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Lim J, Eiber CD, Sun A, Maples A, Powley TL, Ward MP, Lee H. Fractal Microelectrodes for More Energy-Efficient Cervical Vagus Nerve Stimulation. Adv Healthc Mater 2023; 12:e2202619. [PMID: 36973998 PMCID: PMC10522801 DOI: 10.1002/adhm.202202619] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 03/06/2023] [Indexed: 03/29/2023]
Abstract
Vagus nerve stimulation (VNS) has the potential to treat various peripheral dysfunctions, but the traditional cuff electrodes for VNS are susceptible to off-target effects. Microelectrodes may enable highly selective VNS that can mitigate off-target effects, but they suffer from the increased impedance. Recent studies on microelectrodes with non-Euclidean geometries have reported higher energy efficiency in neural stimulation applications. These previous studies use electrodes with mm/cm-scale dimensions, mostly targeted for myelinated fibers. This study evaluates fractal microelectrodes for VNS in a rodent model (N = 3). A thin-film device with fractal and circle microelectrodes is fabricated to compare their neural stimulation performance on the same radial coordinate of the nerve. The results show that fractal microelectrodes can activate C-fibers with up to 52% less energy (p = 0.012) compared to circle microelectrodes. To the best of the knowledge, this work is the first to demonstrate a geometric advantage of fractal microelectrodes for VNS in vivo.
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Affiliation(s)
- Jongcheon Lim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- Center for Implantable Devices, Purdue University, West Lafayette, IN, 47907, USA
| | - Calvin D Eiber
- Synchron Inc., Melbourne, VIC, 3004, Australia
- Department of Medicine (RMH), Faculty of Medicine, Health and Dentistry, the University of Melbourne, Melbourne, VIC, 3050, Australia
| | - Anina Sun
- Department of Biology, Purdue University, West Lafayette, IN, 47907, USA
| | - Amanda Maples
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Terry L Powley
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Department of Psychological Sciences, Purdue University, West Lafayette, IN, 47907, USA
- Purdue Institute of Integrative Neuroscience, Purdue University, West Lafayette, IN, 47907, USA
| | - Matthew P Ward
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Hyowon Lee
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- Center for Implantable Devices, Purdue University, West Lafayette, IN, 47907, USA
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Moslehi S, Rowland C, Smith JH, Griffiths W, Watterson WJ, Niell CM, Alemán BJ, Perez MT, Taylor RP. Comparison of fractal and grid electrodes for studying the effects of spatial confinement on dissociated retinal neuronal and glial behavior. Sci Rep 2022; 12:17513. [PMID: 36266414 PMCID: PMC9584887 DOI: 10.1038/s41598-022-21742-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 09/30/2022] [Indexed: 01/12/2023] Open
Abstract
Understanding the impact of the geometry and material composition of electrodes on the survival and behavior of retinal cells is of importance for both fundamental cell studies and neuromodulation applications. We investigate how dissociated retinal cells from C57BL/6J mice interact with electrodes made of vertically-aligned carbon nanotubes grown on silicon dioxide substrates. We compare electrodes with different degrees of spatial confinement, specifically fractal and grid electrodes featuring connected and disconnected gaps between the electrodes, respectively. For both electrodes, we find that neuron processes predominantly accumulate on the electrode rather than the gap surfaces and that this behavior is strongest for the grid electrodes. However, the 'closed' character of the grid electrode gaps inhibits glia from covering the gap surfaces. This lack of glial coverage for the grids is expected to have long-term detrimental effects on neuronal survival and electrical activity. In contrast, the interconnected gaps within the fractal electrodes promote glial coverage. We describe the differing cell responses to the two electrodes and hypothesize that there is an optimal geometry that maximizes the positive response of both neurons and glia when interacting with electrodes.
