Linear Electrode Research Articles

Modeling electrical impedance in brain tissue with diffusion tensor imaging for functional neurosurgery applications

Objective.Decades ago, neurosurgeons used electrical impedance measurements in the brain for coarse intraoperative tissue differentiation. Over time, these techniques were largely replaced by more refined imaging and electrophysiological localization. Today, advanced methods of diffusion tensor imaging (DTI) and finite element method (FEM) modeling may permit non-invasive, high-resolution intracerebral impedance prediction. However, expectations for tissue-impedance relationships and experimentally verified parameters for impedance modeling in human brains are lacking. This study seeks to address this need.Approach.We used FEM to simulate high-resolution single- and dual-electrode impedance measurements along linear electrode trajectories through (1) canonical gray and white matter tissue models, and (2) selected anatomic structures within whole-brain patient DTI-based models. We then compared intraoperative impedance measurements taken at known locations along deep brain stimulation (DBS) surgical trajectories with model predictions to evaluate model accuracy and refine model parameters.Main results.In DTI-FEM models, single- and dual-electrode configurations performed similarly. While only dual-electrode configurations were sensitive to white matter fiber orientation, other influences on impedance, such as white matter density, enabled single-electrode impedance measurements to display significant spatial variation even within purely white matter structures. We compared 308 intraoperative single-electrode impedance measurements in five DBS patients to DTI-FEM predictions at one-to-one corresponding locations. After calibration of model coefficients to these data, predicted impedances reliably estimated intraoperative measurements in all patients (R=0.784±0.116,n=5). Through this study, we derived an updated value for the slope coefficient of the DTI conductance model published by Tuchet al,k=0.0649 S⋅smm-3 (originalk=0.844), for use specifically in humans at physiological frequencies.Significance.This is the first study to compare impedance estimates from imaging-based models of human brain tissue to experimental measurements at the same locationsin vivo. Accurate, non-invasive, imaging-based impedance prediction has numerous applications in functional neurosurgery, including tissue mapping, intraoperative electrode localization, and DBS.

Removal Forces of a Helical Microwire Structure Electrode.

(1) Background: Medical devices, especially neuromodulation devices, are often explanted for a variety of reasons. The removal process imparts significant forces on these devices, which may result in device fracture and tissue trauma. We hypothesized that a device's form factor interfacing with tissue is a major driver of the force required to remove a device, and we isolated helical and linear electrode structures as a means to study atraumatic removal. (2) Methods: Ductile linear and helical microwire structure electrodes were fabricated from either Gold (Au) or Platinum-Iridium (Pt-Ir, 90-10). Removal forces were captured from synthetic gel models and following chronic implantation in rodent and porcine models. Devices were fully implanted in the animal models, requiring a small incision (<10 mm) and removal via tissue forceps. (3) Results: Helical devices were shown to result in significantly lower maximal removal forces in both synthetic gel and rodent studies compared to their linear counterparts. Chronically (1 yr.), the maximal removal force of helical devices remained under 7.30 N, for which the Platinum-Iridium device's tensile failure force was 32.90 ± 2.09 N, resulting in a safety factor of 4.50. (4) Conclusions: An open-core helical structure that can freely elongate was shown to result in reduced removal forces both acutely and chronically.

MATHEMATICAL MODELLING ELECTRICALLY DRIVEN FREE SHEAR FLOWS IN A DUCT UNDER UNIFORM MAGNETIC FIELD

We consider a mathematical model of two-dimensional electrically driven laminar free shear flows in a straight duct under action of an applied uniform homogeneous magnetic field. The mathematical approach is based on studies by J.C.R. Hunt and W.E. Williams [10], Yu. Kolesnikov and H. Kalis [22,23]. We solve the system of stationary partial differential equations (PDEs) with two unknown functions of velocity U and induced magnetic field H. The flows are generated as a result of the interaction of injected electric current in liquid and the applied field using one or two couples of linear electrodes located on duct walls: three cases are considered. In dependence on direction of current injection and uniform magnetic field, the flows between the end walls are realized. Distributions of velocities and induced magnetic fields, electric current density in dependence on the Hartmann number Ha are studied. The solution of this problem is obtained analytically and numerically, using the Fourier series method and Matlab.

