Biomagnetic measurements using squids

Intrinsic mode functions locate implicit turbulent attractors in time in frontal lobe MEG recordings

In seeking evidence for the presence and characteristic range of coupled time scale(s) of putative implicit turbulent attractors of dorsal frontal lobe magnetic fields, the recorded nonstationary, nonlinear MEG signals were non-orthogonally decomposed using Huang's Empirical Mode Decomposition, EMD, (Huang and Attoh-Okine, 2005) into 16 Intrinsic Mode Functions, EMD→IMFi, i=1…16. Measures known to be invariant in non-uniformly hyperbolic (turbulent) dynamical systems, topological entropy, hT, metric entropy, hM, non-uniform entropy, hU and power spectral scaling exponent, α, were imposed on each of the IMFi which evidenced most clearly an invariant temporal scale zone of IMFi, i=6…11, for hT, which we have found to be the most robust of invariant measures of MEG's magnetic field turbulent attractors (Mandell et al., 2011a,b; Mandell, 2013). The ergodic theory of dynamical systems (Walters, 1982; Pollicott and Yuri, 1998) allows the inference that an implicit attractor with consistently hT>0 will also evidence at least one positive Lyapounov exponent indicating the presence of a turbulent attractor with exponential separation of nearby initial conditions, exponential convergence of distant points and disordering, mixing, of orbital sequences. It appears that this approach permits the inference of the presence of chaotic, turbulent attractor and its characteristic time scales without the invocation of arbitrary n-dimensional embedding, phase space reconstructions or (inappropriate) orthogonal decompositions.

Fetal magnetoencephalographic mapping in normal and pre-eclamptic pregnancies

This study investigates the fetal brain activity in normal and pre-eclamptic pregnancies. Measurements were performed by means of a superconducting quantum interference device (SQUID) in an electrically shielded room of low magnetic noise. The study was prospective. Ten pregnant women with pre-eclampsia and 11 healthy gravidae were included. All were preterm at 28 to 37 weeks' gestation. Biomagnetic signals (waveforms), recorded from the fetal brains in the frequencies 2-7 Hz, were expressed in terms of magnetic power spectral amplitudes: these were low in almost all normal pregnancies, and high in most pregnancies complicated with pre-eclampsia. The pictorial representation of the results in the form of iso-spectral amplitude (ISO-SA) mapping showed two different patterns: (a) iso-contour lines 'organised' in dense concentration zones (pre-eclamptic pattern), (b) iso-contour lines at random distribution without dense concentration zones (normal pattern). Biomagnetic measurements of fetal brain activity is a promising screening procedure for assessing the cerebral function, especially at high risk pregnancies.

Fetal magnetocardiogram recordings and Fourier spectral analysis

Power spectral analysis of fetal magnetocardiogram (FMCG) data was evaluated in 64 pregnancies, using the non-invasive one channel superconducting quantum interference device (DC-SQUID), in order to investigate the power spectral amplitude distribution in the frequency range between 2 and 3 Hz. In all cases with normal and uncomplicated pregnancies, the data from the fetal heart and specifically the QRS complexes, were identifiable and unaffected by any maternal cardiac activity and furthermore the power spectral amplitudes, which varied between 120 and 350 fT/Hz, were directly related to gestational age.

A comparative study of a theoretical neural net model with MEG data from epileptic patients and normal individuals

OBJECTIVE

The aim of this study was to compare a theoretical neural net model with MEG data from epileptic patients and normal individuals.

METHODS

Our experimental study population included 10 epilepsy sufferers and 10 healthy subjects. The recordings were obtained with a one-channel biomagnetometer SQUID in a magnetically shielded room.

RESULTS

Using the method of x2-fitting it was found that the MEG amplitudes in epileptic patients and normal subjects had Poisson and Gauss distributions respectively. The Poisson connectivity derived from the theoretical neural model represents the state of epilepsy, whereas the Gauss connectivity represents normal behavior. The MEG data obtained from epileptic areas had higher amplitudes than the MEG from normal regions and were comparable with the theoretical magnetic fields from Poisson and Gauss distributions. Furthermore, the magnetic field derived from the theoretical model had amplitudes in the same order as the recorded MEG from the 20 participants.

CONCLUSION

The approximation of the theoretical neural net model with real MEG data provides information about the structure of the brain function in epileptic and normal states encouraging further studies to be conducted.

