John C Mosher
Research interests
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InterestsBiomedical Engineering, Medical Imaging, Neuroimaging, Medical Image Processing, Medical Image Analysis, Signal & Image Processing, Signal Analysis, Wavelet Analysis, Biomedical Signal Processing
Publications
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2.61Impact points
Magnetic source imaging in non-lesional neocortical epilepsy: Additional value and comparison with ICEEG.
Epilepsy & behavior : E&B. 04/2012;
OBJECTIVE: To investigate the utility of magnetic source imaging (MSI) for localizing the epileptogenic zone (EZ) and predicting epilepsy surgery outcome in non-lesional neocortical focal epilepsy (NLNE) patients. METHODS: Data from 18 consecutive patients with NLNE who underwent presurgical evaluat... [more] OBJECTIVE: To investigate the utility of magnetic source imaging (MSI) for localizing the epileptogenic zone (EZ) and predicting epilepsy surgery outcome in non-lesional neocortical focal epilepsy (NLNE) patients. METHODS: Data from 18 consecutive patients with NLNE who underwent presurgical evaluation including intracranial electroencephalography (ICEEG) and MSI were studied. Follow-up after epilepsy surgery was ≥24months. Intracranial electroencephalography and MSI results were classified using a sublobar classification. RESULTS: Sublobar ICEEG focus was completely resected in 15 patients; seizure-free rate was 60%. Eight patients showed sublobar-concordant ICEEG/MSI results and complete resection of both regions; seizure-free rate was 87.5%. Seizure-free rate in cases not matching these criteria was only 30% (p=0.013). CONCLUSIONS: Magnetoencephalography is a useful tool to localize the EZ and determine the site of surgical resection in NLNE patients. When sublobar concordance with ICEEG is observed, MSI increases the predictive value for a seizure-free epilepsy surgery outcome in these patients.
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2.48Impact points
Clinical evidence for the utility of movement compensation algorithm in magnetoencephalography: Successful localization during focal seizure.
Epilepsy research. 04/2012;
A movement compensation (MC) algorithm may help to evaluate seizure focus in magnetoencephalography despite patient movement. We report a boy whose ictal MEG focus was localized to the same sublobar region before and after head turning when MC was applied, but which was erroneously localized to a di... [more] A movement compensation (MC) algorithm may help to evaluate seizure focus in magnetoencephalography despite patient movement. We report a boy whose ictal MEG focus was localized to the same sublobar region before and after head turning when MC was applied, but which was erroneously localized to a different area without MC. This study provides the first clinical evidence for utility of MC in magnetoencephalography for localizing focal seizures.
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2.61Impact points
Magnetic source imaging in non-lesional neocortical epilepsy: Additional value and comparison with ICEEG.
Epilepsy & Behavior. 04/2012;
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2.61Impact points
Magnetic source imaging in non-lesional neocortical epilepsy: Additional value and comparison with ICEEG.
Epilepsy & Behavior. 04/2012;
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6.26Impact points
Imag(in)ing seizure propagation: MEG-guided interpretation of epileptic activity from a deep source.
Human brain mapping. 02/2012;
Identification and accurate localization of seizure foci is vital in patients with medically-intractable focal epilepsy, who may be candidates for potentially curative resective epilepsy surgery. We present a patient with difficult-to-control seizures associated with an occult focal cortical dysplas... [more] Identification and accurate localization of seizure foci is vital in patients with medically-intractable focal epilepsy, who may be candidates for potentially curative resective epilepsy surgery. We present a patient with difficult-to-control seizures associated with an occult focal cortical dysplasia residing within the deeper left parietal operculum and underlying posterior insula, which was not detected by conventional MRI analysis. Propagated activities from this deeper generator produced misleading EEG patterns both on surface and subdural electrode recordings suggesting initial activation of the perirolandic and mesial frontal regions. However, careful spatio-temporal analysis of stereotyped interictal activities recorded during MEG, using sequential dipole modeling, revealed a consistent pattern of epileptic propagation originating from the deeper source and propagating within few milliseconds to the dorsal convexity. In this instance, careful dissection of noninvasive investigations (interictal MEG along with ictal SPECT findings) allowed clinicians to dismiss the inaccurate and misleading findings of the traditional "gold-standard" intracranial EEG. In fact, this multimodal noninvasive approach uncovered a subtle dysplastic lesion, resection of which rendered the patient seizure-free. This case highlights the potential benefits of dynamic analysis of interictal MEG in the appropriate clinical context. Pathways of interictal spike propagation may help elucidate essential neural networks underlying focal epilepsy. Hum Brain Mapp, 2012. © 2012 Wiley Periodicals, Inc.