Wide-range, durable, and adaptable miniature pressure sensor based on planar capacitance

Capacitive pressure sensor (CPS) is widely used in the field of industrial equipment, because of the merits of fast dynamic response and high resolution. However, the traditional laminated CPS makes it difficult to achieve a wide detection limit in a small size, and this structure is susceptible to electromagnetic interference. Here we developed a miniature planar capacitive pressure sensor (MPCPS) with high performance, which can realize the response to external touching stimuli through the deformation of the packaging material and the change of the equivalent resistance. A metal shielding layer was added under the insulating substrate to effectively isolate the external interference. The thickness of the sensor is about 200 μm, and the diameter of the core sensing area is less than 1 mm. Two types of electrodes with different shapes were designed, among which the spiral electrode MPCPS (S-MPCPS) has better performance than the linear electrode MPCPS. The S-MPCPS has a sensitivity of 99.2% MPa−1 in the low-pressure range (0–0.1 MPa), fast response (20 ms), wide detection limit (>1 MPa), and high durability (>2000 cycles). In addition, MPCPS is proven to have good resistance to high temperature and oil contamination. Finally, practical applications such as contact pressure measuring on the meshing surface of spur gears and mechanical gripper clamping force monitoring were successfully demonstrated. These results shed light on the potential application of the MPCPS in the pressure detection of industrial equipment.

Polymer Engineering Enables High Linear Capacity Fiber Electrodes by Microenvironment Regulation.

Unlike bulky and rigid traditional power systems, 1D fiber batteries possess appealing features such as flexibility and adaptability, which are promising for use in wearable electronic devices. However, the performance and energy density fiber batteries are limited by the contradiction between ionic transfer and robust structure of fiber electrodes. Herein, these problems are addressed via polymer engineering to regulate the microenvironment in electrodes, realizing high-linear-capacity thick fiber electrodes with excellent cycling performance. The porosity of the electrodes is regulated using polymer crosslink networks designed with various components, and lithium-ion transfer is optimized through ether-abundant polymer chains. Furthermore, reinforced covalent bonding with carbon nanotube networks is established based on the modified functional groups of polymer networks. The multiscale optimizations of the porous structure, ionic transportation, and covalent bonding network enhance the lithium-ion dynamics property and structural stability. Therefore, ultrahigh linear-capacity fiber electrodes (17.8mAh m-1) can be fabricated on a large scale and exhibit excellent stability (92.8% after 800 cycles), demonstrating obvious superiority among the reported fiber electrodes. Moreover, this study highlights the high effectiveness of polymer regulation in fiber electrodes and offers new avenues for designing next-generation wearable energy-storage systems.

Clustering index analysis on EMG-Torque relation-based representation of complex neuromuscular changes after spinal cord injury

Spinal cord injury (SCI) resulting in complex neuromuscular pathology is not sufficiently well understood. To better quantify neuromuscular changes after SCI, this study uses a clustering index (CI) method for surface electromyography (sEMG) clustering representation to investigate the relation between sEMG and torque in SCI survivors. The sEMG signals were recorded from 13 subjects with SCI and 13 gender-age matched able-bodied subjects during isometric contraction of the biceps brachii muscle at different torque levels using a linear electrode array. Two torque representations, maximum voluntary contraction (MVC%) and absolute torque, were used. CI values were calculated for sEMG. Regression analyses were performed on CI values and torque levels of elbow flexion, revealing a strong linear relationship. The slopes of regressions between SCI survivors and control subjects were compared. The findings indicated that the range of distribution of CI values and slopes was greater in subjects with SCI than in control subjects (p < 0.05). The increase or decrease in slope was also observed at the individual level. This suggests that the CI and its sEMG clustering-torque relation may serve as valuable quantitative indicators for determining neuromuscular lesions after SCI, contributing to the development of effective rehabilitation strategies for improving motor performance.

