1
|
Kosta P, Mize J, Warren DJ, Lazzi G. Simulation-Based Optimization of Figure-of-Eight Coil Designs and Orientations for Magnetic Stimulation of Peripheral Nerve. IEEE Trans Neural Syst Rehabil Eng 2020; 28:2901-2913. [PMID: 33201821 DOI: 10.1109/tnsre.2020.3038406] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Although magnetic neural stimulation has many advantages over electrical neural stimulation, its main disadvantages are higher energy requirement and poor stimulation selectivity. The orientation and location of the coil with respect to the stimulation site play a critical role in determining the stimulation threshold and stimulation selectivity. Utilizing numerical simulations in this work, we optimized the design parameters, orientation, and positioning of magnetic coils with respect to the peripheral nerve for improved stimulation efficacy. Specifically, we investigated different orientations and positions of the figure-of-eight coils for neural stimulation of the rat sciatic nerve. We also examined the effect of coil design parameters (number of layers and turns) and different coil electrical configurations (opposite vs. same direction of coil currents and series vs. parallel coil connections) on the stimulation threshold. We leveraged the multi-resolution impedance method and a heterogeneous multi-fascicular anatomical model of rat sciatic nerve to explore the possibility of selective stimulation as well. Neural excitation of a nerve fiber was implemented by an equivalent cable model and Frankenhaeuser-Huxley equations using NEURON software. Results suggest that inter-fascicular selectivity could be achieved by properly orienting and positioning the coil with respect to the nerve. Further, by orienting the figure-of-eight coil at an angle of 90° and 6 mm offset, we could switch between primarily activating one fascicle (and barely activating the other) and reversing those roles by merely switching the current direction in the two coils of the figure-of-eight coil.
Collapse
|
2
|
Wei X, Li Y, Lu M, Wang J, Yi G. Comprehensive Survey on Improved Focality and Penetration Depth of Transcranial Magnetic Stimulation Employing Multi-Coil Arrays. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2017; 14:ijerph14111388. [PMID: 29135963 PMCID: PMC5708027 DOI: 10.3390/ijerph14111388] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 11/10/2017] [Accepted: 11/10/2017] [Indexed: 11/16/2022]
Abstract
Multi-coil arrays applied in transcranial magnetic stimulation (TMS) are proposed to accurately stimulate brain tissues and modulate neural activities by an induced electric field (EF). Composed of numerous independently driven coils, a multi-coil array has alternative energizing strategies to evoke EFs targeting at different cerebral regions. To improve the locating resolution and the stimulating focality, we need to fully understand the variation properties of induced EFs and the quantitative control method of the spatial arrangement of activating coils, both of which unfortunately are still unclear. In this paper, a comprehensive analysis of EF properties was performed based on multi-coil arrays. Four types of planar multi-coil arrays were used to study the relationship between the spatial distribution of EFs and the structure of stimuli coils. By changing coil-driven strategies in a basic 16-coil array, we find that an EF induced by compactly distributed coils decays faster than that induced by dispersedly distributed coils, but the former has an advantage over the latter in terms of the activated brain volume. Simulation results also indicate that the attenuation rate of an EF induced by the 36-coil dense array is 3 times and 1.5 times greater than those induced by the 9-coil array and the 16-coil array, respectively. The EF evoked by the 36-coil dispense array has the slowest decay rate. This result demonstrates that larger multi-coil arrays, compared to smaller ones, activate deeper brain tissues at the expense of decreased focality. A further study on activating a specific field of a prescribed shape and size was conducted based on EF variation. Accurate target location was achieved with a 64-coil array 18 mm in diameter. A comparison between the figure-8 coil, the planar array, and the cap-formed array was made and demonstrates an improvement of multi-coil configurations in the penetration depth and the focality. These findings suggest that there is a tradeoff between attenuation rate and focality in the application of multi-coil arrays. Coil-energizing strategies and array dimensions should be based on an adequate evaluation of these two important demands and the topological structure of target tissues.
