Pair Of Arrays Research Articles

Virtual antenna array for reduced energy per bit transmission at Sub-5 GHz mobile wireless communication systems

This paper presents an innovative technique to synthesize a virtual antenna array (VAA) that consumes less energy than conventional antenna arrays that are used in mobile communications systems. We have shown that for a specific spectral efficiency a wireless system using the proposed virtual antenna array consumes significantly less energy per bit (∼3 dB) than a wireless system using a conventional multiple-input multiple-output (MIMO) array. This means the adoption of the proposed VAA technology in smartphones, iPad, Tablets and even base-stations should significantly reduce the carbon footprint of wireless systems. The proposed VAA is realized by employing a pair of linear antenna arrays that are placed in an orthogonal configuration relative to each other. This orthogonal arrangement ensures the radiation is circularly polarized. The size of the standard radiating elements constituting the VAA were miniaturized using the topology optimization method. The design of the VAA incorporates substrate integrated waveguide (SIW) and metasurface technologies. The function of SIW in the design was twofold, namely, to reduce energy loss in the substrate on which the VAA is implemented, and secondly to mitigate unwanted electromagnetic interactions between the neighboring radiating elements and thereby enhancing isolation which otherwise would degrade the radiation characteristics of the array. Metasurface technology served to effectively increase the effective aperture of the array with no impact on the footprint of the array. The consequence of SIW and metasurface technologies was improvement in the gain and radiation efficiency of the array. The proposed four orthogonal 4-element VAA covers the entire sub-5 GHz frequency range, and it radiates bidirectional in the azimuth plane and omni-directional in the elevation plane. Moreover, it is relatively easy to design and fabricate. The proposed VAA has dimensions of 0.96λ0 × 0.96λ0 × 0.0016λ0 at mid-band frequency of 3 GHz. VAA has a measured gain of 25 dBi and radiates with 90% efficiency. The average isolation between the linear arrays constituting the virtual array is better than 27 dB.

Two-dimensional Golay complementary array pairs with flexible size and large zero correlation zone

Two-dimensional Golay complementary array pairs with flexible size and large zero correlation zone

The Impact of Scalp's Temperature on the Choice of the Best Layout for TTFields Treatment

Background and ObjectivesTumor Treating Fields (TTFields) is an FDA-approved technique used in the treatment of glioblastoma. It consists in applying an electric field (EF) with a frequency of 200 kHz using two pairs of transducer arrays. During treatment planning, the NovoTAL system is used to strategically place the arrays on the head in regions that maximize the EF at the tumor. Current should be injected at least 18 hours/day and induce a minimum EF of 1 V/cm at the tumor. To avoid any thermal harm to the patient, the temperature of the scalp is kept around 39.5°C by changing the injected current. The goal of this study was to investigate how accounting for the temperature of the scalp during treatment planning might affect the choice of the best layout suggested by NovoTAL. Furthermore, we also studied the sensitivity of the results to the metric used to evaluate the layouts. MethodsWe used a realistic head model with a virtual glioblastoma in our studies. Through the NovoTAL system we obtained five realistic array layouts and we predicted the best one for our model based on the approach currently implemented in this system. We then repeated the same type of analysis, but also accounting for the temperature during planning. In both cases we ranked the layouts based on three different criteria: the LMiPD and the LAPD (local minimum and local average power densities, respectively) in the tumor and the SAR (specific absorption rate) in the head ResultsAccounting for the temperature does not significantly affect the choice of the best layout provided that the arrays are at least 1 cm apart from each other. Otherwise, a common temperature hotspot occurs in the scalp between the closest transducers of the adjacent arrays, which limits how much current can be injected and consequently treatment effectiveness. Also, the choice of the best layout depends on the criterion used. ConclusionsAccounting for the temperature might led to significant variations in the current injected. The LMiPD might be used as a first criterion to choose the best treatment layout, followed by the LAPD and then the SAR.