Towards standardisation of surface electromyography measurements in the horse: Bipolar electrode location

The use of surface electromyography in the field of animal locomotion has increased considerably over the past decade. However, no consensus exists on the methodology for data collection in horses. This study aimed to start the development of recommendations for bipolar electrode locations to collect surface electromyographic data from horses during dynamic tasks.Data were collected from 21 superficial muscles of three horses during trot on a treadmill using linear electrode arrays. The data were assessed both quantitatively (signal-to-noise ratio (SNR) and coefficient of variation (CoV)) and qualitatively (presence of crosstalk and activation patterns) to compare and select electrode locations for each muscle.For most muscles and horses, the highest SNR values were detected near or cranial/proximal to the central region of the muscle. Concerning the CoV, there were larger differences between muscles and horses than within muscles. Qualitatively, crosstalk was suspected to be present in the signals of twelve muscles but not in all locations in the arrays.With this study, a first attempt is made to develop recommendations for bipolar electrode locations for muscle activity measurements during dynamic contractions in horses. The results may help to improve the reliability and reproducibility of study results in equine biomechanics.

Effect of the heat treatment on the microstructure of carbide tool electrodes for electrical discharge drilling

Abstract Carbide tool electrodes for electrical discharge drilling were subjected to heat treatment at various temperatures and in different atmospheres for the same duration, respectively, in order to reduce the electrical conductivity of the lateral surface. Hardness tests show that the heat treatment does not induce a loss of strength in the electrode body. Microscopic analyses revealed that the lateral surface, characterized by a two-layer structure comprising a surface and a diffusion layer of varying characteristics and morphology, such as surface roughness, degree of coverage, delaminations, or a columnar microstructure, changes. It is revealed that the electrical conductivity is a function of the total layer thickness made up of the thickness of the surface layer and a diffusion layer. The electrical conductivity drops with increasing total layer thickness. In the context of electric discharge drilling tests, it was found that the reduced electrical conductivity leads to a decreased material removal rate and a simultaneously reduced linear electrode wear. Heat treatments ensuring consistent erosion times resulted in a wear rate reduction of the tool electrodes of up to 10 %.

Triple multivalent aptamers within DNA tetrahedron on reduced graphene oxide electrode: Unlocking enhanced sensitivity and accelerated reactions in electrochemical sensing

DNA nanostructures are emerging as promising biosensing platforms due to their programmability, predictable assembly, and compatibility with aptamers for enhanced selectivity. This study focuses on a triple-multivalent aptamer (tApt) complex immobilized on a tetrahedral DNA nanostructure (TDN) and integrated with an electrochemically reduced graphene oxide (ERGO) electrode for highly sensitive mercury ion (Hg2+) detection. Compared to a linear multivalent aptamer-modified electrode (S2/ERGO-GCE), the 3D tApt/ERGO-GCE aptasensor exhibits superior sensitivity, signal amplification, and reaction kinetics. The tApt/ERGO-GCE sensor achieves an exceptional limit of detection (LOD) of 4.1 zM, surpassing the LOD of 0.71 fM for S2/ERGO-GCE. Additionally, the tApt/ERGO-GCE sensor demonstrates faster response times, with a half-saturation time (T1/2) of 6 minutes compared to 17 minutes for S2/ERGO/GCE. The 3D tApt aptamer's superior performance is attributed to its tetrahedral DNA structure integrated on ERGO, providing multiple aptamer binding sites, facilitating oriented immobilization on the electrode surface, and enhancing analyte capture and concentration. In contrast, the linear S2 aptamers lack rigidity, resulting in a disordered orientation on the electrode surface, hindering efficient Hg2+ binding and reducing target molecule binding efficiency. This study underscores the potential of triple-multivalent aptamer-based nanostructures for ultrasensitive and rapid biosensing applications. The tApt/ERGO-GCE aptasensor's exceptional sensitivity, signal amplification, and reaction kinetics make it a promising tool for Hg2+ detection and other biosensing applications.

