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Objective: To record and characterize features of levator ani muscles (LAM) activity in pregnancy and postpartum using non-invasive and novel Magnetomyography (MMG) technique with amplitude and spectral parameters. Methods: Nulliparous women with uncomplicated pregnancies participated in the MMG data collection during rest and voluntary LAM contractions (Kegels) with modulated intensity in third trimester and approximately 2 months postpartum (PP). Simultaneous surface electromyography was recorded to document the recruitment of accessory muscles. Moderate strength Kegel (MK) MMG trials were analyzed. Amplitude and spectral parameters including root-mean square (RMS) amplitude, power spectrum density (PSD) and normalized PSD (rPSD) in three frequency bands (low, middle, high) were computed on MK epochs. Statistical comparisons between pregnancy and postpartum were calculated. Results: MMG recordings were measured from 10 pregnant women. Results showed decreased RMS and power between third trimester and postpartum, trending towards significance. rPSD values in the low frequency band decreased significantly (p = 0.028) from third trimester to postpartum, while significant increase was observed in the middle frequency band (p = 0.018). Conclusions: This study shows that MMG as non-invasive tool has the ability to detect and characterize changes of LAM activity with amplitude and spectral parameters during pregnancy and postpartum.

Atomic magnetometers operated in spin-exchange relaxation-free (SERF) have the potential to replace superconducting quantum interference devices (SQUIDs) in the field of biomagnetism. Here, we demonstrate the dual-axis closed-loop control of a single-beam SERF magnetometer that allows sensing of two orthogonal magnetic fields simultaneously and independently with suppressed crosstalk effect, achieved by applying a rotating modulation field and using the negative feedback. Operating in the dual-axis closed-loop mode with a miniature 4 $\times $ 4 $\times $ 4 mm 87Rb cell, we achieve the magnetic field sensitivity of 20 fT/Hz1/2 and a bandwidth of 1.8 kHz. In addition to the experimental study of the sensitivity and bandwidth, we perform a theoretical analysis of the dual-axis response and develop an effective decoupling method. The implementation of closed-loop control enables the magnetometer to be robust against the disturbance of the ambient field, which could enlarge the dynamic range, enhance the systematic stability, and suppress the crosstalk effect. Such a simple, yet high-performance SERF magnetometer could be suitable as a promising candidate in the field of biomagnetism, allowing for a denser sensor array and opening up new possibilities for noninvasive biomagnetic imaging.

Detecting magnetic field is of great importance for many applications, such as magnetoencephalography and underground prospecting. There have been many magnetometers being widely used since the age of Hall magnetometer. One of the magnetometers, the superconducting quantum interference device, is capable of measuring femtotesla magnetic fields at cryogenic temperature. However, a solid-state magnetometer with femtotesla sensitivity under ambient conditions remains elusive. Here we present a hybrid magnetometer based on the ensemble nitrogen-vacancy centers in diamond with the sensitivity of ( 195 ± 60 ) fT / Hz 1 / 2 under ambient conditions, which can be further advanced to 11 fT / Hz 1 / 2 at 100 Hz with cutting-edge fabrication technologies. Our method will find potential applications in biomagnetism and geomagnetism.

Biological material has been documented to produce an external magnetic field that radiates out. There have been several papers documenting the magnetic fields produced by steady currents in the body. The most notable was published in 1980 by Cohen et al. where the human hair follicle was used as sentinel and biophysically evaluated via sophisticated equipment such as a double planar Superconducting Quantum Interference Devices (SQUID). Most recently, in 2019 Cohen’s work was duplicated by Khan,S by also using double-planar gladiometers. Of interest to this manuscript is that since the introduction of anovel optical microscopy method in 2016 by Scherlag BJ et al is that numerous papers have been introduced in the literature now identifying intrinsic biomagnetic properties of the follicle such as penetration through glass barriers. In this manuscript, a concept of biomagnetic fields by the concave part of the human hand transferring energy to hair follicles is introduced, this was accomplished by using a novel optical microscopy method, in other words, the hair follicle is not limited to radiate out biomagnetism; but also, to receive externally radiated biomagnetic fields from a body part. This magneto receptive property is herein introduced.

This paper presents a tracking system to find the position and yaw rotation of a handheld device based on the imaging of an adhesive marker attached to a person's body. Our goal is to provide accurate data that can be combined with data from a giant magnetoresistance sensor to be able to locate a foreign body inside a human body for surgical removal. We tested the system with a series of computer simulations and analyzed the results obtained. Our best setup provided a Root Mean Square Error of less than 1.6 mm for the x coordinate, less than 1 mm for the y coordinate, less than 1.2 cm for the z coordinate and less than 1.1° for the yaw rotation value in a test with wide variations of all values. The results obtained are promising and open the way for the combination of data with the portable magnetic sensor.

