Assessing ulnar neuropathy at the elbow using magnetoneurography

OBJECTIVE

To measure neuromagnetic fields of ulnar neuropathy patients at the elbow after electrical stimulation and evaluate ulnar nerve function at the elbow with high spatial resolution.

METHODS

A superconducting quantum interference device magnetometer system recorded neuromagnetic fields of the ulnar nerve at the elbow after electrical stimulation at the wrist in 16 limbs of 16 healthy volunteers and 21 limbs of 20 patients with ulnar neuropathy at the elbow. After artifact removal, neuromagnetic field signals were processed into current distributions, which were superimposed onto X-ray images for visualization.

RESULTS

Based on the results in healthy volunteers, conduction velocity of 30 m/s or 50% attenuation in current amplitude was set as the reference value for conduction disturbance. Of the 21 patient limbs, 15 were measurable and lesion sites were detected, whereas 6 limbs were unmeasurable due to weak neuromagnetic field signals. Seven limbs were deemed normal by nerve conduction study, but 5 showed conduction disturbances on magnetoneurography.

CONCLUSIONS

Measuring the magnetic field after nerve stimulation enabled visualization of neurophysiological activity in patients with ulnar neuropathy at the elbow and evaluation of conduction disturbances.

SIGNIFICANCE

Magnetoneurography may be useful for assessing lesion sites in patients with ulnar neuropathy at the elbow.

SQUID magnetoneurography: an old-fashioned yet new tool for noninvasive functional imaging of spinal cords and peripheral nerves

We are engaged in the development and clinical application of a neural magnetic field measurement system that utilizes biomagnetic measurements to observe the activity of the spinal cord and peripheral nerves. Unlike conventional surface potential measurements, biomagnetic measurements are not affected by the conductivity distribution within the body, making them less influenced by the anatomical structure of body tissues. Consequently, functional testing using biomagnetic measurements can achieve higher spatial resolution compared to surface potential measurements. The neural magnetic field measurement, referred to as magnetoneurography, takes advantage of these benefits to enable functional testing of the spinal cord and peripheral nerves, while maintaining high spatial resolution and noninvasiveness. Our magnetoneurograph system is based on superconducting quantum interference devices (SQUIDs) similar to the conventional biomagnetic measurement systems. Various design considerations have been incorporated into the SQUID sensor array structure and signal processing software to make it suitable for detecting neural signal propagation along spinal cord and peripheral nerve. The technical validation of this system began in 1999 with a 3-channel SQUID system. Over the course of more than 20 years, we have continued technological development through medical-engineering collaboration, and in the latest prototype released in 2020, neural function imaging of the spinal cord and peripheral nerves, which could also be applied for the diagnosis of neurological disorders, has become possible. This paper provides an overview of the technical aspects of the magnetoneurograph system, covering the measurement hardware and software perspectives for providing diagnostic information, and its applications. Additionally, we discuss the integration with a helium recondensing system, which is a key factor in reducing running costs and achieving practicality in hospitals.

LW-6 OKAYAMA ROSAI HOSPITAL GLIOMA SUPPORT CENTER INITIATIVES

For glioblastoma, which is a rare and intractable disease, it is necessary to speed up the development and verification of new treatment methods through nationwide clinical trials by consolidating cases in the High Volume Center. Okayama University-related facilities have consolidated glioblastoma cases at Okayama University Hospital and are actively conducting high-precision surgery, genetic analysis, and clinical trials. On the other hand, there are cases where it is difficult to continue treatment at university hospitals, such as dissemination cases and poor Performance Status cases. In order to respond to this need with One Stop, we established the Okayama Rosai Hospital Glioma Support Center. We provide seamless support for postoperative radiation chemotherapy, rehabilitation, maintenance chemotherapy, alternating current electric field therapy, best supportive care, and end-of-life support including backward coordination. The goal is not to make glioblastoma patients and their families “cancer refugees” but to provide QOL-oriented treatment until the end within the comprehensive regional care system. We will report on the results of 29 cases of glioblastoma intervention from May 2013 to August 2022 and future issues.

Assessment of thoracic spinal cord electrophysiological activity through magnetoneurography

OBJECTIVE

Noninvasive and detailed visualization of electrophysiological activity in the thoracic spinal cord through magnetoneurography.