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Affiliation(s)
- Saba Moslehi
- grid.170202.60000 0004 1936 8008Physics Department, 1371 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Materials Science Institute, 1252 University of Oregon, Eugene, OR 97403 USA
| | - Conor Rowland
- grid.170202.60000 0004 1936 8008Physics Department, 1371 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Materials Science Institute, 1252 University of Oregon, Eugene, OR 97403 USA
| | - Julian H. Smith
- grid.170202.60000 0004 1936 8008Physics Department, 1371 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Materials Science Institute, 1252 University of Oregon, Eugene, OR 97403 USA
| | - Willem Griffiths
- grid.170202.60000 0004 1936 8008Department of Biology, 1210 University of Oregon, Eugene, OR 97403 USA
| | - William J. Watterson
- grid.170202.60000 0004 1936 8008Physics Department, 1371 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Materials Science Institute, 1252 University of Oregon, Eugene, OR 97403 USA
| | - Cristopher M. Niell
- grid.170202.60000 0004 1936 8008Department of Biology, 1210 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403 USA
| | - Benjamín J. Alemán
- grid.170202.60000 0004 1936 8008Physics Department, 1371 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Materials Science Institute, 1252 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Oregon Center for Optical, Molecular and Quantum Science, 1274 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Phil and Penny Knight Campus for Accelerating Scientific Impact, 1505 University of Oregon, Franklin Blvd., Eugene, OR 97403 USA
| | - Maria-Thereza Perez
- grid.4514.40000 0001 0930 2361Division of Ophthalmology, Department of Clinical Sciences Lund, Lund University, 221 84 Lund, Sweden ,grid.4514.40000 0001 0930 2361NanoLund, Lund University, 221 00 Lund, Sweden
| | - Richard P. Taylor
- grid.170202.60000 0004 1936 8008Physics Department, 1371 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Materials Science Institute, 1252 University of Oregon, Eugene, OR 97403 USA ,grid.170202.60000 0004 1936 8008Phil and Penny Knight Campus for Accelerating Scientific Impact, 1505 University of Oregon, Franklin Blvd., Eugene, OR 97403 USA
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3
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Jiang F, Elahi B, Saxena M, Telkes I, DiMarzio M, Pilitsis JG, Golestanirad L. Patient-specific modeling of the volume of tissue activated (VTA) is associated with clinical outcome of DBS in patients with an obsessive-compulsive disorder. Annu Int Conf IEEE Eng Med Biol Soc 2021; 2021:5889-5892. [PMID: 34892459 PMCID: PMC10829536 DOI: 10.1109/embc46164.2021.9630273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Deep brain stimulation (DBS) promises to treat an increasing number of neurological and psychiatric disorders. DBS outcome is directly a factor of optimal targeting of the relevant brain structures. Computational models can help to interpret a patient's outcome by predicting the volume of tissue activated (VTA) around DBS electrode contacts. Here we report results of a preliminary study of DBS in two patients with obsessive-compulsive disorder and show that VTA predictions, which are based on patient-specific volume conductor models, correlate with clinical outcome. Our results suggest that patient specific VTA calculation can help inform device programing to maximize therapeutic effects and minimize side effects.Clinical Relevance- Patient-specific modeling of the volume of activated tissue can predict clinical outcomes and thus, can help to optimize DBS device programing to maximize therapeutic effects.
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4
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Smith JH, Rowland C, Harland B, Moslehi S, Montgomery RD, Schobert K, Watterson WJ, Dalrymple-Alford J, Taylor RP. How neurons exploit fractal geometry to optimize their network connectivity. Sci Rep 2021; 11:2332. [PMID: 33504818 DOI: 10.1038/s41598-021-81421-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 12/30/2020] [Indexed: 11/13/2022] Open
Abstract
We investigate the degree to which neurons are fractal, the origin of this fractality, and its impact on functionality. By analyzing three-dimensional images of rat neurons, we show the way their dendrites fork and weave through space is unexpectedly important for generating fractal-like behavior well-described by an ‘effective’ fractal dimension D. This discovery motivated us to create distorted neuron models by modifying the dendritic patterns, so generating neurons across wide ranges of D extending beyond their natural values. By charting the D-dependent variations in inter-neuron connectivity along with the associated costs, we propose that their D values reflect a network cooperation that optimizes these constraints. We discuss the implications for healthy and pathological neurons, and for connecting neurons to medical implants. Our automated approach also facilitates insights relating form and function, applicable to individual neurons and their networks, providing a crucial tool for addressing massive data collection projects (e.g. connectomes).
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Iwasa SN, Shi HH, Hong SH, Chen T, Marquez-Chin M, Iorio-Morin C, Kalia SK, Popovic MR, Naguib HE, Morshead CM. Novel Electrode Designs for Neurostimulation in Regenerative Medicine: Activation of Stem Cells. Bioelectricity 2020; 2:348-361. [PMID: 34471854 PMCID: PMC8370381 DOI: 10.1089/bioe.2020.0034] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Neural stem and progenitor cells (i.e., neural precursors) are found within specific regions in the central nervous system and have great regenerative capacity. These cells are electrosensitive and their behavior can be regulated by the presence of electric fields (EFs). Electrical stimulation is currently used to treat neurological disorders in a clinical setting. Herein we propose that electrical stimulation can be used to enhance neural repair by regulating neural precursor cell (NPC) kinetics and promoting their migration to sites of injury or disease. We discuss how intrinsic and extrinsic factors can affect NPC migration in the presence of an EF and how this impacts electrode design with the goal of enhancing tissue regeneration. We conclude with an outlook on future clinical applications of electrical stimulation and highlight technological advances that would greatly support these applications.
