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Bardwell Speltz LJ, Lee SK, Shu Y, Tarasek MR, Trzasko JD, Foo TKF, Bernstein MA. Modeling and measurement of lead tip heating and resonant length for implanted, insulated wires. Magn Reson Med 2024; 92:1714-1727. [PMID: 38818673 DOI: 10.1002/mrm.30145] [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: 12/08/2023] [Revised: 04/15/2024] [Accepted: 04/18/2024] [Indexed: 06/01/2024]
Abstract
PURPOSE To study implant lead tip heating because of the RF power deposition by developing mathematical models and comparing them with measurements acquired at 1.5 T and 3 T, especially to predict resonant length. THEORY AND METHODS A simple exponential model and an adapted transmission line model for the electric field transfer function were developed. A set of wavenumbers, including that calculated from insulated antenna theory (King wavenumber) and that of the embedding medium were considered. Experiments on insulated, capped wires of varying lengths were performed to determine maximum temperature rise under RF exposure. The results are compared with model predictions from analytical expressions derived under the assumption of a constant electric field, and with those numerically calculated from spatially varying, simulated electric fields from body coil transmission. Simple expressions for the resonant length bounded between one-quarter and one-half wavelength are developed based on the roots of transcendental equations. RESULTS The King wavenumber for both models more closely matched the experimental data with a maximum root mean square error of 9.81°C at 1.5 T and 5.71°C at 3 T compared to other wavenumbers with a maximum root mean square error of 27.52°C at 1.5 T and 22.01°C for 3 T. Resonant length was more accurately predicted compared to values solely based on the embedding medium. CONCLUSION Analytical expressions were developed for implanted lead heating and resonant lengths under specific assumptions. The value of the wavenumber has a strong effect on the model predictions. Our work could be used to better manage implanted device lead tip heating.
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Affiliation(s)
- Lydia J Bardwell Speltz
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, Minnesota, USA
| | - Seung-Kyun Lee
- Technology and Innovation Center, GE HealthCare, GE Research, Niskayuna, New York, USA
| | - Yunhong Shu
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Matthew R Tarasek
- Technology and Innovation Center, GE HealthCare, GE Research, Niskayuna, New York, USA
| | | | - Thomas K F Foo
- Technology and Innovation Center, GE HealthCare, GE Research, Niskayuna, New York, USA
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Vu J, Bhusal B, Rosenow JM, Pilitsis J, Golestanirad L. Effect of surgical modification of deep brain stimulation lead trajectories on radiofrequency heating during MRI at 3T: from phantom experiments to clinical implementation. J Neurosurg 2024; 140:1459-1470. [PMID: 37948679 PMCID: PMC11065613 DOI: 10.3171/2023.8.jns23580] [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: 03/14/2023] [Accepted: 08/22/2023] [Indexed: 11/12/2023]
Abstract
OBJECTIVE Radiofrequency (RF) tissue heating around deep brain stimulation (DBS) leads is a well-known safety risk during MRI, resulting in strict imaging guidelines and limited allowable protocols. The implanted lead's trajectory and orientation with respect to the MRI electric fields contribute to variations in the magnitude of RF heating across patients. Currently, there are no surgical requirements for implanting the extracranial portion of the DBS lead, resulting in substantial variations in clinical lead trajectories and consequently RF heating. Recent studies have shown that incorporating concentric loops in the extracranial lead trajectory can reduce RF heating. However, optimal positioning of the loops and the quantitative benefit of trajectory modification in terms of added safety margins during MRI remain unknown. In this study, the authors systematically evaluated the characteristics of DBS lead trajectories that minimize RF heating during 3T MRI to develop the best surgical practices for safe access to postoperative MRI, and they present the first surgical implementation of these modified trajectories. METHODS The authors performed experiments to assess the maximum temperature increase of 244 distinct lead trajectories. They investigated the effect of the position, number, and size of the concentric loops on the skull. Experiments were performed in an anthropomorphic phantom implanted with a commercial DBS system, and RF exposure was generated by applying a high specific absorption rate sequence (B1+rms = 2.7 µT). The authors conducted test-retest experiments to assess the reliability of measurements. Additionally, they evaluated the effect of imaging landmarks and perturbations to the DBS device configuration on the efficacy of low-heating trajectories. Finally, two neurosurgeons implanted the recommended modified trajectories in patients, and the authors characterized their RF heating in comparison with unmodified trajectories. RESULTS The maximum temperature increase ranged from 0.09°C to 7.34°C. The authors found that increasing the number of loops and positioning them closer to the surgical burr hole, particularly for the contralateral lead, substantially reduced RF heating. These trajectory modifications were easily incorporated during the surgical procedure and resulted in a threefold reduction in RF heating. CONCLUSIONS Surgically modifying the extracranial portion of the DBS lead trajectory can substantially reduce RF heating during 3T MRI. The authors' results indicate that simple adjustments to the lead's configuration, such as small, concentric loops near the burr hole, can be readily adopted during DBS lead implantation to improve patient safety during MRI.
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Affiliation(s)
- Jasmine Vu
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Bhumi Bhusal
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Joshua M. Rosenow
- Department of Neurosurgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Julie Pilitsis
- Department of Neurosciences and Experimental Therapeutics, Albany Medical College, Albany, New York
| | - Laleh Golestanirad
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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Jacobs P, Fagan AJ. The effect of frequency (64-498 MHz) on specific absorption rate adjacent to metallic orthopedic screws in MRI: A numerical simulation study. Med Phys 2024; 51:1074-1082. [PMID: 38116822 PMCID: PMC10922637 DOI: 10.1002/mp.16902] [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: 08/24/2023] [Revised: 11/04/2023] [Accepted: 12/04/2023] [Indexed: 12/21/2023] Open
Abstract
BACKGROUND The imaging of patients with implanted electrically-conductive devices via magnetic resonance imaging at ultra-high fields is hampered by uncertainties relating to the potential for inducing tissue heating adjacent to the implant due to coupling of energy from the incident electromagnetic field into the implant. Existing data in the peer-reviewed literature of comparisons across field strengths of tissue heating and its surrogate, the specific absorption rate (SAR), is scarce and contradictory, leading to further doubts pertaining to the safety of imaging patients with such devices. PURPOSE The radiofrequency-induced SAR adjacent to orthopedic screws of varying length and at frequencies of 64 to 498 MHz was investigated via full-wave electromagnetic simulations, to provide an accurate comparison of SAR across MRI field strengths. METHODS Dipole antennas were used for RF transmission to achieve a uniform electric field tangential to the screws located 120 mm above the antenna midpoints, embedded in a bone-mimicking material. The input power to the antennas was constrained to achieve the following targets without the screw present: (i) E = 100 V/m, (ii) B1 + = 2 μT, and (iii) global-average-SAR = 3.2 W/kg. Simulations were performed with a spatial resolution of 0.2 mm in the volume surrounding the screws, resulting in 76-137 MCells, noting the maximum 1 g-averaged SAR value in each case. Simulations were repeated at 128 and 297 MHz for screws embedded in muscle tissue. RESULTS The peak SAR, occurring at the resonant screw length, substantially increased as the frequency decreased when the input power to the dipole antenna was constrained to achieve constant electric field in background tissue at the screws' locations. A similar pattern was observed when constraining input power to achieve constant B1 + and global-average-SAR. The dielectric properties of the tissue in which the screws were embedded dominated the SAR comparisons between 297 and 128 MHz. CONCLUSIONS The study design allowed for a direct comparison to be performed of SAR across frequencies and implant lengths without the confounding effect of variable incident electric field. Lower frequencies produced substantially larger SAR values for implants approaching the resonant length for the worst-case uniform incident electric field along the screws' length. The data may inform risk-benefit assessments for imaging patients with orthopedic implants at the new clinical field strength of 7 Tesla.