METHODS

In five healthy volunteers, magnetic fields around current flowing in the thoracic spinal cord after alternating unilateral and synchronized bilateral sciatic nerve stimulation were measured using a magnetoneurograph system with superconductive quantum interference device biomagnetometers. The current distribution was obtained from the magnetic data by spatial filtering and visualized by superimposing it on the X-ray image. Conduction velocity was calculated using the peak latency of the current waveforms.

RESULTS

A sufficiently high magnetic signal intensity and signal-to-noise ratio were obtained in all participants after synchronized bilateral sciatic nerve stimulation. Leading and trailing components along the spinal canal and inward components flowing into the depolarization site ascended to the upper thoracic spine. Conduction velocity of the inward current in the whole thoracic spine was 42.4 m/s.

CONCLUSIONS

Visualization of electrophysiological activity in the thoracic spinal cord was achieved through magnetoneurography and a new method for synchronized bilateral sciatic nerve stimulation. Magnetoneurography is expected to be a useful modality in functional assessment of thoracic myelopathy.

SIGNIFICANCE

This is the first report to use magnetoneurography to noninvasively visualize electrophysiological activity in the thoracic spinal cord in detail.

Noninvasive measurement of sensory action currents in the cervical cord by magnetospinography

OBJECTIVE

To obtain magnetic recordings of electrical activities in the cervical cord and visualize sensory action currents of the dorsal column, intervertebral foramen, and dorsal horn.

METHODS

Neuromagnetic fields were measured at the neck surface upon median nerve stimulation at the wrist using a magnetospinography system with high-sensitivity superconducting quantum interference device sensors. Somatosensory evoked potentials (SEPs) were also recorded. Evoked electrical currents were reconstructed by recursive null-steering beamformer and superimposed on cervical X-ray images.

RESULTS

Estimated electrical currents perpendicular to the cervical cord ascended sequentially. Their peak latency at C5 and N11 peak latency of SEP were well-correlated in all 16 participants (r = 0.94, p < 0.0001). Trailing axonal currents in the intervertebral foramens were estimated in 10 participants. Estimated dorsal-ventral electrical currents were obtained within the spinal canal at C5. Current density peak latency significantly correlated with cervical N13-P13 peak latency of SEPs in 13 participants (r = 0.97, p < 0.0001).

CONCLUSIONS

Magnetospinography shows excellent spatial and temporal resolution after median nerve stimulation and can identify the spinal root entry level, calculate the dorsal column conduction velocity, and analyze segmental dorsal horn activity.

SIGNIFICANCE

This approach is useful for functional electrophysiological diagnosis of somatosensory pathways.

Endothelial-specific Ablation of Non-nuclear Estrogen Receptor alpha Signaling Deteriorates Vascular Remodelling Response

Background and introduction

The difference in cardiovascular disease risk between age-matched women and men narrows as transition through menopause in observational studies. Estrogen exerts complex physiological effects via its non-nuclear and nuclear actions. Experimental studies have shown that endothelial estrogen receptors mediate vasoprotection via endothelial nitric oxide production, reendothelialization, and atherosclerosis. Prior studies in vitro addressed estrogen's effects on endothelial cells and vascular smooth muscle cells, leading to vasoprotection. However, the in vivo evidences are lacking for beneficial effects of endothelium non-nuclear ERα signaling on vascular remodelling in response to injury.

Purpose

This study aims to clarify the impact of endothelial ERα non-nuclear signaling in the vasoprotection, using a novel mouse model lacking tissue-specific ERα non-nuclear signaling.

Methods

We identified the amino acids of ERα which were responsible for its binding to p85α subunit of phosphatidylinositol 3-kinase in vitro. We generated a novel mouse model in which non-nuclear signaling of ERα was ablated in endothelial cells by crossing Tie2-Cre transgenic mice with floxed ERα mutants (RR259/260AA) in which p85α and ERα interaction was disrupted.

Results

In endothelial cells isolated from ERαKI/KITie2 cre/+ animals, E2 failed to induce phosphorylation of Akt, confirming the absence of ERα non-nuclear signaling. Baseline characteristics at 8 to 12 weeks of age were undistinguishable between the genotypes, including body weight, systolic blood pressure, uterine weight and echocardiographic fractional shortening. We then assessed how vascular remodelling process was impacted in a carotid artery wire injury model. Histological analyses with Elastica van Gieson staining two weeks after injury revealed that estrogen dependent suppression of remodelling response (intima to medial ratio) was abolished in ERαki/kiTie2cre/+mice (P=0.0004). Masson's Trichrome staining showed that in the presence of E2 fibrosis was significantly higher in ERαki/kiTie2cre/+ mice than ERαki/kiTie2cre/− mice (P=0.0015).

