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Journal articles on the topic 'Transcranial simulations'

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Published: 7 July 2024
Last updated: 7 July 2024

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1

Antal, Andrea, and Christoph S. Herrmann. "Transcranial Alternating Current and Random Noise Stimulation: Possible Mechanisms." Neural Plasticity 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/3616807.

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Background. Transcranial alternating current stimulation (tACS) is a relatively recent method suited to noninvasively modulate brain oscillations. Technically the method is similar but not identical to transcranial direct current stimulation (tDCS). While decades of research in animals and humans has revealed the main physiological mechanisms of tDCS, less is known about the physiological mechanisms of tACS.Method. Here, we review recent interdisciplinary research that has furthered our understanding of how tACS affects brain oscillations and by what means transcranial random noise stimulation (tRNS) that is a special form of tACS can modulate cortical functions.Results. Animal experiments have demonstrated in what way neurons react to invasively and transcranially applied alternating currents. Such findings are further supported by neural network simulations and knowledge from physics on entraining physical oscillators in the human brain. As a result, fine-grained models of the human skull and brain allow the prediction of the exact pattern of current flow during tDCS and tACS. Finally, recent studies on human physiology and behavior complete the picture of noninvasive modulation of brain oscillations.Conclusion. In future, the methods may be applicable in therapy of neurological and psychiatric disorders that are due to malfunctioning brain oscillations.
2

Vyas, Urvi, Elena Kaye, and Kim Butts Pauly. "Transcranial phase aberration correction using beam simulations and MR-ARFI." Medical Physics 41, no. 3 (February 26, 2014): 032901. http://dx.doi.org/10.1118/1.4865778.

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3

Sigona, Michelle K., Thomas J. Manuel, Huiwen Luo, Marshal A. Phipps, Pai-Feng Yang, Kianoush Banaie Boroujeni, Robert L. Treuting, et al. "Generating patient-specific acoustic simulations for transcranial focused ultrasound procedures based on optical tracking information." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A155. http://dx.doi.org/10.1121/10.0015868.

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During transcranial focused ultrasound (FUS) procedures, accurate targeting is important and neuronavigation with optically tracked tools is used to estimate the free-field focal location on pre-acquired images. Offline neuronavigation systems do not typically incorporate aberrating effects of the skull known to displace and distort the focus. Here, we developed a pipeline that integrated patient-specific acoustic simulations informed by transformations from optically tracked FUS procedures as a tool to evaluate transcranial pressure fields and demonstrated its use in three FUS scenarios: magnetic resonance imaging-guided (MR-guided) phantom experiments, MR-guided non-human primate (NHP) experiments, an offline behaving NHP experiments. Distance vectors between the estimated focus from optical tracking and peak intracranial location from simulations were less than 1 mm for all groups (Phantom: 0.6 ± 0.3 mm, NHP: 0.7 ± 0.3 mm, Behaving NHP: 0.5 ± 0.2 mm). Comparisons of the target registration error of MR measurements with the optically tracked focus (TRETracked) and simulated focus (TRESimulated) suggest that focal location errors are dominated by optical tracking errors rather than aberration through the skull in the NHP (Phantom: TRETracked: 3.3 ± 1.4 mm, Phantom TRESimulated: 3.3 ± 1.9 mm, NHP TRETracked: 3.9 ± 1.9 mm, NHP TRESimulated: 4.1 ± 1.6 mm). Our software pipeline provides patient-specific estimates of the acoustic field during transcranial FUS procedures.
4

Angla, Célestine, Benoit Larrat, Jean-Luc Gennisson, and Sylvain Chatillon. "Improved skull bone acoustic property homogenization for fast transcranial ultrasound simulations." Journal of Physics: Conference Series 2768, no. 1 (May 1, 2024): 012006. http://dx.doi.org/10.1088/1742-6596/2768/1/012006.

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Abstract Transcranial ultrasound simulations are crucial to optimize and secure ultrasound interventions in brain therapy, depending on the patient skull. When performing such simulations, accurate modeling of the skull is essential, although very challenging, because of the inter/intra sample property variability. Simulations based on semi-analytical methods require a homogeneous description of the skull. Averaging the acoustic property maps derived from the CT scan does not modify the focus shift, but it leads to an overestimation of the pressure field amplitude. The purpose of this work is to provide a homogenization method that compensates for this amplitude overestimation. First, the skull acoustic property maps are segmented into a three-layer medium to represent the different types of skull bone (cortical – trabecular – cortical). Then, equivalent properties are computed so as to minimize the time of flight and transmission coefficient errors between the three-layer medium and the one-layer equivalent medium. This method was validated using 3D simulations with CIVA Healthcare and k-Wave and has proven to be very efficient.
5

Dougherty, Edward T., James C. Turner, and Frank Vogel. "Multiscale Coupling of Transcranial Direct Current Stimulation to Neuron Electrodynamics: Modeling the Influence of the Transcranial Electric Field on Neuronal Depolarization." Computational and Mathematical Methods in Medicine 2014 (2014): 1–14. http://dx.doi.org/10.1155/2014/360179.

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Transcranial direct current stimulation (tDCS) continues to demonstrate success as a medical intervention for neurodegenerative diseases, psychological conditions, and traumatic brain injury recovery. One aspect of tDCS still not fully comprehended is the influence of the tDCS electric field on neural functionality. To address this issue, we present a mathematical, multiscale model that couples tDCS administration to neuron electrodynamics. We demonstrate the model’s validity and medical applicability with computational simulations using an idealized two-dimensional domain and then an MRI-derived, three-dimensional human head geometry possessing inhomogeneous and anisotropic tissue conductivities. We exemplify the capabilities of these simulations with real-world tDCS electrode configurations and treatment parameters and compare the model’s predictions to those attained from medical research studies. The model is implemented using efficient numerical strategies and solution techniques to allow the use of fine computational grids needed by the medical community.
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Amanatiadis, Stamatis A., Georgios K. Apostolidis, Chrysanthi S. Bekiari, and Nikolaos V. Kantartzis. "Transcranial ultrasonic propagation and enhanced brain imaging exploiting the focusing effect of the skull." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 39, no. 3 (June 5, 2020): 671–82. http://dx.doi.org/10.1108/compel-10-2019-0387.

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Purpose The reliable transcranial imaging of brain inner structures for diagnostic purposes is deemed crucial owing to the decisive importance and contribution of the brain in human life. The purpose of this paper is to investigate the potential application of medical ultrasounds to transcranial imaging using advanced techniques, such as the total focussing method. Design/methodology/approach Initially, the fundamental details of the total focussing method are presented, while the skull properties, such as the increased acoustic velocity and scattering, are thoroughly examined. Although, these skull characteristics constitute the main drawback of typical transcranial ultrasonic propagation algorithms, they are exploited to focus the acoustic waves towards the brain. To this goal, a virtual source is designed, considering the wave refraction, to efficiently correct the reconstructed brain image. Finally, the verification of the novel method is conducted through numerical simulations of various realistic setups. Findings The theoretically designed virtual source resembles a focussed sensor; therefore, the directivity increment, owing to the propagation through the skull, is confirmed. Moreover, numerical simulations of real-world scenarios indicate that the typical artifacts of the conventional total focussing method are fully overcome because of the increased directivity of the proposed technique, while the reconstructed image is efficiently corrected when the proposed virtual source is used. Originality/value A new systematic methodology along with the design of a flexible virtual source is developed in this paper for the reliable and precise transcranial ultrasonic image reconstruction of the brain. Despite the slight degradation owing to the skull scattering, the combined application of the total focussing method and the featured virtual source can successfully detect arbitrary anomalies in the brain that cannot be spotted by conventional techniques.
7

Palatnik de Sousa, Iam, Carlos R. H. Barbosa, and Elisabeth Costa Monteiro. "Safe exposure distances for transcranial magnetic stimulation based on computer simulations." PeerJ 6 (June 18, 2018): e5034. http://dx.doi.org/10.7717/peerj.5034.