We evaluated the alignment-to-orientation conversion (AOC) at the cesium D1 line to improve a nonlinear magneto–optical rotation (NMOR) optical atomic magnetometer’s signal amplitude and bandwidth. For the 6 2S1/2 F = 3 → 6 2P1/2 F′ = 4 transition, the AOC-related NMOR achieves a 1.7-fold enhancement in signal amplitude compared to the conventional NMOR, benefiting from narrow linewidth and ultraweak power broadening. Therefore, an effective amplitude-to-linewidth ratio is maintained in the high-laser-power region. This method is beneficial for detecting high-frequency magnetic signals in nuclear magnetic resonance and biomagnetism, as the NMOR magnetometer bandwidth increases with laser power.

The electrophysiological activities in the human body generate electric and magnetic fields that can be measured noninvasively by electrodes on the skin, or even, not requiring any contact, by magnetometers. This includes the measurement of electrical activity of brain, heart, muscles and nerves that can be measured in vivo and allows to analyze functional processes with high temporal resolution. To measure these extremely small magnetic biosignals, traditionally highly sensitive superconducting quantum-interference devices have been used, together with advanced magnetic shields. Recently, they have been complemented in usability by a new class of sensors, optically pumped magnetometers (OPMs). These quantum sensors offer a high sensitivity without requiring cryogenic temperatures, allowing the design of small and flexible sensors for clinical applications. In this letter, we describe the advantages of these upcoming OPMs in two exemplary applications that were recently carried out at Physikalisch-Technische Bundesanstalt (PTB): (1) magnetocardiography (MCG) recorded during exercise and (2) auditory-evoked fields registered by magnetoencephalography.

Made available in DSpace on 2020-12-10T19:59:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Aim: This paper aims to investigate a doxorubicin (DOX) chronic kidney disease rat model using magnetic nanoparticles (MNPs) associated with the alternate current biosusceptometry (ACB) to analyze its different perfusion profiles in both healthy and DOX-injured kidneys. Materials & methods: We used the ACB to detect the MNP kidney perfusion in vivo. Furthermore, we performed biochemical and histological analyses, which sustained results obtained from the ACB system. We also studied the MNP biodistribution. Results: We found that DOX kidney injury alters the MNPs' kidney perfusion. These changes became more intense as the disease progressed. Moreover, DOX has an important effect on MNP biodistribution as the disease evolved. Conclusion: This study provides new applications of MNPs in nephrology, instrumentation, pharmacology, physiology and nanomedicine. Graphical abstract Univ Estadual Paulista, Dept Fis & Biofis, IBB, BR-18618689 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Fisiol, IBB, BR-18618689 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Patol, BR-18618689 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Clin Med, BR-18618689 Botucatu, SP, Brazil Univ Fed Goias, Inst Fis, Alameda Palmeiras St, BR-74690900 Goiania, Go, Brazil Univ Estadual Paulista, Dept Fis & Biofis, IBB, BR-18618689 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Fisiol, IBB, BR-18618689 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Patol, BR-18618689 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Clin Med, BR-18618689 Botucatu, SP, Brazil FAPESP: 2015/14923-9 CAPES: 1491705

Objective: Electroneurography has been an essential method for assessing peripheral nerve disorders for decades. During this procedure, a nerve is briefly electrically excited, and nerve conduction properties are identified by indirect means from the behavior of the innervated muscle. The magnetic field of the resulting muscle response can also be recorded by novel, uncooled magnetometers, which have become very attractive for different medical applications over recent years. These highly sensitive magnetometers are called optically pumped magnetometers. Methods: We performed unaveraged and averaged magnetic signal detection of electrically evoked muscle responses using optically pumped magnetometers. We then discussed the suitability of this procedure for clinical applications in the context of diagnostic value and in direct comparison with the current electrical gold standard. Results: The magnetic detection of muscle responses is possible using optically pumped magnetometers. Our magnetic results (averaged and unaveraged) closely match those from electrical measurements. Conclusion: Optically pumped magnetometers provide an alternative, contactless technology for electrode-based motor studies, but they are currently not ready for routine clinical use. This costly technology requires additional earth magnetic shielding because this is a prerequisite for proper operation. Currently, there are no diagnostic advantages over electrical measurements. Additionally, the required measurement setup and procedure are much more complicated. Significance: In contrast to already published proof-of-principle studies for magnetomyography, we report in detail the results of the magnetic measurements of electrically evoked muscle responses in a shielded environment by applying supramaximal stimulation and finally validate our findings with electroneurography data as a reference.

This paper presents an algorithm based on Convolutional Neural Networks (CNN) to find the depth and angles of inclination and rotation of a foreign object inside the human body based on images of the magnetic field generated by it. The key challenge is to provide information with enough accuracy to be used in surgical procedures. We tested three distinct CNN architectures for values prediction, and our best model achieved a mean - average F1-score of 66 %, 100 %, and 98 % in the test dataset for depth and angles of inclination and rotation, respectively. We also propose an approach for converting classification values to real values and we calculate the type A uncertainty for all models, with our best model showing an uncertainty of 10.8 mm for depth, 2.0° for inclination and 7.5° for rotation values.