Performance of CdS/TNTAs Nanocomposite in Removing Ciprofloxacin and Hydrogen Production using Simultaneously Electrocoagulation-Photocatalysis Process

This study used CdS as a pair of TiO2 Nanotube Arrays (TNTAs), considering the position and width of the energy band gap, which is expected to increase photocatalyst performance. The nancomposite was synthesized using the successive ionic layer adsorption reaction (SILAR) method, with Cd(CH3COO)2 and Na2S as precursors. The CdS/TNTAs nanocomposite is expected to reduce the energy band gap to enable the visible and UV spectrum to activate the photocatalyst. Additionally, the formed heterojunction mechanism provides opportunities for the trajectories of electrons and holes to be farther apart and reduce the recombination rate. The degradation ability of CdS/TNTAs nanocomposite in the photocatalytic process was evaluated using samples of ciprofloxacin liquid waste as an antibiotic, which is quite challenging to decompose completely. The ability of the photocatalytic process to produce hydrogen gas was also observed and its performance synergized with the electrocoagulation process. The result showed that the use of CdS as a TNTAs partner in CdS/TNTAs nanocomposites affects increasing photocatalyst performance, both in degrading ciprofloxacin and producing hydrogen gas. Furthermore, the CdS/TNTAs nanocomposite increased the photocatalytic process’s ability to degrade ciprofloxacin and produce hydrogen from 8.5 to 20.5% and 6 to 23.5 mmol/m2 compared to using TNTAs alone. The processing capability is further enhanced when run in synergy with the electrocoagulation process where the removal of ciprofloxacin reaches 86.55% and the hydrogen produced is 2.62×106 mmol/m2. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

MODL-13. Sensitivity of Tumor Treating Fields (TTFields) treatment planning to healthy tissue segmentation inaccuracies

Abstract TTFields are FDA approved for treating patients with GBM. TTFields utilize low intensity electric fields with intermediate frequency (100-500 kHz) that disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields have been shown to disrupt multiple phases of the cell cycle including metaphase, anaphase, and telophase, resulting in cellular apoptosis. TTFields are administered through two pairs of capacitive arrays placed on the patient’s scalp. As TTFields are a dose dependent therapy, optimization of array layout for maximizing field intensity may improve survival rates of patients. Thus, Novocure is developing a treatment planning system, in which MR images are used to create a patient-specific model, which in turn is used for simulating electric fields distribution. However, the segmentation process of the MRIs is prone to errors that may influence the choice of array layout, and consequently provide lower TTFields dose than possible. To test the sensitivity of layout chosen to such inaccuracies, we placed different array layouts on the highly detailed MIDA head model and simulated the resulting LMiPD from each configuration. We then simplified the model in several phases and compared the resulting array layout ranking between the full model and each simplified model. Our results show that though the calculated LMiPD is very sensitive to the quality of the model, the ranking pattern between the detailed and simplified models is similar. Some alterations do occur, but this mostly happens when the LMiPD values between switched layouts are very close, rendering these alterations clinically insignificant. Based on these results, we conclude that the ranking order of array layouts by LMiPD dose does not significantly change between detailed and simplified head models even though the LMiPD dose itself is sensitive to the quality of the head model.

MODL-07. Sensitivity of Tumor Treating Fields (TTFields) treatment planning to tumor segmentation errors

