Electric Field Coverage Research Articles

Enhancing Electric Field Distribution in the Pancreas for Improved TTFields Therapy: A Computational Modeling Investigation.

Tumor treating fields (TTFields) therapy has shown effectiveness in glioblastoma treatment and holds potential for other cancers. However, its application in pancreatic cancer and the distribution of electric fields in pancreas remain unexplored. This study aims to investigate the electric field distributions in pancreatic regions using different array configurations for TTFields therapy. Computational modelling was employed to simulate electric field distributions, and quantitative analysis was conducted. Human body impedance measurements were used to optimize the electric properties of the model. Various array configurations were examined to assess their impact on the electric field distributions. The study revealed that well-positioned arrays, specifically the combination of 20-piece transducer arrays in anterior-posterior orientation and 13-piece transducer arrays in left-right orientation, consistently achieved electric fields exceeding the 1V/cm threshold in over 99.4% of the pancreas. Even with a reduced number of transducers (13 pieces for both orientations), sufficient electric field coverage was achieved, exceeding the threshold in over 92.9% of the pancreas. Additionally, different array placements within the same orientation were explored to address clinical challenges such as skin rash and patient anatomical variations. This research lays the groundwork for understanding TTFields distribution within the abdomen, offering insights into optimizing array configurations for improved electric field delivery. The findings have the potential to guide practical designs of TTFields devices, enhance treatment efficacy, and improve patient outcomes. These results offer promises of advancing TTFields therapy for pancreatic cancer towards clinical applications, and potentially enhancing treatment efficacy and patient outcomes.

Spatiotemporally dynamic electric fields for brain cancer treatment: an in vitro investigation

Objective. The treatment of glioblastoma (GBM) using low intensity electric fields (∼1 V cm−1) is being investigated using multiple implanted bioelectrodes, which was termed intratumoral modulation therapy (IMT). Previous IMT studies theoretically optimized treatment parameters to maximize coverage with rotating fields, which required experimental investigation. In this study, we employed computer simulations to generate spatiotemporally dynamic electric fields, designed and purpose-built an IMT device for in vitro experiments, and evaluated the human GBM cellular responses to these fields. Approach. After measuring the electrical conductivity of the in vitro culturing medium, we designed experiments to evaluate the efficacy of various spatiotemporally dynamic fields: (a) different rotating field magnitudes, (b) rotating versus non-rotating fields, (c) 200 kHz versus 10 kHz stimulation, and (d) constructive versus destructive interference. A custom printed circuit board (PCB) was fabricated to enable four-electrode IMT in a 24-well plate. Patient derived GBM cells were treated and analyzed for viability using bioluminescence imaging. Main results. The optimal PCB design had electrodes placed 6.3 mm from the center. Spatiotemporally dynamic IMT fields at magnitudes of 1, 1.5, and 2 V cm−1 reduced GBM cell viability to 58%, 37% and 2% of sham controls respectively. Rotating versus non-rotating, and 200 kHz versus 10 kHz fields showed no statistical difference. The rotating configuration yielded a significant reduction (p < 0.01) in cell viability (47 ± 4%) compared to the voltage matched (99 ± 2%) and power matched (66 ± 3%) destructive interference cases. Significance. We found the most important factors in GBM cell susceptibility to IMT are electric field strength and homogeneity. Spatiotemporally dynamic electric fields have been evaluated in this study, where improvements to electric field coverage with lower power consumption and minimal field cancellations has been demonstrated. The impact of this optimized paradigm on cell susceptibility justifies its future use in preclinical and clinical trial investigations.

