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Whalen AJ, Fried SI. Thermal safety considerations for implantable micro-coil design. J Neural Eng 2023; 20:10.1088/1741-2552/ace79a. [PMID: 37451256 PMCID: PMC10467159 DOI: 10.1088/1741-2552/ace79a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 07/14/2023] [Indexed: 07/18/2023]
Abstract
Micro magnetic stimulation of the brain via implantable micro-coils is a promising novel technology for neuromodulation. Careful consideration of the thermodynamic profile of such devices is necessary for effective and safe designs.Objective.We seek to quantify the thermal profile of bent wire micro-coils in order to understand and mitigate thermal impacts of micro-coil stimulation.Approach. In this study, we use fine wire thermocouples and COMSOL finite element modeling to examine the profile of the thermal gradients generated near bent wire micro-coils submerged in a water bath during stimulation. We tested a range of stimulation parameters previously reported in the literature such as voltage amplitude, stimulus frequency, stimulus repetition rate and coil wire materials.Main results. We found temperature increases ranging from <1 °C to 8.4 °C depending upon the stimulation parameters tested and coil wire materials used. Numerical modeling of the thermodynamics identified hot spots of the highest temperatures along the micro-coil contributing to the thermal gradients and demonstrated that these thermal gradients can be mitigated by the choice of wire conductor material and construction geometry.Significance. ISO standard 14708-1 designates a thermal safety limit of 2 °C temperature increase for active implantable medical devices. By switching the coil wire material from platinum/iridium to gold, our study achieved a 5-6-fold decrease in the thermal impact of coil stimulation. The thermal gradients generated from the gold wire coil were measured below the 2 °C safety limit for all stimulation parameters tested.
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Affiliation(s)
- Andrew J. Whalen
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, USA
| | - Shelley I. Fried
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, USA
- Boston VA Medical Center, Boston, USA
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Temperature Dependence of Thermal Properties of Ex Vivo Porcine Heart and Lung in Hyperthermia and Ablative Temperature Ranges. Ann Biomed Eng 2023; 51:1181-1198. [PMID: 36656452 PMCID: PMC10172290 DOI: 10.1007/s10439-022-03122-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Accepted: 12/25/2022] [Indexed: 01/20/2023]
Abstract
This work proposes the characterization of the temperature dependence of the thermal properties of heart and lung tissues from room temperature up to > 90 °C. The thermal diffusivity (α), thermal conductivity (k), and volumetric heat capacity (Cv) of ex vivo porcine hearts and deflated lungs were measured with a dual-needle sensor technique. α and k associated with heart tissue remained almost constant until ~ 70 and ~ 80 °C, accordingly. Above ~ 80 °C, a more substantial variation in these thermal properties was registered: at 94 °C, α and k respectively experienced a 2.3- and 1.5- fold increase compared to their nominal values, showing average values of 0.346 mm2/s and 0.828 W/(m·K), accordingly. Conversely, Cv was almost constant until 55 °C and decreased afterward (e.g., Cv = 2.42 MJ/(m3·K) at 94 °C). Concerning the lung tissue, both its α and k were characterized by an exponential increase with temperature, showing a marked increment at supraphysiological and ablative temperatures (at 91 °C, α and k were equal to 2.120 mm2/s and 2.721 W/(m·K), respectively, i.e., 13.7- and 13.1-fold higher compared to their baseline values). Regression analysis was performed to attain the best-fit curves interpolating the measured data, thus providing models of the temperature dependence of the investigated properties. These models can be useful for increasing the accuracy of simulation-based preplanning frameworks of interventional thermal procedures, and the realization of tissue-mimicking materials.