The chaos theory for differentiating fetal biomagnetic brain activity in normal and pre-eclamptic pregnancies

In this study we investigated the fetal biomagnetic brain activity obtained in normal and pre-eclamptic pregnancies using a non-linear analysis. Measurements were performed using a single channel biomagnetometer superconducting quantum interference device (SQUID) in an electrically shielded room of low magnetic noise. Using the application of non-linear analysis and dimensionality calculations we have observed a clear saturation for the dimension of the fetal biomagnetic brain activity from pre-eclamptic pregnancies and no saturation for fetal brain activity in normal pregnancies. Thus, the biomagnetic measurements with the SQUID and the application of non-linear analysis, is a promising procedure in assessing and differentiating fetal biomagnetic brain activity in normal and pre-eclamptic pregnancies.

Fetal magnetoencephalogram recordings and Fourier spectral analysis

This study investigates the fetal brain activity in normal and pre-eclamptic pregnancies. Measurements were performed by means of a Superconducting Quantum Interference Device (SQUID) in an electrically shielded room of low magnetic noise. The study was prospective. Eleven pregnant women with pre-eclampsia and 21 normal pregnancies were included. All were at 37-40 weeks of pregnancy. Biomagnetic signals (waveforms), recorded from the fetal brains in the frequency range of 2-7 Hz, were expressed in terms of magnetic power spectral amplitudes. These were low (mean, 376.67; SD, 28.66) in almost all normal pregnancies, and high (mean, 554.91; SD, 149.56) in most pregnancies complicated with preeclampsia. These findings were of statistical significance (Student's t -test, P < 0.005). Biomagnetic measurements of fetal brain activity is a promising screening procedure for assessing the cerebral function, especially in high risk pregnancies.

Differential diagnosis of prostate lesions with the use of biomagnetic measurements and non-linear analysis

The purpose of this study was to investigate the biomagnetic activity emitted from the prostate gland and to differentiate cancerous from benign prostate lesions with the use of biomagnetic measurement and non-linear analysis. Magnetic recordings were obtained from 47 patients with palpable prostate lesions. Histology revealed 24 prostate cancer patients and 23 benign prostate hyperplasia (BPH) patients. The superconducting quantum interference device (SQUID) biomagnetometer was used to measure the prostate's magnetic field by placing the SQUID detector 3 mm above the symphysis pubis. The magnetic field recorded in the 2-7 Hz frequency range was of high amplitude in most malignant lesions whereas all benign cases were of low amplitude. According to our results, the sensitivity, specificity, positive predictive value and negative predictive value were 83.33%, 100%, 100% and 85.18%, respectively. By applying the Grassberger-Procaccia algorithm to the magnetoprostatogram time series in malignant and benign prostate lesions we found clear saturation in malignant prostate lesions with m>7 whereas in the benign lesions there was not clear saturation. Prostate cancer emits higher biomagnetic activity than the BPH. This confirms a higher angiogenic activity in prostate cancer than the BPH lesions. Furthermore, the saturation value in the estimation of the correlation dimension of the attractor for the cancer lesions confirms the lower complexity of the system in comparison to the BPH, which is characterized by higher complexity.

Fetal magnetoencephalography in intrauterine growth retarded pregnancies

OBJECTIVE

To investigate the fetal brain activity in pre-eclamptic and normal pregnancies. Biomagnetic measurements were performed by means of a superconducting quantum interference device (SQUID) in an electrically shielded room of low magnetic noise.

METHODS

The study population included 28 pre-eclamptic (34-37 weeks' gestation) and 19 normal pregnancies (34-37 weeks' gestation). The pre-eclamptic group consisted of 11 cases with birth weight below the 10th percentile (1969 +/- 129 g) and 17 cases above the 10th percentile (2496 +/- 257 g). Biomagnetic signals (waveforms) recorded from fetal brains were expressed in terms of magnetic power spectral amplitudes.

RESULTS

The total corresponding spectral amplitudes in the frequency range 2-7 Hz were high (719 +/- 69 Ft/ radical Hz in neonates <10th percentile and 537 +/- 105 Ft/ radical Hz in neonates >10th percentile) in most (82%) pre-eclamptic pregnancies and low (382 +/- 35 Ft/ radical Hz) in most normal pregnancies (95%). The difference between normal and all pre-eclamptic pregnancies was highly significant (Student's t-test: p < 0.0001). Comparing the two groups of pre-eclampsia we found also a highly significant difference (Student's t-test: p < 0.0001).

CONCLUSION

Biomagnetic measurements of fetal brain activity could be useful in the assessment of fetal central nervous system development.

