocardial infarction. The main contribution of this paper is to mathematically model and derive the magnetic heart vectors from the MCG system extracted from IGCAR lab and verify it with the conventional VCG extraction..

Value of Topology Approach to Diagnose of CAD Based on Magnetocardiographic Current Distribution Maps in Difficult-to-Diagnose Patients

Objective: The purpose of this work is to examine the usefulness of the topological approach for analysis of current density maps during ST-T interval in detection of coronary artery disease (CAD) in patients with proved CAD but normal results of routine tests. Materials and Methods: The patient group included 123 patients. Coronary angiography was done due to chest pain. The control group consisted of 124 healthy volunteers. The MCG test was done by 4-channels MCG system installed at unshielded setting. An integral topological index Kideal, consisting of 4 parameters, has been counted. Results and Conclusions: It is shown that Kideal was higher in patient group compared to control one. Sensitivity was 87%, and specificity was 64%. The topological analysis of MCG current density maps is a valuable tool in noninvasive detection of CAD in difficult-to-diagnose patients with uninformative results of routine tests.

Multi-channel magnetocardiogardiography system calibration

The field-to-voltage transfer coefficient (∂ B/∂ V) is an important parameter of the multi-channel superconducting quantum interference device (SQUID) magnetic detecting system. The SQUID devices and the readout circuits have the inevitable differences among different channels, so the accurate calibration of system channels is rather significant. In this paper, We first used the circular PCB coils for 36-channel MCG system calibration, and the other one is based on a traditional method in which a uniform field is produced by square Helmholtz coil. The calibration data show that the results are basically the same. The calibrated ∂ B/∂ V values using circular PCB coils are in a range from 1.46-1.73 pT·mV-1. And those of square Helmholtz coils are mostly within a range from 1.56-1.64 pT·mV-1.

Is there any purpose in classifying subtrochanteric fractures? The reproducibility of four classification systems

Classification systems are used for communication, planning treatment options, predicting outcomes and research purposes. The majority of subtrochanteric fractures are now treated with intramedullary nails and therefore questioning the need for classification. To assess the intra- and inter-observer reproducibility of the Seinsheimer, AO and Russell-Taylor (RT) classification systems and to assess a new simple system (MCG). The MCG system was developed to alert the surgeon to potential hazards: type 1-subtrochanteric fracture (ST#) with intact trochanters, type 2-ST# involving greater trochanter (entry point for nailing difficult), and type 3-ST# involving lesser trochanter (most unstable). Thirty-two anteroposterior and lateral radiographs of subtrochanteric fractures were classified independently for each of the 4 classification systems by 4 observers on 2 separate occasions. The intra- and inter-observer variation was poor in all systems (highest Kappa 0.35). MCG had the best reproducibility followed by RT, then AO and Seinsheimer. The data were re-analysed to determine whether the findings were due to the presence of too many subgroups and whether the observers could more accurately identify important individual subclassifications: Seinsheimer 3a, AO31-A3.1, RT 1 or 2, RT a or b, and MCG3. The MCG3 had the narrowest ranges for intra- and inter-observer reproducibility. The classification systems analysed in this study have poor reproducibility and seem to be of little value in predicting the outcome of intramedullary nailing as all of the fractures achieved union. The MCG system may be of some use in alerting the surgeon to potential problems.

A High-sensitivity Magnetocardiography System with 64 Axial Gradiometers Inside a Low Boil-off Dewar