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The results of a computer simulation examining the compliance of a given transcranial magnetic stimulation device to the 2010 International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines are presented. The objective was to update the safe distance estimates with the most current safety guidelines, as well as comparing these to values reported in previous publications. The 3D data generated was compared against results available in the literature, regarding the MCB-70 coil by Medtronic. Regarding occupational exposure, safe distances of 1.46 m and 0.96 m are derived from the simulation according to the 2003 and 2010 ICNIRP guidelines, respectively. These values are then compared to safe distances previously reported in other studies.
8

Zangemeister, Wolfgang H., and Volker Hoemberg. "Eye model simulations of saccadic impairment through transcranial magnetic stimulation (TMS." Neuro-Ophthalmology 13, no. 2 (January 1993): 89–97. http://dx.doi.org/10.3109/01658109309037010.

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9

Pasquinelli, Cristina, Hazael Montanaro, Hyunjoo J. Lee, Lars G. Hanson, Hyungkook Kim, Niels Kuster, Hartwig R. Siebner, Esra Neufeld, and Axel Thielscher. "Transducer modeling for accurate acoustic simulations of transcranial focused ultrasound stimulation." Journal of Neural Engineering 17, no. 4 (July 13, 2020): 046010. http://dx.doi.org/10.1088/1741-2552/ab98dc.

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Drainville, Robert Andrew, Sylvain Chatillon, David Moore, John Snell, Frederic Padilla, and Cyril Lafon. "A simulation study on the sensitivity of transcranial ray-tracing ultrasound modeling to skull properties." Journal of the Acoustical Society of America 154, no. 2 (August 1, 2023): 1211–25. http://dx.doi.org/10.1121/10.0020761.

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In transcranial focused ultrasound therapies, such as treating essential tremor via thermal ablation in the thalamus, acoustic energy is focused through the skull using a phased-array transducer. Ray tracing is a computationally efficient method that can correct skull-induced phase aberrations via per-element phase delay calculations using patient-specific computed tomography (CT) data. However, recent studies show that variations in CT-derived Hounsfield unit may account for only 50% of the speed of sound variability in human skull specimens, potentially limiting clinical transcranial ultrasound applications. Therefore, understanding the sensitivity of treatment planning methods to material parameter variations is essential. The present work uses a ray-tracing simulation model to explore how imprecision in model inputs, arising from clinically significant uncertainties in skull properties or considerations of acoustic phenomena, affects acoustic focusing quality through the skull. We propose and validate new methods to optimize ray-tracing skull simulations for clinical treatment planning, relevant for predicting intracranial target's thermal rise, using experimental data from ex-vivo human skulls.
11

Tian, Zixuan, Yun Jing, and Aiguo Han. "Transcranial ultrasound imaging using pulse-echo ultrasound and deep learning: A numerical study." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A113. http://dx.doi.org/10.1121/10.0015722.

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Phase aberration caused by skulls is a main challenge in transcranial ultrasound imaging for adults. Aberration could be corrected if the skull profile (i.e., thickness distribution) and speed of sound (SOS) are known. We previously designed a deep learning (DL) model to estimate the skull profile and SOS using pulse-echo ultrasound signals. This study’s objective is to develop strategies to improve the estimation and evaluate the effectiveness of aberration correction in transcranial ultrasound imaging. Acoustic simulations were performed using k-Wave in this numerical study. The following strategies were used to improve estimation: (1) A phased array was used instead of a single-element transducer; (2) Channel radiofrequency data were used instead of beamformed data as the DL model input; (3) A DL model was developed to incorporate physics into architecture design and model training. Compared with previously reported results, these strategies improved the correlation coefficient between the estimated and ground-truth values from 0.82 to 0.94 for SOS, and from 0.98 to 0.99 for thickness. Simulated transcranial images of point targets with phase correction using the estimated SOS and thickness values showed significantly reduced artifacts than those without correction. The results demonstrate feasibility of the proposed approach for transcranial ultrasound imaging.
12

Chatillon, Sylvain, Andrew Drainville, John Snell, David Moore, Frederic Padilla, and Cyril Lafon. "Fast and accurate transcranial ultrasound simulation using the asymptotic model of the Civa Healthcare platform." Journal of the Acoustical Society of America 155, no. 3_Supplement (March 1, 2024): A247. http://dx.doi.org/10.1121/10.0027387.

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To ensure its efficacy and safety, transcranial ultrasound therapy treatment planning requires accurate pressure field simulations and phase law corrections. Despite their long computation time and high memory usage, full numerical methods are often used since they are considered more accurate than semi-analytical methods. This work will present the so-called “pencil method“, a fast asymptotic model embedded in the CIVA HealthCare simulation platform. It allows computation in harmonic and impulse mode and the consideration of complex configurations, including solid obstacles, considering, at each interface, refractions and reflections with or without mode conversion of the acoustic field. This model was successfully compared to a recent collaborative work by Aubry et al. that presented a set of numerical benchmarks for transcranial propagation, to allow comparisons between various modeling tools. It was used to investigate the influence of parametric variation of skull material properties on the quality of acoustic focusing through the human skull. Its ability to predict the thermal rise at the intracranial target was validated against experimental data obtained ex-vivo through human skulls. Finally, works in progress will be shared about its connection to the open-source Kranion software developed at the FUS Foundation to facilitate comparison between clinical and simulated data.
13

Vyas, U. "TU-G-210-03: Acoustic Simulations in Transcranial MRgFUS: Treatment Prediction and Analysis." Medical Physics 42, no. 6Part35 (June 2015): 3636. http://dx.doi.org/10.1118/1.4925785.

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14

Rui, Wei, Zhipeng Liu, Chao Tao, and Xiaojun Liu. "Reconstruction of Photoacoustic Tomography Inside a Scattering Layer Using a Matrix Filtering Method." Applied Sciences 9, no. 10 (May 20, 2019): 2071. http://dx.doi.org/10.3390/app9102071.

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Photoacoustic (PA) tomography (PAT) has potential for use in brain imaging due to its rich optical contrast, high acoustic resolution in deep tissue, and good biosafety. However, the skull often poses challenges for transcranial brain imaging. The skull can cause severe distortion and attenuation of the phase and amplitude of PA waves, which leads to poor resolution, low contrast, and strong noise in the images. In this study, we propose an image reconstruction method to recover the PA image insider a skull-like scattering layer. This method reduces the scattering artifacts by combining a correlation matrix filter and a time reversal operator. Both numerical simulations and PA imaging experiments demonstrate that the proposed approach effectively improves the image quality with less speckle noise and better signal-to-noise ratio. The proposed method may improve the quality of PAT in a complex acoustic scattering environment, such as transcranial brain imaging.
15

Bell, Jeff J., Lu Xu, Hong Chen, and Yun Jing. "Validation of mSOUND using a fully heterogeneous skull model." Journal of the Acoustical Society of America 155, no. 3_Supplement (March 1, 2024): A248. http://dx.doi.org/10.1121/10.0027388.