Abstract Tumor Treating Fields (TTFields) are electric fields that disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields are administered through two pairs of capacitive arrays placed on the patient’s scalp. The effect of TTFields has been shown to be dose dependent. An in-silico study based on imaging and survival data from the phase 3 EF-14 study demonstrated a correlation between simulated field intensity and overall survival. Novocure is developing a simulation-based patient-specific treatment planning system aimed towards maximizing TTFields dose delivered to the patient’s tumor. Different options are presented to the treating physician that are ranked based on dose. To create patient-specific planning, physicians are required to segment the pathological tissues on a T1-weighted MRI. These tissues may include the enhancing tumors, resection cavity and necrotic core. Segmentation of medical images is an error-prone procedure. Such errors may influence the calculation of expected TTFields dose delivered to the tumors. In this work, we examined how different segmentations of the tumors affect the delivered dose, by placing mock tumors of different compositions within a simplified ellipsoidal model. Simulations were then used to assess field distributions in these tumors. Tumors of different enhanced volumes were then compared by LMiPD values. Our results show that 10% differences in the segmented enhancement result in less than 5% relative error in LMiPD. To enforce the validity of the simplified model, we performed the same analysis for two patient specific models. In both cases, the relative difference in segmentation was about 5%, and consequent errors in LMiPD was <5% as well. In conclusion, when using a simulation-based TTFields treatment planning system, small differences in the segmentation of the enhancing component of mock glioblastoma tumors in both simplified ellipsoid and patient specific models lead to small differences in LMiPD.

MODL-21. EFFICACY OF DIFFERENT LAYOUTS IN TREATING INFRATENTORIAL TUMORS WITH TUMOR TREATING FIELDS (TTFIELDS)

Abstract TTFields are an anti-mitotic technique used to treat solid tumors by delivering low-intensity (1–4 V/cm) alternating electric fields to the tumor, with frequencies between 100–500 kHz. This modality is FDA-approved for treating glioblastoma (GBM). Administration of TTFields is conducted using two pairs of transducer arrays placed on the patient’s scalp. The layouts of the transducer arrays is a key factor in determining the field distribution within the patient’s body. The NovoTAL system is used for determining the array layouts used for supratentorial tumors. In previous works, we suggested layouts for infratentorial layouts, as well as layouts that target the entirety of the brain with field distribution of higher uniformity. However, in some clinical cases, patients may have an infratentorial tumor and a single supratentorial tumor simultaneously. In such a situation, the question of whether we can treat both tumors with an infratentorial layout arises. In this work, we examined all GBM available layouts (NovoTAL, infratentorial and whole brain). We used a realistic healthy patient model (Duke, by ITI’S, Zurich, Switzerland) to assess field distributions resulting for the different layouts. We then created maps of expected TTFields dose for a 10 cm sized tumor placed in each point in the brain, and ranked the different regions by best layout groups. Our results show that for infra-ventricular tumors, the whole brain layouts may provide higher field distributions than any of the NovoTAL or infratentorial layouts. For supra-ventricular tumors, NovoTAL layouts provide stronger fields. A transition zone in which both layout groups provided similar results was observed as well. We conclude that the best option of currently available transducer array layouts for treating the presented clinical case depends on the location of the supratentorial tumor, whether it is above the large ventricles or beneath them.

Sensitivity of TTFields Dose Distribution in the Lungs to the Deviations in Array Placement