Emerging microfluidic-based cell assays favor label-free red blood cell (RBC) depletion. Magnetic separation of RBC is possible because of the paramagnetism of deoxygenated hemoglobin but the process is slow for open-gradient field configurations. In order to increase the throughput, periodic arrangements of the unit magnets were considered, consisting of commercially available Nd-Fe-B permanent magnets and soft steel flux return pieces. The magnet design is uniquely suitable for multiplexing by magnet tessellation, here meaning the tiling of the magnet assembly cross-sectional plane by periodic repetition of the magnet and the flow channel shapes. The periodic pattern of magnet magnetizations allows a reduction of the magnetic material per channel with minimal distortion of the field cylindrical symmetry inside the magnet apertures. A number of such magnet patterns are investigated for separator performance, size and economy with the goal of designing an open-gradient magnetic separator capable of reducing the RBC number concentration a hundred-fold in 1 mL whole blood per hour.

We have developed a common-mode magnetic field rejection-type magneto-impedance (MI) gradiometer to reduce the common magnetic field applied to the sensing- and reference-type MI elements. Compared with a general-type MI gradiometer, the magnetic noise spectral density was lower and the noise at 60 Hz related to the power source line was reduced by 1/8. Using the developed sensor, we successfully detected a microscopic 5 nT magnetic signal in a common-mode magnetic field that was 14 times larger. We expect this will lead to a simpler method of detecting microscopic magnetic signals such as biomagnetism without the need for magnetic shielding.

The time-domain device localization scheme can be combined with focus-field based shifting of the imaging volume in order to stabilize and manipulate the device position. In the 1D steering experiment, localization and force exertion are interleaved. The device is initially localized on the right side (1) and steered to the center (2). Once arrived and localized at the desired position, the steering algorithm centers the imaging volume on the device position (3) in order to average out the forces. After the user defines a new target position, the device is steered to this point (4) and stabilized there (5). This experiment has been done in a viscous medium to reduce the device velocity explaining the long steering times. In another experiment not shown here, a steering sequence levitates the object in a viscous medium demonstrating that the method can create forces greater than gravitational force.

Magnetography with superconducting quantum interference device (SQUID) sensor arrays is a well-established technique for measuring subtle magnetic fields generated by physiological phenomena in the human body. Unfortunately, the SQUID-based systems have some limitations related to the need to cool them down with liquid helium. The room-temperature alternatives for SQUIDs are optically pumped magnetometers (OPM) operating in spin exchange relaxation-free (SERF) regime, which require a very low ambient magnetic field. The most common two-layer magnetically shielded rooms (MSR) with residual magnetic field of 50 nT may not be sufficiently magnetically attenuated and additional compensation of external magnetic field is required. A cost-efficient compensation system based on square Helmholtz coils was designed and successfully used for preliminary measurements with commercially available zero-field OPM. The presented setup can reduce the static ambient magnetic field inside a magnetically shielded room, which improves the usability of OPMs by providing a proper environment for them to operate, independent of initial conditions in MSR.

Ultrasensitive magnetic field detection based on magneto-optical rotation (the Faraday effect) is important across the sciences. Due to inherent energy-symmetry restrictions, the traditional single-beam measurement configuration suffers from low signal-to-noise ratio, which then demands sophisticated magnetic shielding, high operating temperature and laser power, and complex detectors. This work uses an optical wave-mixing technique to break the energy-symmetry blockade, enhancing signal power by nearly six orders of magnitude. This breakthrough enables applications in many fields, especially biomedical research, with $e.g.$ chip-sized biomagnetism sensors at human body temperature.

Magnetic tweezers are mainly divided into two classes depending on the ability of applying torque or forces to the magnetic probe. We focused on the second category and designed a device composed by a single electromagnet equipped with a core having a special asymmetric profile to exert forces as large as 230 pN–2.8 μm Dynabeads at distances in excess of 100 μm from the magnetic tip. Compared to existing solutions our magnetic tweezers overcome important limitations, opening new experimental paths for the study of a wide range of materials in a variety of biophysical research settings. We discuss the benefits and drawbacks of different magnet core characteristics, which led us to design the current core profile. To demonstrate the usefulness of our magnetic tweezers, we determined the microrheological properties inside embryos of Drosophila melanogaster during the syncytial stage. Measurements in different locations along the dorsal-ventral axis of the embryos showed little variation, with a slight increase in cytoplasm viscosity at the periphery of the embryos. The mean cytoplasm viscosity we obtain by active force exertion inside the embryos is comparable to that determined passively using high-speed video microrheology.

We describe the operation and results of our first generation zero field optically pumped magnetometer (OPM) developed for biomedical applications. The OPM technology is one of the most promising non-cryogenic candidates to replace superconducting quantum interference device (SQUID) magnetometers in key areas of biomagnetism. The first-generation sensors are designed to transition OPM technology from a physics laboratory to researchers in the medical community. The laser and optical components are tightly integrated inside the sensor package, and the sensor is tethered to a dedicated electronics signal processing unit that enables automated and standalone operation inside a magnetically shielded room.