Conclusions

We generated a novel mouse model for tissue-specific ablation of ERα non-nuclear signaling by interfering ERα-PI3K interaction. Our results demonstrate that the pivotal role for ERα non-nuclear signaling of endothelial cells in carotid arterial protection following injury with its minimal impact on baseline cardiovascular phenotype.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Japan Heart Foundation Research Grant, SENSHIN Medical Research Foundation

Nivolumab treatment beyond progressive disease in advanced non-small cell lung cancer

PURPOSE

This study evaluated the efficacy and safety of nivolumab treatment beyond progressive disease (PD) in non-small cell lung cancer (NSCLC).

PATIENTS/METHODS

Medical records of consecutive patients with advanced NSCLC who received nivolumab between December 2015 and December 2018 were reviewed. Clinical outcomes of three groups of eligible patients who received nivolumab as a second-line treatment after PD were compared based on Response Evaluation Criteria in Solid Tumors v1.1. We conducted subgroup analyses in patients with and without new lesions at first PD.

RESULTS

Twenty-eight patients continued nivolumab treatment beyond PD (TBP). Post PD, 46 patients switched to other anti-cancer treatment (OAT), and 21 received no further anti-cancer treatment (NAT). There were no significant differences in overall survival (OS) or survival post progression (SPP) between TBP and OAT groups (OS: 15.6 vs. 13.4 months, P = .40, SPP: 12.2 vs. 9.3 months, P = .42). Subgroup analyses indicated that among patients without new lesions at first PD, SPP was longer in the TBP than in the OAT groups (12.6 vs. 9.3 months, P = .22, HR: 0.64; 95% CI 0.31‒1.31). The frequency of immune-related adverse events leading to discontinuation during nivolumab beyond PD was equivalent to that for pre-PD (10.7 vs. 12.6%).

CONCLUSIONS

No significant benefits were associated with continuation of nivolumab for advanced NSCLC patients. Continuation of nivolumab beyond PD could be a more useful option in patients without new lesions at first PD. Treatment-related toxicities require attention during nivolumab treatment not only before PD but also beyond PD.

Visualization of electrophysiological activity at the carpal tunnel area using magnetoneurography

OBJECTIVE

To establish a noninvasive method to measure the neuromagnetic fields of the median nerve at the carpal tunnel after electrical digital nerve stimulation and evaluate peripheral nerve function.

METHODS

Using a vector-type biomagnetometer system with a superconducting quantum interference device, neuromagnetic fields at the carpal tunnel were recorded after electrical stimulation of the index or middle digital nerve in five healthy volunteers. A novel technique for removing stimulus-induced artifacts was applied, and current distributions were calculated using a spatial filter algorithm and superimposed on X-ray.

RESULTS

A neuromagnetic field propagating from the palm to the carpal tunnel was observed in all participants. Current distributions estimated from the magnetic fields had five components: leading and trailing components parallel to the conduction pathway, outward current preceding the leading component, inward currents between the leading and trailing components, and outward current following the trailing component. The conduction velocity and peak latency of the inward current agreed well with those of sensory nerve action potentials.

CONCLUSION

Removing stimulus-induced artifacts enabled magnetoneurography to noninvasively visualize with high spatial resolution the electrophysiological neural activity from the palm to the carpal tunnel.

SIGNIFICANCE

This is the first report of using magnetoneurography to visualize electrophysiological nerve activity at the palm and carpal tunnel.

124Impact of intimal tracking for recanalization of CTO lesions on long-term clinical outcomes

Background

For recanalization of coronary chronic total occlusion (CTO) lesions, subintimal guidewire tracking in both antegrade and retrograde approaches are commonly used.

Purpose

This study aimed to assess the impact of subintimal tracking on long-term clinical outcomes after recanalization of CTO lesions.

Methods

Between January 2009 and December 2016, 474 CTO lesions (434patients) were successfully recanalized in our center. After guidewire crossing in a CTO lesion, those lesions were divided into intimal tracking group (84.6%, n=401) and subintimal tracking group (15.4%, n=73) according to intravascular ultrasound (IVUS) findings. Long-term clinical outcomes including death, target lesion revascularization (TLR), target vessel revascularization (TVR) were compared between the two groups. In addition, the rate of re-occlusion after successful revascularization was also evaluated.