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Affiliation(s)
- Stephanie N Iwasa
- The KITE Research Institute, Toronto Rehabilitation Institute-University Health Network, Toronto, Canada
- CRANIA, University Health Network and University of Toronto, Toronto, Canada
| | - HaoTian H Shi
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | - Sung Hwa Hong
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Canada
| | - Tianhao Chen
- Institute of Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Melissa Marquez-Chin
- The KITE Research Institute, Toronto Rehabilitation Institute-University Health Network, Toronto, Canada
- Institute of Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Christian Iorio-Morin
- Department of Neurosurgery, University Health Network, University of Toronto, Toronto, Canada
| | - Suneil K Kalia
- The KITE Research Institute, Toronto Rehabilitation Institute-University Health Network, Toronto, Canada
- CRANIA, University Health Network and University of Toronto, Toronto, Canada
- Department of Neurosurgery, University Health Network, University of Toronto, Toronto, Canada
- Krembil Research Institute, Toronto, Canada
| | - Milos R Popovic
- The KITE Research Institute, Toronto Rehabilitation Institute-University Health Network, Toronto, Canada
- CRANIA, University Health Network and University of Toronto, Toronto, Canada
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
- Institute of Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Hani E Naguib
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
- Institute of Biomedical Engineering, University of Toronto, Toronto, Canada
- Department of Materials Science & Engineering, University of Toronto, Toronto, Canada
| | - Cindi M Morshead
- The KITE Research Institute, Toronto Rehabilitation Institute-University Health Network, Toronto, Canada
- CRANIA, University Health Network and University of Toronto, Toronto, Canada
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
- Institute of Biomedical Engineering, University of Toronto, Toronto, Canada
- Department of Surgery, University of Toronto, Toronto, Canada
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6
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Khorrampanah M, Seyedarabi H, Daneshvar S, Farhoudi M. Optimization of montages and electric currents in tDCS. Comput Biol Med 2020; 125:103998. [PMID: 33039799 DOI: 10.1016/j.compbiomed.2020.103998] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/16/2020] [Accepted: 08/31/2020] [Indexed: 11/17/2022]
Abstract
In order to optimize the capability of transcranial Direct Current Stimulation (tDCS), electrode arrangements and the inward current stimulation are taken into account as two crucial factors. In this contribution, in order to specify the electrode positions, a detailed protocol is investigated, in which regarding the intended targeted regions, the optimal montages with an arbitrary number of electrodes are developed. After designing the positions of all active and returned electrodes, the corresponding inward current density is determined for each electrode. The outcomes of the simulation and the electric field distributions in the hand cortex prove that the proposed protocol is capable of improving the tDCS efficiency substantially in all head layers. Furthermore, in order to compare our approach with the other works found in the literature, a performance evaluation is curried out by calculating the maximum electric field distribution in the targeted region. This study shows that it improves tDCS efficiency virtually 2.5 times in comparison to High Definition (HD) montages in the gray matter and nearly 1.5 times in comparison to the other inner layers. Such an outstanding achievement in the gray matter can be regarded as an interesting standpoint in tDCS-rehabilitation studies.
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Affiliation(s)
- Mahsa Khorrampanah
- Faculty of Electrical and Computer Engineering, University of Tabriz, Iran
| | - Hadi Seyedarabi
- Faculty of Electrical and Computer Engineering, University of Tabriz, Iran.