The recognition of brain evoked responses at the single-trial level is a challenging task. Typical non-invasive brain-computer interfaces based on event-related brain responses use eletroencephalograhy. In this study, we consider brain signals recorded with magnetoencephalography (MEG), and we expect to take advantage of the high spatial and temporal resolution for the detection of targets in a series of images. This study was used for the data analysis competition held in the 20th International Conference on Biomagnetism (Biomag) 2016, wherein the goal was to provide a method for single-trial detection of even-related fields corresponding to the presentation of happy faces during the rapid presentation of images of faces with six different facial expressions (anger, disgust, fear, neutrality, sadness, and happiness). The datasets correspond to 204 gradiometers signals obtained from four participants. The best method is based on the combination of several approaches, and mainly based on Riemannian geometry, and it provided an area under the ROC curve of 0.956±0.043. The results show that a high recognition rate of facial expressions can be obtained at the signal-trial level using advanced signal processing and machine learning methodologies.

The superconducting quantum interference device (SQUID) is a highly sensitive detector for magnetic flux or any quantity that can be efficiently converted into flux. This chapter provides a short introduction into the basic function of a SQUID, its operation, and its design for magnetic field and current sensing. It shows by several examples that the device is very versatile and important for a variety of applications such as biomagnetism, astronomy, low-temperature physics, and metrology. The chapter measures with the commercial variant of the electronics and include the noise contribution from the preamplifier and shows the noise spectra as examples. The dc SQUID is dominant in the field of Nbbased sensors, and the rf SQUID is practically obsolete. The dc SQUID is based on two effects: flux quantization and superconducting tunneling. The chapter presents equations for calculating the inductance and the effective field-sensitive area of two representative superconducting structures.

International audience; A methodology for the design of printed magnetically coupled resonant wireless power-transfer (WPT) systems is proposed. The design methodology aims at a well-matched system with a maximized power-transfer efficiency for mid-range applications. The system consists of two identical resonant coils driven by high-quality factor loops. The proposed design criteria allows obtaining maximum achievable transfer efficiency and impedance matching at any defined distance without any external matching circuits connected to the driven loops. For validation purposes, a printed WPT system at 10 MHz is fabricated targeting 1-m distance between the transmitting and receiving sides. Its performances in terms of reflection and transmission coefficients, as well as in terms of generated electric and magnetic fields, have been characterized numerically and experimentally. The impact of human body presence on the system has also been investigated observing the splitting in two frequencies of the common resonant frequency of the coils. A dosimetric study has been conducted using a detailed high-resolution anatomical human body model and considering E99, J1 cm2, and specific absorption rate (SAR) (local and whole body averaged SAR) as exposure metrics. It has been observed that peak exposure levels appear in different tissues depending on the body location. Compliance with the international commission on nonionizing radiation protection (ICNIRP) reference level as well as basic restrictions has been studied followed by computing the maximum allowable input power. It has been found that, with the body located 1 m away from the transmitting coil, the maximum allowable input power satisfying E99 is in the order of MW, whereas it reduces to tens of kilowatt when considering SAR and J1 cm2. The latter has been noticed to be the most restrictive dosimetric quantity. © 2016 IEEE.

This paper presents a neuronal signal detector for biologically generated magnetic fields. The system includes a hardware section implemented with discrete electronics, which has an ultralow-noise dc or dc+ac current source for magnetoresistive sensor biasing, and signal amplification and filtering, and a software interface that allows signal demodulation, visualization, and digital postprocessing. Compared with the previous measurement setup, the results show that, for the same bandwidth, the proposed instrumentation system has approximately 50 times better noise performance, making the sensor noise the dominant noise source. The system is able to record the magnetic field generated by ionic currents from action potentials of in vitro experiments with mice brain slices. In addition, to obtain an increased spatial resolution, by scaling the number of sensors that can be read, and to enhance the system immunity to external interferences, two integrated circuits with an ultralow-noise current source for MR biasing and a low-noise variable gain amplifier were developed and are also presented.

With a growing number of applications utilizing THz radiation appearing on the market the question of health protection against non-ionizing electromagnetic fields arises in this frequency range, as at lower frequencies before. To date, about 50 independent empirical studies on living organisms, model systems and cells have been performed to clarify bio-electromagnetic interaction in the THz frequency range. Many of these studies find behavioral effects or effects on the cellular level, even at non-thermal exposure levels, while others do not report effects other than thermally induced damage. We discuss the general challenges in performing reliable field exposure experiments in the THz frequency range and describe a methodology that was adopted in a large campaign searching for genotoxic effects of THz radiation in vitro.