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Affiliation(s)
- Paul Jacobs
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Andrew J Fagan
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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Silemek B, Seifert F, Petzold J, Brühl R, Ittermann B, Winter L. Wirelessly interfacing sensor-equipped implants and MR scanners for improved safety and imaging. Magn Reson Med 2023; 90:2608-2626. [PMID: 37533167 DOI: 10.1002/mrm.29818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 07/12/2023] [Accepted: 07/13/2023] [Indexed: 08/04/2023]
Abstract
PURPOSE To investigate a novel reduced RF heating method for imaging in the presence of active implanted medical devices (AIMDs) which employs a sensor-equipped implant that provides wireless feedback. METHODS The implant, consisting of a generator case and a lead, measures RF-inducedE $$ E $$ -fields at the implant tip using a simple sensor in the generator case and transmits these values wirelessly to the MR scanner. Based on the sensor signal alone, parallel transmission (pTx) excitation vectors were calculated to suppress tip heating and maintain image quality. A sensor-based imaging metric was introduced to assess the image quality. The methodology was studied at 7T in testbed experiments, and at a 3T scanner in an ASTM phantom containing AIMDs instrumented with six realistic deep brain stimulation (DBS) lead configurations adapted from patients. RESULTS The implant successfully measured RF-inducedE $$ E $$ -fields (Pearson correlation coefficient squared [R2 ] = 0.93) and temperature rises (R2 = 0.95) at the implant tip. The implant acquired the relevant data needed to calculate the pTx excitation vectors and transmitted them wirelessly to the MR scanner within a single shot RF sequence (<60 ms). Temperature rises for six realistic DBS lead configurations were reduced to 0.03-0.14 K for heating suppression modes compared to 0.52-3.33 K for the worst-case heating, while imaging quality remained comparable (five of six lead imaging scores were ≥0.80/1.00) to conventional circular polarization (CP) images. CONCLUSION Implants with sensors that can communicate with an MR scanner can substantially improve safety for patients in a fast and automated manner, easing the current burden for MR personnel.
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Affiliation(s)
- Berk Silemek
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Frank Seifert
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Johannes Petzold
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Rüdiger Brühl
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Bernd Ittermann
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Lukas Winter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
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Jiang F, Bhusal B, Nguyen B, Monge M, Webster G, Kim D, Bonmassar G, Popsecu AR, Golestanirad L. Modifying the trajectory of epicardial leads can substantially reduce MRI-induced RF heating in pediatric patients with a cardiac implantable electronic device at 1.5T. Magn Reson Med 2023; 90:2510-2523. [PMID: 37526134 PMCID: PMC10863853 DOI: 10.1002/mrm.29776] [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: 07/05/2022] [Revised: 05/12/2023] [Accepted: 06/06/2023] [Indexed: 08/02/2023]
Abstract
PURPOSE After epicardial cardiac implantable electronic devices are implanted in pediatric patients, they become ineligible to receive MRI exams due to an elevated risk of RF heating. We investigated whether simple modifications in the trajectories of epicardial leads could substantially and reliably reduce RF heating during MRI at 1.5 T, with benefits extending to abandoned leads. METHODS Electromagnetic simulations were performed to assess RF heating of two common 35-cm epicardial lead trajectories exhibiting different degrees of coupling with MRI incident electric fields. Experiments in anthropomorphic phantoms implanted with commercial cardiac implantable electronic devices confirmed the findings. Both electromagnetic simulations and experimental measurements were performed using head-first and feet-first positioning and various landmarks. Transfer function approach was used to assess the performance of suggested modifications in realistic body models. RESULTS Simulations (head-first, chest landmark) of a 35-cm epicardial lead with a trajectory where the excess length of the lead was looped and placed on the inferior surface of the heart showed an 87-fold reduction in the 0.1 g-averaged specific absorption rate compared with the lead where the excess length was looped on the anterior surface. Repeated experiments with a commercial epicardial device confirmed this. For fully implanted systems following low-specific absorption rate trajectories, there was a 16-fold reduction in the average temperature rise and a 28-fold reduction for abandoned leads. The transfer function method predicted a 7-fold reduction in the RF heating in 336 realistic scenarios. CONCLUSION Surgical modification of epicardial lead trajectory can substantially reduce RF heating at 1.5 T, with benefits extending to abandoned leads.