The use of non-linear analysis for differentiating the biomagnetic activity in ovarian lesions

In this study we investigated the biomagnetic activity measured with the superconducting quantum interference device (SQUID) in benign and malignant ovarian lesions using non-linear analysis. We used a single channel biomagnetometer SQUID in order to measure the magnetic field emitted from benign and malignant ovarian lesions. We can differentiate such biomagnetic activities using non-linear analysis. Using the application of non-linear analysis in the ovarian lesions together with the use of dimensional calculations we have observed a clear saturation value for the dimension of malignant ovarian lesions and non-saturation for benign ovarian lesions. The biomagnetic measurements with the SQUID and the application of non-linear analysis in benign and malignant ovarian lesions, is a promising procedure in assessing and differentiating ovarian tumours.

The hemodynamics of the umbilical artery in normal and pre-eclamptic pregnancies. A new application of SQUID biomagnetometry

This study was set to investigate the hemodynamics of the feto-placental circulation in normal and pre-ecclamptic pregnancies using the biomagnetometer SQUID. Thirteen women with pre-eclampsia and 26 healthy women were studied. All were "near term". Biomagnetic signals (waveforms) were recorded from the umbilical arteries. After statistical Fourier analysis, the findings were assigned arbitrarily in terms of spectral amplitudes as high (200-300 fT/ root of Hz), low (80-150 fT/ root of Hz) and borderline (151-199 fT/ root of Hz). In all cases the frequencies considered were distributed in the range 2-7 Hz. Interestingly, the umbilical artery waveforms and the corresponding spectral densities were of high amplitudes in most (88%) normal pregnancies of low amplitudes in most (84.6%) pregnancies complicated with pre-eclampsia. These findings were of statistical significance and were correlated with fetal heart rate (FHR) monitoring, pH and Apgar score at 1 and 5 minutes; high amplitude cases were related with normal FHR monitoring, pH > 7.25 and Apgar score > 7, while low amplitude recordings were connected with abnormal FHR patterns, pH < 7.25 and Apgar score < 7. It is suggested that biomagnetic measurements of the umbilical artery flow, which is an entirely new application of SQUID technology, is a promising procedure in assessing fetal health, especially in high risk pregnancies.

Attenuation of epilepsy with application of external magnetic fields: a case report

We have previously demonstrated that magnetoencephalographic (MEG) brain measurements in patients with seizure disorders show significant MEG activity often in the absence of conventional EEG abnormalities. We localized foci of seizure activity using the mapping technique characterized by the ISO-Spectral Amplitude (ISO-SA) on the scalp distribution of specified spectral components or frequency bands of the emitted MEG Fourier power spectrum. In addition, using an electronic device, we utilized the above recorded activity to emit back the same intensity and frequency of magnetic field to the presumed epileptic foci. Using this method we were able, over the past two and one-half years, successfully to attenuate seizure activity in a cohort of over 150 patients with various forms of epilepsy. We present a patient with severe epilepsy and behavioral disturbances in whom application of an external artificial magnetic field of low intensity produced a substantial attenuation of seizure frequency which coincided with an improvement in the patient's behavior. This case demonstrates that artificial magnetic treatment may be a valuable adjunctive procedure in the management of epilepsy.

Melatonin as a proconvulsive hormone in humans

The pineal gland and melatonin exert a major influence in the control of brain electrical activity and have been shown to be involved in seizure and sleep mechanisms. Since pinealectomy has been reported to result in seizures in experimental animals, it is assumed that melatonin has anticonvulsant properties. Indeed, limited studies in humans with temporal lobe epilepsy indicate that melatonin attenuates seizure activity. In the present communication we present evidence, based on magnetoencephalographic (MEG) brain measurements, that melatonin may exert proconvulsive activity in humans as well. The proconvulsive properties of melatonin may explain several phenomena associated with epilepsy such as the increased occurrence of seizures at night when melatonin plasma levels are 5 to 8-fold higher than during the day and the observed exacerbation of seizures premenstrually and during pregnancy as well as the attenuation of seizures in the menopause. Furthermore, our findings suggest that anticonvulsants which decrease melatonin secretion, such as the benzodiazepines, may exert their antiepileptic activity by attenuating nocturnal melatonin secretion. Finally, we propose that patients with nocturnal epilepsy or those experiencing exacerbation of seizures premenstrually may benefit from the administration of agents which block the secretion or action of melatonin.