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2.61Impact points
Magnetoencephalography's higher sensitivity to epileptic spikes may elucidate the profile of electroencephalographically negative epileptic seizures.
Epilepsy & behavior : E&B. 02/2012; 23(2):171-3.
Video electroencephalography (EEG) plays an important role in judging whether a clinical spell is an epileptic seizure or paroxysmal event, but its interpretation is not always straightforward. If clinical events without EEG correlates are strongly suggestive of seizures, we usually regard these spe... [more] Video electroencephalography (EEG) plays an important role in judging whether a clinical spell is an epileptic seizure or paroxysmal event, but its interpretation is not always straightforward. If clinical events without EEG correlates are strongly suggestive of seizures, we usually regard these spells as epileptic seizures. However, the electric/magnetic physiological profile of EEG-negative epileptic seizures remains unknown. We describe a 19-year-old man known to have epileptic seizures, in which both magnetoencephalography (MEG)-unique and EEG/MEG spikes were seen. Both types of spikes originated from the same source, but the EEG/MEG spikes were of significantly higher magnitude than the MEG-unique spikes. Therefore, some epileptic seizures, even though generated identically to the MEG-positive seizures, could be EEG-negative because of their smaller magnitude.
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2.61Impact points
Different cortical involvement pattern of generalized and localized spasms: a magnetoencephalography study.
Epilepsy & behavior : E&B. 09/2011; 22(3):599-601.
We report successful magnetoencephalography (MEG) recording in a child who had generalized epileptic spasms (ESs) as well as ESs involving the legs only during the recording. MEG source localization results demonstrated that (1) the interictal epileptiform discharges and both types of ESs had the sa... [more] We report successful magnetoencephalography (MEG) recording in a child who had generalized epileptic spasms (ESs) as well as ESs involving the legs only during the recording. MEG source localization results demonstrated that (1) the interictal epileptiform discharges and both types of ESs had the same origin, that is, the right parietal region, and (2) the two types of ESs had different cortical spread patterns, that is, epileptic involvement localized to the right parietal region in spasms of the legs and rapid diffuse involvement in generalized spasms. In this case, MEG provided new insight into the mechanisms underlying the two types of ESs: both types were generated from the same focus, and in generalized ESs, abnormal excitation spread to cortical areas diffusely.
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1.12Impact points
Intractable focal epilepsy contralateral to the side of facial atrophy in Parry-Romberg syndrome.
Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology. 06/2011; 33(1):165-8.
We report an unusual case of Parry-Romberg syndrome in which medically refractory focal epilepsy with ongoing epilepsia partialis continua (EPC) arose from the hemisphere contralateral to the side of facial atrophy. Unilateral cerebral involvement was confirmed by multi-modal brain imaging, as well ... [more] We report an unusual case of Parry-Romberg syndrome in which medically refractory focal epilepsy with ongoing epilepsia partialis continua (EPC) arose from the hemisphere contralateral to the side of facial atrophy. Unilateral cerebral involvement was confirmed by multi-modal brain imaging, as well as by electroencephalography (EEG) and magnetoencephalography (MEG). While in many cases of Parry-Romberg syndrome, the side of cerebral involvement is ipsilateral to that of the cutaneous lesion, these "discordant" exceptions imply that other yet undefined mechanisms may be responsible for the distribution of the cutaneous and cerebral pathologies.