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Affiliation(s)
- Fuchang Jiang
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA
| | - Bhumi Bhusal
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Bach Nguyen
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Michael Monge
- Division of Cardiovascular-Thoracic Surgery, Ann & Robert H. Lurie Children’s Hospital of Chicago, Box 22, 225 E. Chicago Ave, Chicago, Illinois, 60611, USA
| | - Gregory Webster
- Division of Cardiology, Ann and Robert H. Lurie Children’s Hospital of Chicago, Northwestern University Feinberg School of Medicine, 225 East Chicago Avenue, Box 21, Chicago, IL, 60611, USA
| | - Daniel Kim
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Giorgio Bonmassar
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, USA
| | - Andrada R. Popsecu
- Division of Medical Imaging, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL, USA
| | - Laleh Golestanirad
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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Park BS, Guag JW, Jeong H, Rajan SS, McCright B. A new method to improve RF safety of implantable medical devices using inductive coupling at 3.0 T MRI. MAGMA (NEW YORK, N.Y.) 2023; 36:933-943. [PMID: 37566311 PMCID: PMC10667457 DOI: 10.1007/s10334-023-01109-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 06/21/2023] [Accepted: 07/03/2023] [Indexed: 08/12/2023]
Abstract
OBJECTIVE To enhance RF safety when implantable medical devices are located within the body coil but outside the imaging region by using a secondary resonator (SR) to reduce electric fields, the corresponding specific absorption rate (SAR), and temperature change during MRI. MATERIALS AND METHODS This study was conducted using numerical simulations with an American Society for Testing and Materials (ASTM) phantom and adult human models of Ella and Duke from Virtual Family Models, along with corresponding experimental results of temperature change obtained using the ASTM phantom. The circular SR was designed with an inner diameter of 150 mm and a width of 6 mm. Experimental measurements were carried out using a 3 T Medical Implant Test System (MITS) body coil, electromagnetic (EM) field mapping probes, and an ASTM phantom. RESULTS The magnitudes of B1+ (|B1+|) and SAR1g were reduced by 15.2% and 5.85% within the volume of interest (VoI) of an ASTM phantom, when a SR that generates opposing electromagnetic fields was utilized. Likewise, the Δ|B1+| and ΔSAR1g were reduced by up to 56.7% and 57.5% within the VoI of an Ella model containing a copper rod when an opposing SR was used. CONCLUSION A novel method employing the designed SR, which generates opposing magnetic fields to partially shield a sample, has been proposed to mitigate the risk of induced-RF heating at the VoI through numerical simulations and corresponding experiments under various conditions at 3.0 T.
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Affiliation(s)
- Bu S Park
- Division of Cellular and Gene Therapies (DCGT), OTAT, CBER, Food and Drug Administration (FDA), Silver Spring, MD, USA.
| | - Joshua W Guag
- Division of Biomedical Physics (DBP), OSEL, CDRH, FDA, Silver Spring, MD, USA
| | - Hongbae Jeong
- Division of Biomedical Physics (DBP), OSEL, CDRH, FDA, Silver Spring, MD, USA
| | - Sunder S Rajan
- Division of Biomedical Physics (DBP), OSEL, CDRH, FDA, Silver Spring, MD, USA
| | - Brent McCright
- Division of Cellular and Gene Therapies (DCGT), OTAT, CBER, Food and Drug Administration (FDA), Silver Spring, MD, USA
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Henry KR, Miulli MM, Nuzov NB, Nolt MJ, Rosenow JM, Elahi B, Pilitsis J, Golestanirad L. Variations in Determining Actual Orientations of Segmented Deep Brain Stimulation Leads Using the DiODe Algorithm: A Retrospective Study Across Different Lead Designs and Medical Institutions. Stereotact Funct Neurosurg 2023; 101:338-347. [PMID: 37717576 PMCID: PMC10866684 DOI: 10.1159/000531644] [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: 03/11/2023] [Accepted: 06/12/2023] [Indexed: 09/19/2023]
Abstract
INTRODUCTION Directional deep brain stimulation (DBS) leads have become widely used in the past decade. Understanding the asymmetric stimulation provided by directional leads requires precise knowledge of the exact orientation of the lead in respect to its anatomical target. Recently, the DiODe algorithm was developed to automatically determine the orientation angle of leads from the artifact on postoperative computed tomography (CT) images. However, manual DiODe results are user-dependent. This study analyzed the extent of lead rotation as well as the user agreement of DiODe calculations across the two most common DBS systems, namely, Boston Scientific's Vercise and Abbott's Infinity, and two independent medical institutions. METHODS Data from 104 patients who underwent an anterior-facing unilateral/bilateral directional DBS implantation at either Northwestern Memorial Hospital (NMH) or Albany Medical Center (AMC) were retrospectively analyzed. Actual orientations of the implanted leads were independently calculated by three individual users using the DiODe algorithm in Lead-DBS and patients' postoperative CT images. The deviation from the intended orientation and user agreement were assessed. RESULTS All leads significantly deviated from the intended 0° orientation (p < 0.001), regardless of DBS lead design (p < 0.05) or institution (p < 0.05). However, the Boston Scientific leads showed an implantation bias toward the left at both institutions (p = 0.014 at NMH, p = 0.029 at AMC). A difference of 10° between at least two users occurred in 28% (NMH) and 39% (AMC) of all Boston Scientific and 76% (NMH) and 53% (AMC) of all Abbott leads. CONCLUSION Our results show that there is a significant lead rotation from the intended surgical orientation across both DBS systems and both medical institutions; however, a bias toward a single direction was only seen in the Boston Scientific leads. Additionally, these results raise questions into the user error that occurs when manually refining the orientation angles calculated with DiODe.
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Affiliation(s)
- Kaylee R Henry
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA,
| | - Milina Michelle Miulli
- Department of Neuroscience and Department of Global Health Studies, Northwestern University, Evanston, Illinois, USA
| | - Noa B Nuzov
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA
- Department of Radiology, Northwestern University, Chicago, Illinois, USA
| | - Mark J Nolt
- Department of Neurosurgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Joshua M Rosenow
- Department of Neurosurgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Behzad Elahi
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, Illinois, USA
- Department of Neurology, Loyola Medical Center, Maywood, Illinois, USA
| | - Julie Pilitsis
- Department of Neurosciences and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Laleh Golestanirad
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA
- Department of Radiology, Northwestern University, Chicago, Illinois, USA
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Jiang F, Henry KR, Bhusal B, Sanpitak P, Webster G, Popescu A, Laternser C, Kim D, Golestanirad L. Age Matters: A Comparative Study of RF Heating of Epicardial and Endocardial Electronic Devices in Pediatric and Adult Phantoms during Cardiothoracic MRI. Diagnostics (Basel) 2023; 13:2847. [PMID: 37685385 PMCID: PMC10486594 DOI: 10.3390/diagnostics13172847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 06/29/2023] [Accepted: 08/04/2023] [Indexed: 09/10/2023] Open
Abstract
This study focused on the potential risks of radiofrequency-induced heating of cardiac implantable electronic devices (CIEDs) in children and adults with epicardial and endocardial leads of varying lengths during cardiothoracic MRI scans. Infants and young children are the primary recipients of epicardial CIEDs, though the devices have not been approved as MR conditional by the FDA due to limited data, leading to pediatric hospitals either refusing the MRI service to most pediatric CIED patients or adopting a scan-all strategy based on results from adult studies. The study argues that risk-benefit decisions should be made on an individual basis. We used 120 clinically relevant epicardial and endocardial device configurations in adult and pediatric anthropomorphic phantoms to determine the temperature rise during RF exposure at 1.5 T. The results showed that there was significantly higher RF heating of epicardial leads than endocardial leads in the pediatric phantom, but not in the adult phantom. Additionally, body size and lead length significantly affected RF heating, with RF heating up to 12 °C observed in models based on younger children with short epicardial leads. The study provides evidence-based knowledge on RF-induced heating of CIEDs and highlights the importance of making individual risk-benefit decisions when assessing the potential risks of MRI scans in pediatric CIED patients.