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Transcranial ultrasound has found an increasing number of applications in recent years, including the treatment of neurological conditions through thermal ablation and neuromodulation. Ensuring the success and safety of such treatments necessitates precise numerical simulations of transcranial ultrasound, a pivotal aspect of treatment planning involving phase correction. Addressing this demand, an open-source wave solver named mSOUND (https://m-sound.github.io/mSOUND/home) was developed specifically for modeling focused ultrasound in heterogeneous media. A recent intercomparison study (J. Acoust. Soc. Am. 152, 1003–1019, 2022) scrutinized mSOUND alongside other wave solvers like k-Wave, demonstrating its accuracy in modeling wave propagation through a homogeneous skull. This study extends the assessment to evaluate mSOUND's accuracy in modeling wave propagation through a fully heterogeneous skull, utilizing CT images of an ex vivo human skull. The obtained results are systematically compared with those from k-Wave, revealing a high level of agreement.
16

Ramirez Galindo, Angel D., Juan Carlos Olivares Galván, Manuel A. Corona Sánchez, Rafael Escarela Pérez, Enrique Melgoza Vazquez, and Felipe de Jesús Gonzalez Montañez. "Efficient coil design for transcranial magnetic stimulation using computational tools." Ingeniería Investigación y Tecnología 25, no. 2 (April 1, 2024): 1–12. http://dx.doi.org/10.22201/fi.25940732e.2024.25.2.015.

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In the last two decades, transcranial magnetic stimulation (TMS) has been used in research protocols and clinical treatment of neurological disorders. In this work, we analyze the heating of a transcranial magnetic stimulation equipment, with the aim of reducing it using a novel design of stimulation coils. The operation of the equipment is limited by the overheating of the stimulation coils, such that the continuous use of the equipment during the therapy is impossible, and the device´s life time is affected. The first stage of the analysis consists of studying the response of the electrical excitation circuit through simulations, considering the use of concentric inductors to divide the magnitude of the current. This is complemented by multiphysical analysis with coupling between the magnetic field and heat transfer of two different coil geometries, showing the spatial distribution of the generated magnetic field and temperature rise in the space surrounding the stimulation coil. The main contribution of this research is the design of a stimulation coil using the finite element method, reducing the device´s operating temperature considering a practical coil geometry.
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Alkins, Ryan, Yuexi Huang, Dan Pajek, and Kullervo Hynynen. "Cavitation-based third ventriculostomy using MRI-guided focused ultrasound." Journal of Neurosurgery 119, no. 6 (December 2013): 1520–29. http://dx.doi.org/10.3171/2013.8.jns13969.

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Object Transcranial focused ultrasound is increasingly being investigated as a minimally invasive treatment for a range of intracranial pathologies. At higher peak rarefaction pressures than those used for thermal ablation, focused ultrasound can initiate inertial cavitation and create holes in the brain by fractionation of the tissue elements. The authors investigated the technical feasibility of using MRI-guided focused ultrasound to perform a third ventriculostomy as a possible noninvasive alternative to endoscopic third ventriculostomy for hydrocephalus. Methods A craniectomy was performed in male pigs weighing 13–19 kg to expose the supratentorial brain, leaving the dura mater intact. Seven pigs were treated through the craniectomy, while 2 pigs were treated through ex vivo human skulls placed in the beam path. Registration and targeting was done using T2-weighted MRI sequences. For transcranial treatments a CT scan was used to correct the beam from aberrations due to the skull and maintain a small, high-intensity focus. Sonications were performed at both 650 kHz and 230 kHz at a range of intensities, and the in situ pressures were estimated both from simulations and experimental data to establish a threshold for tissue fractionation in the brain. Results In craniectomized animals at 650 kHz, a peak pressure ≥ 22.7 MPa for 1 second was needed to reliably create a ventriculostomy. Transcranially at this frequency the ExAblate 4000 was unable to generate the required intensity to fractionate tissue, although cavitation was initiated. At 230 kHz, ventriculostomy was successful through the skull with a peak pressure of 8.8 MPa. Conclusions This is the first study to suggest that it is possible to perform a completely noninvasive third ventriculostomy using ultrasound. This may pave the way for future studies and eventually provide an alternative means for the creation of CSF communications in the brain, including perforation of the septum pellucidum or intraventricular membranes.
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Behrens, Anders, Niklas Lenfeldt, Khalid Ambarki, Jan Malm, Anders Eklund, and Lars-Owe Koskinen. "Transcranial Doppler Pulsatility Index: Not an Accurate Method to Assess Intracranial Pressure." Neurosurgery 66, no. 6 (June 1, 2010): 1050–57. http://dx.doi.org/10.1227/01.neu.0000369519.35932.f2.

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Abstract BACKGROUND Transcranial Doppler sonography (TCD) assessment of intracranial blood flow velocity has been suggested to accurately determine intracranial pressure (ICP). OBJECTIVE We attempted to validate this method in patients with communicating cerebrospinal fluid systems using predetermined pressure levels. METHODS Ten patients underwent a lumbar infusion test, applying 4 to 5 preset ICP levels. On each level, the pulsatility index (PI) in the middle cerebral artery was determined by measuring the blood flow velocity using TCD. ICP was simultaneously measured with an intraparenchymal sensor. ICP and PI were compared using correlation analysis. For further understanding of the ICP-PI relationship, a mathematical model of the intracranial dynamics was simulated using a computer. RESULTS The ICP-PI regression equation was based on data from 8 patients. For 2 patients, no audible Doppler signal was obtained. The equation was ICP = 23*PI + 14 (R2 = 0.22, P < .01, N = 35). The 95% confidence interval for a mean ICP of 20 mm Hg was −3.8 to 43.8 mm Hg. Individually, the regression coefficients varied from 42 to 90 and the offsets from −32 to +3. The mathematical simulations suggest that variations in vessel compliance, autoregulation, and arterial pressure have a serious effect on the ICP-PI relationship. CONCLUSIONS The in vivo results show that PI is not a reliable predictor of ICP. Mathematical simulations indicate that this is caused by variations in physiological parameters.
19

Heimbuch, Ian S., Tiffany K. Fan, Allan D. Wu, Guido C. Faas, Andrew C. Charles, and Marco Iacoboni. "Ultrasound stimulation of the motor cortex during tonic muscle contraction." PLOS ONE 17, no. 4 (April 20, 2022): e0267268. http://dx.doi.org/10.1371/journal.pone.0267268.