Study on liquid dielectrophoresis based on double flexible electrodes simulating interdigitated pattern electrodes

Dielectrophoresis affects the surface wettability by applying a non-uniform electric field to dipoles inside dielectric liquid, achieving adjustable droplet contact angle and overcoming the saturation limitation of contact angle caused by the electrowettability effect. However, it is difficult to realize useful three-dimensional tunable optical devices because most of the driving electrodes need to be patterned. In this work, a model of double flexible electrodes simulating planar interdigitated pattern electrodes is proposed based on the dielectrophoresis. Double flexible electrodes, which are wrapped with an insulating dielectric layer and are not conductive to each other are arranged at close intervals and wound along the plane substrate to form a two-dimensional planar line wall. A hydrophobic layer is used to fill the gap and increase the initial contact angle. Ultimately, the “droplet-interdigitated planar line wall” dielectrophoresis driven-droplet model is formed after the dielectric droplets have been deposited on the line wall surface. Firstly, considering the influence of penetration depth and electrode gap area, Young’s equation is theoretically modified to adapt to this model. Then, the finite element algorithm simulation is used to used to comparatively analyze the potential distribution of this model and the planar interdigitated pattern electrode model. The field strength distributions of the electrodes with different wire diameters and insulating layer thickness values are analyzed. It can be found that with the increase of the diameter of the electrode wire and the thickness of the insulating layer, the morphology of the model changes from the tip electrode into the planar electrode, the surface field strength attenuates exponentially and the peak value decreases. This shows that the structure of this electrode in this model is superior to that of the planar electrode. After that, the contact angle of the model is measured experimentally in a range of 58°－90° under 0–250 &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;rms&lt;/sub&gt; voltage, which is in line with the theoretical expectation. At the same time, neither obvious contact angle lag nor saturation is observed in the experiment. Finally, the new electrophoretic driving droplet model constructed in this paper transforms the dielectric electrophoretic driving mode from a two-dimensional planar electrode to a one-dimensional flexible linear electrode. Because of its flexibility and plasticity, it is convenient to form a three-dimensional cavity and can be applied to more complex device structures.

Sustainable Laser Induced Supercapacitors from Cork Natural Substrates

A novel type of eco-friendly and cost-effective supercapacitor has been developed by fabricating interdigitated and squared supercapacitors made of porous graphitic carbon electrodes and Polyvinyl alcohol (PVA) electrolyte. The electrodes were fabricated using a simple, fast, and low-cost laser engraving process, using visible irradiation wavelengths (450 nm) and performed under ambient conditions, resulting in highly three-dimensional, electrically conductive, and porous graphitic carbon structures.By adjusting the laser power and wavelength, it was possible to produce electrode materials with highly porous and high surface area morphology, which are promising for electrochemical applications. Spectral investigation using Raman and FTIR spectroscopies confirmed the formation of graphitic carbon structures and the full conversion of the cork precursor under visible laser irradiation.The obtained electrodes exhibited excellent supercapacitive behavior when exposed to a PVA electrolyte, achieving a specific areal capacitance of up to 11.24 mF/cm2 with PVA at 30% laser power. The supercapacitive properties showed excellent stability over time, with no significant loss after 10000 charge/discharge cycles.To evaluate the performance of the new supercapacitors, linear electrodes were used as working electrodes in a three-electrode configuration electrochemical cell. The electrodes showed diffusion-limited electrochemical behavior with fast heterogeneous electron transfer rates (HET), which was superior to that of traditional glassy carbon electrodes.The innovative and efficient electrode fabrication method presented in this study, which utilizes low-cost instrumentation, environmentally friendly fabrication methods, and Earth-abundant precursor materials, shows great promise for producing large-scale "green" electrochemical sensing platforms and devices in the future.

Muscle Fiber Conduction Velocity During Electrically Stimulated Contraction at Various Joint Angles, During Joint Movements, and During Voluntary Contractions.