| | - Sabalan Daneshvar
- Faculty of Electrical and Computer Engineering, University of Tabriz, Iran; Department of Electronic and Computer Engineering, College of Engineering. Design and Physical Sciences, Brunel University, UK
| | - Mehdi Farhoudi
- Neurosciences Research Center (NSRC), Tabriz University of Medical Sciences, Tabriz, Iran
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7
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RaviChandran N, Teo MY, Aw K, McDaid A. Design of Transcutaneous Stimulation Electrodes for Wearable Neuroprostheses. IEEE Trans Neural Syst Rehabil Eng 2020; 28:1651-1660. [DOI: 10.1109/tnsre.2020.2994900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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8
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Jiang F, Nguyen BT, Elahi B, Pilitsis J, Golestanirad L. Effect of Biophysical Model Complexity on Predictions of Volume of Tissue Activated (VTA) during Deep Brain Stimulation. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2020:3629-3633. [PMID: 33018788 PMCID: PMC10883758 DOI: 10.1109/embc44109.2020.9175300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Deep brain stimulation (DBS) has evolved to an important treatment for several drug-resistant neurological and psychiatric disorders, such as epilepsy, Parkinson's disease, essential tremor and dystonia. Despite general effectiveness of DBS, however, its mechanisms of action are not completely understood. Simulations are commonly used to predict the volume of tissue activated (VTA) around DBS electrodes, which in turn helps interpreting clinical outcomes and understand therapeutic mechanisms. Computational models are commonly used to visualize the extend of volume of activated tissue (VTA) for different stimulation schemes, which in turn helps interpreting and understanding the outcomes. The degree of model complexity, however, can affect the predicted VTA. In this work we investigate the effect of volume conductor model complexity on the predicted VTA, when the VTA is estimated from activation function field metrics. Our results can help clinicians to decide what level of model complexity is suitable for their specific need.
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9
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Eles JR, Kozai TDY. In vivo imaging of calcium and glutamate responses to intracortical microstimulation reveals distinct temporal responses of the neuropil and somatic compartments in layer II/III neurons. Biomaterials 2020; 234:119767. [PMID: 31954232 DOI: 10.1016/j.biomaterials.2020.119767] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 12/22/2019] [Accepted: 01/05/2020] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Intracortical microelectrode implants can generate a tissue response hallmarked by glial scarring and neuron cell death within 100-150 μm of the biomaterial device. Many have proposed that any performance decline in intracortical microstimulation (ICMS) due to this foreign body tissue response could be offset by increasing the stimulation amplitude. The mechanisms of this approach are unclear, however, as there has not been consensus on how increasing amplitude affects the spatial and temporal recruitment patterns of ICMS. APPROACH We clarify these unknowns using in vivo two-photon imaging of mice transgenically expressing the calcium sensor GCaMP6s in Thy1 neurons or virally expressing the glutamate sensor iGluSnFr in neurons. Calcium and neurotransmitter activity are tracked in the neuronal somas and neuropil during long-train stimulation in Layer II/III of somatosensory cortex. MAIN RESULTS Neural calcium activity and glutamate release are dense and strongest within 20-40 μm around the electrode, falling off with distance from the electrode. Neuronal calcium increases with higher amplitude stimulations. During prolonged stimulation trains, a sub-population of somas fail to maintain calcium activity. Interestingly, neuropil calcium activity is 3-fold less correlated to somatic calcium activity for cells that drop-out during the long stimulation train compared to cells that sustain activity throughout the train. Glutamate release is apparent only within 20 μm of the electrode and is sustained for at least 10s after cessation of the 15 and 20 μA stimulation train, but not lower amplitudes. SIGNIFICANCE These results demonstrate that increasing amplitude can increase the radius and intensity of neural recruitment, but it also alters the temporal response of some neurons. Further, dense glutamate release is highest within the first 20 μm of the electrode site even at high amplitudes, suggesting that there may be spatial limitations to the amplitude parameter space. The glutamate elevation outlasts stimulation, suggesting that high-amplitude stimulation may affect neurotransmitter re-uptake. This ultimately suggests that increasing the amplitude of ICMS device stimulation may fundamentally alter the temporal neural response, which could have implications for using amplitude to improve the ICMS effect or "offset" the effects of glial scarring.
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Affiliation(s)
- James R Eles
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Takashi D Y Kozai
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, Carnegie Mellon University, Pittsburgh, PA, USA; Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; NeuroTech Center, University of Pittsburgh Brain Institute, Pittsburgh, PA, USA.