We conducted a dosimetry study of a wireless power transfer (WPT) system, which is based on magnetically coupled resonances. The electric and magnetic fields produced by the system have been calculated using the method of moments. We calculated the induced electric fields and the specific absorption rates in a Japanese adult male model by the scattered-field finite-difference time-domain method, taking into account both the incident electric and magnetic fields, and also by the impedance method, but only taking into account the incident magnetic fields. We discuss the differences between the results obtained by the two methods. We also discuss the compliance of the WPT system with international safety guidelines.

The design of a spherical coil system for pulsed magnetic field (PMF) exposure is presented for in vivo experiments with tumor-bearing animals. The system has greater focusing capability than conventional systems and has advantages in terms of effectiveness and safety. In the simulation part of the study, the magnetic field distribution of two spherical coil systems were studied using a finite element code, where the influences of coil radius and wire diameter were analyzed to optimize the final design. The simulation results indicate that the coil radius has significant effects on the magnetic field distribution, while the effect of wire diameter is negligible. Based on the designed parameters, a coil system was then developed and the magnetic field focusing ability of the system was measured and evaluated. The coil system has a better focusing performance with the central magnetic induction Bm of 1.3×10-4 T and S80% of 2.8×10-3 m2. The spherical coil system contributes to the system's focusing ability, which is expected to help in experiments for tumor treatment in the near future.

In this work an alternative neuroscience tool for electromagnetic measurements of neurons at the level of individual cells is developed. To perform such measurements we propose the integration of an array of magnetoresistive sensors on micro-machined Si probes capable of being inserted within the brain without further damage. Si-etch based micromachining process for neural probes is demonstrated in the manufacture of a probe with 15 magnetoresistive sensors in the tip of each shaft. Magnetic tunnel junction sensors with dimensions of 30 μm × 2 μm, sensitivities of 3.32 V/T and detectivity of ≈13 nT/Sqrt (Hz) are placed in the end of the sharply defined probe tips. In order to measure the small signals coming from the neurons, a homemade signal amplifying system was used with a noise level of 240 n V RMS for the system bandwidth. The full system noise is 2772 n V RMS., This work was supported in part by FCT projects NanoSciEra/0002/2008, PTDC/EEA-ELC/108555/2008 and PTDC/CTM-NAN/110793/2009. J Amaral thanks FCT for grant SFRH/BD/45488/2008. INL acknowledges partial funding from the ON2 project from PO-Norte. INESC-MN acknowledges FCT funding through the Instituto de Nanociência e Nanotecnologia (IN) Associated Laboratory

Magnetic coupling is one of the few physical phenomena capable of transmitting motion across a physical barrier. In gastrointestinal endoscopy, remote magnetic manipulation has the potential to make screening less invasive and more acceptable, thus saving lives by early diagnoses and treatment. Closed-loop control of the magnetic device position is crucial for a safe and reliable operation. In order to implement closed-loop control, the pose (position and orientation) of the device must be available in real-time. This becomes challenging if magnetic coupling is achieved by permanent magnets, since the strong magnetic field required for manipulation interferes with current localization techniques. In this work, we present a novel real-time pose detection strategy that is compatible with magnetic manipulation based on permanent magnets. The localization algorithm combines multiple sensor readings with a pre-calculated magnetic field map. The proposed approach is able to provide an average error below 5 mm in position detection, and below 19° for angular motion within a spherical workspace of 15 cm in radius.

The present study was designed to explore a novel method of electromagnetic control of cellular activity of aquatic organisms by utilizing a strong magnetic field and weak current stimulation. Three kinds of aquatic organisms, Chlamydomonas pumilio, Daphnia pulex, and Hydra, were exposed to 10 T magnetic fields, and the effects of applying weak electric currents at several milli-amperes on the transmission of polarized light on aquatic organisms at 550 nm was measured. Under ambient fields, the transmission of polarized light was not changed by the electric currents. However, in the presence of a 10 T magnetic field, a strong change in the transmission was observed during and after the electrical stimulation. It was speculated that the cellular components, having both mechanical flexibility and a higher charge density, were affected by the Lorentz force that was generated by the weak electric current and the strong magnetic field. The results indicated that the combination of a 10 T magnetic field and weak stimulation at a mA current level was effective for the measurement and control of the viability of aquatic organisms.

It has recently been demonstrated that superparamagnetic iron oxide nanoparticles can be used as magnetomotive ultrasound contrast agents. A time-varying external magnetic field acts to move the particles and, thus, the nanoparticle-laden tissue. However, the difficulty of distinguishing this magnetomotive motion from undesired movement induced in regions without nanoparticles or other motion artifacts has not been well reported. Using a high-frequency linear-array system, we found that displacements outside nanoparticle-laden regions can be similar in magnitude to those in regions containing nanoparticles. We also found that the displacement outside the nanoparticle regions had a phase shift of approximately π radians relative to that in the nanoparticle regions. To suppress signals arising from undesirable movements, we developed an algorithm based on quadrature detection and phase gating at the precise frequency of nanoparticle displacement. Thus, clutter at other frequencies can be filtered out, and the processed signal can be color-coded and superimposed on the B-mode image. The median signal-to-clutter ratio improvement using the proposed algorithm was 36 dB compared with simply summing the movement energy at all frequencies. This clutter rejection is a crucial step to move magnetomotive ultrasound imaging of nanoparticles toward in vivo investigations.