Results

The median follow-up period was 4.7 years (interquartile range, 2.8–6.1). There was no significant difference of the rate of cardiac death between the two groups (intimal tracking vs. subintimal tracking: 7.0% vs. 4.1%; hazard ratio, 0.61; 95% confidence interval [CI], 0.19 to 2.00; p=0.41), TLR (14.3% vs. 16.2%; hazard ratio, 1.34; 95% CI, 0.71 to 2.53; p=0.37), and TVR (17.5% vs. 20.3%; hazard ratio, 1.27; 95% CI, 0.72 to 2.23; p=0.42). However, the rate of re-occlusion was significantly higher in the subintimal tracking group than intimal tracking group at 3-years re-occlusion (4.2% vs. 14.5%; log-rank test, p=0.002, Figure). In the multivariate COX regression, subintimal guidewire tracking was an independent predictor of re-occlusion after CTO recanalization (HR: 5.40; 95% CI: 2.11–13.80; p<0.001).

Figure 1

Conclusions

Subintimal guidewire tracking for recanalization of coronary CTO was associated with significantly higher incidence of target lesion re-occlusion during long-term follow-up period.

Visualization of the electrical activity of the cauda equina using a magnetospinography system in healthy subjects

OBJECTIVE

To establish a method to measure cauda equina action fields (CEAFs) and visualize the electrical activities of the cauda equina in a broadly aged group of healthy adults.

METHODS

Using a 124-channel magnetospinography (MSG) system with superconducting interference devices, the CEAFs of 43 healthy volunteers (22-64 years of age) were measured after stimulation of the peroneal nerve at the knee. Reconstructed currents were obtained from the CEAFs and superimposed on the X-ray image. Conduction velocities were also calculated from the waveform of the reconstructed currents.

RESULTS

The reconstructed currents were successfully visualized. They flowed into the L5/S1 foramen about 8.25-8.95 ms after the stimulation and propagated cranially along the spinal canal. In 32 subjects (74%), the conduction velocities of the reconstructed currents in the cauda equina could be calculated from the peak latency at the L2-L5 level.

CONCLUSIONS

MSG visualized the electrical activity of the cauda equina after peroneal nerve stimulation in healthy adults. In addition, the conduction velocities of the reconstructed currents in the cauda equina could be calculated, despite previously being difficult to measure.

SIGNIFICANCE

MSG has the potential to be a novel and noninvasive functional examination for lumbar spinal disease.

Prognostic nutritional index and early mortality with percutaneous endoscopic gastrostomy

BACKGROUND

Although percutaneous endoscopic gastrostomy (PEG) is a well-accepted and less invasive method of feeding tube placement in patients with swallowing difficulties, complications and early death after PEG have been reported.

AIM

This study aimed to evaluate predictive factors associated with 30-day mortality after PEG, and to assess the utility of nutritional supporting period before PEG in reducing early mortality following PEG.

DESIGN

An observational study.

METHODS

We retrospectively analyzed 268 patients who underwent PEG at Sapporo Shirakaba-dai Hospital from 2006 to 2010, using clinical and laboratory data to analyze predictive factors associated with early death after PEG. Then, we prospectively assessed 152 consecutive patients assessed for eligibility for PEG from 2011 to 2014. We assessed the patients' nutritional condition using Onodera's prognostic nutritional index (PNI), and supported nutrition for more than 10 days before PEG in patients with a poor nutritional index (PNI < 37).

RESULTS

In both univariate and multivariate analyses in the retrospective study, Onodera's PNI of less than 37 was the only predictive factor for early mortality. In the second study, among the 115 patients who finally underwent PEG, early mortality rates improved to 1.7% from 5.2% in the first study. Conversely, 32% of patients with malnutrition who did not undergo PEG died within 30 days.

CONCLUSION

Nutritional status might be a predictive factor for early mortality after PEG. In patients with poor nutritional status, nutritional supporting period before PEG might improve the outcomes and reduce unnecessary PEG.

Beamspace dual signal space projection (bDSSP): a method for selective detection of deep sources in MEG measurements

OBJECTIVE

Magnetoencephalography (MEG) has a well-recognized weakness at detecting deeper brain activities. This paper proposes a novel algorithm for selective detection of deep sources by suppressing interference signals from superficial sources in MEG measurements.

