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ABSTRACT: The correlation between neuronal activity and cortical hemodynamics, namely, neurovascular coupling (NVC), is important to shed light on the mechanism of a variety of brain functions or neuronal diseases. NVC can be studied by simultaneously measuring neuronal activity and cortical hemodynamics. Consequently, noninvasive measurements of the NVC have been widely studied using both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). However, electromagnetic interference between EEG and fMRI is still a major problem. On the other hand, near-infrared spectroscopy (NIRS) is another promising tool for detecting cortical hemodynamics because it can be combined with EEG or magnetoencephalography (MEG) without any electromagnetic interference. Accordingly, in the present study, a simultaneous measurement system-combining an unshielded MEG using a two-dimensional gradiometer based on a low-Tc superconducting quantum interference device (SQUID) and an NIRS using nonmagnetic thin probes-was developed. This combined system was used to simultaneously measure both an auditory-evoked magnetic field and blood flow change in the auditory cortex. It was experimentally demonstrated that the combined unshielded MEG/NIRS system can simultaneously measure neuronal activity and cortical hemodynamics.
Journal of Biomedical Optics 10/2012; 17(10):107001-1. · 3.16 Impact Factor
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ABSTRACT: We propose a linear discriminant regression analysis (LDRA) that provides an estimated severity marker for discriminating between healthy and patient groups and estimating severities of the patient group simultaneously. This method combines an evaluation function for discriminating between two groups and one for estimating severities of one group. The combined function is optimized to obtain an equation for calculating estimated severities. The method was evaluated with finger-tapping data of healthy and Parkinson's disease (PD) groups and PD severities assessed by a doctor. As a result, the discrimination ability of LDRA (AUC: 0.8835) was higher than that of discriminant analysis (DA. AUC: 0.8442), which is a conventional method for classification, and the regression ability of LDRA (mean square error (MSE): 1.27) was superior to that of multiple regression analysis (MRA. MSE: 1.68), which is a conventional method for regression. The results show that LDRA is an effective method for estimating the presence and severity of Parkinson's disease.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:4315-8.
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ABSTRACT: A one-channel low temperature superconductor superconducting quantum interference device system comprising a second-order axial gradiometer with a sensing area of 10 mm × 190 mm was developed. The gradiometer was mounted in a liquid-helium dewar (450-mm diameter; 975-mm length), with a gap of 12 mm between the pickup coil and the dewar-tail surface. The magnetic field sensitivity was measured to be 16 fT/Hz(1/2) in the white noise regime above 2 Hz. The system was used to measure stainless steel particles of different sizes passing through the sensing area. A 100-μm diameter SUS304 particle was readily detected passing at different positions underneath the large pickup coil by measuring its 1.3-pT magnetic field. Thus, the system was shown to be applicable to quality control of lamination sheet products such as lithium ion batteries.
The Review of scientific instruments 07/2012; 83(7):076108. · 1.52 Impact Factor
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Kentaro Yoshida,
Hiroshi Tada,
Kuniomi Ogata,
Yukio Sekiguchi,
Takeshi Inaba,
Yoko Ito,
Yoko Sato,
Akira Sato,
Yoshihiro Seo, Akihiko Kandori,
Kazutaka Aonuma
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ABSTRACT: BACKGROUND: Despite the informative nature of atrial fibrillation (AF) electrograms, electrophysiological aspects of predicting reversal of structural remodeling of the left atrium (LA) have not been evaluated. OBJECTIVES: To identify predictors of reverse remodeling after restoration of sinus rhythm by catheter ablation in patients with persistent AF. METHODS: This study included 90 patients with persistent AF and enlarged LA (left atrial volume indexed to body surface area [LAVi] ≥32 mL/m(2)). LAVi was measured by echocardiography before ablation and 12 months after sinus rhythm restoration. We divided 73 (81%) patients free from recurrences into 2 groups according to reduction in LAVi: responders, reduction ≥23% (n = 35); nonresponders, reduction <23% (n = 38). Serological testing and electrophysiological characteristics on electrocardiogram and magnetocardiogram were analyzed. RESULTS: LAVi decreased from 43 ± 12 to 27 ± 7 mL/m(2) in responders and from 37 ± 8 to 33 ± 8 mL/m(2) in nonresponders. Higher LAVi at baseline (P = .01), lower age (59 ± 7 years vs 63 ± 7 years; P <.05), higher brain natriuretic peptide level (median = 92, interquartile range [IQR] = 98 pg/mL vs median = 60, IQR = 64 pg/mL; P = 0.01), higher atrial natriuretic peptide level (median = 73, IQR = 74 pg/mL vs median = 54, IQR = 70 pg/mL; P = .02), and higher organization index of AF signals (0.51 ± 0.11 vs 0.42 ± 0.09; P = .0001) were observed in responders. There was a linear correlation between organization index and % reduction in LAVi (R = 0.63; P <.0001). Multiple linear regression analysis showed relations between reverse remodeling and age (η = -0.28; P = .002), atrial natriuretic peptide level (η = 0.21; P = .03), and organization index (η = 0.53; P <.0001). CONCLUSIONS: Electrogram organization was a robust predictor of reverse remodeling of the enlarged LA after sinus rhythm restoration by catheter ablation in patients with persistent AF.