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Transcranial ultrasound stimulation (tUS) shows potential as a noninvasive brain stimulation (NIBS) technique, offering increased spatial precision compared to other NIBS techniques. However, its reported effects on primary motor cortex (M1) are limited. We aimed to better understand tUS effects in human M1 by performing tUS of the hand area of M1 (M1hand) during tonic muscle contraction of the index finger. Stimulation during muscle contraction was chosen because of the transcranial magnetic stimulation-induced phenomenon known as cortical silent period (cSP), in which transcranial magnetic stimulation (TMS) of M1hand involuntarily suppresses voluntary motor activity. Since cSP is widely considered an inhibitory phenomenon, it presents an ideal parallel for tUS, which has often been proposed to preferentially influence inhibitory interneurons. Recording electromyography (EMG) of the first dorsal interosseous (FDI) muscle, we investigated effects on muscle activity both during and after tUS. We found no change in FDI EMG activity concurrent with tUS stimulation. Using single-pulse TMS, we found no difference in M1 excitability before versus after sparsely repetitive tUS exposure. Using acoustic simulations in models made from structural MRI of the participants that matched the experimental setups, we estimated in-brain pressures and generated an estimate of cumulative tUS exposure experienced by M1hand for each subject. We were unable to find any correlation between cumulative M1hand exposure and M1 excitability change. We also present data that suggest a TMS-induced MEP always preceded a near-threshold cSP.
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Pérez-Benítez, J. A., P. Martínez-Ortiz, and J. Aguila-Muñoz. "A Review of Formulations, Boundary Value Problems and Solutions for Numerical Computation of Transcranial Magnetic Stimulation Fields." Brain Sciences 13, no. 8 (July 29, 2023): 1142. http://dx.doi.org/10.3390/brainsci13081142.

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Since the inception of the transcranial magnetic stimulation (TMS) technique, it has become imperative to numerically compute the distribution of the electric field induced in the brain. Various models of the coil-brain system have been proposed for this purpose. These models yield a set of formulations and boundary conditions that can be employed to calculate the induced electric field. However, the literature on TMS simulation presents several of these formulations, leading to potential confusion regarding the interpretation and contribution of each source of electric field. The present study undertakes an extensive compilation of widely utilized formulations, boundary value problems and numerical solutions employed in TMS fields simulations, analyzing the advantages and disadvantages associated with each used formulation and numerical method. Additionally, it explores the implementation strategies employed for their numerical computation. Furthermore, this work provides numerical expressions that can be utilized for the numerical computation of TMS fields using the finite difference and finite element methods. Notably, some of these expressions are deduced within the present study. Finally, an overview of some of the most significant results obtained from numerical computation of TMS fields is presented. The aim of this work is to serve as a guide for future research endeavors concerning the numerical simulation of TMS.
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Saturnino, Guilherme B., Kristoffer H. Madsen, and Axel Thielscher. "Electric field simulations for transcranial brain stimulation using FEM: an efficient implementation and error analysis." Journal of Neural Engineering 16, no. 6 (November 6, 2019): 066032. http://dx.doi.org/10.1088/1741-2552/ab41ba.

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Slezak, Cyrill, Jonas Flatscher, and Paul Slezak. "A Comparative Feasibility Study for Transcranial Extracorporeal Shock Wave Therapy." Biomedicines 10, no. 6 (June 20, 2022): 1457. http://dx.doi.org/10.3390/biomedicines10061457.

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The potential beneficial regenerative and stimulatory extracorporeal shock wave therapy (ESWT) applications to the central nervous system have garnered interest in recent years. Treatment zones for these indications are acoustically shielded by bones, which heavily impact generated sound fields. We present the results of high-resolution tissue-realistic simulations, comparing the viability of different ESWT applicators in their use for transcranial applications. The performances of electrohydraulic, electromagnetic, and piezoelectric transducers for key reflector geometries are compared. Based on density information obtained from CT imaging of the head, we utilized the non-linear wave propagation toolset Matlab k-Wave to obtain spatial therapeutic sound field geometries and waveforms. In order to understand the reliability of results on the appropriate modeling of the skull, three different bone attenuation models were compared. We find that all currently clinically ESWT applicator technologies show significant retention of peak pressures and energies past the bone barrier. Electromagnetic transducers maintain a significantly higher energy flux density compared to other technologies while low focusing strength piezoelectric applicators have the weakest transmissions. Attenuation estimates provide insights into sound field degradation and energy losses, indicating that effective transcranial therapies can readily be attained with current applicators. Furthermore, the presented approach will allow for future targeted in silico development and the design of applicators and therapy plans to ultimately improve therapeutic outcomes.
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Jones, Ryan, Meaghan O'Reilly, and Kullervo Hynynen. "Simulations of transcranial passive acoustic mapping with hemispherical sparse arrays using computed tomography-based aberration corrections." Journal of the Acoustical Society of America 133, no. 5 (May 2013): 3262. http://dx.doi.org/10.1121/1.4805278.

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Frohlich, F., K. Sellers, M. Boyle, M. Ali, A. Cordle, B. Vaughn, and J. Gilmore. "OP 9. Tailoring transcranial current stimulation to modulate cortical oscillations in computer simulations, ferrets, and humans." Clinical Neurophysiology 124, no. 10 (October 2013): e60. http://dx.doi.org/10.1016/j.clinph.2013.04.076.

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Stanziola, Antonio, Simon Arridge, Ben Cox, and Bradley Treeby. "A learned born series for highly scattering media." Journal of the Acoustical Society of America 155, no. 3_Supplement (March 1, 2024): A106. http://dx.doi.org/10.1121/10.0026967.

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The Helmholtz equation with heterogeneous material properties is essential in various fields requiring single-frequency wave simulations, including optics, seismology, acoustics, and electromagnetics. Traditional methods for solving this equation, such as the Born Series, face limitations in converging for high-contrast scattering potentials. To address this challenge, we introduce a novel method called the Learned Born Series (LBS). The LBS is derived from the convergent Born Series but employs components that are learned through training. It demonstrates significantly improved accuracy compared to the conventional convergent Born Series, especially in scenarios with high-contrast scatterers, while maintaining similar computational complexity. The LBS can rapidly generate reasonably accurate predictions of the global pressure field with only a few iterations, and the errors decrease as more iterations are learned. We show its effectiveness through experiments on simulated datasets. The LBS offers promising prospects for accelerating simulations in scenarios with strong sound speed contrasts, potentially revolutionizing applications in transcranial treatment planning and full waveform inversion.
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Dougherty, Edward T., and James C. Turner. "An Object-Oriented Framework for Versatile Finite Element Based Simulations of Neurostimulation." Journal of Computational Medicine 2016 (February 9, 2016): 1–15. http://dx.doi.org/10.1155/2016/9826596.

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Computational simulations of transcranial electrical stimulation (TES) are commonly utilized by the neurostimulation community, and while vastly different TES application areas can be investigated, the mathematical equations and physiological characteristics that govern this research are identical. The goal of this work was to develop a robust software framework for TES that efficiently supports the spectrum of computational simulations routinely utilized by the TES community and in addition easily extends to support alternative neurostimulation research objectives. Using well-established object-oriented software engineering techniques, we have designed a software framework based upon the physical and computational aspects of TES. The framework’s versatility is demonstrated with a set of diverse neurostimulation simulations that (i) reinforce the importance of using anisotropic tissue conductivities, (ii) demonstrate the enhanced precision of high-definition stimulation electrodes, and (iii) highlight the benefits of utilizing multigrid solution algorithms. Our approaches result in a framework that facilitates rapid prototyping of real-world, customized TES administrations and supports virtually any clinical, biomedical, or computational aspect of this treatment. Software reuse and maintainability are optimized, and in addition, the same code can be effortlessly augmented to provide support for alternative neurostimulation research endeavors.
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Zhang, Naming, Ziang Wang, Jinhua Shi, Shuya Ning, Yukuo Zhang, Shuhong Wang, and Hao Qiu. "Theoretical Analysis and Design of an Innovative Coil Structure for Transcranial Magnetic Stimulation." Applied Sciences 11, no. 4 (February 23, 2021): 1960. http://dx.doi.org/10.3390/app11041960.