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Affiliation(s)
- Fuchang Jiang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Kaylee R. Henry
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Bhumi Bhusal
- Department of Radiology, Northwestern University, Chicago, IL 60611, USA
| | - Pia Sanpitak
- Department of Radiology, Northwestern University, Chicago, IL 60611, USA
| | - Gregory Webster
- Division of Cardiology, Ann and Robert H. Lurie Children’s Hospital of Chicago, Northwestern University, Chicago, IL 60611, USA
| | - Andrada Popescu
- Division of Medical Imaging, Ann and Robert H. Lurie Children’s Hospital of Chicago, Northwestern University, Chicago, IL 60611, USA
| | - Christina Laternser
- Division of Cardiology, Ann and Robert H. Lurie Children’s Hospital of Chicago, Northwestern University, Chicago, IL 60611, USA
| | - Daniel Kim
- Department of Radiology, Northwestern University, Chicago, IL 60611, USA
| | - Laleh Golestanirad
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Radiology, Northwestern University, Chicago, IL 60611, USA
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Qian E, Poojar P, Fung M, Jin Z, Vaughan JT, Shrivastava D, Gultekin D, Fernandes T, Geethanath S. Magnetic resonance fingerprinting based thermometry (MRFT): application to ex vivoimaging near DBS leads. Phys Med Biol 2023; 68:17NT01. [PMID: 37489867 DOI: 10.1088/1361-6560/acea54] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Accepted: 07/25/2023] [Indexed: 07/26/2023]
Abstract
The purpose of this study is to demonstrate the first work ofT1-based magnetic resonance thermometry using magnetic resonance fingerprinting (dubbed MRFT). We compared temperature estimation of MRFT with proton resonance frequency shift (PRFS) thermometry onex vivobovine muscle. We demonstrated MRFT's feasibility in predicting temperature onex vivobovine muscles with deep brain stimulation (DBS) lead.B0maps generated from MRFT were compared with gold standardB0maps near the DBS lead. MRFT and PRFS estimated temperatures were compared in the presence of motion. All experiments were performed on a 3 Tesla whole-body GE Premier system with a 21-channel receive head coil (GE Healthcare, Milwaukee, WI). Four fluoroptic probes were used to measure the temperature at the center of a cold muscle (probe 1), the room temperature water bottle (probe 2), and the center and periphery of the heated muscle (probes 3 and 4). We selected regions of interest (ROIs) around the location of the probes and used simple linear regression to generate the temperature sensitivity calibration equations that convertT1maps and Δsmaps to temperature maps. We then repeated the same setup and compared MRFT and PRFS thermometry temperature estimation with gold standard probe measurements. For the MRFT experiment on DBS lead, we taped the probe to the tip of the DBS lead and used a turbo spin echo sequence to induce heating near the lead. We selected ROIs around the tip of the lead to compare MRFT temperature estimation with probe measurements and compared with PRFS temperature estimation. Vendor-suppliedB0mapping sequence was acquired to compare with MRFT-generatedB0maps. We found strong linear relationships (R2> 0.958) betweenT1and temperature and Δsand temperatures in our temperature sensitivity calibration experiment. MRFT and PRFS thermometry both accurately predict temperature (RMSE < 1.55 °C) compared to probe measurements. MRFT estimated temperature near DBS lead has a similar trend as the probe temperature. BothB0maps show inhomogeneities around the lead. MRFT estimated temperature is less sensitive to motion.
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Affiliation(s)
- Enlin Qian
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
- Department of Biomedical Engineering, Columbia University, New York, NY, United States of America
| | - Pavan Poojar
- Accessible MR Laboratory, Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mt. Sinai, New York, NY, United States of America
| | - Maggie Fung
- GE Healthcare, New York, NY, United States of America
| | - Zhezhen Jin
- Department of Biostatistics, Columbia University, New York, NY, United States of America
| | - John Thomas Vaughan
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
- Department of Biomedical Engineering, Columbia University, New York, NY, United States of America
| | - Devashish Shrivastava
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
| | - David Gultekin
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
| | - Tiago Fernandes
- Accessible MR Laboratory, Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mt. Sinai, New York, NY, United States of America
- ISR - Lisboa/LARSyS and Department of Bioengineering, Instituto Superior Técnico-Universidade de Lisboa, Lisbon, Portugal
| | - Sairam Geethanath
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
- Accessible MR Laboratory, Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mt. Sinai, New York, NY, United States of America
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Jiang F, Henry KR, Bhusal B, Webster G, Bonmassar G, Kim D, Golestanirad L. RF-induced heating of capped and uncapped abandoned epicardial leads during MRI at 1.5 T and 3 T. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-5. [PMID: 38082570 PMCID: PMC10838566 DOI: 10.1109/embc40787.2023.10340533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
There is a paucity of data regarding the safety of magnetic resonance imaging (MRI) in patients with abandoned epicardial leads. Few studies have reported temperature rises up to 76 °C during MRI at 1.5 T in gel phantoms implanted with epicardial leads; however, lead trajectories used in these experiments were not clinically relevant. This work reports patient-specific RF heating of both capped and uncapped abandoned epicardial lead configurations during MRI at both 1.5 T and 3 T field strengths. We found that leads routed along realistic, patient-derived trajectories generated substantially lower RF heating than the previously reported worst-case phantom experiments. We also found that MRI at the head imaging landmark leads to substantially lower RF heating compared to MRI at the chest or abdomen landmarks at both 1.5 T and 3 T. Our results suggest that patients with abandoned epicardial leads may safely undergo MRI for head imaging, but caution is warranted during chest and abdominal imaging.Clinical Relevance- Patients with abandoned epicardial leads may safely undergo MRI for head imaging, but caution is warranted during chest and abdominal imaging.
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Bhusal B, Jiang F, Vu J, Sanpitak P, Golestanirad L. Implants talk to each-other: RF heating changes when two DBS leads are present simultaneously during MRI. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-5. [PMID: 38082747 PMCID: PMC10838603 DOI: 10.1109/embc40787.2023.10340769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Deep brain stimulation (DBS) has proven to be an effective treatment for Parkinson's disease and other brain disorders. The procedure often involves implanting two elongated leads aimed at specific brain nuclei in both the left and right hemispheres. However, evaluating the safety of MRI in patients with such implants has only been done on an individual lead basis, ignoring the possibility of crosstalk between the leads. This study evaluates the impact of crosstalk on power deposition at the lead tip through numerical simulation and phantom experiments. We used CT images to obtain patient-specific lead trajectories and compared the power deposition at the lead tip in cases with bilateral and unilateral DBS implants. Our results indicate that the RF power deposition at the lead tip can vary by up to 6-fold when two DBS leads are present together compared to when only one lead is present. Experimental measurements in a simplified case of two lead-only DBS systems confirmed the existence of crosstalk.Clinical Relevance-Our results indicate that RF heating of implanted leads during MRI can be affected by the presence of another lead in the body, which may increase or decrease the power deposition in the tissue depending on the position and configuration of the leads.