Finite element analysis of Tumor Treating Fields in a patient with posterior fossa glioblastoma

IntroductionTumor Treating Fields (TTFields) are alternating electric fields at 200 kHz that disrupt tumor cells as they undergo mitosis. Patient survival benefit has been demonstrated in randomized clinical trials but much of the data are available only for supratentorial glioblastomas. We investigated a series of alternative array configurations for the posterior fossa to determine the electric field coverage of a cerebellar glioblastoma.MethodsSemi-automated segmentation of neuro-anatomical structures was performed while the gross tumor volume (GTV) was manually delineated. A three-dimensional finite-element mesh was generated and then solved for field distribution.ResultsCompared to the supratentorial array configuration, the alternative array configurations consist of posterior displacement the 2 lateral opposing arrays and inferior displacement of the posteroanterior array, resulting in an average increase of 46.6% electric field coverage of the GTV as measured by the area under the curve of the electric field-volume histogram (EAUC). Hotspots, or regions of interest with the highest 5% of TTFields intensity (E5%), had an average increase of 95.6%. Of the 6 posterior fossa configurations modeled, the PAHorizontal arrangement provided the greatest field coverage at the GTV when the posteroanterior array was placed centrally along the patient’s posterior neck and horizontally parallel, along the longer axis, to the coronal plane of the patient’s head. Varying the arrays also produced hotspots proportional to TTFields coverage.ConclusionsOur finite element modeling showed that the alternative array configurations offer an improved TTFields coverage to the cerebellar tumor compared to the conventional supratentorial configuration.

Modelling of the focal spot intensity distribution and the off-focal spot radiation in kilovoltage x-ray tubes for imaging

X-ray tubes for medical applications typically generate x-rays by accelerating electrons, emitted from a cathode, with an interelectrode electric field, towards an anode target. X-rays are not emitted from one point, but from an irregularly shaped area on the anode, the focal spot. Focal spot intensity distributions and off-focal radiation negatively affect the imaging spatial resolution and broadens the beam penumbra. In this study, a Monte Carlo simulation model of an x-ray tube was developed to evaluate the spectral and spatial characteristics of off-focal radiation for multiple photon energies. Slit camera measurements were used to determine the horizontal and vertical intensity profiles of the small and the large focal spot of a diagnostic x-ray tube. First, electron beamlet weighting factors were obtained via an iterative optimization method to represent both focal spot sizes. These weighting factors were then used to extract off-focal spot radiation characteristics for the small and large focal spot sizes at 80, 100, and 120 kV. Finally, 120 kV simulations of a steel sphere (d = 4 mm) were performed to investigate image blurring with a point source, the small focal spot, and the large focal spot. The magnitude of off-focal radiation strongly depends on the anode size and the electric field coverage, and only minimally on the tube potential and the primary focal spot size. In conclusion, an x-ray tube Monte Carlo simulation model was developed to simulate focal spot intensity distributions and to evaluate off-focal radiation characteristics at several energies. This model can be further employed to investigate focal spot correction methods and to improve cone-beam CT image quality.

Abstract 4871: Comparative analysis of tumor treating fields using conventional versus alternative array placement for posterior fossa Glioblastoma

Abstract Background: Tumor Treating Fields (TTFields) therapy is an approved treatment modality for glioblastoma. Optimal transducer array placement can be defined by anatomy-based finite element analysis (FEA), which helps to delineate electric field coverage of the tumor. The conventional array placement was designed to provide adequate electric field coverage for supratentorial glioblastomas. There is an alternative array placement configuration for infratentorial tumors, but the extent of coverage to posterior fossa glioblastoma is unknown. Methods: Patient anatomy-based FEA models were created by segmenting MRI images — using the NewSegment algorithm from Statistical Paramedic Mapping 8 — into tissue “masks” utilizing ScanIP from Simpleware (Exeter, UK). The physical properties of each tissue type were first applied to these masks and then boundary conditions for physics modeling was set up within COMSOL Multiphysics (Burlington, MA). COMSOL generated electric field maps were compared for models using the conventional array placement configuration for supratentorial tumors versus the alternative array placement configuration for infratentorial tumors. Electric field-volume histograms (EVHs) and specific absorption rate-volume histograms (SARVHs) were constructed to numerically evaluate the relative and/or absolute magnitude volumetric differences between models. Results: The alternative configuration consists of array placement at the vertex, the bi-occipital regions and the upper neck. The highest EAUC was found at the epidural space surrounding the spinal cord and scalp for both types of configurations, whereas the lowest was located at the tongue and orbits. Using the conventional configuration, the gross tumor volume (GTV) had an electric field area under the curve (EAUC) of 40.5 V/m, volume covered with electric field intensity of 150 V/m (VE150) of 0.01%, 95% electric field intensity (E95%) of 30.9 V/m, E50% of 41.1 V/m, and E20% of 46.6 V/m. The GTV also had a SARAUC of 4.0 W/kg, volume covered with SAR of 6 W/kg (VSAR6) of 0%, SAR95% of 0.6 W/kg, SAR50% of 0.7 W/kg, and SAR20% of 0.8 W/kg. The alternative configuration produced EAUC of 52.3 V/m, VE150 of 3.6%, E95% of 29.1 V/m, E50% of 44.7 V/m, and E20% of 58.1 V/m, as well as SARAUC of 0.9 W/kg, VSAR6 of 0.3%, SAR95% of 0.6 W/kg, SAR50% of 0.8 W/kg, and SAR20% of 0.9 W/kg. Conclusions: The alternative array placement configuration provides a higher coverage of electric field (+29%) to the posterior fossa glioblastoma when compared to the conventional configuration. Citation Format: Edwin Lok, Pyay San, Victoria White, Eric T. Wong. Comparative analysis of tumor treating fields using conventional versus alternative array placement for posterior fossa Glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4871.