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Previous research showed that pulsed functional magnetic stimulation can activate brain tissue with optimum intensity and frequency. Conventional stimulation coils are always set as a figure-8 type or Helmholtz. However, the magnetic fields generated by these coils are uniform around the target, and their magnetic stimulation performance still needs improvement. In this paper, a novel type of stimulation coil is proposed to shrink the irritative zone and strengthen the stimulation intensity. Furthermore, the electromagnetic field distribution is calculated and measured. Based on numerical simulations, the proposed coil is compared to traditional coil types. Moreover, the influential factors, such as the diameter and the intersection angle, are also analyzed. It was demonstrated that the proposed coil has a better performance in comparison with the figure-8 coil. Thus, this work suggests a new way to design stimulation coils for transcranial magnetic stimulation.
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Kohtanen, Eetu, Ahmed Allam, and Alper Erturk. "3D-printed gradient-index phononic crystal lens for transcranial focused ultrasound." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A245. http://dx.doi.org/10.1121/10.0016154.

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Transcranial focused ultrasound (tFUS) shows great promise as a noninvasive tool to treat neurological conditions such as essential tremor. The existing clinical phased array systems are mostly intended for ultrasound delivery to the center of the brain (as in thalamotomy for essential tremor), in addition to being complex and expensive. To seek an alternative focusing approach especially for the brain periphery, we explore a 3D-printed gradient-index (GRIN) lens as a simple and an orders of magnitude more cost-effective approach. The lens is constructed using a phononic crystal (PC) architecture with varying lattice geometry and hence refractive index distribution. Specifically, the lens uses an axisymmetric hyperbolic secant refractive index profile to focus ultrasonic waves generated by a 1 MHz single-element ultrasonic transducer. Finite element simulations are performed to design and analyze the GRIN-PC lens, and to explore the effects of various parameters such as the distance from the skull and the incidence angle. The numerical results are validated experimentally for a 3D-printed lens by scanning the 3D pressure field generated through a temporal bone. This cost-effective approach to tFUS can open new possibilities to 3D print lenses based on patient computed tomography scans for various applications from tissue ablation to neurostimulation.
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Favre, Hugues, Mathieu Pernot, Mickael Tanter, and Clément Papadacci. "Boosting transducer matrix sensitivity for 3D large field ultrasound localization microscopy using a multi-lens diffracting layer: a simulation study." Physics in Medicine & Biology 67, no. 8 (April 7, 2022): 085009. http://dx.doi.org/10.1088/1361-6560/ac5f72.

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Abstract Mapping blood microflows of the whole brain is crucial for early diagnosis of cerebral diseases. Ultrasound localization microscopy (ULM) was recently applied to map and quantify blood microflows in 2D in the brain of adult patients down to the micron scale. Whole brain 3D clinical ULM remains challenging due to the transcranial energy loss which significantly reduces the imaging sensitivity. Large aperture probes with a large surface can increase both resolution and sensitivity. However, a large active surface implies thousands of acoustic elements, with limited clinical translation. In this study, we investigate via simulations a new high-sensitive 3D imaging approach based on large diverging elements, combined with an adapted beamforming with corrected delay laws, to increase sensitivity. First, pressure fields from single elements with different sizes and shapes were simulated. High directivity was measured for curved element while maintaining high transmit pressure. Matrix arrays of 256 elements with a dimension of 10 × 10 cm with small (λ/2), large (4λ), and curved elements (4λ) were compared through point spread functions analysis. A large synthetic microvessel phantom filled with 100 microbubbles per frame was imaged using the matrix arrays in a transcranial configuration. 93% of the bubbles were detected with the proposed approach demonstrating that the multi-lens diffracting layer has a strong potential to enable 3D ULM over a large field of view through the bones.
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Obrist, Walter D., Zihong Zhang, and Howard Yonas. "Effect of Xenon-Induced Flow Activation on Xenon-Enhanced Computed Tomography Cerebral Blood Flow Calculations." Journal of Cerebral Blood Flow & Metabolism 18, no. 11 (November 1998): 1192–95. http://dx.doi.org/10.1097/00004647-199811000-00005.

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Computer simulations of stable xenon (sXe) uptake curves were used to evaluate the effect of xenon-induced flow activation on CBF calculations by xenon-enhanced computed tomography, Estimates of flow activation were based on repeated transcranial Doppler measurements of blood velocity during 4,5 minutes of sXe inhalation, The synthetic curves were generated from a generalized Kety equation that included time-varying blood flow activation, In contrast to the peak 35% increase in blood flow velocity during sXe inhalation, a standard analysis of the flow-varying synthetic curves revealed only minor 3% to 5% increases in calculated CBF. It is concluded that brief xenon inhalations can provide blood flow estimates that contain minimal bias from activation.
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Mantell, K., E. Sutter, S. Nemanich, B. Gillick, and A. Opitz. "P180 Comparing Transcranial Magnetic Stimulation (TMS) simulations for lesioned and non-lesioned hemispheres in pediatric stroke models." Clinical Neurophysiology 131, no. 4 (April 2020): e116. http://dx.doi.org/10.1016/j.clinph.2019.12.291.

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Pulkkinen, Aki, Yuexi Huang, Junho Song, and Kullervo Hynynen. "Simulations and measurements of transcranial low-frequency ultrasound therapy: skull-base heating and effective area of treatment." Physics in Medicine and Biology 56, no. 15 (July 6, 2011): 4661–83. http://dx.doi.org/10.1088/0031-9155/56/15/003.

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Tashli, Mohannad, George Weistroffer, Aryan Mhaskar, Deepak Kumbhare, Mark S. Baron, and Ravi L. Hadimani. "Investigation of soft magnetic material cores in transcranial magnetic stimulation coils and the effect of changing core shapes on the induced electric field in small animals." AIP Advances 13, no. 2 (February 1, 2023): 025319. http://dx.doi.org/10.1063/9.0000550.

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Transcranial magnetic stimulation (TMS) is a safe, effective and non-invasive treatment for several psychiatric and neurological disorders. Lately, there has been a surge in research utilizing this novel technology in treating other neurological and psychiatric ailments. The application of TMS on several neurological disorders requires the induced electric and magnetic fields to be focused and targeted to a small region in the brain. TMS of a focal cortical territory will ensure modulation of specific brain circuitry without affecting unwanted surrounding regions. This can be achieved by altering the properties of the magnetic core material used for the TMS system. In this study, soft ferromagnetic materials having high permeability, high saturation magnetization and low coercivity have been investigated as TMS coil cores in finite element simulations. Also, magnetic field measurements have been carried out using different cores in the TMS coil. Finite element analysis of the rat head model is carried out using Sim4life software while investigating variations associated with changing the ferromagnetic core material and shape in the coil. Materials proposed for the analysis in this study include Iron Cobalt Vanadium alloy (Fe-Co-V) also known as Permendur, Carbon Steel (AISI 1010) and Manganese Zinc ferrites (MnZn ferrites). Simulation results indicated significant magnetic field distribution variation when introducing a ferromagnetic core in TMS coil, concentrating the magnetic field to the targeted region in the rat head model without stimulating adjacent regions. It was observed that the v-tip sharpened core attained the highest magnetic field and best focality among other cores in simulations and experimentally.
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Witte, Russell S., Margaret Allard, Teodoro Trujillo, Alex Alvarez, Chet Preston, Jinbum Kang, and Matthew O'Donnell. "Transcranial acoustoelectric imaging: Towards noninvasive mapping of current densities in the human brain." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A154. http://dx.doi.org/10.1121/10.0018479.