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12
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Vu J, Sanpitak P, Bhusal B, Jiang F, Golestanirad L. Rapid prediction of MRI-induced RF heating of active implantable medical devices using machine learning. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082837 PMCID: PMC10848153 DOI: 10.1109/embc40787.2023.10340900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
The interaction between an active implantable medical device and magnetic resonance imaging (MRI) radiofrequency (RF) fields can cause excessive tissue heating. Existing methods for predicting RF heating in the presence of an implant rely on either extensive phantom experiments or electromagnetic (EM) simulations with varying degrees of approximation of the MR environment, the patient, or the implant. On the contrary, fast MR thermometry techniques can provide a reliable real-time map of temperature rise in the tissue in the vicinity of conductive implants. In this proof-of-concept study, we examined whether a machine learning (ML) based model could predict the temperature increase in the tissue near the tip of an implanted lead after several minutes of RF exposure based on only a few seconds of experimentally measured temperature values. We performed phantom experiments with a commercial deep brain stimulation (DBS) system to train a fully connected feedforward neural network (NN) to predict temperature rise after ~3 minutes of scanning at a 3 T scanner using only data from the first 5 seconds. The NN effectively predicted ΔTmax-R2 = 0.99 for predictions in the test dataset. Our model also showed potential in predicting RF heating for other various scenarios, including a DBS system at a different field strength (1.5 T MRI, R2 = 0.87), different field polarization (1.2 T vertical MRI, R2 = 0.79), and an unseen implant (cardiac leads at 1.5 T MRI, R2 = 0.91). Our results indicate great potential for the application of ML in combination with fast MR thermometry techniques for rapid prediction of RF heating for implants in various MR environments.Clinical Relevance- Machine learning-based algorithms can potentially enable rapid prediction of MRI-induced RF heating in the presence of unknown AIMDs in various MR environments.
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Vu J, Bhusal B, Rosenow J, Pilitsis J, Golestanirad L. Optimizing the trajectory of deep brain stimulation leads reduces RF heating during MRI at 3 T: Characteristics and clinical translation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-5. [PMID: 38083480 PMCID: PMC10838567 DOI: 10.1109/embc40787.2023.10340979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Radiofrequency (RF) induced tissue heating around deep brain stimulation (DBS) leads is a well-known safety risk during magnetic resonance imaging (MRI), hindering routine protocols for patients. Known factors that contribute to variations in the magnitude of RF heating across patients include the implanted lead's trajectory and its orientation with respect to the MRI electric fields. Currently, there are no consistent requirements for surgically implanting the extracranial portion of the DBS lead. Recent studies have shown that incorporating concentric loops in the extracranial trajectory of the lead can reduce RF heating, but the optimal positioning of the loop is unknown. In this study, we evaluated RF heating of 77 unique lead trajectories to determine how different characteristics of the trajectory affect RF heating during MRI at 3 T. We performed phantom experiments with commercial DBS systems from two manufacturers to determine how consistently modifying the lead trajectory mitigates RF heating. We also presented the first surgical implementation of these modified trajectories in patients. Low-heating trajectories included small concentric loops near the surgical burr hole which were readily implemented during the surgical procedure; these trajectories generated nearly a 2-fold reduction in RF heating compared to unmodified trajectories.Clinical Relevance- Surgically modifying the DBS lead trajectory can be a cost-effective strategy for reducing RF-induced heating during MRI at 3 T.
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Chen X, Zheng C, Golestanirad L. Application of Machine learning to predict RF heating of cardiac leads during magnetic resonance imaging at 1.5 T and 3 T: A simulation study. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 349:107384. [PMID: 36842429 DOI: 10.1016/j.jmr.2023.107384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 01/04/2023] [Accepted: 01/20/2023] [Indexed: 06/18/2023]
Abstract
Predicting magnetic resonance imaging (MRI)-induced heating of elongated conductive implants, such as leads in cardiovascular implantable electronic devices, is essential to assessing patient safety. Phantom experiments have traditionally been used to estimate radio-frequency (RF) heating of implants, but they are time-consuming. Recently, machine learning has shown promise for fast prediction of RF heating of orthopaedic implants when the implant position within the MRI RF coil was predetermined. We explored whether deep learning could be applied to predict RF heating of conductive leads with variable positions and orientations during MRI at 1.5 T and 3 T. Models of 600 cardiac leads with clinically relevant trajectories were generated, and electromagnetic simulations were performed to calculate the maximum of the 1 g-averaged specific absorption rate (SAR) of RF energy at the tips of lead models during MRI at 1.5 T and 3 T. Neural networks were trained to predict the maximum SAR at the lead tip from the knowledge of the coordinates of points along the lead trajectory. Despite the large range of SAR values (∼230 W/kg to ∼ 3200 W/kg and ∼ 10 W/kg to ∼ 3300 W/kg), the root- mean-square error of the predicted vs ground truth SAR remained at 223 W/kg and 206 W/kg, with the R2 scores of 0.89 and 0.85 on the testing set for 1.5 T and 3 T models, respectively. The results suggest that machine learning is a promising approach for fast assessment of RF heating of lead-like implants when only the knowledge of the lead geometry and MRI RF coil features are in hand.
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Affiliation(s)
- Xinlu Chen
- Department of Electrical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Can Zheng
- Department of Electrical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - L Golestanirad
- Department of Electrical Engineering, Northwestern University, Evanston, IL, 60208, USA; Departmeng of Radiology, Northwestern University Chicago, IL 60611, USA; Departmeng of Biomedical Engineering, Northwestern University, Evanston, IL 60608, USA.