Muscle fiber conduction velocity (MFCV) can be affected by muscle fiber geometry at different joint angles and during joint movements. This study aimed to investigate MFCV during electrically evoked contraction at different joint angles, during joint movements, and during voluntary contractions. Sixteen healthy young men participated. A stimulation electrode was attached on the innervation zone of the vastus lateralis, and a linear electrode array was attached on the vastus lateralis. Under a static condition, electrically evoked electromyography signals were recorded at knee joint angles set every 15° between 0° and 105°. Under a passive movement condition, signals were recorded during knee extension and flexion passively. Under a voluntary contraction condition, signals were recorded while performing 30% or 60% of maximum voluntary contraction. MFCV was calculated using cross-correlation coefficients. Under the static condition, there were no differences in MFCV among various joint angles. Under the passive movement condition, MFCV was significantly greater during high velocity or shortening. Under the voluntary contraction condition, MFCV was significantly greater during high-intensity voluntary contraction and with a shortened muscle length. Joint angles do not influence MFCV markedly during relaxation, but it is possible to overestimate MFCV during movement or voluntary contraction.

Performance in microfluidic electrochemical cell with gradient or double-layers porous electrode for CO2 diffusion

To obtain better electrical behavior, the linear or double-layers porous electrode is set in microfluidic electrochemical cell for CO2 diffusion, which couples Tafel's law and Ohm's law with the flow equation and species transport equation for numerical calculations. This research analyzes the effects of linear or double-layer porosity, the thickness of double-layer porosity, and electrode structure in the electrode on current density, CO2 conversion, and Faraday efficiency under different working conditions. The higher current density and CO2 conversion occur in the case with smaller porosity in the electrode due to more reactive sites, and poor gas transport is observed simultaneously. Optimizing linear or double-layers porosity distribution results in higher current density, CO2 conversion, and Faraday efficiency. The Faraday efficiency can reach 91.54% in the case of stepwise increasing porosity from 0.3 to 0.9 in the electrode. Poor electrical behavior occurs as linear increasing porosity compared to stepwise porosity due to different porosity distributions, and the opposite is the case for decreasing linear porosity. Setting the double-layer porosity along the electrode thickness direction results in larger Faraday efficiency as a thickness ratio of 1:1 and larger current density and CO2 conversion as a thickness ratio of 4:1 in the case of porosity from 0.3 to 0.9. Better electrochemical behavior occurs with electrode thickness to length ratio of 10–20 and the CO2 gas channel to electrode thickness ratio of 1:1–4:1, and optimized electrode porosities tend to show higher Faraday efficiencies during electrode structural changes.

Can we improve electrocorticography using a circular grid array in brain tumor surgery?

Intraoperative electrocorticography (iECoG) is used as an adjunct to localize the epileptogenic zone during surgical resection of brain tumors in patients with focal epilepsies. It also enables monitoring of after-discharges and seizures with EEG during functional brain mapping with electrical stimulation. When seizures or after-discharges are present, they complicate accurate interpretation of the mapping strategy to outline the brain’s eloquent function and can affect the surgical procedure. Recurrent seizures during surgery requires urgent treatment and, when occurring during awake craniotomy, often leads to premature termination of brain mapping due to post-ictal confusion or sedation from acute rescue therapy. There are mixed results in studies on efficacy with iECoG in patients with epilepsy and brain tumors influencing survival and functional outcomes following surgery. Commercially available electrode arrays have inherent limitations. These could be improved with customization potentially leading to greater precision in safe and maximal resection of brain tumors. Few studies have assessed customized electrode grid designs as an alternative to commercially available products. Higher density electrode grids with intercontact distances less than 1 cm improve spatial delineation of electrophysiologic sources, including epileptiform activity, electrographic seizures, and afterdischarges on iECoG during functional brain mapping. In response to the shortcomings of current iECoG grid technologies, we designed and developed a novel higher-density hollow circular electrode grid array. The 360-degree iECoG monitoring capability allows continuous EEG recording during surgical intervention through the aperture with and without electrical stimulation mapping. Compared with linear strip electrodes that are commonly used for iECoG during surgery, the circular grid demonstrates significant benefits in brain tumor surgery. This includes quicker recovery of post-operative motor deficits (2.4 days versus 9 days, p = 0.05), more extensive tumor resection (92.0% versus 77.6%, p = 0.003), lesser reduction in Karnofsky Performance scale postoperatively (−2 versus −11.6, p = 0.007), and more sensitivity to recording afterdischarges. In this narrative review, we discuss the advantages and disadvantages of commercially available recording devices in the operating room and focus on the usefulness of the higher-density circular grid.