Collapse
Affiliation(s)
- Xile Wei
- Tianjin Key Laboratory of Process Measurement and Control, School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China.
| | - Yao Li
- Tianjin Key Laboratory of Process Measurement and Control, School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China.
| | - Meili Lu
- School of Information Technology Engineering, Tianjin University of Technology and Education, Tianjin 300222, China.
| | - Jiang Wang
- Tianjin Key Laboratory of Process Measurement and Control, School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China.
| | - Guosheng Yi
- Tianjin Key Laboratory of Process Measurement and Control, School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China.
| |
Collapse
|
3
|
Deng B, Li S, Li B, Wang J, Zhang Z. Noninvasive Brain Stimulation Using Strong-Coupling Effect of Resonant Magnetics. IEEE TRANSACTIONS ON MAGNETICS 2017; 53:1-9. [DOI: 10.1109/tmag.2017.2661244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
|
4
|
Weak electric fields detectability in a noisy neural network. Cogn Neurodyn 2016; 11:81-90. [PMID: 28174614 DOI: 10.1007/s11571-016-9409-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 08/16/2016] [Accepted: 09/06/2016] [Indexed: 12/18/2022] Open
Abstract
We investigate the detectability of weak electric field in a noisy neural network based on Izhikevich neuron model systematically. The neural network is composed of excitatory and inhibitory neurons with similar ratio as that in the mammalian neocortex, and the axonal conduction delays between neurons are also considered. It is found that the noise intensity can modulate the detectability of weak electric field. Stochastic resonance (SR) phenomenon induced by white noise is observed when the weak electric field is added to the network. It is interesting that SR almost disappeared when the connections between neurons are cancelled, suggesting the amplification effects of the neural coupling on the synchronization of neuronal spiking. Furthermore, the network parameters, such as the connection probability, the synaptic coupling strength, the scale of neuron population and the neuron heterogeneity, can also affect the detectability of the weak electric field. Finally, the model sensitivity is studied in detail, and results show that the neural network model has an optimal region for the detectability of weak electric field signal.
Collapse
|
5
|
A smart, phase transitional and injectable DOX/PLGA-Fe implant for magnetic-hyperthermia-induced synergistic tumor eradication. Acta Biomater 2016; 29:298-306. [PMID: 26432438 DOI: 10.1016/j.actbio.2015.09.037] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 09/09/2015] [Accepted: 09/28/2015] [Indexed: 12/15/2022]
Abstract
Magnetic hyperthermia ablation is a new and minimally invasive modality for localized tumor removal. However, an inadequate ablation dosage can leave a residual tumor or cause a variety of complications. In addition, commonly used magnetic nanoparticles can easily escape from the tumor tissue, which present potential safety problems. In this study, a smart phase transitional and injectable implant based on biocompatible poly lactic-co-glycolic acid (PLGA) implant incorporating magnetic material (Fe powder) and anti-cancer drug (doxorubicin (DOX)) was developed. The magnetic-induced hyperthermia and release efficiency of DOX were evaluated in vitro. Drug release can be controlled under external alternating current magnetic field (AMF). The results of the in vivo tumor therapeutic efficacy showed that when exposed to external AMF, this smart injectable DOX/PLGA-Fe implant could converse magnetic energy into heat and accelerate the release of DOX, which leads to increasing the temperature to achieve tumor coagulative necrosis and accelerating the release of DOX to enhance residual tumor apoptosis. Furthermore, there was no leakage of magnetic material, as demonstrated using real-time ultrasound (US) and computerized tomography (CT) imaging, realizing the guidance and monitoring of tumor therapy. In conclusion, this smart phase transitional and injectable implant DOX/PLGA-Fe has the ability to improve the efficiency of this newly developed minimally invasive magnetic ablation of tumor treatment technique, and will provide a new avenue of developing minimally invasive synergistic tumor therapy.