Heart rhythm: the official journal of the Heart Rhythm Society 06/2012; · 4.56 Impact Factor
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Yoko Sato,
Kentaro Yoshida,
Kuniomi Ogata,
Takeshi Inaba,
Hiroshi Tada,
Yukio Sekiguchi,
Yoko Ito,
Tomoko Ishizu,
Yoshihiro Seo,
Iwao Yamaguchi, Akihiko Kandori,
Kazutaka Aonuma
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ABSTRACT: Differences in electrical properties between left and right atria (LA and RA) after pulmonary vein isolation (PVI) for atrial fibrillation (AF) are currently poorly understood. Magnetocardiograms were used to investigate the effect of PVI on bi-atrial magnetic field changes and their relationship to clinical outcomes.
This study included 71 patients undergoing PVI for paroxysmal AF. Magnetocardiograms were recorded at baseline and 1 day, 8 weeks, and 24 weeks after ablation. Peak magnitude of LA and RA segments on P waves was separately compared before and after PVI. During a 16-month post-ablation period, 53 (75%) patients were free from AF recurrences. LA magnetic strength in patients without recurrence persistently decreased for 24 weeks and was significantly lower at 8 weeks than that in patients with recurrence (1.28±0.69 vs. 1.74±0.71 pico-Tesla, P=0.02). RA magnetic strength in patients with recurrence persistently rose for 24 weeks and was significantly higher at 8 weeks than that in patients without recurrence (2.17±0.82 vs. 3.00±1.12 pico-Tesla, P=0.001). Multivariate analysis showed RA magnetic strength at 8 weeks to be the strongest predictor of AF recurrence (odds ratio=3.335; 95% confidence interval=1.181-9.416; P=0.02).
PVI resulted in distinct changes in magnetic strength in both the LA and the RA. A persistent rise in RA magnetic strength might be a robust predictor of AF recurrence after ablation.
Circulation Journal 04/2012; 76(7):1601-8. · 3.77 Impact Factor
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ABSTRACT: This paper proposes the CPG synergy model--a biomimetic rhythm generator model based on central pattern generators (CPGs) and muscle synergy theory to enable evaluation of rhythmic motions with non-stationary characteristics such as human finger tapping movements. The model consists of multiple CPGs to approximate the complex rhythmic movement of humans, and has the potential to allow evaluation of abnormal movements in patients with motor function impairments such as Parkinson's disease (PD). To verify the validity of the proposed model, comparison experiments were conducted using model parameters (i.e., synergies, weight coefficients and time-shift parameters) extracted from finger tapping movements performed by individuals in a healthy subject group and a PD patient group. The results showed that the number of synergies, the second moment of synergy shapes and the coefficient of variation of maximum weight coefficients show significant differences for each subject group, and indicated that the model could be used to evaluate irregular rhythmic movements as well as regular ones.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:4443-8.
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ABSTRACT: To assess psychometrics of hand dominance during the 9-Hole Peg Test.