Local field potential responses associated with perceptual filling-in at blind spot in macaque primary visual cortex.

To understand the neural mechanisms of perceptual filling-in at the blind spot (BS), we analyzed neural activity in the region representing the visual field corresponding to the BS (BS region) in the primary visual cortex (V1) of the macaque monkey. We inserted a linear array electrode into the BS region or surrounding region and recorded the multiunit activities (MUAs) and local field potential (LFP). We examined the responses of MUAs and LFP to a large visual stimulus that entirely covered the BS (surface stimuli) while the monkey performed a visual fixation task in either the monocular condition without receiving direct retinal input or the binocular condition receiving retinal information. We observed clear MUA responses in the deep layers within the BS region under monocular conditions, confirming previous reports that V1 neurons in the BS region are activated when perceptual filling-in occurs. Current source density analysis using LFP showed that MUA responses were mainly observed in layer 5. Although LFP responses were generally stronger in the binocular condition than in the monocular condition, a notable exception was observed in the BS region. LFP responses in the low-beta band in the superficial layers were stronger in the monocular condition than in the binocular condition. These results suggest that low-beta activity in the superficial layer is related to the occurrence of perceptual filling-in in the BS. The origin of this activity is considered to be feedback signals from the extrastriate areas to the V1.NEW & NOTEWORTHY Two characteristic activities were induced in the blind spot (BS) region in response to the stimulus, causing perceptual filling-in: 1) beta-band LFP responses in the superficial layers and 2) neuronal responses in the deep layers, mainly in layer 5. These data suggest that the feedback signal from the extrastriate areas to the BS region in V1 is involved in perceptual filling-in.

Modeling Heater Electrodes on Sheet Metal for Arbitrary Temperature Distributions

We present a method for the design of heater electrodes on substrates with high thermal conductivity such as sheet metal. The substrate is covered with a thin polymer insulation layer on both faces, which are, in turn, carrying screen printed, electrically conductive heater electrodes and another protective polymer overlayer. The temperature inside a predetermined optimization area is required to be as uniform as possible, which is desirable for various high-precision heating applications. We alternatively also aim to design a heater structure to create non-uniform temperature distributions such as a temperature dip, a peak or a gradient. These temperature distributions are required for droplet operations like splitting, merging, and moving droplets, subsequently realizing a newly proposed “lab on metal” approach in microfluidics. For this purpose, an optimization algorithm yields the required distances between linear heater electrodes. The resulting electrode distribution was numerically obtained for different optimization areas. Finally we describe the fabrication of a test device and show infrared measurements of the FEM modeled temperature distributions on the experimental realized heaters. We describe the design of heater electrodes, capable of triggering droplet motion on a “Lab-On-Metal”, as an alternative technology in Lab-On-a-Chip applications.

Electrophysiology of Laminar Cortical Activity in the Common Marmoset.

The marmoset monkey provides an ideal model for examining laminar cortical circuits due to its smooth cortical surface, which facilitates recordings with linear arrays. The marmoset has recently grown in popularity due to its similar neural functional organization to other primates and its technical advantages for recording and imaging. However, neurophysiology in this model poses some unique challenges due to the small size and lack of gyri as anatomical landmarks. Using custom-built micro-drives, researchers can manipulate linear array placement to sub-millimeter precision and reliably record at the same retinotopically targeted location across recording days. This protocol describes the step-by-step construction of the micro-drive positioning system and the neurophysiological recording technique with silicon linear electrode arrays. With precise control of electrode placement across recording sessions, researchers can easily traverse the cortex to identify areas of interest based on their retinotopic organization and the tuning properties of the recorded neurons. Further, using this laminar array electrode system, it is possible to apply a current source density analysis (CSD) to determine the recording depth of individual neurons. This protocol also demonstrates examples of laminar recordings, including spike waveforms isolated in Kilosort, which span multiple channels on the arrays.