<h3>Purpose/Objective(s)</h3> Tumor Treating Fields (TTFields) are an anti-mitotic novel therapy, utilizing low-intensity alternating electric fields to arrest cell proliferation. The effect of TTFields is dose dependent: higher field intensities correlate with better survival rates for patients. TTFields are currently FDA-approved for treating Glioblastoma Multiforme (GBM) and Malignant Pleural Mesothelioma (MPM). The technology is currently begin tested for other diseases, such as Non-Small Cell Lung Cancer. TTFields are delivered using two pairs of arrays, placed on the patient's skin. The distribution of the fields is determined by the electric properties of the tissues and by the geometry of the patient and the system. Thus, the location of the arrays on the patient's body has a significant influence on the TTFields dose that is received at the tumor. The array layout (TAL) is prescribed according to clinical guidelines for thoracic disease, taking into account the size of the patient. However, actual placement of the arrays may pose challenges. Lung cancer patients also have shunts that may overlap the location of the arrays. In addition, areas with skin damage due to surgery or radiation therapy may prevent placing the arrays on their location, ultimately resulting in different field distributions than expected. In this work, we examined the sensitivity of the field distribution in the lungs to the array placement. <h3>Materials/Methods</h3> Using a simulation platform, we have simulated the electric field distribution within a healthy human model (Duke, by ITI'S foundation, Zurich). We applied boundary conditions on surfaces of different sizes adhered to the model's skin. The surfaces where in different sizes (25% to 121% of the area of the actual arrays used for the thorax) and locations (top of the lung, center and lower). We then analyzed the field distribution in the lungs resulting from each placement and compared it to the distribution from a surface roughly at the size of the real-world arrays. We also analyzed the resistance of the model in each case since this has implications on actual current delivery. <h3>Results</h3> Analysis of the resistance showed that it is highly sensitive to the size of the arrays, with resistance increasing by up to 2.5-fold from the baseline size. However, the array location had little impact on the resistance, with a span of 3Ω over a resistance of 45Ω for the smallest arrays, which showed the highest variability. The lung region with higher field intensities has moved with the array location, and in general stayed near the centerline connecting the arrays. However, therapeutic levels may still be reached outside this area, but field intensities will decrease as we go further from the arrays. <h3>Conclusion</h3> Our results show that the field intensities in the lungs are sensitive to the location of the arrays. Nevertheless, as the arrays get larger, the regions being treated effectively stayed nearly the same.

Examining Array Layouts for Targeting a Single Lung with TTFields

<h3>Purpose/Objective(s)</h3> Tumor Treating Fields (TTFields) are an anti-mitotic novel therapy, utilizing low-intensity alternating electric fields to arrest cell proliferation. TTFields are currently FDA-approved for treating Glioblastoma Multiforme (GBM) and Malignant Pleural Mesothelioma (MPM). The effect of TTFields is dose dependent: higher field intensities correlate with better survival rates for patients. TTFields are delivered using two pairs of arrays, placed on the patient's skin. The distribution of the fields is determined by the electric properties of the tissues and by the geometry of the patient and the system. Thus, the location of the arrays on the patient's body has a significant influence on the TTFields dose he or she may get. The array layout (TAL) is prescribed according to clinical guidelines for thoracic disease, taking into account the size of the patient. These guidelines are meant to target both lungs as a whole. However, in MPM patients, the disease is usually concentrated in one lung. In this study, we examined how placing one channel over a single lung and modifying the lateral channel will affect field distribution in the lungs. <h3>Materials/Methods</h3> To test new layouts, we placed cylinders imitating the arrays on the skin of a realistic human computerized model. We then used a simulation platform to simulate the TTFields distribution resulting from the different layouts. We tested the recommended layout by the guidelines, in which all four arrays are placed on the front and back of the thorax and are coupled in a cross formation (i.e., posterior left with anterior right and vice versa). We then compared this to layouts where one channel is focused around the right lung (front and back), paired with a layout in which one array is placed at the front or back of the left lung and the other under the right armpit. A current of 4A was set for channels consisting 20-disks arrays while a current of 2.6A was set for channels consisting at least one 13-disks array. For each layout, we calculated the average field intensity delivered to each lung. <h3>Results</h3> For patients receiving the recommended layout, average field intensity resulting from the recommended layout was 1.69 V/cm for each lung. The modified layouts provided 1.6-1.68 V/cm for the right lung, and 0.88-0.99 V/cm to the left lung. In terms of local minimum power density (LMiPD), the recommended layout provided 0.83 mW/cm³ for both lungs, while the modified layouts provided 0.62-0.81 mW/cm³ and 0.22-0.27 mW/cm³ to the right and left lungs, respectively. <h3>Conclusion</h3> Our results show that for patients eligible to be treated with the large cross layout, the modified single-lung layouts are not expected to provide a benefit in terms of TTFields dose. This is due the need for smaller arrays under the armpits, which reduces the expected output current from the device. However, further investigation is required for patients that are prescribed smaller arrays according to the guidelines.