Collapse
|
6
|
Yeung SH, Pradhan R, Feng X, Zheng Y. Focused Magnetic Resonance Coupling Coils for Electromagnetic Therapy Applications. IEEE Trans Biomed Eng 2015; 62:2602-2610. [PMID: 25751862 DOI: 10.1109/tbme.2015.2408432] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper presents the design and construction of a pair of figure-of-eight coils, coupled by magnetic resonance coupling (MRC), which could generate (150 V/m per Ampere) electric field at the focal points for electromagnetic therapy related applications. The E field generated at the targeted site would be significantly enhanced under the same amount of current flowing through the MRC figure-of-eight coils compared to normal coils, due to the superposition of E field contributed by the coils. Furthermore, the MRC figure-of-eight coil is designed and the results are verified in theory, simulation, and experiments. In the ex vivo tissue measurement, 35% current and 82% ohmic power improvements were observed. Since it can enhance the current and ohmic power, the MRC figure-of-eight coils are promising solutions for electromagnetic therapy applications. The potential applications of the coils include noninvasive radio frequency (RF) stimulation, thermoacoustic imaging, electromagnetic field therapies, and RF ablation, etc.
Collapse
Affiliation(s)
- Sai Ho Yeung
- School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore
| | - Raunaq Pradhan
- School of Electrical and Electronic Engineering, Nanyang Technological University
| | - Xiaohua Feng
- School of Electrical and Electronic Engineering, Nanyang Technological University
| | - Yuanjin Zheng
- School of Electrical and Electronic Engineering, Nanyang Technological University
| |
Collapse
|
7
|
Sekino M, Ohsaki H, Takiyama Y, Yamamoto K, Matsuzaki T, Yasumuro Y, Nishikawa A, Maruo T, Hosomi K, Saitoh Y. Eccentric figure-eight coils for transcranial magnetic stimulation. Bioelectromagnetics 2014; 36:55-65. [DOI: 10.1002/bem.21886] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 09/26/2014] [Indexed: 11/06/2022]
Affiliation(s)
- Masaki Sekino
- Department of Electrical Engineering and Information Systems; Graduate School of Engineering; University of Tokyo; Tokyo Japan
- Department of Neuromodulation and Neurosurgery; Graduate School of Medicine; Osaka University; Suita Japan
| | - Hiroyuki Ohsaki
- Department of Electrical Engineering and Information Systems; Graduate School of Engineering; University of Tokyo; Tokyo Japan
- Department of Advanced Energy; Graduate School of Frontier Sciences; University of Tokyo; Kashiwa Japan
| | - Yoshihiro Takiyama
- Department of Electrical Engineering and Information Systems; Graduate School of Engineering; University of Tokyo; Tokyo Japan
| | - Keita Yamamoto
- Department of Electrical Engineering and Information Systems; Graduate School of Engineering; University of Tokyo; Tokyo Japan
| | - Taiga Matsuzaki
- Department of Neuromodulation and Neurosurgery; Graduate School of Medicine; Osaka University; Suita Japan
- Home Healthcare Research and Development Planning Department; Teijin Pharma Limited; Tokyo Japan
| | - Yoshihiro Yasumuro
- Department of Neuromodulation and Neurosurgery; Graduate School of Medicine; Osaka University; Suita Japan
- Department of Civil, Environmental and Applied System Engineering; Faculty of Environmental Urban Engineering, Kansai University; Suita Japan
| | - Atsushi Nishikawa
- Department of Neuromodulation and Neurosurgery; Graduate School of Medicine; Osaka University; Suita Japan
- Bioengineering Course; Division of Mechanical Engineering and Robotics; Faculty of Textile Science and Technology; Shinshu University; Ueda Japan
| | - Tomoyuki Maruo
- Department of Neuromodulation and Neurosurgery; Graduate School of Medicine; Osaka University; Suita Japan
| | - Koichi Hosomi
- Department of Neuromodulation and Neurosurgery; Graduate School of Medicine; Osaka University; Suita Japan
| | - Youichi Saitoh
- Department of Neuromodulation and Neurosurgery; Graduate School of Medicine; Osaka University; Suita Japan
| |
Collapse
|
8
|
Popescu D, Popescu B, Lugli P, Locci S. A magnetic manipulation system using an active filter for electronic detection of target cells. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2012; 6:319-325. [PMID: 23853176 DOI: 10.1109/tbcas.2012.2184540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Important advances in the development of magnetic manipulation devices have been recorded over the last few years and promising experimental results have been presented. In this article we first perform a detailed analysis on one of most widely used magnetic actuators, namely a planar microcoil. Key parameters that affect the performance of the actuator are identified and our results are in accordance with measured data. Making use of these findings, a lab-on-a-chip system is proposed, that also integrates a novel electronic sensing concept for live monitoring of its activity. Possible applications of this system include highly selective bioseparation or the possibility to manipulate and assemble marked particles with great precision.