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15
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Xu Y, Qin G, Tan B, Fan S, An Q, Gao Y, Fan H, Xie H, Wu D, Liu H, Yang G, Fang H, Xiao Z, Zhang J, Zhang H, Shi L, Yang A. Deep Brain Stimulation Electrode Reconstruction: Comparison between Lead-DBS and Surgical Planning System. J Clin Med 2023; 12:jcm12051781. [PMID: 36902568 PMCID: PMC10002993 DOI: 10.3390/jcm12051781] [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: 01/11/2023] [Revised: 02/12/2023] [Accepted: 02/16/2023] [Indexed: 02/25/2023] Open
Abstract
BACKGROUND Electrode reconstruction for postoperative deep brain simulation (DBS) can be achieved manually using a surgical planning system such as Surgiplan, or in a semi-automated manner using software such as the Lead-DBS toolbox. However, the accuracy of Lead-DBS has not been thoroughly addressed. METHODS In our study, we compared the DBS reconstruction results of Lead-DBS and Surgiplan. We included 26 patients (21 with Parkinson's disease and 5 with dystonia) who underwent subthalamic nucleus (STN)-DBS, and reconstructed the DBS electrodes using the Lead-DBS toolbox and Surgiplan. The electrode contact coordinates were compared between Lead-DBS and Surgiplan with postoperative CT and MRI. The relative positions of the electrode and STN were also compared between the methods. Finally, the optimal contact during follow-up was mapped onto the Lead-DBS reconstruction results to check for overlap between the contacts and the STN. RESULTS We found significant differences in all axes between Lead-DBS and Surgiplan with postoperative CT, with the mean variance for the X, Y, and Z coordinates being -0.13, -1.16, and 0.59 mm, respectively. Y and Z coordinates showed significant differences between Lead-DBS and Surgiplan with either postoperative CT or MRI. However, no significant difference in the relative distance of the electrode and the STN was found between the methods. All optimal contacts were located in the STN, with 70% of them located within the dorsolateral region of the STN in the Lead-DBS results. CONCLUSIONS Although significant differences in electrode coordinates existed between Lead-DBS and Surgiplan, our results suggest that the coordinate difference was around 1 mm, and Lead-DBS can capture the relative distance between the electrode and the DBS target, suggesting it is reasonably accurate for postoperative DBS reconstruction.
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Affiliation(s)
- Yichen Xu
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Guofan Qin
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Bojing Tan
- Department of Neurosurgery, Capital Institute of Pediatrics, Beijing 100020, China
| | - Shiying Fan
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Qi An
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Yuan Gao
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Houyou Fan
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Hutao Xie
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Delong Wu
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Huanguang Liu
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
| | - Guang Yang
- Department of Neurosurgery, The First Affiliated Hospital of Harbin Medical University, Harbin 150007, China
| | - Huaying Fang
- Beijing Advanced Innovation Center for Imaging Theory and Technology, Capital Normal University, Beijing 100089, China
- Academy for Multidisciplinary Studies, Capital Normal University, Beijing 100089, China
| | - Zunyu Xiao
- Molecular Imaging Research Center, Harbin Medical University, Harbin 150076, China
| | - Jianguo Zhang
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
- Beijing Neurosurgical Institute, Capital Medical University, Beijing 100070, China
| | - Hua Zhang
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
- Correspondence: (H.Z.); (L.S.); (A.Y.)
| | - Lin Shi
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
- Correspondence: (H.Z.); (L.S.); (A.Y.)
| | - Anchao Yang
- Department of Functional Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
- Beijing Neurosurgical Institute, Capital Medical University, Beijing 100070, China
- Correspondence: (H.Z.); (L.S.); (A.Y.)
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16
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Nuzov NB, Bhusal B, Henry KR, Jiang F, Vu J, Rosenow JM, Pilitsis JG, Elahi B, Golestanirad L. Artifacts Can Be Deceiving: The Actual Location of Deep Brain Stimulation Electrodes Differs from the Artifact Seen on Magnetic Resonance Images. Stereotact Funct Neurosurg 2023; 101:47-59. [PMID: 36529124 PMCID: PMC9932848 DOI: 10.1159/000526877] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 08/04/2022] [Indexed: 12/23/2022]
Abstract
INTRODUCTION Deep brain stimulation (DBS) is a common treatment for a variety of neurological and psychiatric disorders. Recent studies have highlighted the role of neuroimaging in localizing the position of electrode contacts relative to target brain areas in order to optimize DBS programming. Among different imaging methods, postoperative magnetic resonance imaging (MRI) has been widely used for DBS electrode localization; however, the geometrical distortion induced by the lead limits its accuracy. In this work, we investigated to what degree the difference between the actual location of the lead's tip and the location of the tip estimated from the MRI artifact varies depending on the MRI sequence parameters such as acquisition plane and phase encoding direction, as well as the lead's extracranial configuration. Accordingly, an imaging technique to increase the accuracy of lead localization was devised and discussed. METHODS We designed and constructed an anthropomorphic phantom with an implanted DBS system following 18 clinically relevant configurations. The phantom was scanned at a Siemens 1.5 Tesla Aera scanner using a T1MPRAGE sequence optimized for clinical use and a T1TSE sequence optimized for research purposes. We varied slice acquisition plane and phase encoding direction and calculated the distance between the caudal tip of the DBS lead MRI artifact and the actual tip of the lead, as estimated from MRI reference markers. RESULTS Imaging parameters and lead configuration substantially altered the difference in the depth of the lead within its MRI artifact on the scale of several millimeters - with a difference as large as 4.99 mm. The actual tip of the DBS lead was found to be consistently more rostral than the tip estimated from the MR image artifact. The smallest difference between the tip of the DBS lead and the tip of the MRI artifact using the clinically relevant sequence (i.e., T1MPRAGE) was found with the sagittal acquisition plane and anterior-posterior phase encoding direction. DISCUSSION/CONCLUSION The actual tip of an implanted DBS lead is located up to several millimeters rostral to the tip of the lead's artifact on postoperative MR images. This distance depends on the MRI sequence parameters and the DBS system's extracranial trajectory. MRI parameters may be altered to improve this localization.