Event Abstract Back to Event A High-sensitivity Magnetocardiography System with 64 Axial Gradiometers Inside a Low Boil-off Dewar Yong-Ho Lee1*, Kwon-Kyu Yu1, Hyukchan Kwon1, Jin-Mok Kim1 and Kiwoong Kim1 1 Korea Research Institute of Standards and Science, South Korea For accurate diagnosis and high-throughput screening of ischemic heart disease or arrhythmia, high-sensitivity economic MCG system is needed. We fabricated an MCG system having axial gradiometers with low stray pickup area and dewar with low boil-off rate of liquid He. The axial gradiometers have very simple structure for the superconductive connection. The two ends of pickup coil wires were placed near the input coil pads of SQUID, and annealed Nb wires were bonded directly between pickup coil wires and input coil pads. In this way, the stray pickup area (intrinsic balance) made by the connection structure is about 0.1 % of the pickup coil area, and the gradiometers can be operated inside a thin magnetically shielded room. The baseline of the first-order gradiometer is 70 mm, and diameter of pickup coil is 20 mm. The neck diameter of the dewar is smaller than the diameter of gradiometer array (dewar inner bottom). By dividing the gradiometer array into 4 plates, each plate can be installed separately into the dewar bottom. In this way, the boil-off rate of liquid He can be reduced to 3 L/day, for the inner bottom diameter of 280 mm. The SQUIDs are double relaxation oscillation SQUIDs with large flux-to-voltage transfer coefficients, enabling compact flux-locked loop electronics. The developed 64-channel system was installed inside a thin (80 mm thick) shielded room, and showed field noise level of 3 fT/sqrt(Hz) at 100 Hz. Measurements of adult and fetal MCG signals were done successfully using the developed system. Analysis software allows parameter analysis for the screening of ischemic heart disease and 3-dimensional imaging of myocardium current (reentry current source) on the realistic image of the heart. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: MCG: Instrumentation, Modeling, Basic and Clinical Studies Citation: Lee Y, Yu K, Kwon H, Kim J and Kim K (2010). A High-sensitivity Magnetocardiography System with 64 Axial Gradiometers Inside a Low Boil-off Dewar. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00367 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 08 Apr 2010; Published Online: 08 Apr 2010. * Correspondence: Yong-Ho Lee, Korea Research Institute of Standards and Science, Daejeon, South Korea, yhlee@kriss.re.kr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Yong-Ho Lee Kwon-Kyu Yu Hyukchan Kwon Jin-Mok Kim Kiwoong Kim Google Yong-Ho Lee Kwon-Kyu Yu Hyukchan Kwon Jin-Mok Kim Kiwoong Kim Google Scholar Yong-Ho Lee Kwon-Kyu Yu Hyukchan Kwon Jin-Mok Kim Kiwoong Kim PubMed Yong-Ho Lee Kwon-Kyu Yu Hyukchan Kwon Jin-Mok Kim Kiwoong Kim Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Improvement of small-channel MCG System

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Magnetic reconstruction of circulating excitation

Event Abstract Back to Event Magnetic reconstruction of circulating excitation Taysia Sosnytska1*, Pavlo Sutkovyy2, Volodymyr Sosnytskyy2 and Ekaterina Koronovska2 1 P.L. Shupik Medical Academy for Postgraduate Education of UH Ministry, Ukraine 2 Glushkov Institute of Cybernetics, MCG Laboratory, Ukraine Objective. Cardiac arrhythmia re-entry is most important mechanism of fatal tachy arrhythmias such as ventricular fibrillation. This arrhythmia re-entry may be provoked by such anisotropic factor as circulating fiber orientation. Our hypothesis is that the circulating excitation can be modeled by a set of electrical sources with a different orientation. The purpose of this study was to investigate how well two dimensional current density distribution (CDD) reflects real distribution of the circulating excitation of the set of electrochemical “cells”. Methods. A simple realistic torso model and source model (SM) [Sosnytskyy,2004] suitable for magnetic measurements was constructed by layers of discrete electrochemical “cells” mounted inside a torso phantom with saline solution. The continuous and discontinuous nature of active circulating excitation were simulated by a set of electrical sources arranged in a circle. Cells were switched on stepwise one after the other. Magnetic signals (MS) were recorded by means of 4x3–channel MCG system (Kiev Medical Group Ltd, Ukraine) in an unshielded setting. After averaging the beat at rectangle grid 6x6, magnetic field distribution maps were ploted in the course of an SM activity. CDD maps were plotted by Magnetic Moments Method of the “ inverse problem solution “ [Romanovych,1997,1999] Results. Results show a good correspondence between current density vector maps determined from the actual measured magnetic maps and active circulating excitation. Pattern of activation and regions of earliest and latest activation were observed with acceptable accuracy. Conclusions. Our study confirmed the good correlation between CDD and circulating spatial distribution of current flow sources. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: MCG: Instrumentation, Modeling, Basic and Clinical Studies Citation: Sosnytska T, Sutkovyy P, Sosnytskyy V and Koronovska E (2010). Magnetic reconstruction of circulating excitation. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00317 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 06 Apr 2010; Published Online: 06 Apr 2010. * Correspondence: Taysia Sosnytska, P.L. Shupik Medical Academy for Postgraduate Education of UH Ministry, Kiev, Ukraine, t_sosnytskaya@mail.ru Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Taysia Sosnytska Pavlo Sutkovyy Volodymyr Sosnytskyy Ekaterina Koronovska Google Taysia Sosnytska Pavlo Sutkovyy Volodymyr Sosnytskyy Ekaterina Koronovska Google Scholar Taysia Sosnytska Pavlo Sutkovyy Volodymyr Sosnytskyy Ekaterina Koronovska PubMed Taysia Sosnytska Pavlo Sutkovyy Volodymyr Sosnytskyy Ekaterina Koronovska Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Performance Investigation of a Three-Dimensional SQUID MCG System by Using a Computer Simulation