Surface-Electrode Ion Trap Development

We present a segmented linear surface electrode ion trap design that can be used for various applications in optical clocks and quantum computation based on trapped 171Yb+ ions. Our simulations show that calculated trap depth can reach up to several electronvolts and that the pseudopotential minimum of the trap is located above the trap surface at a distance greater than 80 μm. The described pseudopotential simulations and calculations of different trap parameters can be used to design the planar trap with required parameters. This design could be scaled to store a long chain of ions and used for quantum logic applications as well.

Comparative Study of Terminal Cortical Potentials Using Iridium and Ag/AgCl Electrodes.

Brain ischemia induces slow voltage shifts in the cerebral cortex, including waves of spreading depolarization (SD) and negative ultraslow potentials (NUPs), which are considered as brain injury markers. However, different electrode materials and locations yield variable SD and NUP features. Here, we compared terminal cortical events during isoflurane or sevoflurane euthanasia using intracortical linear iridium electrode arrays and Ag/AgCl-based electrodes in the rat somatosensory cortex. Inhalation of anesthetics caused respiratory arrest, associated with hyperpolarization and followed by SD and NUP on both Ir and Ag electrodes. Ag-NUPs were bell shaped and waned within half an hour after death. Ir-NUPs were biphasic, with the early fast phase corresponding to Ag-NUP, and the late absent on Ag electrodes, phase of a progressive depolarizing voltage shift reaching -100 mV by two hours after death. In addition, late Ir-NUPs were more ample in the deep layers than at the cortical surface. Thus, intracortical Ag and Ir electrodes reliably assess early manifestations of terminal brain injury including hyperpolarization, SD and the early phase of NUP, while the late, giant amplitude phase of NUP, which is present only on Ir electrodes, is probably related to the sensitivity of Ir electrodes to a yet unidentified factor related to brain death.

DS12 Experience of electrochemotherapy in cutaneous tumours and skin metastases within a UK specialist tertiary centre

Abstract Electrochemotherapy (ECT) has gained recognition as an effective treatment that uses electrical pulses to permeabilize cell membranes in tumours, enhancing the cytotoxicity of anticancer agents. The National Institute for Health and Care Excellence suggests use of ECT for the management of primary basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) in selected patients after discussion within a specialist skin cancer multidisciplinary team. It also supports ECT as a palliative treatment for metastases in the skin from tumours of nonskin origin and malignant melanoma (MM). The objective of the study was to evaluate the outcomes and complications of ECT with bleomycin when used for palliative and curative intent. A retrospective cohort study of all patients who underwent ECT in a UK tertiary centre was performed between June 2016 and December 2022. Seventy-one patients (28 men and 43 women) with a total of 89 tumours were included in the study (mean age 69 years; range 29–99). Prior treatments included surgery (n = 9; 13%), immunotherapy (n = 14; 20%), radiotherapy (n = 26; 37%) and chemotherapy (n = 18; 25%). The linear array electrode was used in most cases with median sequence of 47 (range 1–500). Electrochemotherapy was used for palliative intent in 73% (n = 52) and for curative intent in 27% (n = 19). For palliation, ECT was used to treat patients with MM (n = 18/52; 35%), SCC (n = 17/52; 33%) and breast cancer metastases (n = 11/52; 21%), often in patients who had progressed despite conventional management. The most common site treated was the lower limb (n = 16/52; 31%). Twenty-two patients in this group had a good or partial response, with reduction in tumour size, and 52% had improvement in their symptoms (n = 27/52). The crude 1-year survival in this group was 83% (n = 43/52). Complications of ECT when used for palliation included pain, ulceration, tonic–clonic seizure and pneumothorax. In those where ECT was used for curative intent, the majority had ECT for BCCs (n = 12/19; 63%). The most common site treated was the head and neck. Resolution was reported in 58% (n = 11/19) and partial response in 11% (n = 2/19), while two patients underwent excision following recurrence. Complications when used for curative intent included ectropion, indented scarring, nerve palsy, ulceration, pain and webbing. In our opinion, ECT may represent a robust and efficacious treatment option particularly for smaller, lower-risk tumours which may produce improved outcomes. Electrochemotherapy may serve as an alternative to surgical intervention, particularly in patients with multiple comorbidities, and can be used for primary tumour management.