Sixteen healthy volunteers (23-40 years of age, 10 female and 6 male subjects, all fortuitously right handed).
As is conventional protocol, the total time to perform the task was recorded as a dexterity index. In addition, the relative distance between points (distal phalanges) on the index finger and thumb was continuously monitored by the use of a magnetic sensing system. Time required, mean values for peak distance, and cumulative total motion distance were analyzed separately for the peg-placement and peg-removal phases. Data for dominant and nondominant hands were compared by the use of paired t-tests (P < .05).
Total time to perform the 9-Hole Peg Test was shorter for the dominant hands (mean, 18.65 seconds) than the nondominant hands (mean, 20.11 seconds). During the peg-placement phase, lower values for peak distance, cumulative total motion distance, and time required were recorded for dominant hands, suggesting more efficient movement. By contrast, during peg-removal phase, no statistically significant differences between dominant- and nondominant-hand values were apparent.
Although healthy subjects perform the 9-Hole Peg Test more efficiently using their dominant hands, the difference in measured dexterity was observed only during the peg-placement phase. This discrepancy between the peg-placement and peg-removal efficiency suggests the need for phase discrimination in future studies.
Der Notarzt 01/2011; 3(1):40-4. · 0.28 Impact Factor
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ABSTRACT: A large-scale magnetocardiogram (MCG) database was produced, and standard MCG waveforms of healthy patients were calculated by using this database. It was clarified that the standard MCG waveforms are formed with the same shape and current distribution in healthy patients. A new subtraction method for detecting abnormal ST-T waveforms in coronary heart disease (CHD) patients by using the standard MCG waveform was developed.
We used MCGs of 56 CHD patients (63 ± 3 years old) and 101 age-matched normal control patients (65 ± 5 years old). To construct a subtracted ST-T waveform, we used standard MCG waveforms produced from 464 normal MCGs (male: 268, female: 196). The standard MCG waveforms were subtracted from each subject's measured MCGs, which were shortened or lengthened and normalized to adjust to the data length and magnitude of the standard waveform. We evaluated the maximum amplitude and maximum current-arrow magnitude of the subtracted ST-T waveform.
The maximum magnetic field, maximum magnitude of current arrows, and maximum magnitude of total current vector increased according to the number of coronary artery lesions. The sensitivity and specificity of detecting CHD and normal control patients were 74.6% and 84.1%, respectively.
The subtraction MCG method can be used to detect CHD with high accuracy, namely, sensitivity of 74.6% and specificity of 84.1% (in the case of maximum amplitude of total current vector). Furthermore, the subtraction MCG magnitude and its current distribution can reflect the expanse of the ischemic lesion area and the progress from ischemia to myocardial infarction.
Annals of Noninvasive Electrocardiology 10/2010; 15(4):360-8. · 1.10 Impact Factor
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ABSTRACT: Magnetoencephalography (MEG) noninvasively measures neuronal activity with high temporal resolution. The aim of this study was to develop a new type of MEG system that can measure bilateral MEG waveforms without a magnetically shielded room, which is an obstacle to reducing both the cost and size of an MEG system. An unshielded bilateral MEG system was developed using four two-dimensional (2D) gradiometers and two symmetric cryostats. The 2D gradiometer, which is based on a low-T(c) superconducting quantum interference device and wire-wound pickup coil detects a magnetic-field gradient in two orthogonal directions, or ∂/∂x(∂(2)B(z)/∂z(2)), and reduces environmental magnetic-field noise by more than 50 dB. The cryostats can be symmetrically positioned in three directions: vertical, horizontal, and rotational. This makes it possible to detect bilateral neuronal activity in the cerebral cortex simultaneously. Bilateral auditory-evoked fields (AEF) of 18 elderly subjects were measured in an unshielded hospital environment using the MEG system. As a result, both the ipsilateral and the contralateral AEF component N100m, which is the magnetic counterpart of electric N100 in electroencephalography and appears about 100 ms after the onset of an auditory stimulus, were successfully detected for all the subjects. Moreover, the ipsilateral P50m and the contralateral P50m were also detected for 12 (67%) and 16 (89%) subjects, respectively. Experimental results demonstrate that the unshielded bilateral MEG system can detect MEG waveforms, which are associated with brain dysfunction such as epilepsy, Alzheimer's disease, and Down syndrome.