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2.61Impact points
Generalized 3-Hz spike-and-wave complexes emanating from focal epileptic activity in pediatric patients.
Epilepsy & behavior : E&B. 01/2011; 20(1):103-6.
We describe two pediatric patients with an uncommon electrophysiological seizure propagation pattern. Both had dialeptic seizures as the main or only symptom. Case 1 had a small mass in the left medial temporal structures; case 2 had no lesion on magnetic resonance imaging. In both, the electroencep... [more] We describe two pediatric patients with an uncommon electrophysiological seizure propagation pattern. Both had dialeptic seizures as the main or only symptom. Case 1 had a small mass in the left medial temporal structures; case 2 had no lesion on magnetic resonance imaging. In both, the electroencephalogram showed not only left temporal spikes, but also bilaterally synchronous 3-Hz spike-and-wave complexes (SWCs) from onset and unusual secondarily generalized 3-Hz SWC patterns arising from the left temporal region. Case 1 was seizure free following resection of the mass; focal or generalized epileptiform electroencephalographic abnormalities were no longer present. In case 2, magnetoencephalography localized the spikes to the left superior and midtemporal gyrus, which ictal single-photon-emission computed tomography suggested was the origin of onset. These cases illustrate the close relationship between the focal epileptic area and 3-Hz SWCs and suggest that the focal area can trigger 3-Hz SWCs. The therapeutic strategy may need to be altered in such patients.
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Brainstorm: a user-friendly application for MEG/EEG analysis.
Computational intelligence and neuroscience. 01/2011; 2011:879716.
Brainstorm is a collaborative open-source application dedicated to magnetoencephalography (MEG) and electroencephalography (EEG) data visualization and processing, with an emphasis on cortical source estimation techniques and their integration with anatomical magnetic resonance imaging (MRI) data. T... [more] Brainstorm is a collaborative open-source application dedicated to magnetoencephalography (MEG) and electroencephalography (EEG) data visualization and processing, with an emphasis on cortical source estimation techniques and their integration with anatomical magnetic resonance imaging (MRI) data. The primary objective of the software is to connect MEG/EEG neuroscience investigators with both the best-established and cutting-edge methods through a simple and intuitive graphical user interface (GUI).
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GENERALIZED SIDELOBE CANCELLER FOR MAGNETOENCEPHALOGRAPHY ARRAYS.
Proceedings / IEEE International Symposium on Biomedical Imaging: from nano to macro. IEEE International Symposium on Biomedical Imaging. 08/2009; 2009:149-152.
In the last decade, large arrays of sensors for magnetoencephalography (MEG) (and electroencephalography (EEG)) have become more commonplace, allowing new opportunities for the application of beamforming techniques to the joint problems of signal estimation and noise reduction. We introduce a new ap... [more] In the last decade, large arrays of sensors for magnetoencephalography (MEG) (and electroencephalography (EEG)) have become more commonplace, allowing new opportunities for the application of beamforming techniques to the joint problems of signal estimation and noise reduction. We introduce a new approach to noise cancellation, the generalized sidelobe canceller (GSC), itself an alternative to the linearly constrained minimum variance (LCMV) algorithm. The GSC framework naturally fits within the other noise reduction techniques that employ real or virtual reference arrays. Using expository human subject data with strong environmental and biological artifacts, we demonstrate a straightforward sequence of steps for practical noise filtering, applicable to any large array sensor design.