Performance Investigation of a Three-Dimensional SQUID MCG System by Using a Computer Simulation

MCG on heart disease modified mice

We have developed a MCG system for mice as a powerful tool to study the incidence of heart disease non-invasively. The spatial resolution and the magnetic field sensitivity of the system are 500 μm and 0.75 pT/Hz1/2 in the frequency range of 100 Hz–10 kHz. The objective of this study is the evaluation of the incidence of heart disease without individual difference by using MCG measurement on disease-model mice. First, we measured the MCG on aconitine-induced arrhythmia model mice and a drug-free wild-type mice to confirm the ability of the system to detect anomalies due to heart diseases. The results show that the system could give significant information relevant to heart disease. Second, MCG could track the course of a disease and the recovery because of non-invasive measurement. We routinely measured mice from 7 to 13 weeks old with a high incidence of cardiac infarction (CI). Abnormal MCG was measured from 2 weeks before death. The results suggest that the MCG on mice has a potential to monitor the progress of heart disease.

Emulation Circuit for Superconducting Quantum Interference Device (SQUID) Sensor in Magnetocardiography System

The superconducting quantum interference device (SQUID) is a transducer that converts magnetic flux into voltage. Its range of linear conversion, however, is very restricted. To overcome its narrow dynamic range, a flux-locked loop (FLL) is used to feedback the output field to cancel the input field. This prevents the operating point of the SQUID from moving far away from the null point. In this paper, an emulator for the SQUID sensor and the feedback coil has been proposed. Magnetic coupling between the original field and the generated field by the feedback coil was emulated by electronic circuits. By using the emulator, FLL circuits can be analyzed and optimized without use of SQUID sensors. This is a useful feature, especially in the early stage of development of the MCG system when a magnetically shielded room or real SQUID sensors may not yet be available. The emulator may also be used as a test signal generator for multi-channel gain calibration and for system maintenance.

Process of Fabricating YBCO SQUIDs for 51-Channel HTS MCG System

We have constructed a high throughput HTS SQUID fabrication process to develop a 51-channel HTS MCG system. To increase the process throughput of the YBCO deposition, we designed and developed a new deposition system based on a pulsed laser deposition technique. In this deposition system, nine YBCO thin films could be deposited in one deposition sequence by successively depositing the YBCO thin films one by one. In addition to the improvement of the fabrication throughput, the magnetometer pattern was designed to improve the yield of the SQUID fabrication. In our magnetometer design, four SQUIDs were connected with one pickup coil. The yield of good magnetometer chips could be increased by selecting the best SQUID among the four. Using the developed SQUID fabrication process, about one hundred magnetometers were fabricated in a month. The 51-channel HTS MCG system was successfully developed and used for clinical testing.