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Chen L, Zou X, Tang R, Ke A, He J. Effect of electrode-electrolyte spatial mismatch on transcranial direct current stimulation: a finite element modeling study. J Neural Eng 2019; 16:056012. [DOI: 10.1088/1741-2552/ab29c5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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11
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Kazemivalipour E, Keil B, Vali A, Rajan S, Elahi B, Atalar E, Wald LL, Rosenow J, Pilitsis J, Golestanirad L. Reconfigurable MRI technology for low-SAR imaging of deep brain stimulation at 3T: Application in bilateral leads, fully-implanted systems, and surgically modified lead trajectories. Neuroimage 2019; 199:18-29. [PMID: 31096058 DOI: 10.1016/j.neuroimage.2019.05.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Revised: 04/24/2019] [Accepted: 05/06/2019] [Indexed: 11/22/2022] Open
Abstract
Patients with deep brain stimulation devices highly benefit from postoperative MRI exams, however MRI is not readily accessible to these patients due to safety risks associated with RF heating of the implants. Recently we introduced a patient-adjustable reconfigurable coil technology that substantially reduced local SAR at tips of single isolated DBS leads during MRI at 1.5 T in 9 realistic patient models. This contribution extends our work to higher fields by demonstrating the feasibility of scaling the technology to 3T and assessing its performance in patients with bilateral leads as well as fully implanted systems. We developed patient-derived models of bilateral DBS leads and fully implanted DBS systems from postoperative CT images of 13 patients and performed finite element simulations to calculate SAR amplification at electrode contacts during MRI with a reconfigurable rotating coil at 3T. Compared to a conventional quadrature body coil, the reconfigurable coil system reduced the SAR on average by 83% for unilateral leads and by 59% for bilateral leads. A simple surgical modification in trajectory of implanted leads was demonstrated to increase the SAR reduction efficiency of the rotating coil to >90% in a patient with a fully implanted bilateral DBS system. Thermal analysis of temperature-rise around electrode contacts during typical brain exams showed a 15-fold heating reduction using the rotating coil, generating <1°C temperature rise during ∼4-min imaging with high-SAR sequences where a conventional CP coil generated >10°C temperature rise in the tissue for the same flip angle.
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Golestanirad L, Angelone LM, Kirsch J, Downs S, Keil B, Bonmassar G, Wald LL. Reducing RF-induced Heating near Implanted Leads through High-Dielectric Capacitive Bleeding of Current (CBLOC). IEEE Trans Microw Theory Tech 2019; 67:1265-1273. [PMID: 31607756 PMCID: PMC6788634 DOI: 10.1109/tmtt.2018.2885517] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Patients with implanted medical devices such as deep brain stimulation or spinal cord stimulation are often unable to receive magnetic resonance imaging (MRI). This is because once the device is within the radiofrequency (RF) field of the MRI scanner, electrically conductive leads act as antenna, amplifying the RF energy deposition in the tissue and causing possible excessive tissue heating. Here we propose a novel concept in lead design in which 40cm lead wires are coated with a ~1.2mm layer of high dielectric constant material (155 < ε r < 250) embedded in a weakly conductive insulation (σ = 20S/m). The technique called High-Dielectric Capacitive Bleeding of Current, or CBLOC, works by forming a distributed capacitance along the lengths of the lead, efficiently dissipating RF energy before it reaches the exposed tip. Measurements during RF exposure at 64 MHz and 123 MHz demonstrated that CBLOC leads generated 20-fold less heating at 1.5 T, and 40-fold less heating at 3 T compared to control leads. Numerical simulations of RF exposure at 297 MHz (7T) predicted a 15-fold reduction in specific absorption rate (SAR) of RF energy around the tip of CBLOC leads compared to control leads.
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Affiliation(s)
- Laleh Golestanirad
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Department of Radiology, Harvard Medical School, Charlestown, MA 02129 USA, and the Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago IL 60611 USA
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Device and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD
| | - John Kirsch
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
| | - Sean Downs
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
| | - Boris Keil
- Department of Life Science Engineering, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Giorgio Bonmassar
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
| | - Lawrence L Wald
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
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Golestanirad L, Kirsch J, Bonmassar G, Downs S, Elahi B, Martin A, Iacono MI, Angelone LM, Keil B, Wald LL, Pilitsis J. RF-induced heating in tissue near bilateral DBS implants during MRI at 1.5 T and 3T: The role of surgical lead management. Neuroimage 2019; 184:566-76. [PMID: 30243973 DOI: 10.1016/j.neuroimage.2018.09.034] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 09/10/2018] [Accepted: 09/14/2018] [Indexed: 11/21/2022] Open
Abstract
Access to MRI is limited for patients with deep brain stimulation (DBS) implants due to safety hazards, including radiofrequency (RF) heating of tissue surrounding the leads. Computational models provide an exquisite tool to explore the multi-variate problem of RF heating and help better understand the interaction of electromagnetic fields and biological tissues. This paper presents a computational approach to assess RF-induced heating, in terms of specific absorption rate (SAR) in the tissue, around the tip of bilateral DBS leads during MRI at 64MHz/1.5 T and 127 MHz/3T. Patient-specific realistic lead models were constructed from post-operative CT images of nine patients operated for sub-thalamic nucleus DBS. Finite element method was applied to calculate the SAR at the tip of left and right DBS contact electrodes. Both transmit head coils and transmit body coils were analyzed. We found a substantial difference between the SAR and temperature rise at the tip of right and left DBS leads, with the lead contralateral to the implanted pulse generator (IPG) exhibiting up to 7 times higher SAR in simulations, and up to 10 times higher temperature rise during measurements. The orientation of incident electric field with respect to lead trajectories was explored and a metric to predict local SAR amplification was introduced. Modification of the lead trajectory was shown to substantially reduce the heating in phantom experiments using both conductive wires and commercially available DBS leads. Finally, the surgical feasibility of implementing the modified trajectories was demonstrated in a patient operated for bilateral DBS.