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Generalized sidelobe canceller for magnetoencephalography arrays
Biomedical Imaging: From Nano to Macro, 2009. ISBI '09. IEEE International Symposium on; 08/2009
In the last decade, large arrays of sensors for magnetoencephalography (MEG) (and electroencephalography (EEG)) have become more common place, allowing new opportunities for the application of beamforming techniques to the joint problems of signal estimation and noise reduction. We introduce a new a... [more] In the last decade, large arrays of sensors for magnetoencephalography (MEG) (and electroencephalography (EEG)) have become more common place, allowing new opportunities for the application of beamforming techniques to the joint problems of signal estimation and noise reduction. We introduce a new approach to noise cancellation, the generalized sidelobe canceller (GSC), itself an alternative to the linearly constrained minimum variance (LCMV) algorithm. The GSC framework naturally fits within the other noise reduction techniques that employ real or virtual reference arrays. Using expository human subject data with strong environmental and biological artifacts, we demonstrate a straightforward sequence of steps for practical noise filtering, applicable to any large array sensor design.
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2.53Impact points
Microtesla MRI of the human brain combined with MEG.
Journal of magnetic resonance (San Diego, Calif. : 1997). 07/2008;
One of the challenges in functional brain imaging is integration of complementary imaging modalities, such as magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). MEG, which uses highly sensitive superconducting quantum interference devices (SQUIDs) to directly measure magn... [more] One of the challenges in functional brain imaging is integration of complementary imaging modalities, such as magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). MEG, which uses highly sensitive superconducting quantum interference devices (SQUIDs) to directly measure magnetic fields of neuronal currents, cannot be combined with conventional high-field MRI in a single instrument. Indirect matching of MEG and MRI data leads to significant co-registration errors. A recently proposed imaging method-SQUID-based microtesla MRI-can be naturally combined with MEG in the same system to directly provide structural maps for MEG-localized sources. It enables easy and accurate integration of MEG and MRI/fMRI, because microtesla MR images can be precisely matched to structural images provided by high-field MRI and other techniques. Here we report the first images of the human brain by microtesla MRI, together with auditory MEG (functional) data, recorded using the same seven-channel SQUID system during the same imaging session. The images were acquired at 46muT measurement field with pre-polarization at 30mT. We also estimated transverse relaxation times for different tissues at microtesla fields. Our results demonstrate feasibility and potential of human brain imaging by microtesla MRI. They also show that two new types of imaging equipment-low-cost systems for anatomical MRI of the human brain at microtesla fields, and more advanced instruments for combined functional (MEG) and structural (microtesla MRI) brain imaging-are practical.
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2.53Impact points
Parallel MRI at microtesla fields.
Journal of magnetic resonance (San Diego, Calif. : 1997). 07/2008; 192(2):197-208.
Parallel imaging techniques have been widely used in high-field magnetic resonance imaging (MRI). Multiple receiver coils have been shown to improve image quality and allow accelerated image acquisition. Magnetic resonance imaging at ultra-low fields (ULF MRI) is a new imaging approach that uses SQU... [more] Parallel imaging techniques have been widely used in high-field magnetic resonance imaging (MRI). Multiple receiver coils have been shown to improve image quality and allow accelerated image acquisition. Magnetic resonance imaging at ultra-low fields (ULF MRI) is a new imaging approach that uses SQUID (superconducting quantum interference device) sensors to measure the spatially encoded precession of pre-polarized nuclear spin populations at microtesla-range measurement fields. In this work, parallel imaging at microtesla fields is systematically studied for the first time. A seven-channel SQUID system, designed for both ULF MRI and magnetoencephalography (MEG), is used to acquire 3D images of a human hand, as well as 2D images of a large water phantom. The imaging is performed at 46 mu T measurement field with pre-polarization at 40 mT. It is shown how the use of seven channels increases imaging field of view and improves signal-to-noise ratio for the hand images. A simple procedure for approximate correction of concomitant gradient artifacts is described. Noise propagation is analyzed experimentally, and the main source of correlated noise is identified. Accelerated imaging based on one-dimensional undersampling and 1D SENSE (sensitivity encoding) image reconstruction is studied in the case of the 2D phantom. Actual threefold imaging acceleration in comparison to single-average fully encoded Fourier imaging is demonstrated. These results show that parallel imaging methods are efficient in ULF MRI, and that imaging performance of SQUID-based instruments improves substantially as the number of channels is increased.