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Acoustoelectric Imaging (AEI) is a disruptive technology that exploits an ultrasound (US) beam to transiently interact with physiologic or artificial currents, producing a radiofrequency signature detected by one or more surface electrodes. By rapidly sweeping the US beam and simultaneously detecting the acoustoelectric modulations, 4D current density images are generated at high spatial resolution determined by the ultrasound beam focus. The principle has been used for in vivo mapping of currents in the swine heart during the cardiac activation wave. When applied to the brain, transcranial acoustoelectric imaging (tABI) overcomes limitations with electroencephalography (EEG), which suffers from poor spatial resolution and inaccuracies due to blurring of electrical signals as they pass through the brain and skull, and, unlike fMRI and PET that measure slow metabolic or hemodynamic signals, tABI directly maps fast time-varying current within a defined brain volume at the mm and ms scales. This invited presentation will describe the underlying physics and mathematics of tABI, recent progress and challenges using numerical simulations and bench-top models, and its potential impact as a cutting-edge noninvasive modality for fast and accurate electrical brain mapping in humans.
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Molero-Chamizo, Andrés, Michael A. Nitsche, Carolina Gutiérrez Lérida, Ángeles Salas Sánchez, Raquel Martín Riquel, Rafael Tomás Andújar Barroso, José Ramón Alameda Bailén, Jesús Carlos García Palomeque, and Guadalupe Nathzidy Rivera-Urbina. "Standard Non-Personalized Electric Field Modeling of Twenty Typical tDCS Electrode Configurations via the Computational Finite Element Method: Contributions and Limitations of Two Different Approaches." Biology 10, no. 12 (November 25, 2021): 1230. http://dx.doi.org/10.3390/biology10121230.

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Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation procedure to modulate cortical excitability and related brain functions. tDCS can effectively alter multiple brain functions in healthy humans and is suggested as a therapeutic tool in several neurological and psychiatric diseases. However, variability of results is an important limitation of this method. This variability may be due to multiple factors, including age, head and brain anatomy (including skull, skin, CSF and meninges), cognitive reserve and baseline performance level, specific task demands, as well as comorbidities in clinical settings. Different electrode montages are a further source of variability between tDCS studies. A procedure to estimate the electric field generated by specific tDCS electrode configurations, which can be helpful to adapt stimulation protocols, is the computational finite element method. This approach is useful to provide a priori modeling of the current spread and electric field intensity that will be generated according to the implemented electrode montage. Here, we present standard, non-personalized model-based electric field simulations for motor, dorsolateral prefrontal, and posterior parietal cortex stimulation according to twenty typical tDCS electrode configurations using two different current flow modeling software packages. The resulting simulated maximum intensity of the electric field, focality, and current spread were similar, but not identical, between models. The advantages and limitations of both mathematical simulations of the electric field are presented and discussed systematically, including aspects that, at present, prevent more widespread application of respective simulation approaches in the field of non-invasive brain stimulation.
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Zhang, Hao, Luis J. Gomez, and Johann Guilleminot. "Uncertainty quantification of TMS simulations considering MRI segmentation errors." Journal of Neural Engineering 19, no. 2 (March 30, 2022): 026022. http://dx.doi.org/10.1088/1741-2552/ac5586.

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Abstract Objective. Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation method that is used to study brain function and conduct neuropsychiatric therapy. Computational methods that are commonly used for electric field (E-field) dosimetry of TMS are limited in accuracy and precision because of possible geometric errors introduced in the generation of head models by segmenting medical images into tissue types. This paper studies E-field prediction fidelity as a function of segmentation accuracy. Approach.The errors in the segmentation of medical images into tissue types are modeled as geometric uncertainty in the shape of the boundary between tissue types. For each tissue boundary realization, we then use an in-house boundary element method to perform a forward propagation analysis and quantify the impact of tissue boundary uncertainties on the induced cortical E-field. Main results. Our results indicate that predictions of E-field induced in the brain are negligibly sensitive to segmentation errors in scalp, skull and white matter (WM), compartments. In contrast, E-field predictions are highly sensitive to possible cerebrospinal fluid (CSF) segmentation errors. Specifically, the segmentation errors on the CSF and gray matter interface lead to higher E-field uncertainties in the gyral crowns, and the segmentation errors on CSF and WM interface lead to higher uncertainties in the sulci. Furthermore, the uncertainty of the average cortical E-fields over a region exhibits lower uncertainty relative to point-wise estimates. Significance. The accuracy of current cortical E-field simulations is limited by the accuracy of CSF segmentation accuracy. Other quantities of interest like the average of the E-field over a cortical region could provide a dose quantity that is robust to possible segmentation errors.
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Montanaro, Hazael, Cristina Pasquinelli, Hyunjoo J. Lee, Hyunggug Kim, Hartwig R. Siebner, Niels Kuster, Axel Thielscher, and Esra Neufeld. "The impact of CT image parameters and skull heterogeneity modeling on the accuracy of transcranial focused ultrasound simulations." Journal of Neural Engineering 18, no. 4 (May 4, 2021): 046041. http://dx.doi.org/10.1088/1741-2552/abf68d.

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Petrov, Petar I., Stefano Mandija, Iris E. C. Sommer, Cornelis A. T. van den Berg, and Sebastiaan F. W. Neggers. "How much detail is needed in modeling a transcranial magnetic stimulation figure-8 coil: Measurements and brain simulations." PLOS ONE 12, no. 6 (June 22, 2017): e0178952. http://dx.doi.org/10.1371/journal.pone.0178952.

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Kwon, Oh In, Saurav Z. K. Sajib, Igor Sersa, Tong In Oh, Woo Chul Jeong, Hyung Joong Kim, and Eung Je Woo. "Current Density Imaging During Transcranial Direct Current Stimulation Using DT-MRI and MREIT: Algorithm Development and Numerical Simulations." IEEE Transactions on Biomedical Engineering 63, no. 1 (January 2016): 168–75. http://dx.doi.org/10.1109/tbme.2015.2448555.

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Abbasi, Shaghayegh, Sravya Alluri, Vincent Leung, Peter Asbeck, and Milan T. Makale. "Design and Validation of Miniaturized Repetitive Transcranial Magnetic Stimulation (rTMS) Head Coils." Sensors 24, no. 5 (February 29, 2024): 1584. http://dx.doi.org/10.3390/s24051584.