Superparamagnetic beads are increasingly used in biomedical assays to manipulate, transport, and maneuver biomaterials. We present a low-cost integrated system designed in bulk CMOS to manipulate and separate biomedical magnetic beads. The system consists of 8 × 8 coil-arrays suitable for single bead manipulation, or collaborative multi-bead manipulation, using pseudo-parallel executions. We demonstrate the flexibility of the design in terms of different coil sizes, DC current levels, and layout techniques. In one array module example, the size of a single coil is 30 μm × 30 μm and the full array occupies an area of 248 μm × 248 μm in 0.5 μm CMOS technology. The programmable DC current source supports 8 discrete levels up to 1.5 mA. The total power consumption of the entire module is 9 mW when running at full power.

SUMMARY The voltage biased SQUID Bootstrap Circuit (SBC) was recently demonstrated for direct readout of SQUID signals. The SBC combines current- and voltage-feedbacks in one circuit to suppress the preamplifier noise. It offers not only a good noise performance, but also wide tolerance of SQUID parameters. Using SBC gradiometer, the bio-magnetic signals were successfully measured. In this paper, we overview the concept of SBC and its applications.

This article is a review of the book “Biomagnetics: Principles and Applications of Biomagnetic Stimulation and Imaging” (ISBN 978-1-4822-3920-1, 343 pages) edited by Shoogo Ueno and Masaki Sekino published by CRC Press, Taylor and Francis Group, LLC in 2015. The content of the book and its importance for biomedical engineering have been discussed in this invited review.

We review the development of low parasitic capacitance sub-micrometer cross-type Josephson tunnel junctions for their use in highly sensitive and field-stable SQUID magnetometers. The potential of such junctions is shown on I – V characteristics as well as on Fraunhofer diffraction patterns. The evaluation of Fiske steps lead to a specific junction capacitance of about 62 fF/μm 2 for a critical current density of about 1.7 kA/cm 2 . The avoidance of any idle-region – the undesired overlap between superconducting electrodes around the junction – due to a self-aligned junction definition process lead to highly sensitive SQUIDs; multiloop SQUID magnetometers exhibiting exceptionally low magnetic field noise levels as low as 0.3 fT/Hz 1/2 , as well as large usable voltage swings of more than 150 μVpp. Furthermore, junction dimensions in the sub-micrometer range allowed for very high tolerable background fields during cool-down of up to 6.5 mT. In operation mode, the SQUID magnetometers recovered completely from magnetization pulses of up to 76 mT. With respect to their easy and reliable usage as well as their high sensitivity, the presented SQUID sensors are adequate for many applications, like in geophysics, biomagnetism or low-field magnetic resonance imaging.

We have developed sensitive micro magnetic sensors referred to as MI sensors based on magneto-impedance effect in amorphous wires and CMOS IC electronic circuits providing a sharp-pulse excitation. Micro sized MI-HIC chips have been in mass production of electronic compasses by Aichi Steel Corp. since 2002 for mobile phones and since 2010 for smart phones. Recently we have realized pico-Tesla (10-8 Oe) resolution for micro MI sensors making use of ultralow intrinsic magnetic noise in amorphous wires with the pulse magnetoimpedance effect. The pico-Tesla MI sensor is useful especially for bio-magnetic measurements without any magnetic shielding at room temperature. In order to avoid a risk of traffic accident due to noise reduction electric vehicles, an alert system for the pedestrians having a smart phone would be useful, if pico-Tesla MI sensor were built in the smart phones.

Magnetic stimulation has more advantages than electric stimulation. Acupuncture point (acupoint) is a specific point in human body with high sensitivity to acupuncture treatment. In this paper, magnetic stimulation was used to stimulate Neiguan (PC6) acupoint and a mock point. 64-channel EEG signals in three stages (before, during and after magnetic stimulation) were recorded to study the difference of EEG characteristics when magnetic stimulation at PC6 acupoint and at the mock point. Brain evoked-potential component P300 was extracted during magnetic stimulation at PC6 acupoint, which was not extracted during magnetic stimulation at the mock point. Frontal, temporal, parietal-occipital and occipital lobes of cerebral cortex were activated after magnetic stimulation at PC6 acupoint. Parietal lobe of cerebral cortex was inactivated after magnetic stimulation at the mock point. It suggested that EEG characteristics under magnetic stimulation at PC6 acupoint were different from those under magnetic stimulation at the mock point.