Magnetic stimulation in the treatment of partial seizures

We have recently demonstrated that Magnetoencephalographic (MEG) brain measurements in patients with seizure disorders show significant MEG activity often in the absence of conventional EEG abnormalities. We localized foci of seizure activity using the mapping technique characterized by the ISO-Spectral Amplitude (ISO-SA) on the scalp distribution of specified spectral components or frequency bands of the emitted MEG Fourier power spectrum. In addition, using an electronic device, we utilized the above recorded activity to emit back the same intensity and frequency of magnetic field to the presumed epileptic foci. Using this method we were able, over the past two years, successfully to attenuate seizure activity in a cohort of over 100 patients with various forms of epilepsy. We now present in more detail three randomly selected patients with partial seizures in whom application of an external artificial magnetic field of low intensity produced a substantial attenuation of seizure frequency during an observation period extending from 10 to 14 months. All patients had previously obtained only partial response to conventional anticonvulsant therapy. Attenuation in seizure frequency was associated with normalization of the MEG activity. These cases demonstrate that artificial magnetic treatment may be a valuable adjunctive procedure in the management of partial seizures. The possible mechanisms underlying the anticonvulsant properties of magnetic stimulation at both cellular and systemic levels are discussed. Specifically, since the pineal gland has been shown to be a magnetosensitive organ which forms part of a combined compass-solar clock system, and since it exerts an inhibitory action on seizure activity in both experimental animals and humans, we discuss the potential pivotal role of the pineal gland in the long term anticonvulsant effects of external artificial magnetic stimulation.

Magnetocardiographic patterns in complicated and uncomplicated pregnancies

Magnetocardiographic (MCG) patterns, produced by the electrical activity of the heart, were investigated in 38 full term pregnant women (17 pre-eclamptic and 21 with uncomplicated pregnancies), by means of a superconducting quantum interference device (SQUID). The most important difference was noted in the waveform amplitudes of the MCG recordings; these were appreciably lower in women with pre-eclampsia compared to those in the normal control series, although in both groups the emitted magnetic fields ranged at approximately the same frequency band. Electrocardiographic (ECG) QRS complexes were represented clearly only in the low MCG waveform amplitudes, and these were related to the presence of widespread obliterative endarteritis in the fetal vasculature of the placentae. The above MCG findings are consistent with an increased contractibility of the myocardium in pregnant women with hypertensive disease secondary to the increased peripheral resistance.

Biomagnetic measurements of the brain activity of preeclamptic pregnant women using a superconducting quantum interference device

Biomagnetic brain activity was studied in 17 full-term pregnant women with symptoms of pre-eclampsia using the biomagnetometer SQUID. The results show obvious differences both in the waveforms and in the spectra that obtained from statistical Fourier analysis by comparing them with the corresponding results from 87 pregnant women with normal full-term pregnancies. Specifically, in the pathological pregnancies the high magnetic field activity emitted from points of the mother's brain is distributed in the 2-7 Hz band frequency range whereas in normal pregnancies we found low magnetic field activity distributed over the 7 Hz band frequency.

Localization and cure of epileptic foci with the use of MEG measurements

Systematic studies with pathological subjects with focal and general epilepsies using magnetoencephalographic (MEG) measurements showed significant brain activities even if they are not present in the electroencephalogram EEG. Using a mapping technique characterized by an isospectral amplitude (ISO-SA) of the scalp distribution of specified spectral components or frequency bands of the MEG power spectrum we were able to localize the epileptic foci. This localization of epileptic foci gives us information on the emitted magnetic field intensity and frequency for each focal point on the map of the patient. Using this information we can cure the patient by adjusting an electronic device which can emit back to the specific scalp point a magnetic field of the same intensity and frequency as the one which-is emitted from it. The principle of this technique is based on the physical phenomenon of Young's double-slit experiment by which under certain condition light plus light gives darkness.

Biomagnetic measurements in uterine leiomyomas using a superconducting quantum interference device (SQUID)

Using the biomagnetometer superconducting quantum interference device (SQUID), the magnetic signals relating to spontaneous uterine activity were measured for the first time in 25 women with uterine leiomyomas, and 12 women with normal, non-leiomyomatous, uteri. Magnetic radiation, in the range of low frequency (below 2 Hz), was of low amplitudes in normal uterine tissues and of high amplitudes in benign leiomyomas. The observed differences were confirmed by the corresponding power spectra obtained from the statistical Fourier analysis. It is suggested that biomagnetic measurements may facilitate the detection of uterine leiomyomas in equivocal cases.

Evaluation of epileptic patients by means of magnetoencephalography

Studies of the magnetoencephalogram (MEG) in epileptic patients suffering from focal epilepsies showed that activities in the MEG appear which are detectable in the scalp-recorded electroencephalogram. A novel technique was developed (Anninos et al., 1987) characterized by mapping the scalp distribution of the amplitude of the spectral components (or specific bands) of the MEG and which was termed "ISO-Spectral-Amplitude (ISO-SA) mapping." The most important findings in the 19 patients we studied from these maps were that in the frequency domain 2-7 HZ the major concentrated activity were projected on the scalp of the epileptic focus. Thus with the above noninvasive method we believe that it is possible to determine the localization of epileptiform foci via a method which will be a very useful tool for clinicians.