The Review of scientific instruments 09/2010; 81(9):096103. · 1.52 Impact Factor
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ABSTRACT: Immunoassays are one main detection system used in the field of clinical chemistry. Recent developments of a new detection method utilizing a magnetic marker and magnetic sensor have enabled rapid and sensitive immunoassay without the need for bound/free (BF) separation.
Newly-synthesized conjugated avidin was used as the magnetic marker for quantitative analysis of human interleukin-8 (hIL-8) and immunoglobulin E (hIgE) in several media. A superconducting quantum interference device sensor detected the magnetic fields from markers fixed to antigens by the sandwich method. Magnetic signals from unbound markers were nearly zero due to Brownian rotation.
Our magnetic immunoassay could detect four attomoles of model proteins (hIL-8, hIgE) in phosphate buffer without BF separation. Using our standard curve, the range of protein detected ranged from 40 femtomoles to 4 attomoles, and we observed a strong association between protein amounts and magnetic signals from the bound markers. The homogeneous immunoassay could also quantify three hundred cells from the fungus Candida albicans in phosphate buffer.
The present study demonstrates the ability of magnetic markers for measuring biological targets without BF separation. This detection system has great potential for use as the next generation's analytical system.
Clinical Chemistry and Laboratory Medicine 09/2010; 48(9):1263-9. · 2.15 Impact Factor
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ABSTRACT: We have developed the simple estimation method of a finger tapping dynamics model for investigating muscle resistance and stiffness during tapping movement in normal subjects. We measured finger tapping movements of 207 normal subjects using a magnetic finger tapping detection system. Each subject tapped two fingers in time with a metronome at 1, 2, 3, 4, and 5 Hz. The velocity and acceleration values for both the closing and opening tapping data were used to estimate a finger tapping dynamics model. Using the frequency response of the ratio of acceleration to velocity of the mechanical impedance parameters, we estimated the resistance (friction coefficient) and compliance (stiffness). We found two dynamics models for the maximum open position and tap position. In the maximum open position, the extensor muscle resistance was twice as high as the flexor muscle resistance and males had a higher spring constant. In the tap position, the flexor muscle resistance was much higher than the extensor muscle resistance. This indicates that the tapping dynamics in the maximum open position are controlled by the balance of extensor and flexor muscle friction resistances and the flexor stiffness, and the flexor friction resistance is the main component in the tap position. It can be concluded that our estimation method makes it possible to understand the tapping dynamics.
The Review of scientific instruments 05/2010; 81(5):054303. · 1.52 Impact Factor
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01/2010; , ISBN: 978-953-7619-57-2
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Kuniomi Ogata, Akihiko Kandori,
Yasushi Watanabe,
Akihiro Suzuki,
Kimio Tanaka,
Yuji Oka,
Hiroshi Takaki,
Hideaki Kanzaki,
Satoshi Nakatani,
Kunio Miyatake,
Shigeyuki Watanabe,
Iwao Yamaguchi,
Tsuyoshi Miyashita,
Shiro Kamakura
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ABSTRACT: Magnetocardiography (MCG) is a new technique for visualizing a current distribution in the myocardium. In recent years, current distribution parameters (CDPs) have been developed based on the distribution. The CDPs reflect spatial-time current abnormalities in patients with coronary heart disease (CHD). However, the criteria and scoring method of the abnormalities using CDPs are still controversial.
We measured MCG signals for 101 normal controls and 56 CHD patients (single-, double-, and triple-vessel diseases) using a MCG system. The CDPs (maximum current vector [MCV], total current vector [TCV], current integral map, and current rotation) during ventricular repolarization were analyzed. To evaluate the CDPs that are effective in distinguishing between normal controls and CHD patients, the areas under the receiver operating characteristic curve (A(z)) are calculated. Furthermore, the total scores ("0" to "4") of four CDPs with high A(z) values are also calculated.