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14
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Golestanirad L, Gale JT, Manzoor NF, Park HJ, Glait L, Haer F, Kaltenbach JA, Bonmassar G. Solenoidal Micromagnetic Stimulation Enables Activation of Axons With Specific Orientation. Front Physiol 2018; 9:724. [PMID: 30140230 PMCID: PMC6094965 DOI: 10.3389/fphys.2018.00724] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/24/2018] [Indexed: 01/28/2023] Open
Abstract
Electrical stimulation of the central and peripheral nervous systems - such as deep brain stimulation, spinal cord stimulation, and epidural cortical stimulation are common therapeutic options increasingly used to treat a large variety of neurological and psychiatric conditions. Despite their remarkable success, there are limitations which if overcome, could enhance outcomes and potentially reduce common side-effects. Micromagnetic stimulation (μMS) was introduced to address some of these limitations. One of the most remarkable properties is that μMS is theoretically capable of activating neurons with specific axonal orientations. Here, we used computational electromagnetic models of the μMS coils adjacent to neuronal tissue combined with axon cable models to investigate μMS orientation-specific properties. We found a 20-fold reduction in the stimulation threshold of the preferred axonal orientation compared to the orthogonal direction. We also studied the directional specificity of μMS coils by recording the responses evoked in the inferior colliculus of rodents when a pulsed magnetic stimulus was applied to the surface of the dorsal cochlear nucleus. The results confirmed that the neuronal responses were highly sensitive to changes in the μMS coil orientation. Accordingly, our results suggest that μMS has the potential of stimulating target nuclei in the brain without affecting the surrounding white matter tracts.
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Affiliation(s)
- Laleh Golestanirad
- Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, United States.,Harvard Medical School, Boston, MA, United States
| | - John T Gale
- Department of Neurosurgery, Emory University, Atlanta, GA, United States
| | - Nauman F Manzoor
- Department of Neurosciences, Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States.,Ear, Nose and Throat Institute, University Hospitals Cleveland Medical Center, Case Western Reserve University, Cleveland, OH, United States
| | - Hyun-Joo Park
- Department of Neurosciences, Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States
| | - Lyall Glait
- Department of Neurosciences, Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States.,Ear, Nose and Throat Institute, University Hospitals Cleveland Medical Center, Case Western Reserve University, Cleveland, OH, United States
| | | | - James A Kaltenbach
- Department of Neurosciences, Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, United States.,Harvard Medical School, Boston, MA, United States
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15
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Watterson WJ, Montgomery RD, Taylor RP. Modeling the Improved Visual Acuity Using Photodiode Based Retinal Implants Featuring Fractal Electrodes. Front Neurosci 2018; 12:277. [PMID: 29740278 PMCID: PMC5928399 DOI: 10.3389/fnins.2018.00277] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 04/10/2018] [Indexed: 11/23/2022] Open
Abstract
Electronically restoring vision to patients blinded by severe retinal degenerations is rapidly becoming a realizable feat through retinal implants. Upon receiving an implant, previously blind patients can now detect light, locate objects, and determine object motion direction. However, the restored visual acuity (VA) is still significantly below the legal blindness level (VA < 20/200). The goal of this research is to optimize the inner electrode geometry in photovoltaic subretinal implants in order to restore vision to a VA better than blindness level. We simulated neural stimulation by 20 μm subretinal photovoltaic implants featuring square or fractal inner electrodes by: (1) calculating the voltage generated on the inner electrode based on the amount of light entering the photodiode, (2) mapping how this voltage spreads throughout the extracellular space surrounding retinal bipolar neurons, and (3) determining if these extracellular voltages are sufficient for neural stimulation. By optimizing the fractal inner electrode geometry, we show that all neighboring neurons can be stimulated using an irradiance of 12 mW/mm2, while the optimized square only stimulates ~10% of these neurons at an equivalent irradiance. The 20 μm fractal electrode can thus theoretically restore VA up to 20/80, if other limiting factors common to retinal degenerations, such as glia scarring and rewiring of retinal circuits, could be reduced. For the optimized square to stimulate all neighboring neurons, the irradiance has to be increased by almost 300%, which is very near the maximum permissible exposure safety limit. This demonstration that fractal electrodes can stimulate targeted neurons for long periods using safe irradiance levels highlights the possibility for restoring vision to a VA better than the blindness level using photodiode-based retinal implants.
