In vivo imaging of deep neural activity from the cortical surface during hippocampal epileptiform events in the rat brain using electrical impedance tomography

Hannan, Sana; Faulkner, Mayo; Aristovich, Kirill; Avery, James; Walker, Matthew C.; Holder, David

doi:10.1016/j.neuroimage.2020.116525

Cited by 25 publications

(36 citation statements)

References 70 publications

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“…Previous fast neural EIT studies have shown that EIT can image neural activity during ictal and interictal epileptiform discharges, induced by chemical and electrical models of epilepsy, as deep as the hippocampus using non-penetrating electrodes implanted on the cortical surface of the anaesthetised rat (Vongerichten, et al, 2016;Hannan, et al, 2018a;Hannan, et al, 2020a). In these studies, an epicortical array containing up to 57 electrodes was implanted on the rat cortex and impedance measurements were recorded by sequentially injecting current through electrode pairs.…”

Section: Imaging the Fast Neural Impedance Changementioning

confidence: 99%

“…To image ictal spikes during neocortical or hippocampal seizures, an independent impedance measurement was obtained during each of 30 reproducible seizures and the impedance changes associated with repeatable spikes were averaged within seizures. This averaging is a requirement to improve SNR by noise reduction due to the low magnitude of the fast neural impedance signal during ictal spikes (≤0.3%) (Hannan, et al, 2018a;Hannan, et al, 2020a). To extract impedance signals, a bandpass filter with a ±500 Hz bandwidth around the carrier frequency of injected current was used which gave a temporal resolution of 2 ms.…”

Section: Imaging the Fast Neural Impedance Changementioning

confidence: 99%

“…Electrical impedance tomography (EIT) is a medical imaging modality that holds potential for improving the accuracy with which the epileptogenic zone is localised and, consequently, the post-surgical outcome in these patients (Fabrizi, et al, 2006). EIT is able to image neural activity during epileptiform discharges as deep as the hippocampus with a spatiotemporal resolution of 2 ms and ~300 μm from the rat cortical surface (Hannan, et al, 2020a). However, this method requires averaging of repetitive neural events over long recording periods to obtain an adequate signal-to-noise ratio (SNR) for imaging (Aristovich, et al, 2018;Hannan, et al, 2020a).…”

Section: Introductionmentioning

confidence: 99%

“…EIT is able to image neural activity during epileptiform discharges as deep as the hippocampus with a spatiotemporal resolution of 2 ms and ~300 μm from the rat cortical surface (Hannan, et al, 2020a). However, this method requires averaging of repetitive neural events over long recording periods to obtain an adequate signal-to-noise ratio (SNR) for imaging (Aristovich, et al, 2018;Hannan, et al, 2020a). An alternative approach is to use EIT to image the slower impedance signal that occurs secondarily to neural activity on a timescale of seconds during seizures.…”

Section: Introductionmentioning

confidence: 99%

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Imaging slow brain activity during neocortical and hippocampal epileptiform events with electrical impedance tomography

et al. 2021

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Objective: Electrical impedance tomography (EIT) is an imaging technique that produces tomographic images of internal impedance changes within an object using surface electrodes. It can be used to image the slow increase in cerebral tissue impedance that occurs over seconds during epileptic seizures, which is attributed to cell swelling due to disturbances in ion homeostasis following hypersynchronous neuronal firing and its associated metabolic demands. In this study, we characterised and imaged this slow impedance response during neocortical and hippocampal epileptiform events in the rat brain and evaluated its relationship to the underlying neural activity. Approach: Neocortical or hippocampal seizures, comprising repeatable series of high-amplitude ictal spikes, were induced by electrically stimulating the sensorimotor cortex or perforant path of rats anaesthetised with fentanyl-isoflurane. Transfer impedances were measured during ≥30 consecutive seizures, by applying a sinusoidal current through independent electrode pairs on an epicortical array, and combined to generate an EIT image of slow activity. Main results: The slow impedance responses were consistently time-matched to the end of seizures and EIT images of this activity were reconstructed reproducibly in all animals (p < 0.03125, N = 5). These displayed foci of activity that were spatially confined to the facial somatosensory cortex and dentate gyrus for neocortical and hippocampal seizures, respectively, and encompassed a larger volume as the seizure progressed. Centre of mass analysis of reconstructions revealed that this activity corresponded to the true location of the epileptogenic zone, as determined by EEG recordings and fast neural EIT measurements which were obtained simultaneously. Significance: These findings suggest that the slow impedance response presents a reliable marker of hypersynchronous neuronal activity during epileptic seizures and can thus be utilised for investigating the mechanisms of epileptogenesis in vivo and for aiding localisation of the epileptogenic zone during presurgical evaluation of patients with refractory epilepsies.