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Repetitive transcranial magnetic stimulation (rTMS) is a rapidly developing therapeutic modality for the safe and effective treatment of neuropsychiatric disorders. However, clinical rTMS driving systems and head coils are large, heavy, and expensive, so miniaturized, affordable rTMS devices may facilitate treatment access for patients at home, in underserved areas, in field and mobile hospitals, on ships and submarines, and in space. The central component of a portable rTMS system is a miniaturized, lightweight coil. Such a coil, when mated to lightweight driving circuits, must be able to induce B and E fields of sufficient intensity for medical use. This paper newly identifies and validates salient theoretical considerations specific to the dimensional scaling and miniaturization of coil geometries, particularly figure-8 coils, and delineates novel, key design criteria. In this context, the essential requirement of matching coil inductance with the characteristic resistance of the driver switches is highlighted. Computer simulations predicted E- and B-fields which were validated via benchtop experiments. Using a miniaturized coil with dimensions of 76 mm × 38 mm and weighing only 12.6 g, the peak E-field was 87 V/m at a distance of 1.5 cm. Practical considerations limited the maximum voltage and current to 350 V and 3.1 kA, respectively; nonetheless, this peak E-field value was well within the intensity range, 60–120 V/m, generally held to be therapeutically relevant. The presented parameters and results delineate coil and circuit guidelines for a future miniaturized, power-scalable rTMS system able to generate pulsed E-fields of sufficient amplitude for potential clinical use.
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Surendran, Sudeep, Srdan Prodanovic, and Stefan Stenfelt. "Hearing Through Bone Conduction Headsets." Trends in Hearing 27 (January 2023): 233121652311687. http://dx.doi.org/10.1177/23312165231168741.

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Bone conduction (BC) stimulation has mainly been used for clinical hearing assessment and hearing aids where stimulation is applied at the mastoid behind the ear. Recently, BC has become popular for communication headsets where the stimulation position often is close to the anterior part of the ear canal opening. The BC sound transmission for this stimulation position is here investigated in 21 participants by ear canal sound pressure measurements and hearing threshold assessment as well as simulations in the LiUHead. The results indicated that a stimulation position close to the ear canal opening improves the sensitivity for BC sound by around 20 dB but by up to 40 dB at some frequencies. The transcranial transmission ranges typically between −40 and −25 dB. This decreased transcranial transmission facilitates saliency of binaural cues and implies that BC headsets are suitable for virtual and augmented reality applications. The findings suggest that with BC stimulation close to the ear canal opening, the sound pressure in the ear canal dominates the perception of BC sound. With this stimulation, the ear canal pathway was estimated to be around 25 dB greater than other contributors, like skull bone vibrations, for hearing BC sound in a healthy ear. This increased contribution from the ear canal sound pressure to BC hearing means that a position close to the ear canal is not appropriate for clinical use since, in such case, a conductive hearing loss affects BC and air conduction thresholds by a similar amount.
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Kozlov, Mikhail, Marc Horner, Wolfgang Kainz, Nikolaus Weiskopf, and Harald E. Möller. "Modeling radio-frequency energy-induced heating due to the presence of transcranial electric stimulation setup at 3T." Magnetic Resonance Materials in Physics, Biology and Medicine 33, no. 6 (May 27, 2020): 793–807. http://dx.doi.org/10.1007/s10334-020-00853-5.

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Abstract Purpose The purpose of the present study was to develop a numerical workflow for simulating temperature increase in a high-resolution human head and torso model positioned in a whole-body magnetic resonance imaging (MRI) radio-frequency (RF) coil in the presence of a transcranial electric stimulation (tES) setup. Methods A customized human head and torso model was developed from medical image data. Power deposition and temperature rise (ΔT) were evaluated with the model positioned in a whole-body birdcage RF coil in the presence of a tES setup. Multiphysics modeling at 3T (123.2 MHz) on unstructured meshes was based on RF circuit, 3D electromagnetic, and thermal co-simulations. ΔT was obtained for (1) a set of electrical and thermal properties assigned to the scalp region, (2) a set of electrical properties of the gel used to ensure proper electrical contact between the tES electrodes and the scalp, (3) a set of electrical conductivity values of skin tissue, (4) four gel patch shapes, and (5) three electrode shapes. Results Significant dependence of power deposition and ΔT on the skin’s electrical properties and electrode and gel patch geometries was observed. Differences in maximum ΔT (> 100%) and its location were observed when comparing the results from a model using realistic human tissue properties and one with an external container made of acrylic material. The electrical and thermal properties of the phantom container material also significantly (> 250%) impacted the ΔT results. Conclusion Simulation results predicted that the electrode and gel geometries, skin electrical conductivity, and position of the temperature sensors have a significant impact on the estimated temperature rise. Therefore, these factors must be considered for reliable assessment of ΔT in subjects undergoing an MRI examination in the presence of a tES setup.
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McDannold, Nathan, P. Jason White, and Rees Cosgrove. "Predicting Bone Marrow Damage in the Skull After Clinical Transcranial MRI-Guided Focused Ultrasound With Acoustic and Thermal Simulations." IEEE Transactions on Medical Imaging 39, no. 10 (October 2020): 3231–39. http://dx.doi.org/10.1109/tmi.2020.2989121.

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44

Lewis, Connor J., Laura M. Franke, Joseph V. Lee, Neil Mittal, George T. Gitchel, Robert A. Perera, Kathryn L. Holloway, William C. Walker, Carrie L. Peterson, and Ravi L. Hadimani. "The relationship of neuroanatomy on resting motor threshold and induced electric field strength on treatment outcomes in mild to moderate traumatic brain injury patients during transcranial magnetic stimulation." AIP Advances 13, no. 2 (February 1, 2023): 025260. http://dx.doi.org/10.1063/9.0000567.

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Transcranial magnetic stimulation (TMS) is a non-invasive treatment protocol for treating several psychiatric conditions, including depression, migraine, smoking cessation, and obsessive-compulsive disorder. Past research suggests that TMS treatment outcomes vary based on neuroanatomy, functional connectivity, and tractography-based structural connectivity. In a previous study, 26 mild to moderate traumatic brain injury (mTBI) patients underwent repetitive transcranial magnetic stimulation (rTMS) and showed improvements in depression, post-concussive symptoms, and sleep dysfunction. The present study was a secondary analysis of that data. Anatomically accurate head models were derived from magnetic resonance imaging (MRI), and finite element analysis simulations were performed to mimic empirical data collection. This allowed for examination of the roles that age, brain scalp distance (BSD), gray matter volume (GMV), site-specific electrical field strength (EFS), and depolarized gray matter volume (DGMV) had on resting motor threshold (RMT) at the precentral gyrus (PreCG). We also investigated how EFS simulated at the dorsolateral prefrontal cortex (DLPFC) and RMT influenced rTMS treatment outcomes. Linear regression showed BSD was associated with EFS, RMT, and DGMV supporting efforts to derive accurate parameters from MRI-based modeling. Furthermore, linear mixed effects modeling showed RMT was associated with EFS and DGMV at the PreCG when age and individual neuroanatomy was accounted for suggesting MRI based anatomy and simulated EFS potentially determine TMS dosage. We did not observe any significant relationship between any of the measures from this study on empirically collected rTMS outcomes in mTBI suggesting further investigations into the mechanisms behind these outcomes are needed.
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Tayebi Meybodi, Ali, Arnau Benet, Vera Vigo, Roberto Rodriguez Rubio, Sonia Yousef, Pooneh Mokhtari, Flavia Dones, Sofia Kakaizada, and Michael T. Lawton. "Assessment of the endoscopic endonasal approach to the basilar apex region for aneurysm clipping." Journal of Neurosurgery 130, no. 6 (June 2019): 1937–48. http://dx.doi.org/10.3171/2018.1.jns172813.