Collapse
Affiliation(s)
- Dan Popescu
- Institute for Nanoelectronics, Technical University Munich (TUM), D-80333, Munich, Germany.
| | | | | | | |
Collapse
|
9
|
Kato T, Sekino M, Matsuzaki T, Nishikawa A, Saitoh Y, Ohsaki H. Fabrication of a prototype magnetic stimulator equipped with eccentric spiral coils. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:1985-8. [PMID: 22254723 DOI: 10.1109/iembs.2011.6090559] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The development of compact magnetic stimulators will enable us to treat some intractable neurological diseases at one's home. In this study, we propose eccentric spiral coils which induce sufficient eddy currents in the brain at lower driving currents for the stimulator circuit. Numerical simulations based on the finite element method showed the advantages of the proposed design. A prototype coil and driving circuit were fabricated. The coil generated a magnetic field of 1.41 T at the maximum output level of stimulator.
Collapse
Affiliation(s)
- Takuya Kato
- Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
| | | | | | | | | | | |
Collapse
|
10
|
Deng ZD, Lisanby SH, Peterchev AV. Electric field depth-focality tradeoff in transcranial magnetic stimulation: simulation comparison of 50 coil designs. Brain Stimul 2012; 6:1-13. [PMID: 22483681 DOI: 10.1016/j.brs.2012.02.005] [Citation(s) in RCA: 531] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 02/29/2012] [Accepted: 02/29/2012] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Various transcranial magnetic stimulation (TMS) coil designs are available or have been proposed. However, key coil characteristics such as electric field focality and attenuation in depth have not been adequately compared. Knowledge of the coil focality and depth characteristics can help TMS researchers and clinicians with coil selection and interpretation of TMS studies. OBJECTIVE To quantify the electric field focality and depth of penetration of various TMS coils. METHODS The electric field distributions induced by 50 TMS coils were simulated in a spherical human head model using the finite element method. For each coil design, we quantified the electric field penetration by the half-value depth, d(1/2), and focality by the tangential spread, S(1/2), defined as the half-value volume (V(1/2)) divided by the half-value depth, S(1/2) = V(1/2)/d(1/2). RESULTS The 50 TMS coils exhibit a wide range of electric field focality and depth, but all followed a depth-focality tradeoff: coils with larger half-value depth cannot be as focal as more superficial coils. The ranges of achievable d(1/2) are similar between coils producing circular and figure-8 electric field patterns, ranging 1.0-3.5 cm and 0.9-3.4 cm, respectively. However, figure-8 field coils are more focal, having S(1/2) as low as 5 cm(2) compared to 34 cm(2) for circular field coils. CONCLUSIONS For any coil design, the ability to directly stimulate deeper brain structures is obtained at the expense of inducing wider electrical field spread. Novel coil designs should be benchmarked against comparison coils with consistent metrics such as d(1/2) and S(1/2).