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Affiliation(s)
- Noa B Nuzov
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA, .,Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA,
| | - Bhumi Bhusal
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Kaylee R Henry
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA
| | - Fuchang Jiang
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA
| | - Jasmine Vu
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA.,Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Joshua M Rosenow
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Julie G Pilitsis
- Department of Neurosciences & Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Behzad Elahi
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Laleh Golestanirad
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA.,Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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17
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Effect of field strength on RF power deposition near conductive leads: A simulation study of SAR in DBS lead models during MRI at 1.5 T-10.5 T. PLoS One 2023; 18:e0280655. [PMID: 36701285 PMCID: PMC9879463 DOI: 10.1371/journal.pone.0280655] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 01/05/2023] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Since the advent of magnetic resonance imaging (MRI) nearly four decades ago, there has been a quest for ever-higher magnetic field strengths. Strong incentives exist to do so, as increasing the magnetic field strength increases the signal-to-noise ratio of images. However, ensuring patient safety becomes more challenging at high and ultrahigh field MRI (i.e., ≥3 T) compared to lower fields. The problem is exacerbated for patients with conductive implants, such as those with deep brain stimulation (DBS) devices, as excessive local heating can occur around implanted lead tips. Despite extensive effort to assess radio frequency (RF) heating of implants during MRI at 1.5 T, a comparative study that systematically examines the effects of field strength and various exposure limits on RF heating is missing. PURPOSE This study aims to perform numerical simulations that systematically compare RF power deposition near DBS lead models during MRI at common clinical and ultra-high field strengths, namely 1.5, 3, 7, and 10.5 T. Furthermore, we assess the effects of different exposure constraints on RF power deposition by imposing limits on either the B1+ or global head specific absorption rate (SAR) as these two exposure limits commonly appear in MRI guidelines. METHODS We created 33 unique DBS lead models based on postoperative computed tomography (CT) images of patients with implanted DBS devices and performed electromagnetic simulations to evaluate the SAR of RF energy in the tissue surrounding lead tips during RF exposure at frequencies ranging from 64 MHz (1.5 T) to 447 MHz (10.5 T). The RF exposure was implemented via realistic MRI RF coil models created based on physical prototypes built in our institutions. We systematically examined the distribution of local SAR at different frequencies with the input coil power adjusted to either limit the B1+ or the global head SAR. RESULTS The MRI RF coils at higher resonant frequencies generated lower SARs around the lead tips when the global head SAR was constrained. The trend was reversed when the constraint was imposed on B1+. CONCLUSION At higher static fields, MRI is not necessarily more dangerous than at lower fields for patients with conductive leads. Specifically, when a conservative safety criterion, such as constraints on the global SAR, is imposed, coils at a higher resonant frequency tend to generate a lower local SAR around implanted leads due to the decreased B1+ and, by proxy, E field levels.
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18
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Vu J, Bhusal B, Nguyen BT, Sanpitak P, Nowac E, Pilitsis J, Rosenow J, Golestanirad L. A comparative study of RF heating of deep brain stimulation devices in vertical vs. horizontal MRI systems. PLoS One 2022; 17:e0278187. [PMID: 36490249 PMCID: PMC9733854 DOI: 10.1371/journal.pone.0278187] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 11/11/2022] [Indexed: 12/13/2022] Open
Abstract
The majority of studies that assess magnetic resonance imaging (MRI) induced radiofrequency (RF) heating of the tissue when active electronic implants are present have been performed in horizontal, closed-bore MRI systems. Vertical, open-bore MRI systems have a 90° rotated magnet and a fundamentally different RF coil geometry, thus generating a substantially different RF field distribution inside the body. Little is known about the RF heating of elongated implants such as deep brain stimulation (DBS) devices in this class of scanners. Here, we conducted the first large-scale experimental study investigating whether RF heating was significantly different in a 1.2 T vertical field MRI scanner (Oasis, Fujifilm Healthcare) compared to a 1.5 T horizontal field MRI scanner (Aera, Siemens Healthineers). A commercial DBS device mimicking 30 realistic patient-derived lead trajectories extracted from postoperative computed tomography images of patients who underwent DBS surgery at our institution was implanted in a multi-material, anthropomorphic phantom. RF heating around the DBS lead was measured during four minutes of high-SAR RF exposure. Additionally, we performed electromagnetic simulations with leads of various internal structures to examine this effect on RF heating. When controlling for RMS B1+, the temperature increase around the DBS lead-tip was significantly lower in the vertical scanner compared to the horizontal scanner (0.33 ± 0.24°C vs. 4.19 ± 2.29°C). Electromagnetic simulations demonstrated up to a 17-fold reduction in the maximum of 0.1g-averaged SAR in the tissue surrounding the lead-tip in the vertical scanner compared to the horizontal scanner. Results were consistent across leads with straight and helical internal wires. Radiofrequency heating and power deposition around the DBS lead-tip were substantially lower in the 1.2 T vertical scanner compared to the 1.5 T horizontal scanner. Simulations with different lead structures suggest that the results may extend to leads from other manufacturers.
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Affiliation(s)
- Jasmine Vu
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, United States of America
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Bhumi Bhusal
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Bach T. Nguyen
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Pia Sanpitak
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, United States of America
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Elizabeth Nowac
- Illinois Bone and Joint Institute (IBJI), Wilmette, Illinois, United States of America
| | - Julie Pilitsis
- Department of Neurosciences & Experimental Therapeutics, Albany Medical College, Albany, New York, United States of America
| | - Joshua Rosenow
- Department of Neurosurgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Laleh Golestanirad
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, United States of America
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- * E-mail:
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19
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Akdogan G, Istanbullu OB. Analysing the effects of metallic biomaterial design and imaging sequences on MRI interpretation challenges due to image artefacts. Phys Eng Sci Med 2022; 45:1163-1174. [PMID: 36306073 DOI: 10.1007/s13246-022-01183-7] [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: 10/31/2021] [Accepted: 10/01/2022] [Indexed: 12/15/2022]
Abstract
Biometals cause signal loss and susceptibility artefacts in the surrounding tissue, resulting in deterioration in magnetic resonance (MR) images. This metal-artefact effect may lead to interpretation challenges for MR images. Therefore, artefact reduction is required to obtain higher-quality images. This paper aims to analyse the impact of imaging sequence and metallic biomaterial design on MR image artefacts. In this respect, implant specimens were designed in thin, thick, and pointed forms and manufactured using 316LVM, 316L, CoCr-alloy, and Ti-alloy, which are commonly utilized materials in the biomaterials field. Specimens were placed in a phantom that simulates average human anatomy separately and scanned in a 1.5 T MRI under four imaging conditions: "Axial-T1-Gradient-Echo (GRE)", "Sagittal-T1-GRE", "Axial-T2-Spin-Echo (SE)" and "Sagittal-T2-SE". Images were analysed regarding image artefact amount. The lower magnetic susceptibility of Ti-alloy specimens caused 84.76% less deterioration than 316LVM specimens in the MR images with the mean image artefact-to-specimen size ratio. Thinner implant designs provided better performance regarding the metal artefact by reducing the artefact-to-specimen size ratio. T2SE decreased the image artefact by 44.7% for 316LVM and 54.6% for Ti-Alloy specimens and provided better image quality than T1GRE for clinical interpretation. This study reveals that image artefacts directly depend on material content, implant volume, geometry, and imaging sequence selection. The minor artefact effect of T2SE provides more accurate MR images than T1GRE regarding the interpretation of the images of the patients with biometals. The higher magnetic susceptibility of biometals causes more deterioration of the images.