Characterization of Fetal Arrhythmias by Means of Fetal Magnetocardiography in Three Cases of Difficult Ultrasonographic Imaging

Characterization of ultrasound detected fetal arrhythmias is generally performed by means of M-mode and pulsed Doppler echocardiography (fECHO), sonographic techniques that allow only indirect and approximate reconstruction of the true electrophysiological events that occur in the fetal heart. Several studies demonstrated the ability of fetal magnetocardiography (fMCG) to identify fetal arrhythmias. We report on three women, studied after the 32nd gestational week, who were referred for fMCG because of unsatisfying fetal cardiac visualization with fECHO due to maternal obesity, fetus in constant dorsal position hiding the fetal heart, intrauterine growth retardation, and oligohydramnios. Minor pericardial effusion was present in the third patient and digoxin therapy was given. FMCG were recorded with a 77-channel MCG system working in a shielded room. Independent Component Analysis (FastICA algorithm) was used to reconstruct fetal signals. The good quality of the retrieved fetal signals allowed real-time detection of arrhythmias and their classification as supraventricular extrasystoles (SVE), with/without aberrant ventricular conduction and/or atrioventricular block. The time course of the fetal cardiac rhythm was reconstructed for the entire recording duration; hence, fetal heart rate variability could be studied in time and frequency. Since isolated extrasystoles may progress to more hazardous supraventricular tachycardias, the noninvasive antenatal characterization of, even transient, fetal arrhythmias and their monitoring during pregnancy can be of great clinical impact.

Fetal magnetocardiographic mapping using independent component analysis

Fetal magnetocardiography (fMCG) is the only noninvasive technique allowing effective assessment of fetal cardiac electrical activity during the prenatal period. The reconstruction of reliable magnetic field mapping associated with fetal heart activity would allow three-dimensional source localization. The efficiency of independent component analysis (ICA) in restoring reliable fetal traces from multichannel fMCG has already been demonstrated. In this paper, we describe a method of reconstructing a complete set of fetal signals hidden in multichannel fMCG preserving their correct spatial distribution, waveform, polarity and amplitude. Fetal independent components, retrieved with an ICA algorithm (FastICA), were interpolated (fICI method) using information gathered during FastICA iterations. The restored fetal signals were used to reconstruct accurate magnetic mapping for every millisecond during the average beat. The procedure was validated on fMCG recorded from the 22nd gestational week onward with a multichannel MCG system working in a shielded room. The interpolated traces were compared with those obtained with a standard technique, and the consistency of fetal mapping was checked evaluating source localizations relative to fetal echocardiographic information. Good magnetic field distributions during the P-QRS-T waves were attained with fICI for all gestational periods; their reliability was confirmed by three-dimensional source localizations.

A Mobile and Space-saving High-temperature Superconducting Multichannel Magnetocardiograph in a Vertical Magnetically Shielded Cylinder

A high-temperature superconducting (HTS) magnetocardiographic system composed of 16-channels HTS-Superconducting Quantum Interference Device (SQUID) magnetometers and a vertical magnetically shielded cylinder has been developed. The cylinder is designed to save space and provide mobility for the entire system, including the magnetically shielded cylinder. It consists of two fixed semicircular shells and a sliding semicircular door, all of which are made from sheets of a flexible nanocrystalline soft-magnetic material. The cardiomagnetic field from a subject seated in the vertical magnetically shielded cylinder is measured by multichannel HTS-SQUID magnetometers that are sensitive to field strengths weaker than 100 fT/(Hz)1/2. The high signal-to-noise ratio of the magnetometer signals makes beat-to-beat measurement of the cardiomagnetic field possible. This HTS-based multichannel MCG system is being applied to medical applications such as the detection of arrhythmias and ischemic heart disease.