A Low-Profile Dual-Band Directional Antenna for Unmanned Aerial Vehicle Applications

A low-profile dual-band directional antenna operating at both 2.4 and 5 GHz for wireless local area networks (WLANs) for unmanned aerial vehicles (UAVs) applications is proposed in the paper. Two pairs of dipole antenna arrays with different electrical lengths are utilized to achieve dual-band directional radiation performance, which is desirable for a remote-control unit of the UAVs. Note that the directional radiation characteristic is obtained according to the double-dipole antennas driven by antiphase signals (W8JK), provided the distances between different dipole antennas are properly optimized. Note that the distance between the two longer dipoles, as well as the two shorter dipoles, can be calculated by equations. For each pair of dipoles with equal electrical lengths, an antiphase along the two dipoles can be obtained, and directional radiation characteristics can be achieved in the dual band. Coplanar strips (CPS) are employed as feeding networks, which lie on the same substrate layer as the antenna arrays, resulting in a low profile of merely 0.762 mm. Also, the overall size of the antenna together with the feeding network is 58.42 × 32.58 × 0.762 mm3. To verify the performance of the proposed antenna, a prototype is fabricated and measured. The measured gain is 5.2 and 7.0 dBi, respectively, in the 2.4 and 5.8 GHz bands. The measured reflection coefficients as well as radiation patterns are consistent with those of the simulated results. The proposed antenna scheme can be a good candidate for UAV applications with the advantages of a lower profile, dual-band characteristics, directional radiation characteristics, and a simple assembly. Since the remote-control unit operates at 2.4 GHz and 5.8 GHz to control the UAV unit, the low-profile dual-band directional radiation antenna has extensive application prospects when integrated into the space-limited unit.

A z-gradient array coil with a dedicated active-shielded array coil for MRI.

An array-based z-gradient coil with a set of programmable power amplifiers can outperform a conventional z-gradient coil and make it highly customizable with a broader range of tunable features. A dynamically adjustable imaging volume can be achieved using a pair of independent arrays and a modified optimization procedure based on analytic equations. Two modes of operation are provided: (a) standard mode that resembles a conventional coil; (b) advanced mode, where all performance parameters can be adjusted employing a controllable feeding mechanism. Commercial software is used to demonstrate the validity and feasibility of the proposed coil. Primary and shield array diameters are 24 and 30 cm, both of which comprise 12 bundles of 10 turns copper wires. Maximum feeding voltage/current is 250 V/100 A for all array elements. Four distinct magnetic profiles are provided: (a) conventional profile with 140 mm diameter spherical region of interest, 120 mT/m gradient, and up to 4500 T/m/s slew rate; (b) profile of 200 mT/m, 70 mm region of interest, and up to 6900 T/m/s slew rate; (c) 60 mm axially shifted 70 mm region of interest with 120 mT/m strength and 3600 T/m/s slew rate; and (d) profile of 370 mT/m, 120 mm region of interest, and 3700 T/m/s slew rate when the active shield is reverse fed. By using an active-shielded gradient array coil, the magnetic field profile of the imaging volume can be adjusted dynamically, and it can provide new features and a wide range of field profiles for diverse applications in MRI.

Anesthetic modulations dissociate neuroelectric characteristics between sensory-evoked and spontaneous activities across bilateral rat somatosensory cortical laminae