Collapse
Affiliation(s)
- Zhi-De Deng
- Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, USA.
| | | | | |
Collapse
|
11
|
Tomazin K, Verges S, Decorte N, Oulerich A, Maffiuletti NA, Millet GY. Fat tissue alters quadriceps response to femoral nerve magnetic stimulation. Clin Neurophysiol 2011; 122:842-7. [DOI: 10.1016/j.clinph.2010.10.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 10/13/2010] [Accepted: 10/14/2010] [Indexed: 10/18/2022]
|
12
|
Xu G, Chen Y, Yang S, Wang M, Yan W. The optimal design of magnetic coil in transcranial magnetic stimulation. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2008; 2005:6221-4. [PMID: 17281687 DOI: 10.1109/iembs.2005.1615917] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Transcranial magnetic stimulation (TMS) is a new tool for the study of the human brain and for neurological therapeutics. Magnetic coil design is very important in the TMS technique. Precise spatial localization of stimulation sites is the key of efficient functional magnetic stimulations. This paper develops circular coils, figure-of-8 coils and coil array elements in order to realize a transcranial magnetic stimulator, and analyses the coil properties. The results show that different coils have different focus.
Collapse
Affiliation(s)
- Guizhi Xu
- Department of Precision Instrument, Tianjin University, Tianjin 300072, China, Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Heibei University of Technology, Tianjin 300130, China.
| | | | | | | | | |
Collapse
|
13
|
Abstract
Noninvasive brain stimulation with transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS) is valuable in research and has potential therapeutic applications in cognitive neuroscience, neurophysiology, psychiatry, and neurology. TMS allows neurostimulation and neuromodulation, while tDCS is a purely neuromodulatory application. TMS and tDCS allow diagnostic and interventional neurophysiology applications, and focal neuropharmacology delivery. However, the physics and basic mechanisms of action remain incompletely explored. Following an overview of the history and current applications of noninvasive brain stimulation, we review stimulation device design principles, the electromagnetic and physical foundations of the techniques, and the current knowledge about the electrophysiologic basis of the effects. Finally, we discuss potential biomedical and electrical engineering developments that could lead to more effective stimulation devices, better suited for the specific applications.
Collapse
Affiliation(s)
- Timothy Wagner
- Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Department of Neurology, Harvard Medical School, Boston, Massachusetts 02215, USA
| | | | | |
Collapse
|
14
|
Giannì M, Liberti M, Apollonio F, D'Inzeo G. Modeling electromagnetic fields detectability in a HH-like neuronal system: stochastic resonance and window behavior. BIOLOGICAL CYBERNETICS 2006; 94:118-27. [PMID: 16369796 DOI: 10.1007/s00422-005-0029-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Accepted: 09/22/2005] [Indexed: 05/05/2023]
Abstract
Noise has already been shown to play a constructive role in neuronal processing and reliability, according to stochastic resonance (SR). Here another issue is addressed, concerning noise role in the detectability of an exogenous signal, here representing an electromagnetic (EM) field. A Hodgkin-Huxley like neuronal model describing a myelinated nerve fiber is proposed and validated, excited with a suprathreshold stimulation. EM field is introduced as an additive voltage input and its detectability in neuronal response is evaluated in terms of the output signal-to-noise ratio. Noise intensities maximizing spiking activity coherence with the exogenous EM signal are clearly shown, indicating a stochastic resonant behavior, strictly connected to the model frequency sensitivity. In this study SR exhibits a window of occurrence in the values of field frequency and intensity, which is a kind of effect long reported in bioelectromagnetic experimental studies. The spatial distribution of the modeled structure also allows to investigate possible effects on action potentials saltatory propagation, which results to be reliable and robust over the presence of an exogenous EM field and biological noise. The proposed approach can be seen as assessing biophysical bases of medical applications funded on electric and magnetic stimulation where the role of noise as a cooperative factor has recently gained growing attention.