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Affiliation(s)
| | | | - Richard P Taylor
- Physics Department, University of Oregon, Eugene, OR, United States
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16
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Abstract
Advancements in microfabrication has enabled manufacturing of microscopic neurostimulation electrodes with smaller footprint than ever possible. The smaller electrodes can potentially reduce tissue damage and allow better spatial resolution for neural stimulation. Although electrodes of any shape can easily be fabricated, substantial effort have been focused on identification and characterization of new materials and surface morphology for efficient charge injection, while maintaining simple circular or rectangular Euclidean electrode geometries. In this work we provide a systematic electrochemical evaluation of charge injection capacities of serpentine and fractal-shaped platinum microelectrodes and compare their performance with traditional circular microelectrodes. Our findings indicate that the increase in electrode perimeter leads to an increase in maximum charge injection capacity. Furthermore, we found that the electrode geometry can have even more significant impact on electrode performance than having a larger perimeter for a given surface area. The fractal-shaped microelectrodes, despite having smaller perimeter than other designs, demonstrated superior charge injection capacity. Our results suggest that electrode design can significantly affect both Faradaic and non-Faradaic electrochemical processes, which may be optimized to enable a more energy efficient design for neurostimulation.
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17
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Abstract
This work further advances the micromagnetic stimulation (μMS) technology, which has shown the capability of stimulating the nervous system using magnetic induction in a focal region of tissue by discharging a time-varying current through a sub-millimeter size coil. However, μMS was originally based on commercial off the shelf (COTS) inductors, which are designed to maximize efficiency and minimize its losses albeit shielding off the magnetic field from reaching the neural tissue. In this work, we study and fabricate microscale coil structures for next-generation μMS devices. The coil was designed to optimize the flux injected into the tissue by using a planar square spiral coil geometry, which was previously shown to be optimal for neuronal stimulation. The results of the electromagnetic Finite Elements Method (FEM) simulations of the proposed μMS device show that even though the spiral has a fully symmetric design, it nonetheless exhibits an asymmetry in the induced electric field in the tissue that can potentially be used for activating neurons with a specific axonal orientation. Such devices could become the brain and heart stimulators of the future with their contactless ability to deliver the neuronal stimulation needed for therapeutic efficacy in patients in need of implantable cardioverter-defibrillators or pace-makers, or patients with Parkinson's disease, epilepsy.
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Affiliation(s)
- Giorgio Bonmassar
- A. A. Martinos Center, Harvard Medical School, Massachusetts General Hospital, Charlestown, 02129 MA, USA
| | - Laleh Golestanirad
- A. A. Martinos Center, Harvard Medical School, Massachusetts General Hospital, Charlestown, 02129 MA, USA
| | - Jiangdong Deng
- Center for Nanoscale Systems., Harvard University. Cambridge, 02138 MA, USA
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18
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Abstract
The prospect of replacing damaged body parts with artificial implants is being transformed from science fiction to science fact through the increasing application of electronics to interface with human neurons in the limbs, the brain, and the retina. We propose bio-inspired electronics which adopt the fractal geometry of the neurons they interface with. Our focus is on retinal implants, although performance improvements will be generic to many neuronal types. The key component is a multifunctional electrode; light passes through this electrode into a photodiode which charges the electrode. Its electric field then stimulates the neurons. A fractal electrode might increase both light transmission and neuron proximity compared to conventional Euclidean electrodes. These advantages are negated if the fractal’s field is less effective at stimulating neurons. We present simulations demonstrating how an interplay of fractal properties generates enhanced stimulation; the electrode voltage necessary to stimulate all neighboring neurons is over 50% less for fractal than Euclidean electrodes. This smaller voltage can be achieved by a single diode compared to three diodes required for the Euclidean electrode’s higher voltage. This will allow patients, for the first time, to see with the visual acuity necessary for navigating rooms and streets.