International audience; This paper deals with the benefits of using a nonlinear model-based approach for controlling magnetically guided therapeutic microrobots in the cardiovascular system. Such robots used for minimally invasive interventions consist of a polymer binded aggregate of nanosized ferromagnetic particles functionalized by drug-conjugated micelles. The proposed modeling addresses wall effects (blood velocity in minor and major vessels bifurcations, pulsatile blood flow and vessel walls, and effect of robot-to-vessel diameter ratio), wall interactions (contact, van der Waals, electrostatic and steric forces), non- Newtonian behaviour of blood and different driving designs as well. Despite nonlinear and thorough, the resulting model can both be exploited to improve the targeting ability and be controlled in closed-loop using nonlinear control theory tools. In particular, we infer from the model an optimization of both the designs and the reference trajectory to minimize the control efforts. Efficiency and robustness to noise and model parameters uncertainties are then illustrated through simulations results for a bead pulled robot of radius 250μm in a small artery.

Purpose: MR-visible markers have already been used for various purposes such as image registration, motion detection, and device tracking. Inductively coupled RF (ICRF) coils, in particular, provide a high contrast and do not require connecting wires to the scanner, which makes their application highly flexible and safe. This work aims to thoroughly characterize the MR signals of such ICRF markers under various conditions with a special emphasis on fully automatic detection. Methods: The small markers consisted of a solenoid coil that was wound around a glass tube containing the MR signal source and tuned to the resonance frequency of a 1.5 T MRI. Marker imaging was performed with a spoiled gradient echo sequence (FLASH) and a balanced steady-state free precession (SSFP) sequence (TrueFISP) in three standard projections. The signal intensities of the markers were recorded for both pulse sequences, three source materials (tap water, distilled water, and contrast agent solution), different flip angles and coil alignments with respect to theB 0 direction as well as for different marker positions in the entire imaging volume (field of view, FOV). Heating of the ICRF coils was measured during 10-min RF expositions to three conventional pulse sequences. Clinical utility of the markers was assessed from their performance in computer-aided detection and in defining double oblique scan planes. Results: For almost the entire FOV (±215 mm) and an estimated 82% of all possible RF coil alignments with respect toB 0, the ICRF markers generated clearly visible MR signals and could be reliably localized over a large range of flip angles, in particular with the TrueFISP sequence (0.3°–4.0°). Generally, TrueFISP provided a higher marker contrast than FLASH. RF exposition caused a moderate heating (≤5 °C) of the ICRF coils only. Conclusions : Small ICRF coils,imaged at low flip angles with a balanced SSFP sequence showed an excellent performance under a variety of experimental conditions and therefore make for a reliable, compact, flexible, and relatively safe marker for clinical use.

Functional electrical stimulation (FES) is a type of therapy used for paralyzed patients. In FES, the implant direct feeding method is an ideal stimulus method. In this method, small stimulators are implanted in the paralyzed limbs, and magnetic coupling is used to simultaneously power the implants and enable digital communication with the mounted system. To realize this method, we have developed an implant antenna (magnetic connective dual-resonance antenna) that can transmit as well as receive signals and a mounted communication system that is responsible for supplying power and communication from outside the body to the implanted antenna inside of the body. However, to guarantee safe stimulation, this system requires the closed-loop control function. For this purpose, we have proposed a communication protocol that is inexpensive, and a new communication system that supports bidirectional communication. In this paper, we present the new protocol, the composition and mechanisms of the proposed system, and the experimental results that verify the efficiency of this system.

A system to evaluate nanoparticles efficiency in hyperthermia applications is presented. The method allows a direct measurement of the power dissipated by the nanoparticles through the determination of the first harmonic component of the in quadrature magnetic moment induced by the applied field. The magnetic moment is measured by using an induction method. To avoid errors and reduce the noise signal a double in phase demodulation technique is used. To test the system viability we have measured nanowires, nanoparticles and copper samples of different volumes to prove by comparing experimental and modeled results.

In this paper, we propose a new method for imaging the distribution of electric currents; this method involves a combination of ultrasonography and SQUID magnetometry. To evaluate this new method, we used a block of gelatin pierced through by a lead wire as a model of a biological object. An electric current was applied to the wire and the magnetic signal generated around the wire was measured by a superconducting quantum interference device (SQUID). At the same time, an ultrasound image of the wire was taken by means of an ultrasound imaging machine. Subsequently, the magnetic field image was aligned with the ultrasound image with respect to the position of marker coils relative to the ultrasound probe. The source of the magnetic signal was localized by solving the inverse problem and visualized on the ultrasound image of the wire. The position error was 2.9 mm. The results demonstrated the applicability of the new technique combining SQUID magnetometry with ultrasound imaging.

An essential role of a superconducting magnetic shield is described for study of higher function of human brains. The present SQUID has a sensitivity of 0.9 fT/(Hz)1/2 at 100 Hz in a superconducting magnetic shield. SQUID sensors are made of SNS (Superconductor/Normal metal/Superconductor) junctions. Recent theories of beamformer and MUSIC (multiple signal classification) emphasize the importance of SNR (signal-to-noise ratio) of data to locate equivalent current dipoles in brains. For instance, MUSIC uses the noise subspace of the covariant matrix practically calculated by measured magnetic fields. Dynamical responses of hippocampus to novelty or unexpectedness are measured by the SQUID system in a superconducting magnetic shield and visualized by swLORETA-an extension of sLORETA (standardized low-resolution electromagnetic tomography). The SQUID system in a magnetic shield of high-Tc superconductor is yielding new information of deep areas of human brains. The sensitivity of neuromagnetic SQUID measurements is proved to be limited by the system noise temperature of a SQUID hardware system but not so-called “brain noises”.