APPROACH

The proposed algorithm combines the beamspace preprocessing method with the dual signal space projection (DSSP) interference suppression method. A prerequisite of the proposed algorithm is prior knowledge of the location of the deep sources. The proposed algorithm first derives the basis vectors that span a local region just covering the locations of the deep sources. It then estimates the time-domain signal subspace of the superficial sources by using the projector composed of these basis vectors. Signals from the deep sources are extracted by projecting the row space of the data matrix onto the direction orthogonal to the signal subspace of the superficial sources.

MAIN RESULTS

Compared with the previously proposed beamspace signal space separation (SSS) method, the proposed algorithm is capable of suppressing much stronger interference from superficial sources. This capability is demonstrated in our computer simulation as well as experiments using phantom data.

SIGNIFICANCE

The proposed bDSSP algorithm can be a powerful tool in studies of physiological functions of midbrain and deep brain structures.

Abstract P2-01-09: Circulating tumor cells (CTCs) in the venous drainage of the breast in patients with primary breast cancer

Background:

CTCs are shed from tumors and circulate in the peripheral blood after passing through the drainage vein. Axillary lymph node dissection (ALND) provides access to the lateral thoracic vein which flows directly into the axillary vein. In this preliminary study, we evaluated the feasibility of detecting CTCs in the peripheral blood and in the lateral thoracic venous blood for breast cancer patients who underwent ALND.

Methods:

From June 2016 to March 2017, breast cancer patients who underwent ALND in our institute were eligible for this study. A peripheral blood sample,10ml, was drawn just before the surgery or one day before the surgery. A lateral thoracic venous blood sample was taken from the resected breast just after resection. A blood sample of 0.2ml or more was necessary for CTC isolation. The CTCs in the peripheral blood before surgery (periCTC) and in the blood from the lateral thoracic vein of the resected breast (ltvCTC) were quantitatively examined by using a size-selective CTC isolation platform.

Results:

A total of 21 patients with median age 51 years (37-75) were enrolled to the study. Of the 21 patients, 38% were premenopausal, 52% had neoadjuvant chemotherapy. Fifty-seven percent were ER and/or PgR positive, 24% were HER2 positive. Fifty-seven percent were stage II disease and 43% were stage III. In 3 patients, we couldn't obtain sufficient blood samples from the lateral thoracic vein. Of the remaining 18 patients, we were able to obtain the median 0.5ml (0.2-2.0) blood samples from the lateral thoracic vein. CTCs were detected in peripheral blood in 15 patients (71%) and median periCTC count was 1 CTC/10ml (0-39). In lateral thoracic venous blood, CTCs were detected in all patients who had sufficient blood samples and the median ltv CTC count was 35.5 CTC/ml (2.5-370). In 5 of 6 patients whom CTCs in peripheral blood samples were not detected, CTCs could be detected in the blood samples from lateral thoracic vein.

Conclusion:

CTCs can be detected in the peripheral blood and in the blood from lateral thoracic vein in patients with localized breast cancer, and can be detected at a higher rate and at a higher concentration in the blood from lateral thoracic vein than in peripheral blood.

Citation Format: Hattori M, Nakanishi H, Yoshimura A, Adachi Y, Iwase M, Gondo N, Kotani H, Sawaki M, Yatabe Y, Iwata H. Circulating tumor cells (CTCs) in the venous drainage of the breast in patients with primary breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-01-09.

Abstract P2-12-13: Withdrawn

This abstract was withdrawn by the authors.

Magnetospinography visualizes electrophysiological activity in the cervical spinal cord

Diagnosis of nervous system disease is greatly aided by functional assessments and imaging techniques that localize neural activity abnormalities. Electrophysiological methods are helpful but often insufficient to locate neural lesions precisely. One proposed noninvasive alternative is magnetoneurography (MNG); we have developed MNG of the spinal cord (magnetospinography, MSG). Using a 120-channel superconducting quantum interference device biomagnetometer system in a magnetically shielded room, cervical spinal cord evoked magnetic fields (SCEFs) were recorded after stimulation of the lower thoracic cord in healthy subjects and a patient with cervical spondylotic myelopathy and after median nerve stimulation in healthy subjects. Electrophysiological activities in the spinal cord were reconstructed from SCEFs and visualized by a spatial filter, a recursive null-steering beamformer. Here, we show for the first time that MSG with high spatial and temporal resolution can be used to map electrophysiological activities in the cervical spinal cord and spinal nerve.