Spontaneous neural activity has been widely adopted to construct functional connectivity (FC) amongst distant brain regions. Although informative, the functional role and signaling mechanism of the resting state FC are not intuitive as those in stimulus/task-evoked activity. In order to bridge the gap, we investigated anesthetic modulation of both resting-state and sensory-evoked activities. We used two well-studied GABAergic anesthetics of varying dose (isoflurane: 0.5–2.0% and α-chloralose: 30 and 60 mg/kg∙h) and recorded changes in electrophysiology using a pair of laminar electrode arrays that encompass the entire depth of the bilateral somatosensory cortices (S1fl) in rats. Specifically, the study focused to describe how varying anesthesia conditions affect the resting state activities and resultant FC between bilateral hemispheres in comparison to those obtained by evoked responses. As results, isoflurane decreased the amplitude of evoked responses in a dose-dependent manner mostly due to the habituation of repetitive responses. However, α-chloralose rather intensified the amplitude without exhibiting habituation. No such diverging trend was observed for the spontaneous activity, in which both anesthetics increased the signal power. For α-chloralose, overall FC was similar to that obtained with the lowest dose of isoflurane at 0.5% while higher doses of isoflurane displayed increased FC. Interestingly, only α-chloralose elicited relatively much greater increases in the ipsi-stimulus evoked response (i.e., in S1fl ipsilateral to the stimulated forelimb) than those associated with the contra-stimulus response, suggesting enhanced neuronal excitability. Taken together, the findings demonstrate modulation of the FC profiles by anesthesia is highly non-linear, possibly with a distinct underlying mechanism that affects either resting state or evoked activities differently. Further, the current study warrants thorough investigation of the basal neuronal states prior to the interpretation of resting state FC and evoked activities for accurate understanding of neural signal processing and circuitry.

Two-Dimensional Golay Complementary Array Pairs/Sets With Bounded Row and Column Sequence PAPRs

The one-dimensional (1-D) Golay complementary set (GCS) has many well-known properties and has been widely employed in communications engineering. The concept of 1-D GCS can be extended to the two-dimensional (2-D) Golay complementary array set (GCAS) where the 2-D aperiodic autocorrelations of constituent arrays sum to zero except for the 2-D zero shift. The 2-D GCAS includes the 2-D Golay complementary array pair (GCAP) as a special case when the set size is 2. In this paper, 2-D generalized Boolean functions are introduced and constructions of 2-D GCAPs, 2-D GCASs, and 2-D Golay complementary array mates based on generalized Boolean functions are proposed. Explicit expressions of 2-D Boolean functions for 2-D GCAPs and 2-D GCASs are given. Therefore, they are all direct constructions without the aid of other existing 1-D or 2-D sequences. Moreover, the peak-to-average power ratio (PAPR) properties of the column sequences and row sequences of the constructed 2-D GCAPs and 2-D GCASs are investigated and the PAPRs are proved to be upper bounded.

Constructions of two-dimensional Z-complementary array pairs with large ZCZ ratio

Constructions of two-dimensional Z-complementary array pairs with large ZCZ ratio

Undulators Consisting of Magnetized Helices

A ferromagnetic helix magnetized axially or radially is apparently the simplest helical undulator. Four helices with alternating magnetization can provide a stronger helical field than a pair of conventional planar Halbach arrays. Such undulators and microundulators seem promising for various powerful high frequency sources. The fields of infinite helices uniformly magnetized in the longitudinal and radial directions are found analytically by integration of contributions from elementary dipoles. The analytical values of the field magnitudes are close to the numerically calculated ones for a helix with a relatively small number of periods five–ten. According to simulation, a magnitude of about 1 T can be obtained on the axis of a system of helices with small inner radii.

Moiré graphene nanoribbons: nearly perfect absorptions and highly efficient reflections with wide angles.

The strong absorption and reflection from atomically thin graphene nanoribbons has been demonstrated over the past decade. However, due to the significant band dispersion of graphene nanoribbons, the angle of incident wave has remained limited to a very narrow range. Obtaining strong absorption and reflection with a wide range of incident angles from atomically thin graphene layers has remained an unsolvable problem. Here, we construct a tunable moiré superlattice composed of a pair of graphene nanoribbon arrays to achieve this goal. By designing the interlayer coupling between two graphene nanoribbon arrays with mismatched periods, the moiré flat bands and the localization of their eigen-fields was realized. Based on the moiré flat bands of graphene nanoribbons, highly efficient reflection and nearly perfect absorption was achieved with a wide range of incident angles. Even more interesting, is how these novel phenomena can be tuned through the adjustment of the graphene's Fermi energy, either electrostatically or chemically. Our designed moiré graphene nanoribbons suggest a promising platform to engineer moiré physics with tunable behaviors, and may have potential applications in the field of wide-angle absorbers and reflectors in the mid-infrared region.