Collapse
Affiliation(s)
- Matteo Giannì
- ICEmB at Department of Electronic Engineering, La Sapienza University of Rome, 00184 Rome, Italy.
| | | | | | | |
Collapse
|
15
|
Crowe MJ, Sun ZP, Battocletti JH, Macias MY, Pintar FA, Maiman DJ. Exposure to pulsed magnetic fields enhances motor recovery in cats after spinal cord injury. Spine (Phila Pa 1976) 2003; 28:2660-6. [PMID: 14673366 DOI: 10.1097/01.brs.0000099385.46102.0d] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Animal model study of eight healthy commercial cats was conducted. OBJECTIVE To determine whether pulsed electromagnetic field (PMF) stimulation results in improvement of function after contusive spinal cord injury in cats. SUMMARY OF BACKGROUND DATA PMF stimulation has been shown to enhance nerve growth, regeneration, and functional recovery of peripheral nerves. Little research has been performed examining the effects of PMF stimulation on the central nervous system and no studies of PMF effects on in vivo spinal cord injury (SCI) models have been reported. MATERIALS AND METHODS PMF stimulation was noninvasively applied for up to 12 weeks to the midthoracic spine of cats with acute contusive spinal cord injury. The injury was produced using a weight-drop apparatus. Motor functions were evaluated with the modified Tarlov assessment scale. Morphologic analyses of the injury sites and somatosensory-evoked potential measurements were conducted to compare results between PMF-stimulated and control groups. RESULTS There was a significant difference in locomotor recovery between the PMF-stimulated and control groups. Although not statistically significant, PMF-stimulated spinal cords demonstrated greater sparing of peripheral white matter and smaller lesion volumes compared to controls. Somatosensory-evoked potential measurements indicated that the PMF-stimulated group had better recovery of preinjury waveforms than the control group; however, this observation also was not statistically significant because of the small sample size. CONCLUSIONS This preliminary study indicates that pulsed magnetic fields may have beneficial effects on motor function recovery and lesion volume size after acute spinal cord injury.
Collapse
Affiliation(s)
- Maria J Crowe
- Neuroscience Research Laboratories, The Clement J. Zablocki VA Medical Center, Milwaukee, WI 53295, USA.
| | | | | | | | | | | |
Collapse
|
16
|
Papazov SP, Daskalov IK. Effect of contour shape of nervous system electromagnetic stimulation coils on the induced electrical field distribution. Biomed Eng Online 2002; 1:1. [PMID: 12437767 PMCID: PMC130993 DOI: 10.1186/1475-925x-1-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2002] [Accepted: 05/14/2002] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Electromagnetic stimulation of the nervous system has the advantage of reduced discomfort in activating nerves. For brain structures stimulation, it has become a clinically accepted modality. Coil designs usually consider factors such as optimization of induced power, focussing, field shape etc. In this study we are attempting to find the effect of the coil contour shape on the electrical field distribution for magnetic stimulation. METHOD AND RESULTS We use the maximum of the induced electric field stimulation in the region of interest as the optimization criterion. This choice required the application of the calculus of variation, with the contour perimeter taken as a pre-set condition. Four types of coils are studied and compared: circular, square, triangular and an 'optimally' shaped contour. The latter yields higher values of the induced electrical field in depths up to about 30 mm, but for depths around 100 mm, the circular shape has a slight advantage. The validity of the model results was checked by experimental measurements in a tank with saline solution, where differences of about 12% were found. In view the accuracy limitations of the computational and measurement methods used, such differences are considered acceptable. CONCLUSION We applied an optimization approach, using the calculus of variation, which allows to obtain a coil contour shape corresponding to a selected criterion. In this case, the optimal contour showed higher intensities for a longer line along the depth-axis. The method allows modifying the induced field structure and focussing the field to a selected zone or line.