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OBJECTIVEThe expanded endoscopic endonasal approach (EEA) has shown promising results in treatment of midline skull base lesions. Several case reports exist on the utilization of the EEA for treatment of aneurysms. However, a comparison of this approach with the classic transcranial orbitozygomatic approach to the basilar apex (BAX) region is missing.The present study summarizes the results of a series of cadaveric surgical simulations for assessment of the EEA to the BAX region for aneurysm clipping and its comparison with the transcranial orbitozygomatic approach as one of the most common approaches used to treat BAX aneurysms.METHODSFifteen cadaveric specimens underwent bilateral orbitozygomatic craniotomies as well as an EEA (first without a pituitary transposition [PT] and then with a PT) to expose the BAX. The following variables were measured, recorded, and compared between the orbitozygomatic approach and the EEA: 1) number of perforating arteries counted on bilateral posterior cerebral arteries (PCAs); 2) exposure and clipping lengths of the PCAs, superior cerebellar arteries (SCAs), and proximal basilar artery; and 3) surgical area of exposure in the BAX region.RESULTSExcept for the proximal basilar artery exposure and clipping, the orbitozygomatic approach provided statistically significantly greater values for vascular exposure and control in the BAX region (i.e., exposure and clipping of ipsilateral and contralateral SCAs and PCAs). The EEA with PT was significantly better in exposing and clipping bilateral PCAs compared to EEA without a PT, but not in terms of other measured variables. The surgical area of exposure and PCA perforator counts were not significantly different between the 3 approaches. The EEA provided better exposure and control if the BAX was located ≥ 4 mm inferior to the dorsum sellae.CONCLUSIONSFor BAX aneurysms located in the retrosellar area, PT is usually required to obtain improved exposure and control for the bilateral PCAs. However, the transcranial approach is generally superior to both endoscopic approaches for accessing the BAX region. Considering the superior exposure of the proximal basilar artery obtained with the EEA, it could be a viable option when surgical treatment is considered for a low-lying BAX or mid–basilar trunk aneurysms (≥ 4 mm inferior to dorsum sellae).
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Samoudi, Amine M., Emmeric Tanghe, Luc Martens, and Wout Joseph. "Deep Transcranial Magnetic Stimulation: Improved Coil Design and Assessment of the Induced Fields Using MIDA Model." BioMed Research International 2018 (June 5, 2018): 1–9. http://dx.doi.org/10.1155/2018/7061420.

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Stimulation of deep brain structures by transcranial magnetic stimulation (TMS) is a method for activating deep neurons in the brain and can be beneficial for the treatment of psychiatric and neurological disorders. To numerically investigate the possibility for deeper brain stimulation (electric fields reaching the hippocampus, the nucleus accumbens, and the cerebellum), combined TMS coils using the double-cone coil with the Halo coil (HDA) were modeled and investigated. Numerical simulations were performed using MIDA: a new multimodal imaging-based detailed anatomical model of the human head and neck. The 3D distributions of magnetic flux density and electric field were calculated. The percentage of volume of each tissue that is exposed to electric field amplitude equal or greater than 50% of the maximum amplitude of E in the cortex for each coil was calculated to quantify the electric field spread (V50). Results show that only the HDA coil can spread electric fields to the hippocampus, the nucleus accumbens, and the cerebellum with V50 equal to 0.04%, 1.21%, and 6.2%, respectively.
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Verstynen, Timothy, Talia Konkle, and Richard B. Ivry. "Two Types of TMS-Induced Movement Variability After Stimulation of the Primary Motor Cortex." Journal of Neurophysiology 96, no. 3 (September 2006): 1018–29. http://dx.doi.org/10.1152/jn.01358.2005.

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Using transcranial magnetic stimulation, we studied the role of the primary motor cortex (M1) in repetitive movements, examining whether the functional contribution of this region is associated with controlling response timing, response implementation, or both. In two experiments, participants performed a rhythmic tapping task, attempting to produce isochronous intervals (range of 350–550 ms) while stimulation was applied over M1 or a control site. M1 stimulation was associated with increased variability of the inter-tap intervals (ITI), and, by manipulating stimulation intensity, we identified two distinct changes in performance: a generalized increase in ITI variability and a delay in the subsequent response when the pulse fell within a restricted window prior to movement onset. Using a series of simulations, we demonstrate that the general increase in variability and the temporally specific delay reflect disruption of response implementation processes rather than an increase in noise associated with response timing.
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Mandija, Stefano, Petar I. Petrov, Sebastian F. W. Neggers, Peter R. Luijten, and Cornelis A. T. van den Berg. "MR-based measurements and simulations of the magnetic field created by a realistic transcranial magnetic stimulation (TMS) coil and stimulator." NMR in Biomedicine 29, no. 11 (September 27, 2016): 1590–600. http://dx.doi.org/10.1002/nbm.3618.

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Ferri, Marcelino, José María Bravo, Javier Redondo, Sergio Jiménez-Gambín, Noé Jiménez, Francisco Camarena, and Juan Vicente Sánchez-Pérez. "On the Evaluation of the Suitability of the Materials Used to 3D Print Holographic Acoustic Lenses to Correct Transcranial Focused Ultrasound Aberrations." Polymers 11, no. 9 (September 19, 2019): 1521. http://dx.doi.org/10.3390/polym11091521.

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The correction of transcranial focused ultrasound aberrations is a relevant topic for enhancing various non-invasive medical treatments. Presently, the most widely accepted method to improve focusing is the emission through multi-element phased arrays; however, a new disruptive technology, based on 3D printed holographic acoustic lenses, has recently been proposed, overcoming the spatial limitations of phased arrays due to the submillimetric precision of the latest generation of 3D printers. This work aims to optimize this recent solution. Particularly, the preferred acoustic properties of the polymers used for printing the lenses are systematically analyzed, paying special attention to the effect of p-wave speed and its relationship to the achievable voxel size of 3D printers. Results from simulations and experiments clearly show that, given a particular voxel size, there are optimal ranges for lens thickness and p-wave speed, fairly independent of the emitted frequency, the transducer aperture, or the transducer-target distance.
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Rahnev, Dobromir, Derek Evan Nee, Justin Riddle, Alina Sue Larson, and Mark D’Esposito. "Causal evidence for frontal cortex organization for perceptual decision making." Proceedings of the National Academy of Sciences 113, no. 21 (May 9, 2016): 6059–64. http://dx.doi.org/10.1073/pnas.1522551113.

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Although recent research has shown that the frontal cortex has a critical role in perceptual decision making, an overarching theory of frontal functional organization for perception has yet to emerge. Perceptual decision making is temporally organized such that it requires the processes of selection, criterion setting, and evaluation. We hypothesized that exploring this temporal structure would reveal a large-scale frontal organization for perception. A causal intervention with transcranial magnetic stimulation revealed clear specialization along the rostrocaudal axis such that the control of successive stages of perceptual decision making was selectively affected by perturbation of successively rostral areas. Simulations with a dynamic model of decision making suggested distinct computational contributions of each region. Finally, the emergent frontal gradient was further corroborated by functional MRI. These causal results provide an organizational principle for the role of frontal cortex in the control of perceptual decision making and suggest specific mechanistic contributions for its different subregions.

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