Production and loss of O2(1Δ g ) at atmospheric pressure using microwave-driven microplasmas

We have used arrays of microwave-generated microplasmas operating at atmospheric pressure to generate high concentrations of singlet molecular oxygen, O2(1Δ g ), which is of interest for biomedical applications. The discharge is sustained by a pair of microstrip-based microwave resonator arrays which force helium/oxygen gas mixtures through a narrow plasma channel. We have demonstrated the efficacy of both NO and less-hazardous N2O additives for suppression of ozone and associated enhancement of the O2(1Δ g ) yield. Quenching of O2(1Δ g ) by ozone is sufficiently suppressed such that quenching by ground state molecular oxygen becomes the dominant loss mechanism in the post-discharge outflow. We verified the absence of other significant gas-phase quenching mechanisms by measuring the O2(1Δ g ) decay along a quartz flow tube. These measurements indicated a first-order rate constant of (1.2 ± 0.3) × 10−24 m3 s−1, slightly slower than but consistent with prior measurements of singlet oxygen quenching on ground state oxygen. The discharge-initiated reaction mechanisms and data analysis are discussed in terms of a chemical kinetics model of the system.

Collective Resonances of a Twisted Plasmonic Array Pair

Plasmonic SLR (surface lattice resonance) has sharp and intense extinction or absorption peaks, which facilitates a variety of optical and spectral applications, e.g., optical filters, absorbers, reflectors, sensors, etc. In this work, we propose a plasmonic array pair structure composed of two stacked finite square array panels. By twisting it, its plasmonic SLR changes, since the break of periodicity alters the inter-layer plasmonic coupling. Numerical simulation is carried out using the DDA (discrete dipole approximation) method. Simulation results show that its optical properties such as extinction spectra/absorption spectra change dramatically when the two-layer structure is twisted by only a small angle. More interestingly, two resonance peaks at different wavelengths show an inverse trend while twisting, one gets lower and broader, while the other gets higher and narrower. Dipole mapping of amplitude and phase is checked to reveal the plasmonic coupling under twist. The influence of environment/material permittivity on spectra is also examined. Results introduced in this work may work as a scientific tool to reveal more properties of plasmonic SLR and can serve as an angle sensor, tunable optical filter, chiral sensor, etc.

Treating Spinal-Cord Tumors with TTFields — A Simulation Study

<h3>Purpose/Objective(s)</h3> Tumor Treating Fields (TTFields) are an anti-mitotic non-invasive therapy approved for the treatment of certain solid tumors such as glioblastoma (GBM) and malignant pleural mesothelioma (MPM). TTFields are low intensity electrical fields in the medium frequency range (100-500 kHz). TTFields are applied to the patient using two pairs of transducer arrays (TAs) placed on the patient skin. The therapeutic threshold for treatment is considered to be 1 V/cm. The distribution of the electric field within the body is determined by the geometry of the arrays, the anatomical area being treated, and the electric parameters of the different tissues, specifically their electrical conductivity. Treatment planning is necessary to maximize the efficacy of the treatment. However, some regions of the body are more challenging to treat with TTFields due to their geometrical characteristics. One such example is the spinal cord. The spinal cord is an elongated structure with high electric conductivity encompassed within relatively electrically insulating bone structure of the spine. This results in a cable-like structure. The unique structure of the spine makes delivering TTFields to spinal tumors a non-trivial task. While the electric fields can propagate well along the spinal cord, they cannot easily penetrate the vertebrae to reach the spinal cord. In this study, we used simulations to establish ground rules for treating the spinal cord. Specifically, we tested the feasibility of using TTFields for treating leptomeningeal metastases of breast cancer. <h3>Materials/Methods</h3> A realistic computational full body model of a healthy female was used in the study. Virtual transducer arrays were placed on the model's back at different heights, to the left and right of the spine. Arrays were also placed on the head and hips of the model. To simulate the delivery of TTFields to the spinal cord and CSF, we used Sim4Life v6.0 (ZMT Zürich) Ohmic-quasi-static solver. We applied 1A current at 150 kHz to the virtual arrays. In each simulation, we paired one array on the left to one array on the right, with different heights. The resulting field distribution along the spinal cord, CSF and nerves was then extracted. <h3>Results</h3> The field distribution has been analyzed along the axial plane of the patient. The mean field value for every slice was calculated, and the resulting axial-distribution was compared to the location of the two arrays along the models back. The results show that the maximal slice-averaged field intensity in the spinal cord is obtained between the arrays and in most cases is above the required 1 V/cm. <h3>Conclusion</h3> This work demonstrates that by orthogonally positioning the two pairs of arrays on the patient back to surround the tumor area, it may be possible to provide sufficient field intensity to tumors within the CSF or of the spinal cord.