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Section: Imaging the Fast Neural Impedance Changementioning

confidence: 99%

Section: Imaging the Fast Neural Impedance Changementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Imaging slow brain activity during neocortical and hippocampal epileptiform events with electrical impedance tomography

et al. 2021

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“…Además del uso de la TIE en la localización de carcinomas mamarios, se tiene una amplia gama de aplicaciones clínicas entre las que se han reportado: evaluación dinámica cardiovascular (Kerrouche, McLeod y Lionheart, 2001), (de Gelidi et al, 2020); ventilación pulmonar (Ferichs, 2000), (de Castro Martins et al, 2019); vaciado gástrico (Nakae et al, 1999), (Vaisman et al, 1999); y la respuesta neuronal evocada (Tidswell et al, 2001a), (Tidswell et al, 2001b), (Hannan et al, 2020).…”

Section: Iterativeunclassified

Localización de emuladores de carcinomas en modelos experimentales de mama mediante tomografía de impedancia eléctrica basada en linear back projection

Díaz-Carmona

Prado-Olivarez

Gnecchi

et al. 2020

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Introducción: La medición y caracterización de la impedancia eléctrica de los tejidos biológicos permite distinguir entre tejidos sanos y patológicos. El uso de técnicas como la tomografía de impedancia eléctrica es muy utilizada en pruebas clínicas a través de diversas aplicaciones. En este trabajo se emplea el método Linear Back Proyection (LBP) para reconstruir imágenes a partir de la medición de impedancia eléctrica con el objetivo de localizar emuladores de carcinoma insertados en modelos de agar-agar con forma de mama femenina.Método: Un arreglo anillar de ocho electrodos fue empleado para realizar mediciones de impedancia en siete modelos de agar-agar con forma de mama femenina. Se diseñó y simuló en el software COMSOL un corte transversal de una mama femenina sana (sin emuladores) que representa el plano de medición del arreglo anillar de electrodos. Se calcularon los mapas de sensibilidad de cada par de electrodos a lo largo de la medición de impedancia utilizando los datos de la distribución de conductividad del modelo simulado. Finalmente, la reconstrucción de la imagen de tomografía eléctrica para cada modelo se obtuvo aplicando el algoritmo LBP a los valores de impedancia eléctrica medidos en el arreglo anillar de electrodos.Resultados: Se calcularon los mapas de sensibilidad a partir de las mediciones de impedancia obtenidas de cada modelo experimental considerado. Como resultado se generó una matriz de sensibilidad que caracteriza la distribución de los potenciales eléctricos dentro del plano de medición simulado en COMSOL. La zona de localización obtenida fue correcta para todos los modelos experimentales con emuladores de carcinomas insertados fuera del centro del arreglo anillar de electrodos.Discusión o Conclusión: De acuerdo con los resultados obtenidos del proyecto descrito, la metodología propuesta permite la generación de imágenes para localizar emuladores de carcinoma con diámetros aproximados de 1 cm, ello a través de un enfoque no iterativo. Por lo anterior, la localización no requiere una alta complejidad computacional. La localización de un emulador de carcinoma insertado en la zona central del modelo de mama femenina no se obtuvo correctamente debido a la baja sensibilidad de la configuración anillar de los electrodos en dicha zona.

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Single‐Cell Impedance Tomography Using Rolled‐Up Microtubular Sensors

Weiz,

Jha,

Lee

et al. 2023

Adv Materials Technologies

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Single‐cell analysis techniques provide the opportunity to study the cellular heterogeneity that occurs between cells of the same tissue. These methods should ideally be non‐destructive and label‐free to allow long‐term measurements that do not impede with healthy cellular functions. To that end, a miniaturized electrical impedance tomography (µEIT) system is fabricated via rolled‐up nanotechnology to study the electrical properties of individual cells. The tube contains an array of 12 electrodes on its interior wall, and its diameter of ca. 30 µm is tuned to fit the size of a cell. First proof‐of‐concept measurements are carried out with silica and half‐metal coated microparticle phantoms. Additionally, the death of a single HeLa cell is monitored with the µEIT device over time. In the future, the system can be applied to study, e.g. the efficiency of drugs or the biocompatibility of materials on a single‐cell level.

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In vivo imaging of deep neural activity from the cortical surface during hippocampal epileptiform events in the rat brain using electrical impedance tomography

Cited by 25 publications

References 70 publications

Imaging slow brain activity during neocortical and hippocampal epileptiform events with electrical impedance tomography

Imaging slow brain activity during neocortical and hippocampal epileptiform events with electrical impedance tomography

Localización de emuladores de carcinomas en modelos experimentales de mama mediante tomografía de impedancia eléctrica basada en linear back projection

Single‐Cell Impedance Tomography Using Rolled‐Up Microtubular Sensors

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