MCV and TCV angles at the T-wave peak had the highest A(z) value. Furthermore, TCV angular differences between the ST-T segment also had high A(z) values. Using the four CDPs, the averaged total score for patients with triple-vessel disease was the highest ("2.67") compared to the other groups (normal controls: 0.53). Furthermore, based on the assumption that subjects with a total score over "1" were suspected of having CHD, sensitivity and specificity were 85.7% and 74.3%, respectively.
We concluded that the score and criteria using MCV and TCV during repolarization in CHD patients can reflect lesion areas and time changes of electrical activation dispersion due to ischemia.
Pacing and Clinical Electrophysiology 05/2009; 32(4):516-24. · 1.35 Impact Factor
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ABSTRACT: This paper proposes a method to quantitatively measure and evaluate finger tapping movements for the assessment of motor function using log-linearized Gaussian mixture networks (LLGMNs). First, finger tapping movements are measured using magnetic sensors, and eleven indices are computed for evaluation. After standardizing these indices based on those of normal subjects, they are input to LLGMNs to assess motor function. Then, motor ability is probabilistically discriminated to determine whether it is normal or not using a classifier combined with the output of multiple LLGMNs based on bagging and entropy. This paper reports on evaluation and discrimination experiments performed on finger tapping movements in 33 Parkinson's disease (PD) patients and 32 normal elderly subjects. The results showed that the patients could be classified correctly in terms of their impairment status with a high degree of accuracy (average rate: 93.1 ± 3.69%) using 12 LLGMNs, which was about 5% higher than the results obtained using a single LLGMN.
Sensors 01/2009; 9(3):2187-201. · 1.74 Impact Factor
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ABSTRACT: AC susceptibility measurement of magnetic markers in solution was applied to biological immunoassays. In this method, the markers that bound to biological target can be detected in the presence of unbound markers. The bound markers were distinguished from the unbound ones by using their different frequency dependence of susceptibility. We detected biotin-conjugated polymer beads with avidin-coated Fe3O4 markers. Changes of the susceptibility caused by the binding reaction between them were shown. Good relationship was obtained between the decrease of susceptibility and the number of polymer beads. Sensitivity of the system was estimated as 3×10-16 mol/ml in terms of molecular-number concentration.
Applied Physics Express. 01/2009; 2(3):037001-037003.
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Keiji Enpuku,
Yuki Sugimoto,
Yuya Tamai,
Akira Tsukamoto,
Takako Mizoguchi, Akihiko Kandori,
Naoki Usuki,
Hisao Kanzaki,
Kohji Yoshinaga,
Yoshinori Sugiura,
Hiroyuki Kuma,
Naotaka Hamasaki
IEICE Transactions. 01/2009; 92-C:315-322.
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ABSTRACT: This paper proposes a method of estimating fingertip forces in finger tapping movements based on human fingerpad characteristics. Since the human fingerpad exhibits elasticity, the proposed technique recreates the relationship between the fingertip force and the displacement generated between the thumb and index fingerpads as a fingerpad-stiffness model. Then, using this model, the force between the two fingertips (the fingertip force) can be estimated from the measured fingerpad deformation only. As the method does not require any sensors to be attached to the finger contact surface to measure fingertip force, it can be used to evaluate the tendency of force in natural and unconstrained finger tapping movements conducted by the subject. In the experiments conducted, fingertip forces and the displacement of the two fingerpads generated when the subjects pinched and pushed a force sensor with the thumb and index finger were measured to approximate the relationships between fingerpad force and deformation. The results indicated that human fingerpad characteristics can be expressed using a fingerpad-stiffness function (including an exponential function), and that fingerpad forces can be estimated using the proposed model. Furthermore, comparison between a Parkinson's disease (PD) patient and a healthy subject confirmed differences in the finger tapping forces for each. This implies the possibility of assessing motor function in PD patients using the finger tapping force evaluation method proposed in this paper.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:2663-7.