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Affiliation(s)
- W J Watterson
- Physics Department, University of Oregon, Eugene, OR, 97403, USA.
| | - R D Montgomery
- Physics Department, University of Oregon, Eugene, OR, 97403, USA
| | - R P Taylor
- Physics Department, University of Oregon, Eugene, OR, 97403, USA
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19
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Willsie A, Dorval A. Fabrication and initial testing of the μDBS: a novel Deep Brain Stimulation electrode with thousands of individually controllable contacts. Biomed Microdevices 2015; 17:9961. [PMID: 25981752 DOI: 10.1007/s10544-015-9961-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
High frequency electrical stimulation of deep brain structures such as the subthalamic nucleus in Parkinson's disease or thalamus for essential tremor is used clinically to reduce symptom severity. Deep brain stimulation activates neurons in specific brain structures and connection pathways, overriding aberrant neural activity associated with symptoms. While optimal deep brain stimulation might activate a particular neural structure precisely, existing deep brain stimulation can only generate roughly-spherical regions of activation that do not overlap with any target anatomy. Additionally, side effects linked to stimulation may be the result of limited control over placement of stimulation and its subsequent spread out of optimal target boundaries. We propose a novel lead with thousands of individually controllable contacts capable of asymmetric stimulation profiles. Here we outline the design motivation, manufacturing process, and initial testing of this new electrode design, placing it on track for further directional stimulation studies.
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20
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Latorre MA, Chan ADC, Wårdell K. A physical action potential generator: design, implementation and evaluation. Front Neurosci 2015; 9:371. [PMID: 26539072 PMCID: PMC4611155 DOI: 10.3389/fnins.2015.00371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 09/22/2015] [Indexed: 11/13/2022] Open
Abstract
The objective was to develop a physical action potential generator (Paxon) with the ability to generate a stable, repeatable, programmable, and physiological-like action potential. The Paxon has an equivalent of 40 nodes of Ranvier that were mimicked using resin embedded gold wires (Ø = 20 μm). These nodes were software controlled and the action potentials were initiated by a start trigger. Clinically used Ag-AgCl electrodes were coupled to the Paxon for functional testing. The Paxon's action potential parameters were tunable using a second order mathematical equation to generate physiologically relevant output, which was accomplished by varying the number of nodes involved (1–40 in incremental steps of 1) and the node drive potential (0–2.8 V in 0.7 mV steps), while keeping a fixed inter-nodal timing and test electrode configuration. A system noise floor of 0.07 ± 0.01 μV was calculated over 50 runs. A differential test electrode recorded a peak positive amplitude of 1.5 ± 0.05 mV (gain of 40x) at time 196.4 ± 0.06 ms, including a post trigger delay. The Paxon's programmable action potential like signal has the possibility to be used as a validation test platform for medical surface electrodes and their attached systems.
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Affiliation(s)
- Malcolm A Latorre
- Department of Biomedical Engineering, Linköping University Linköping, Sweden
| | - Adrian D C Chan
- Department of Systems and Computer Engineering, Carleton University Ottawa, ON, Canada
| | - Karin Wårdell
- Department of Biomedical Engineering, Linköping University Linköping, Sweden
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21
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Willsie AC, Dorval AD. Computational Field Shaping for Deep Brain Stimulation With Thousands of Contacts in a Novel Electrode Geometry. Neuromodulation 2015; 18:542-50; discussion 550-1. [PMID: 26245306 DOI: 10.1111/ner.12330] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 05/17/2015] [Accepted: 06/04/2015] [Indexed: 12/23/2022]
Affiliation(s)
- Andrew C. Willsie
- Department of Bioengineering; University of Utah; Salt Lake City UT USA
| | - Alan D. Dorval
- Department of Bioengineering; University of Utah; Salt Lake City UT USA
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22
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Fan JA, Yeo W, Su Y, Hattori Y, Lee W, Jung S, Zhang Y, Liu Z, Cheng H, Falgout L, Bajema M, Coleman T, Gregoire D, Larsen RJ, Huang Y, Rogers JA. Fractal design concepts for stretchable electronics. Nat Commun 2014; 5. [DOI: 10.1038/ncomms4266] [Citation(s) in RCA: 663] [Impact Index Per Article: 66.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 01/15/2014] [Indexed: 02/01/2023] Open
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