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Liu HX, Cheng YY, Tian Z, Gao X, Zhang M, Nan Q. Flow field study of radiofrequency ablation of renal sympathetic nerve: Numerical simulation and PIV experiments. Electromagn Biol Med 2020; 39:262-272. [DOI: 10.1080/15368378.2020.1793167] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Hong-Xing Liu
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Yan-Yan Cheng
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Zhen Tian
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Xiang Gao
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Meng Zhang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Qun Nan
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
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Kezurer N, Heldenberg E, Farah N, Ivzan N, Mandel Y. Endovascular Electrical Stimulation - A Novel Hemorrhage Control Technique. IEEE Trans Biomed Eng 2018; 66:2072-2080. [PMID: 30489259 DOI: 10.1109/tbme.2018.2883212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
OBJECTIVE In this study we present a novel approach for inducing vasoconstriction by pulsed electrical treatment delivered via endovascular electrodes, which can be used in cases where external access to the vessel is limited. METHODS Using computer simulations, we optimized various geometries of endovascular electrodes to maximize the induced electric field on the arterial wall. Using the optimal configuration parameters, we investigated endovascular induced vasoconstriction in both the carotid and femoral sheep arteries. RESULTS Endovascular electrodes induced robust vasoconstriction in the carotid artery of sheep, showing gradual recovery following treatment. Moreover, the obtained vasoconstriction was accompanied by a sevenfold decrease in blood loss for 100% constriction, compared with no treatment (6ml vs 42ml, p<0.001). The femoral artery was less amenable to the electrical treatment, which we hypothesize results from the reduced density of the sympathetic system's innervation of the adventitia of the sheep femoral artery, as was validated by immunohistochemical analysis. Finally, treatment safety was validated through arterial histological studies, in which no adverse effect was observed, and through computer modeling, which depicted a negligible temperature increase. SIGNIFICANCE These results are an important step toward developing a novel approach for inducing reversible and controlled vasoconstriction in arteries that are remote from access.
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Awojoyogbe BO, Dada MO. Computational Design of an RF Controlled Theranostic Model for Evaluation of Tissue Biothermal Response. J Med Biol Eng 2018. [DOI: 10.1007/s40846-018-0386-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Myoung HS, Kim DH, Kim HS, Lee KJ. Design of a stimulation protocol to predict temperature distribution in subcutaneous tissue using the finite element model. Biomed Eng Lett 2017; 7:261-266. [PMID: 30603174 DOI: 10.1007/s13534-017-0029-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 04/05/2017] [Accepted: 04/07/2017] [Indexed: 12/30/2022] Open
Abstract
Moxibustion is a traditional Oriental medicine therapy that treats the symptoms of a disease with thermal stimulation. However, it is difficult to control the strength of the thermal or chemical stimulus generated by the various types and amounts of moxa and to prevent energy loss through the skin. To overcome these problems, we previously developed a method to efficiently provide RF thermal stimulation to subcutaneous tissue. In this paper, we propose a finite element model (FEM) to predict temperature distributions in subcutaneous tissue after radio-frequency thermal stimulation. To evaluate the performance of the developed FEM, temperature distributions were obtained from the FEM, and in vivo experiments were conducted using the RF stimulation system at subcutaneous tissue depths of 5 and 10 mm in the femoral region of a rabbit model. High correlation coefficients between simulated and actual temperature distributions-0.98 at 5 mm and 0.99 at 10 mm-were obtained, despite some slight errors in the temperature distribution at each depth. These results demonstrate that the FEM described here can be used to determine thermal stimulation profiles produced by RF stimulation of subcutaneous tissue.
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Affiliation(s)
- Hyoun-Seok Myoung
- Department of Biomedical Engineering, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwondo 220-710 Republic of Korea
| | - Dong-Hyun Kim
- Department of Biomedical Engineering, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwondo 220-710 Republic of Korea
| | - Han-Sung Kim
- Department of Biomedical Engineering, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwondo 220-710 Republic of Korea
| | - Kyoung-Joung Lee
- Department of Biomedical Engineering, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwondo 220-710 Republic of Korea
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Amri A, Pulko SH, Wilkinson AJ. Potentialities of steady-state and transient thermography in breast tumour depth detection: A numerical study. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2016; 123:68-80. [PMID: 26522612 DOI: 10.1016/j.cmpb.2015.09.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 09/01/2015] [Accepted: 09/16/2015] [Indexed: 06/05/2023]
Abstract
Breast thermography still has inherent limitations that prevent it from being fully accepted as a breast screening modality in medicine. The main challenges of breast thermography are to reduce false positive results and to increase the sensitivity of a thermogram. Further, it is still difficult to obtain information about tumour parameters such as metabolic heat, tumour depth and diameter from a thermogram. However, infrared technology and image processing have advanced significantly and recent clinical studies have shown increased sensitivity of thermography in cancer diagnosis. The aim of this paper is to study numerically the possibilities of extracting information about the tumour depth from steady state thermography and transient thermography after cold stress with no need to use any specific inversion technique. Both methods are based on the numerical solution of Pennes bioheat equation for a simple three-dimensional breast model. The effectiveness of two approaches used for depth detection from steady state thermography is assessed. The effect of breast density on the steady state thermal contrast has also been studied. The use of a cold stress test and the recording of transient contrasts during rewarming were found to be potentially suitable for tumour depth detection during the rewarming process. Sensitivity to parameters such as cold stress temperature and cooling time is investigated using the numerical model and simulation results reveal two prominent depth-related characteristic times which do not strongly depend on the temperature of the cold stress or on the cooling period.