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Akihiko Kandori,
Kuniomi Ogata,
Tsuyoshi Miyashita,
Yasushi Watanabe,
Kimio Tanaka,
Masahiro Murakami,
Yuji Oka,
Hiroshi Takaki,
Syuji Hashimoto,
Yuko Yamada,
Kazuo Komamura,
Wataru Shimizu,
Shiro Kamakura,
Shigeyuki Watanabe,
Iwao Yamaguchi
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ABSTRACT: We need to know the magnetocardiogram (MCG) features regarding waveform and two-dimensional current distribution in normal subjects in order to classify the abnormal waveform in patients with heart disease. However, a standard MCG waveform has not been produced yet, therefore, we have first made the standard template MCG waveform.
We used data from 464 normal control subjects' 64-channel MCGs (268 males, 196 females) to produce a template MCG waveform. The measured data were averaged after shortening or lengthening and normalization. The time interval and amplitude of the averaged data were adjusted to mean values obtained from a database. Furthermore, the current distributions (current arrow maps [CAMs]) were calculated from the produced templates to determine the current distribution pattern. The produced template of the QRS complex had a typical shape in six regions that we defined (M1, M2, M3, M4, M5, and M6). In the P wave, the main current arrow in CAMs pointing in a lower-left direction appeared in M1. In the QRS complex, the typical wave appeared in each region, and there were two main current arrows in M2 and M5. There were negative T waves in M1, M4, and M5, and positive T waves in M3 and M6, and the main current arrow pointing in a lower-left direction appeared in M2.
Template MCG waveforms were produced. These morphologic features were classified into six regions, and the current distribution was characterized in each region. Consequently, the templates and classifications enable understanding MCG features and writing clinical reports.
Annals of Noninvasive Electrocardiology 11/2008; 13(4):391-400. · 1.10 Impact Factor
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ABSTRACT: This paper proposes a quantitative measurement and evaluation method of finger tapping movements for diagnosis support and assessment of motor function. In this method, a magnetic sensor consisting of two coils is used to measure movement. The coil voltage induced by the electromagnetic induction law changes depending on the distance between the two coils; this enables estimation of the distance between two coil-bearing fingertips from the voltage measured by the nonlinear modeling relationships between the voltages and distances. Further, the finger movements measured are evaluated by computing ten indices such as the finger tapping interval, and radar charts of the evaluation indices and phase-plane trajectories of the finger movements are then displayed in real time on a monitor. Evaluation experiments were performed on finger movement in 16 Parkinson's disease patients and 32 normal elderly subjects, with the results showing that all evaluation indices differ significantly for each subject (p < 0.05).
Engineering in Medicine and Biology Society, 2008. EMBS 2008. 30th Annual International Conference of the IEEE; 09/2008
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ABSTRACT: The magnetocardiogram (MCG) is a promising medical tool for detecting and visualizing abnormal cardiac electrical activation in heart-disease patients. However, there is no large-scale MCG database of healthy subjects, and there is little knowledge of gender- and age-related influences on MCG data.
We obtained MCG data from 869 subjects (554 men, 315 women) using a conventional 64-channel MCG system, which covers the whole heart. Electrocardiogram (ECG) data were also obtained; 464 people (268 men, 196 women) were identified as a normal group using ECG data. Time intervals (PQ, QRS, QT, and QTc), current distributions (maximum current vector (MCV), and the total current vector (TCV)) of MCG data of the 464 normal subjects were analyzed to obtain basic MCG parameters. Although mean values of PQ and QRS intervals of the male subjects were slightly longer than those of the female subjects, no intervals were correlated with gender or age. The correlation between PQ intervals of ECG and those of MCG was better than the correlation between QRS and QT intervals of ECG and those of MCG. Both MCV and TCV angles were much smaller than the electrical-axis angle in ECG. Although TCVs of the QRS and T waves were stable, the women's mean T-wave-TCV angles significantly increased with age. The maximum amplitude of the P wave was about 1.7 pT, and the value of the QRS complex was about 20-25 pT. Moreover, the T-wave amplitude decreases with age.
The MCG standard space-time parameters determined here provide a normal range for MCG parameters.
Pacing and Clinical Electrophysiology 05/2008; 31(4):422-31. · 1.35 Impact Factor