Abstract 1317: inovivo: a dedicated system for delivery of therapeutic level Tumor Treating Fields (TTFields) to mice

Abstract Purpose/objective: Tumor Treating Fields (TTFields) therapy is a noninvasive antineoplastic treatment modality that is FDA approved for treatment of glioblastoma and malignant pleural mesothelioma. TTFields are delivered to the patient continuously by 2 pairs of transducer arrays attached to the skin. In vivo TTFields experiments were so far limited due to the lack of a dedicated animal delivery system. Two main challenges are associated with TTFields application to the animal: 1) there is an absolute requirement for adequate and continuous contact between the electrodes and the animal skin throughout treatment; and 2) the wires connected to the electrodes require individual housing and limit animal movement, thus imposing stress. This work aimed to develop an in vivo system for continuous TTFields delivery to mice bearing cancer tumors in the torso or flank while addressing these challenges. Materials/Methods: To tackle the challenges and develop a viable in vivo system, several solutions were tested: 1) various electrode layouts; 2) a variety of adhesive materials; and 3) devices for preventing wire entanglement. Results: The final design of the transducer array electrodes included 2 adhesive layers, an inner layer for improved adherence, and an outer layer for securing the electrodes to the skin. Conductors were compacted into a single printed circuit cable connected to a novel electric swivel machine, that prevented cable coiling by sensing and rotating according to animal movement. These improvements resulted in fewer electrode entanglements and replacements, and thus in higher compliance (continuity) and less need for animal handling. To further reduce the impact of stress factors on the mice, a new cage was developed, that allows for 2 mice to be housed separately while still maintaining an interaction with one another. Indeed, animals treated with the inovivo system for 1-week displayed lower weight loss than animals treated with the previous non-dedicated system, indicative of reduced stress. Simulation were performed to ensure electric fields were indeed generated at the desired locations, showing above threshold TTFields intensities around the tumor for the flank subcutaneous model. For the torso orthotopic model, TTFields were shown to generate effective electric fields in the lung, liver, and pancreas, suggesting tumors in these organs may be treated effectively using the inovivo system. Conclusion: The new inovivo system provides means for continuous, 2 directions TTFields delivery to tumors in the torso or flank while minimizing stress on the mice. The inovivo system thus provides a tool for conducting TTFields experiments in mice, facilitating further in vivo studies for gaining additional mechanistical insight. The development of mouse head arrays to allow further research of the effect TTFields on glioblastoma, an application of widespread interest, is currently underway. Citation Format: Shiri Davidi, Roni Blatt, Mijal Munster, Anna Shteingauz, Yaara Porat, Adel Zeidan, Tal Marciano, Zeev Bomzon, Moshe Giladi, Uri Weinberg, Yoram Palti. inovivo: a dedicated system for delivery of therapeutic level Tumor Treating Fields (TTFields) to mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1317.