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Affiliation(s)
- Amina Amri
- Ecole Nationale Polytechnique, Algiers, Algeria; Ecole National Préparatoire aux Etudes d'Ingéniorat, Algeria.
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Li Y, Poon CCY, Zhang YT. Analog integrated circuits design for processing physiological signals. IEEE Rev Biomed Eng 2010; 3:93-105. [PMID: 22275203 DOI: 10.1109/rbme.2010.2082521] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Analog integrated circuits (ICs) designed for processing physiological signals are important building blocks of wearable and implantable medical devices used for health monitoring or restoring lost body functions. Due to the nature of physiological signals and the corresponding application scenarios, the ICs designed for these applications should have low power consumption, low cutoff frequency, and low input-referred noise. In this paper, techniques for designing the analog front-end circuits with these three characteristics will be reviewed, including subthreshold circuits, bulk-driven MOSFETs, floating gate MOSFETs, and log-domain circuits to reduce power consumption; methods for designing fully integrated low cutoff frequency circuits; as well as chopper stabilization (CHS) and other techniques that can be used to achieve a high signal-to-noise performance. Novel applications using these techniques will also be discussed.
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Affiliation(s)
- Yan Li
- Joint Research Centre for Biomedical Engineering, Chinese University of Hong Kong, Hong Kong, China
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Rizk M, Bossetti CA, Jochum TA, Callender SH, Nicolelis MAL, Turner DA, Wolf PD. A fully implantable 96-channel neural data acquisition system. J Neural Eng 2009; 6:026002. [PMID: 19255459 PMCID: PMC2680289 DOI: 10.1088/1741-2560/6/2/026002] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A fully implantable neural data acquisition system is a key component of a clinically viable brain-machine interface. This type of system must communicate with the outside world and obtain power without the use of wires that cross through the skin. We present a 96-channel fully implantable neural data acquisition system. This system performs spike detection and extraction within the body and wirelessly transmits data to an external unit. Power is supplied wirelessly through the use of inductively coupled coils. The system was implanted acutely in sheep and successfully recorded, processed and transmitted neural data. Bidirectional communication between the implanted system and an external unit was successful over a range of 2 m. The system is also shown to integrate well into a brain-machine interface. This demonstration of a high channel-count fully implanted neural data acquisition system is a critical step in the development of a clinically viable brain-machine interface.
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Affiliation(s)
- Michael Rizk
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA.
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Shih TC, Yuan P, Lin WL, Kou HS. Analytical analysis of the Pennes bioheat transfer equation with sinusoidal heat flux condition on skin surface. Med Eng Phys 2007; 29:946-53. [PMID: 17137825 DOI: 10.1016/j.medengphy.2006.10.008] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2006] [Revised: 10/13/2006] [Accepted: 10/16/2006] [Indexed: 11/30/2022]
Abstract
This study focuses on the effect of the temperature response of a semi-infinite biological tissue due to a sinusoidal heat flux at the skin. The Pennes bioheat transfer equation such as rho(t)c(t)( partial differentialT/ partial differentialt)+W(b)c(b)(T-T(a))=k partial differential(2)T/ partial differentialx(2) with the oscillatory heat flux boundary condition such as q(0,t)=q(0)e(iomegat) was investigated. By using the Laplace transform, the analytical solution of the Pennes bioheat transfer equation with surface sinusoidal heating condition is found. This analytical expression is suitable for describing the transient temperature response of tissue for the whole time domain from the starting periodic oscillation to the final steady periodic oscillation. The results show that the temperature oscillation due to the sinusoidal heating on the skin surface is unstable in the initial period. Further, it is unavailable to predict the blood perfusion rate via the phase shifting between the surface heat flux and the surface temperature. Moreover, the lower frequency of sinusoidal heat flux on the skin surface induces a more sensitive phase shift response to the blood perfusion rate change, but extends the beginning time of sampling because of the avoidance of the unavailable first cyclic oscillation.