Electric field distribution in relation to cell membrane electroporation in potato tuber tissue studied by magnetic resonance techniques

Abstract Magnetic resonance electrical impedance tomography (MREIT) enables determination of electric field distribution during electroporation in which cell membrane permeability is increased by application of an external high electric field. In this study, MREIT was performed for the first time to predict electroporated areas in a pulsed electric field (PEF) treated vegetable tissue. The study was performed on potato tubers using different amplitudes of electric pulses and results were evaluated also by means of multiparametric MRI. MREIT determined regions of electric field distribution corresponded to visible darkened areas of the treated potatoes, as well to the results of multiparametric MRI. Results of this study suggest that MREIT could be used as an efficient tool for improving the effectiveness of PEF treatment applications. Industrial relevance This study presents a method capable of determining electric field distribution during PEF treatment using magnetic resonance electrical impedance tomography. The method has a practical value as it can potentially enable monitoring of the outcome of PEF applications which strongly depends on local electric field. Measurement of electric field distribution would enable detection of insufficient electric field coverage before the end of the PEF treatment, thus increasing and assuring its effectiveness.

Parametric study of irreversible electroporation with different needle electrodes: Electrical and thermal analysis

Purpose: Irreversible electroporation (IRE) is a new tumour ablation method used in cancer treatment procedures. In a successful IRE treatment it is crucial to impose minimum thermal damage to the tumour and its surrounding healthy tissue, while subjecting the entire tumour to a strong electric field. Method: Here we present a 3D model of a subcutaneous tumour in a four-layer skin using a geometry-based finite element approach. Four common needle electrode configurations were studied in this paper. The study evaluated six essential factors which are important in the electrical and thermal distributions in tumour and normal tissue. Results: The results revealed that a hexagonal 3 × 3 geometry provides the maximum electrical coverage of the tumour, compared to other electrode configurations. However, in some cases the hexagonal 2 × 2 geometry can ablate the entire tumour with less damage to normal tissue. We found that the deeper insertion of 2- and 4-electrode geometries can lead to more damage to healthy tissue. The results also indicate that the insertion of the electrodes into tumour tissue can increase thermal damage dramatically due to existing large electrical conductivity. Conclusion: These findings suggest that needle electrodes should not be placed within the tumour tissue if the goal is to prevent thermal damage. This method can be used as a trade-off between electric field coverage in tumour tissue and thermal damage to both tumour and normal tissue.