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A two-step imaging procedure for MEG characterization of cortical currents: Location and spatial extent
Biomedical Imaging: From Nano to Macro, 2008. ISBI 2008. 5th IEEE International Symposium on; 06/2008
There is theoretical and experimental evidence that the spatial extent of mass neural activity is an important factor of brain response in neuroimaging studies. Direct estimation of the surface area of activated regions would importantly complement the quantitative analysis of amplitude variations o... [more] There is theoretical and experimental evidence that the spatial extent of mass neural activity is an important factor of brain response in neuroimaging studies. Direct estimation of the surface area of activated regions would importantly complement the quantitative analysis of amplitude variations of cortical currents. These latter are accessible at the regional scale through source modeling of magnetoencephalographic signals. Here we present a joint approach to the estimation of both the local spatial extent and amplitude variations of neural current sources. The technique operates in two consecutive steps: 1) the compact modeling of regional cortical currents using equivalent current multipoles and 2) the remapping of these latter back onto the cortical surface using a sparse-focal imaging model. This Multipole Cortical Remapping technique operates in a Bayesian framework. Performances are evaluated using extensive Monte-Carlo simulations and are complemented with real data from a somatosensory mapping MEG experiment.
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A two-step imaging procedure for MEG characterization of cortical currents: Location and spatial extent.
Proceedings of the 2008 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, Paris, France, May 14-17, 2008; 01/2008
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Microtesla MRI of the human brain combined with MEG
12/2007;
One of the challenges in functional brain imaging is integration of complementary imaging modalities, such as magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). MEG, which uses highly sensitive superconducting quantum interference devices (SQUIDs) to directly measure magn... [more] One of the challenges in functional brain imaging is integration of complementary imaging modalities, such as magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). MEG, which uses highly sensitive superconducting quantum interference devices (SQUIDs) to directly measure magnetic fields of neuronal currents, cannot be combined with conventional high-field MRI in a single instrument. Indirect matching of MEG and MRI data leads to significant co-registration errors. A recently proposed imaging method - SQUID-based microtesla MRI - can be naturally combined with MEG in the same system to directly provide structural maps for MEG-localized sources. It enables easy and accurate integration of MEG and MRI/fMRI, because microtesla MR images can be precisely matched to structural images provided by high-field MRI and other techniques. Here we report the first images of the human brain by microtesla MRI, together with auditory MEG (functional) data, recorded using the same seven-channel SQUID system during the same imaging session. The images were acquired at 46 microtesla measurement field with pre-polarization at 30 mT. We also estimated transverse relaxation times for different tissues at microtesla fields. Our results demonstrate feasibility and potential of human brain imaging by microtesla MRI. They also show that two new types of imaging equipment - low-cost systems for anatomical MRI of the human brain at microtesla fields, and more advanced instruments for combined functional (MEG) and structural (microtesla MRI) brain imaging - are practical.
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1.31Impact points
Toward SQUID-Based Direct Measurement of Neural Currents by Nuclear Magnetic Resonance
Applied Superconductivity, IEEE Transactions on. 07/2007;
Modern high field (HF) MRI uses magnetic fields greater than 1.5 T to yield exquisite anatomical features. We have also seen an explosion in functional MRI in the last decade that measures hemodynamic responses that are ultimately sluggish (~one sec) and only indirectly related to electrophysiologic... [more] Modern high field (HF) MRI uses magnetic fields greater than 1.5 T to yield exquisite anatomical features. We have also seen an explosion in functional MRI in the last decade that measures hemodynamic responses that are ultimately sluggish (~one sec) and only indirectly related to electrophysiological processes. Magnetoencephalography (MEG) is a direct measure of the external fields generated by neuronal currents with exquisite temporal information (less than one msec). Spatial localization, however, is inferred from modeling priors, making MEG ldquoimagingrdquo only indirect at best. Ultra low field (ULF) MRI has recently been demonstrated with 2-3 mm resolution using fields in the microtesla regime. While the nuclear magnetic resonance (NMR) signal at ULF is dramatically weaker than at HF, we acquired high signal-to-noise measurements for a variety of samples at ULF using SQUID technology. Several researchers have proposed that electrophysiological activity may interact with the nuclear spins in a volume of interest, causing measurable variations in the NMR signal. We have developed a new approach to directly measuring neuronal activity with SQUID-based ULF-NMR techniques based on the hypothesis that interactions between the spin population and neural activity in cortex can be dominated by resonant mechanisms unique to ULF. We have experimentally demonstrated the feasibility of this approach via ULF-NMR using a single-channel SQUID system.