Inhibition by a CD14 monoclonal antibody of lipopolysaccharide binding to murine macrophages

We have established an anti-CD14 mAb named 4C1 against murine macrophages. 4C1 can bind to thioglycolate-elicited peritoneal macrophages, bone marrow-derived macrophages and casein-induced peritoneal neutrophils. Immunostaining with 4C1 was inhibited by treatment of the cells with phosphatidylinositol specific phospholipase C, suggesting that the antigen is GPI-anchored. Immunoprecipitates from biotin-labeled RAW264.7 cell lysate with 4C1 were around 55 kDa and were visualized with rmC5-3, the only commercially available anti-murine CD14 mAb. 4C1 positively stained COS7 cells transfected with an expression vector containing cDNA of murine CD14. Pretreatment of macrophages with 4C1 reduced LPS-mediated production of TNFα, IL-6, and nitrite. The binding of FITC-LPS to RAW264.7 cells was blocked by pretreatment with 4C1 but not with rmC5. Pretreatment of cells with unlabeled 4C1 mAb but not unlabeled rmC5-3 reduced binding of FITC-4C1. These results suggest that the 4C1 epitope on murine CD14 plays an important role in LPS binding and is distinct from the rmC5-3 epitope.

Candida Soluble Cell Wall β-D-Glucan Induces Lung Inflammation in Mice

Bioactivity of cell wall component(s) of fungi has not been fully elucidated, especially in vivo. We isolated Candida soluble beta-D-glucan (CSBG) from Candida albicans (C. albicans). We investigated the effects of airway exposure to CSBG on the immune systems in the airways in mice. CSBG exposure induced neutrophilic and eosinophilic inflammation in the lung, which was concomitant with the increased local expression of proinflammatory cytokines including tumor necrosis factor - α, interleukin (IL)-1 β, IL-6, macrophage inflammatory protein -1 α, macrophage chemoattractant protein -1, RANTES (regulated on activation and normal T cells expressed and secreted), and eotaxin. The lung inflammation with enhanced expression of proinflammatory proteins caused by CSBG was directly related to its structure, since structurally degraded products of CSBG by formic acid induced negligible responses in the lung. CSBG enhanced nuclear localization of phosphorylated signal transducer and activator of transcription (STAT)-6 in the lung. These results suggest that airway exposure to CSBG induces lung inflammation, at least partly, via the enhanced expression of proinflammatory cytokines and the activation of STAT-6 pathway, and can be a proper murine model for fungal lung inflammation.

Dual signal subspace projection (DSSP): a novel algorithm for removing large interference in biomagnetic measurements

OBJECTIVE

In functional electrophysiological imaging, signals are often contaminated by interference that can be of considerable magnitude compared to the signals of interest. This paper proposes a novel algorithm for removing such interferences that does not require separate noise measurements.

APPROACH

The algorithm is based on a dual definition of the signal subspace in the spatial- and time-domains. Since the algorithm makes use of this duality, it is named the dual signal subspace projection (DSSP). The DSSP algorithm first projects the columns of the measured data matrix onto the inside and outside of the spatial-domain signal subspace, creating a set of two preprocessed data matrices. The intersection of the row spans of these two matrices is estimated as the time-domain interference subspace. The original data matrix is projected onto the subspace that is orthogonal to this interference subspace.

MAIN RESULTS

The DSSP algorithm is validated by using the computer simulation, and using two sets of real biomagnetic data: spinal cord evoked field data measured from a healthy volunteer and magnetoencephalography data from a patient with a vagus nerve stimulator.

SIGNIFICANCE

The proposed DSSP algorithm is effective for removing overlapped interference in a wide variety of biomagnetic measurements.

Biomagnetic measurement system for supine subjects with expanded sensor array and real-time noise reduction

A biomagnetic measurement system was developed, suitable for the detection of magnetospinogram (MSG) and magnetocardiogram (MCG) signals from the dorsal surface of supine subjects. It is effective for noninvasively observing the electric activity of the spinal cord and/or heart. These biomagnetic signals are extremely weak, and magnetic flux sensors based on superconducting quantum interference devices (SQUIDs) are necessary to detect them. However, highly sensitive magnetic field measurement often suffers from ultra low-band circumstance noise mainly caused by transportation in urban areas. We applied reference sensors for monitoring the circumstance noise, and their outputs multiplied by appropriate weight coefficients were directly input to the feedback coil of a SQUID gradiometer. Synthesized in-phase components reduced the ultra low-band noise by approximately 90%. Both the MSG and MCG signals were successfully detected in a moderately magnetically shielded room. Even though the MCG signal band overlapped the ultra low-band noise, the signal-to-noise ratio was improved.