In the last decades there has been an increasing interest in biomagnetism—a field of biophysics concerned with the magnetic properties of living organisms. Biomagnetism focuses on the measurement of magnetic properties of biological samples in the clinical environment. Progress in this field can provide new data for the understanding of the pathomechanism of atherosclerosis and support the diagnostic options for the evaluation and treatment of atherothrombotic complications. Lyophilized human blood samples from patients with atherosclerotic lesions (calcium scoring (CS) CS>0) and without atherosclerotic lesions (CS=0) were magnetically investigated. Magnetic measurements (performed in room and low temperature) indicated significant magnetic differences between these two groups of patients. Atherosclerotic blood samples are characterized by higher concentration of ferrimagnetic particles (magnetite and/or maghemite) and significant changes in the superparamagnetic behaviour. This research presents that magnetometry, in combination with medical research can lead to a better understanding of iron physiology in the atherosclerotic process.

We have implemented a new noninvasive multiobjective tracking system, which can be used for localization of an endoscope and monitoring of heart valve prostheses and gastrointestinal transit of solid oral dosage forms or nutrients. The marker is modeled as a magnetic dipole, and the magnetic field at some point is regarded as summation of those from three dipoles. By minimizing the squared errors of magnetic field values between measurements and calculation using a hybrid of the particle swarm optimization (PSO) algorithm and the clone algorithm, an iterative result can be obtained, which is taken as the initial guess of the Levenberg-Marquardt (L-M) optimization method, and the first point can be determined. Subsequently, the previous computed point is used as the next initial guess of L-M algorithm, and the successive points are calculated. The tracking results demonstrate that the average position error for three objectives is 3.7 mm and the average orientation error is 1.8 when the objectives move randomly in the space surrounded by the sensor array.

Purpose - The purpose of this paper is to develop a source reconstruction technique, applied to a case study in biomagnetism, using both evolutionary optimization and regularization techniques. Design/methodology/approach - The magnetic field, produced by a current dipole in a spheroidal domain modeling the head, is calculated. Although the model is very simple, the magnetic effect of a brain source is appropriately simulated. In order to solve the source identification problem, the following approaches have been implemented: a single-objective minimization of a residual function, based on an evolutionary algorithm, is applied first; then, the L-curve criterion for regularization is implemented by means of an iterative search. Findings - A variable number of unknown parameters, defining direction and magnitude of the current dipole, have been considered. As a consequence, several optimization problems are solved: a technique based on the use of the lead field matrix identifies the source with the smallest error. Eventually, an iterative procedure based on Tikhonov regularization is proposed. The algorithm is tested with and without noise affecting data. The results showed an accuracy comparable to that obtained independently with the optimization approach. Originality/value - A model problem in inverse biomagnetism, which is both simple and significant, has been formulated and solved. The magnetic source of brain activity is reconstructed in a fast way and with small errors by means of two techniques of field inversion.

Recently, destruction and disturbance of marine ecosystem have been caused by adventive aquatic organisms. To solve the problems, water treatment technique is necessary to remove aquatic organisms efficiently. In this study, magnetic separation system for continuous removal of the aquatic organisms using superconducting magnet which generates strong magnetic field was developed. The jar tests to remove aquatic organisms using permanent magnet showed that nearly 100% of separation efficiency was achieved by aggregation of aquatic organisms using ferromagnetic particles and flocculants. Cost and waste reduction by lowering agent dosages was examined for practical application of magnetic separation system, and continuous processing equipment was designed by simulation and experiment using superconducting magnet.

When coupled to a giant magnetoresistive (GMR) sensor, a superconducting loop containing a constriction can be a very sensitive magnetometer. It has thermal noise levels of few fT/sqrt(Hz), comparable to low-Tc SQUID noise, with a flat frequency response. These mixed sensors are good candidates for detection of weak biomagnetic signals, like a cardiac or neuronal signature. Furthermore, being sensitive to the flux, mixed sensors can be used for nuclear magnetic resonance (NMR) detection and Magnetic Resonance Imaging (MRI) especially at low fields. They are very robust and accept strong RF pulses with a very short recovery time compared to tuned RF coils, which allow measurements of broad signals (short relaxation time or multiple resonances). We will first present the last generation sensors having a noise level of 3 fT/sqrt(Hz) and we will show signals measured at low frequency (magnetocardiography–magnetoencephalography range) and at higher frequency (NMR signals). The use of additional flux transformers for improving the signal-to-noise will be discussed. Finally, we will present perspectives for low-field MRI, which can be combined with neural signal detection (MEG), especially for brain anatomy and temporal response on the same experimental setup.