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1.31Impact points
Multi-Channel SQUID System for MEG and Ultra-Low-Field MRI
Applied Superconductivity, IEEE Transactions on. 07/2007;
A seven-channel system capable of performing both magnetoencephalography (MEG) and ultra-low-field magnetic resonance imaging (ULF MRI) is described. The system consists of seven second-order SQUID gradiometers with 37 mm diameter and 60 mm baseline, having magnetic field resolution of 1.2-2.8 fT/ra... [more] A seven-channel system capable of performing both magnetoencephalography (MEG) and ultra-low-field magnetic resonance imaging (ULF MRI) is described. The system consists of seven second-order SQUID gradiometers with 37 mm diameter and 60 mm baseline, having magnetic field resolution of 1.2-2.8 fT/radicHz . It also includes four sets of coils for 2D Fourier imaging with pre-polarization. The system's MEG performance was demonstrated by measurements of auditory evoked response. The system was also used to obtain a multi-channel 2D image of a whole human hand at the measurement field of 46 microtesla with 3 by 3 mm resolution.
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Parallel MRI at microtesla fields
02/2007;
Parallel imaging techniques have been widely used in high-field magnetic resonance imaging (MRI). Multiple receiver coils have been shown to improve image quality and allow accelerated image acquisition. Magnetic resonance imaging at ultra-low fields (ULF MRI) is a new imaging approach that uses SQU... [more] Parallel imaging techniques have been widely used in high-field magnetic resonance imaging (MRI). Multiple receiver coils have been shown to improve image quality and allow accelerated image acquisition. Magnetic resonance imaging at ultra-low fields (ULF MRI) is a new imaging approach that uses SQUID (superconducting quantum interference device) sensors to measure the spatially encoded precession of pre-polarized nuclear spin populations at microtesla-range measurement fields. In this work, parallel imaging at microtesla fields is systematically studied for the first time. A seven-channel SQUID system, designed for both ULF MRI and magnetoencephalography (MEG), is used to acquire 3D images of a human hand, as well as 2D images of a large water phantom. The imaging is performed at 46 microtesla measurement field with pre-polarization at 40 mT. It is shown how the use of seven channels increases imaging field of view and improves signal-to-noise ratio for the hand images. A simple procedure for approximate correction of concomitant gradient artifacts is described. Noise propagation is analyzed experimentally, and the main source of correlated noise is identified. Accelerated imaging based on one-dimensional undersampling and 1D SENSE (sensitivity encoding) image reconstruction is studied in the case of the 2D phantom. Actual 3-fold imaging acceleration in comparison to single-average fully encoded Fourier imaging is demonstrated. These results show that parallel imaging methods are efficient in ULF MRI, and that imaging performance of SQUID-based instruments improves substantially as the number of channels is increased.
Following (10)
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Andreas Alexopoulos
Cleveland Clinic -
Masaki Iwasaki
Tohoku University -
Karim Jerbi
Institut national de la santé et de la recherche médicale -
Damir Janigro
Cleveland Clinic -
Alexei Ossadtchi
Saint Petersburg State University