Collapse
Affiliation(s)
- Sava P Papazov
- Center of Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Ivan K Daskalov
- Center of Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| |
Collapse
|
17
|
Hsiao IN, Lin VW. Improved coil design for functional magnetic stimulation of expiratory muscles. IEEE Trans Biomed Eng 2001; 48:684-94. [PMID: 11396598 DOI: 10.1109/10.923786] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Our studies have demonstrated effective stimulation of the expiratory muscles in patients with spinal cord injury (SCI) using functional magnetic stimulation (FMS). The observed contraction of the expiratory muscles and functional improvement of the pulmonary functions make functional magnetic stimulation an appropriate tool for expiratory muscle training. To fully capitalize on the benefits of FMS for expiratory muscle training, this study aimed to optimize the magnetic coils (MCs). The primary goal of this study was to investigate how two parameters of the MC size and winding structure, would affect expiratory muscle training. By varying these parameters, our approach was to conceptualize and evaluate the induced electric field and nerve activation function distributions of six coils, round 9.2, 13.7, and 20 cm, and spiral 9.2-, 13.7-, and 20-cm coils in the computer modeling phase. Round 9.2 cm, spiral 13.7 cm, and spiral 20-cm coils were also evaluated in experimental studies for induced electrical field and in clinical studies of expiratory muscles. Both the computer models and experimental measurements indicated that the spiral 20-cm coil can not only stimulate more expiratory spinal nerves but can also stimulate them more evenly. In addition, coils with larger diameters had better penetration than those with smaller diameters. The clinical results showed that the spiral 20-cm coil produced higher expiratory pressure, flow, and volume in five able-bodied subjects, and it was the coil of choice among the subjects when asked their preferences. In our attempt to optimize MC design for FMS of expiratory muscle training, we followed the designing guidelines set out in our previous study and arrived at a more effective tool.
Collapse
Affiliation(s)
- I N Hsiao
- Department of Physical Medicine and Rehabilitation, School of Medicine, University of California, Irvine 92717, USA
| | | |
Collapse
|
18
|
Lin VW, Hsiao IN, Zhu E, Perkash I. Functional magnetic stimulation for conditioning of expiratory muscles in patients with spinal cord injury. Arch Phys Med Rehabil 2001; 82:162-6. [PMID: 11239305 DOI: 10.1053/apmr.2001.18230] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To evaluate the effectiveness of functional magnetic stimulation (FMS) in conditioning expiratory muscles patients with spinal cord injury (SCI). DESIGN A prospective before-after trial. SETTING The Functional Magnetic Stimulation Laboratory of the SCI Health Care Group, VA Long Beach Health Care System, and the Spinal Cord Injury Services, Department of Veterans Affairs, Palo Alto Health Care System. PARTICIPANTS Eight men with tetraplegia. INTERVENTION Expiratory muscle training was achieved by placing a magnetic stimulator with a round magnetic coil along subjects' lower thoracic spine. MAIN OUTCOME MEASURES Measures taken were the maximal expired pressure at total lung capacity (MEP-TLC) and at functional residual capacity (MEP-FRC), expiratory reserve volume (ERV), and the forced expiratory flow rate at TLC (FEF-TLC) and at FRC (FEF-FRC) by subjects' voluntary maximal efforts. RESULTS After 4 weeks of conditioning, the mean +/- standard error of the mean values were: MEP-TLC, 55.3 +/- 8.6cmH(2)O; MEP-FRC, 29.6 +/- 5.6cmH(2)O; ERV,.57 +/-.08L; FEF-TLC, 4.3 +/- 0.5L/s; and FEF-FRC, 1.9 +/- 0.2L/s. These values correspond to, respectively, 129%, 137%, 162%, 109%, and 127% of pre-FMS conditioning values. When FMS was discontinued for 2 weeks, the MEP-TLC returned to its pre-FMS training value. CONCLUSION A 4-week protocol of FMS of the expiratory muscles improves voluntary expiratory muscle strength significantly, indicating that FMS can be a noninvasive therapeutic technology in respiratory muscle training for persons with tetraplegia.
Collapse
Affiliation(s)
- V W Lin
- Functional Magnetic Stimulation Laboratory, Spinal Cord Injury/Disorder, Health Care Group, VA Long Beach Health Care System, Long Beach, CA 90822, USA
| | | | | | | |
Collapse
|