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Affiliation(s)
- Tzu-Ching Shih
- Department of Medical Radiology Technology, China Medical University, Taiwan
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Gosselin B, Sawan M, Chapman CA. A low-power integrated bioamplifier with active low-frequency suppression. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2007; 1:184-192. [PMID: 23852412 DOI: 10.1109/tbcas.2007.914490] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We present in this paper a low-power bioamplifier suitable for massive integration in dense multichannel recording devices. This bioamplifier achieves reduced-size compared to previous designs by means of active low-frequency suppression. An active integrator located in the feedback path of a low-noise amplifier is employed for placing a highpass cutoff frequency within the transfer function. A very long integrating time constant is achieved using a small integrated capacitor and a MOS-bipolar equivalent resistor. This configuration rejects unwanted low-frequency contents without the need for input RC networks or large feedback capacitors. Therefore, the bioamplifier high-input impedance and small size are preserved. The bioamplifier, implemented in a 0.18-mum CMOS process, has been designed for neural recording of action potentials, and optimised through a transconductance-ef-ficiency design methodology for micropower operation. Measured performance and results obtained from in vivo recordings are presented. The integrated bioamplifier provides a midband gain of 50 dB, and achieves an input-referred noise of 5.6 muVrms. It occupies less than 0.050 mm(2) of chip area and dissipates 8.6 muW.
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Gardiner JM, Wu J, Noh MD, Antaki JF, Snyder TA, Paden DB, Paden BE. Thermal Analysis of the PediaFlow Pediatric Ventricular Assist Device. ASAIO J 2007; 53:65-73. [PMID: 17237651 DOI: 10.1097/01.mat.0000247156.94587.6c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Accurate modeling of heat dissipation in pediatric intracorporeal devices is crucial in avoiding tissue and blood thermotrauma. Thermal models of new Maglev ventricular assist device (VAD) concepts for the PediaFlow VAD are developed by incorporating empirical heat transfer equations with thermal finite element analysis (FEA). The models assume three main sources of waste heat generation: copper motor windings, active magnetic thrust bearing windings, and eddy currents generated within the titanium housing due to the two-pole motor. Waste heat leaves the pump by convection into blood passing through the pump and conduction through surrounding tissue. Coefficients of convection are calculated and assigned locally along fluid path surfaces of the three-dimensional pump housing model. FEA thermal analysis yields a three-dimensional temperature distribution for each of the three candidate pump models. Thermal impedances from the motor and thrust bearing windings to tissue and blood contacting surfaces are estimated based on maximum temperature rise at respective surfaces. A new updated model for the chosen pump topology is created incorporating computational fluid dynamics with empirical fluid and heat transfer equations. This model represents the final geometry of the first generation prototype, incorporates eddy current heating, and has 60 discrete convection regions. Thermal analysis is performed at nominal and maximum flow rates, and temperature distributions are plotted. Results suggest that the pump will not exceed a temperature rise of 2 degrees C during normal operation.
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Baumann M, Jörgensen B, Rohde E, Bindig U, Müller G, Eric Scheller E. Influence of wavelength, power density and exposure time of laser radiation on chondrocyte cultures – An in-vitro investigation. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.mla.2006.05.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Berjano EJ. Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future. Biomed Eng Online 2006; 5:24. [PMID: 16620380 PMCID: PMC1459161 DOI: 10.1186/1475-925x-5-24] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 04/18/2006] [Indexed: 01/09/2023] Open
Abstract
Radiofrequency ablation is an interventional technique that in recent years has come to be employed in very different medical fields, such as the elimination of cardiac arrhythmias or the destruction of tumors in different locations. In order to investigate and develop new techniques, and also to improve those currently employed, theoretical models and computer simulations are a powerful tool since they provide vital information on the electrical and thermal behavior of ablation rapidly and at low cost. In the future they could even help to plan individual treatment for each patient. This review analyzes the state-of-the-art in theoretical modeling as applied to the study of radiofrequency ablation techniques. Firstly, it describes the most important issues involved in this methodology, including the experimental validation. Secondly, it points out the present limitations, especially those related to the lack of an accurate characterization of the biological tissues. After analyzing the current and future benefits of this technique it finally suggests future lines and trends in the research of this area.
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Affiliation(s)
- Enrique J Berjano
- Center for Research and Innovation on Bioengineering, Valencia Polytechnic University, Camino de Vera s/n, 46022 Valencia, Spain.
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