Ex Vivo and In Silico Feasibility Study of Monitoring Electric Field Distribution in Tissue during Electroporation Based Treatments

Magnetic resonance electrical impedance tomography (MREIT) was recently proposed for determining electric field distribution during electroporation in which cell membrane permeability is temporary increased by application of an external high electric field. The method was already successfully applied for reconstruction of electric field distribution in agar phantoms. Before the next step towards in vivo experiments is taken, monitoring of electric field distribution during electroporation of ex vivo tissue ex vivo and feasibility for its use in electroporation based treatments needed to be evaluated. Sequences of high voltage pulses were applied to chicken liver tissue in order to expose it to electric field which was measured by means of MREIT. MREIT was also evaluated for its use in electroporation based treatments by calculating electric field distribution for two regions, the tumor and the tumor-liver region, in a numerical model based on data obtained from clinical study on electrochemotherapy treatment of deep-seated tumors. Electric field distribution inside tissue was successfully measured ex vivo using MREIT and significant changes of tissue electrical conductivity were observed in the region of the highest electric field. A good agreement was obtained between the electric field distribution obtained by MREIT and the actual electric field distribution in evaluated regions of a numerical model, suggesting that implementation of MREIT could thus enable efficient detection of areas with insufficient electric field coverage during electroporation based treatments, thus assuring the effectiveness of the treatment.

On Multipath Propagation in Electrically Large Reflective Spaces

A simple model for predicting the characteristic energy decay time of wireless RF emissions in confined, reflective spaces is presented. Based on this cavity decay time, accurate estimates of room quality factor, diffuse (multipath propagation) insertion loss, and statistical electric field coverage can be easily obtained. Spaces of interest for model applications include aircraft cabins, below-deck compartments in ships, metallic storage buildings and reflective room enclosures. Decay time predictions are shown to be in excellent agreement with measured data in a reverberant test chamber over the 110 GHz frequency range.

Research on the Radiation Characteristics of Patched Leaky Coaxial Cable by FDTD Method and Mode Expansion Method

Patched leaky coaxial cable (PLCX) is proposed as an alternative to the conventional leaky cable for wireless links in a complex environment. It is expected to have the capability of adjusting the coupling between the cable and the environment and give smoother electric field coverage. In this paper, the radiation characteristics of the PLCX with general inclined patches are studied by a hybrid method that involves the finite-difference time-domain (FDTD) method for the near-field computation and the mode expansion method for the transformation of near field to far field. In the method, the space around the patched leaky cable is divided into two regions by an artificial closed cylindrical surface that is incorporated with the FDTD lattice surface when implementing the FDTD iteration. The field distribution on the artificial surface is obtained after the implementation of the FDTD method. Meanwhile, the field outside the artificial boundary is expanded in terms of the Floquet modes with coefficients to be determined. By matching the field expressed by modes and the field obtained from the FDTD method at the artificial boundary, a matrix equation with unknown coefficients is obtained. Solving this matrix equation, the expansion coefficients are known, and the field outside the artificial boundary is ready to be obtained.

Technique: Large‐scale ionospheric conductance estimated from combined satellite and ground‐based electromagnetic data

A technique for estimating the large‐scale spatial distribution of the height‐integrated electrical conductivity (conductance) of the Earth's high‐latitude ionosphere is presented. By combining satellite magnetic perturbation data with ground‐based magnetometer and HF radar observations the Hall (ΣH) and Pedersen (ΣP) conductances are independently calculated. Magnetic perturbations observed at the Earth's surface are combined with those recorded by satellites to calculate the horizontal ionospheric current (⊥). Combined HF radar and satellite ion drift data give the ionospheric electric field (⊥), which combined with ⊥ allows ΣH and ΣP to be estimated from Ohm's law. Conductance results from preliminary application of the technique to an event with a 1 hour integration time are presented. Significant uncertainties arise due to sparse ground magnetometer and electric field coverage. The resulting conductance distribution shows an enhancement in the auroral regions as expected from a statistical model conductance. However, the calculated conductance enhancement is located between the region 1 and region 2 Birkeland currents. This agrees with the statistical model data in the morning sector but disagrees in the evening sector. Comparison of the conductance results with conductance data inferred from in situ precipitating particle observations shows colocated enhancements. The calculated data also show a low (&lt;1) Hall to Pedersen conductance ratio in regions near downward Birkeland current.