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Affiliation(s)
- Gulsen Akdogan
- Department of Biomedical Engineering, Faculty of Engineering, Erciyes University, Kayseri, Turkey.
| | - Omer Burak Istanbullu
- Department of Biomedical Engineering, Faculty of Engineering, Erciyes University, Kayseri, Turkey
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20
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Hayley J, Hart MG, Mostofi A, Morgante F, Pereira EA. No Adverse Effects following Off-Label Magnetic Resonance Imaging in a Patient with Two Deep Brain Stimulation Systems: A Case Report. Stereotact Funct Neurosurg 2022; 100:253-258. [PMID: 35820403 DOI: 10.1159/000525538] [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: 01/15/2022] [Accepted: 06/08/2022] [Indexed: 11/19/2022]
Abstract
Magnetic resonance imaging (MRI) in patients with implanted deep brain stimulation (DBS) systems is subject to strict guidelines in order to ensure patient safety. Criteria include limits on the number of implanted leads. Here, we describe the case of a 29-year-old patient with generalized dystonia implanted with 4 DBS electrodes and 2 implantable pulse generators, who had an off-label spinal MRI without regard for manufacturer guidance yet suffered no adverse effects. This suggests that manufacturer guidelines might be overly restrictive with regards to limits on implanted DBS hardware. Further research in this area is needed to widen access to this fundamental imaging modality for patients with DBS.
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Affiliation(s)
- James Hayley
- Neurosciences Research Centre, Molecular and Clinical Sciences Institute, St George's University of London, London, United Kingdom
| | - Michael G Hart
- Neurosciences Research Centre, Molecular and Clinical Sciences Institute, St George's University of London, London, United Kingdom.,St. George's University Hospital, London, United Kingdom
| | - Abteen Mostofi
- Neurosciences Research Centre, Molecular and Clinical Sciences Institute, St George's University of London, London, United Kingdom.,St. George's University Hospital, London, United Kingdom
| | - Francesca Morgante
- Neurosciences Research Centre, Molecular and Clinical Sciences Institute, St George's University of London, London, United Kingdom.,St. George's University Hospital, London, United Kingdom.,Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Erlick A Pereira
- Neurosciences Research Centre, Molecular and Clinical Sciences Institute, St George's University of London, London, United Kingdom.,St. George's University Hospital, London, United Kingdom
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21
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Sadeghi-Tarakameh A, Zulkarnain NIH, He X, Atalar E, Harel N, Eryaman Y. A workflow for predicting temperature increase at the electrical contacts of deep brain stimulation electrodes undergoing MRI. Magn Reson Med 2022; 88:2311-2325. [PMID: 35781696 PMCID: PMC9545305 DOI: 10.1002/mrm.29375] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 06/08/2022] [Accepted: 06/09/2022] [Indexed: 11/13/2022]
Abstract
Purpose The purpose of this study is to present a workflow for predicting the radiofrequency (RF) heating around the contacts of a deep brain stimulation (DBS) lead during an MRI scan. Methods The induced RF current on the DBS lead accumulates electric charge on the metallic contacts, which may cause a high local specific absorption rate (SAR), and therefore, heating. The accumulated charge was modeled by imposing a voltage boundary condition on the contacts in a quasi‐static electromagnetic (EM) simulation allowing thermal simulations to be performed with the resulting SAR distributions. Estimating SAR and temperature increases from a lead in vivo through EM simulation is not practical given anatomic differences and variations in lead geometry. To overcome this limitation, a new parameter, transimpedance, was defined to characterize a given lead. By combining the transimpedance, which can be measured in a single calibration scan, along with MR‐based current measurements of the lead in a unique orientation and anatomy, local heating can be estimated. Heating determined with this approach was compared with results from heating studies of a commercial DBS electrode in a gel phantom with different lead configurations to validate the proposed method. Results Using data from a single calibration experiment, the transimpedance of a commercial DBS electrode (directional lead, Infinity DBS system, Abbott Laboratories, Chicago, IL) was determined to be 88 Ω. Heating predictions using the DBS transimpedance and rapidly acquired MR‐based current measurements in 26 different lead configurations resulted in a <23% (on average 11.3%) normalized root‐mean‐square error compared to experimental heating measurements during RF scans. Conclusion In this study, a workflow consisting of an MR‐based current measurement on the DBS lead and simple quasi‐static EM/thermal simulations to predict the temperature increase around a DBS electrode undergoing an MRI scan is proposed and validated using a commercial DBS electrode. Click here for author‐reader discussions
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Affiliation(s)
| | | | - Xiaoxuan He
- Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, Minnesota, USA
| | - Ergin Atalar
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.,National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Noam Harel
- Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, Minnesota, USA
| | - Yigitcan Eryaman
- Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, Minnesota, USA
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Jiang F, Bhusal B, Sanpitak P, Webster G, Popescu A, Kim D, Bonmassar G, Golestanirad L. A comparative study of MRI-induced RF heating in pediatric and adult populations with epicardial and endocardial implantable electronic devices. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:4014-4017. [PMID: 36086095 PMCID: PMC10848149 DOI: 10.1109/embc48229.2022.9871087] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Patients with congenital heart defects, inherited arrhythmia syndromes, and congenital disorders of cardiac conduction often receive a cardiac implantable electronic device (CIED). At least 75% of patients with CIEDs will need magnetic resonance imaging (MRI) during their lifetime. In 2011, the US Food and Drug Administration approved the first MR-conditional CIEDs for patients with endocardial systems, in which leads are passed through the vein and affixed to the endocardium. The majority of children, however, receive an epicardial CIED, where leads are directly sewn to the epicardium. Unfortunately, an epicardial CIED is a relative contraindication to MRI due to the unknown risk of RF heating. In this work, we performed anthropomorphic phantom experiments to investigate differences in RF heating between endocardial and epicardial leads in both pediatric and adult-sized phantoms, where adult endocardial CIED was the control. Clinical Relevance-This work provides a quantitative comparison of MRI RF heating of epicardial and endocardial leads in pediatric and adult populations.
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23
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Nuzov NB, Bhusal B, Henry KR, Jiang F, Rosenow J, Elahi B, Golestanirad L. True location of deep brain stimulation electrodes differs from what is seen on postoperative magnetic resonance images: An anthropomorphic phantom study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:1863-1866. [PMID: 36086639 PMCID: PMC10848148 DOI: 10.1109/embc48229.2022.9871619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Deep brain stimulation (DBS) is an established yet growing treatment for a range of neurological and psychiatric disorders. Over the last decade, numerous studies have underscored the effect of electrode placement on the clinical outcome of DBS. As a result, imaging is now extensively used for DBS electrode localization, even though the accuracy of different modalities in determining the true coordinates of DBS electrodes is less explored. Postoperative magnetic resonance imaging (MRI) is a gold standard method for DBS electrode localization, however, the geometrical distortion induced by the lead's artifact could limit the accuracy. In this work, we investigated to what degree the difference between the true location of the lead's tip and the location of the tip estimated from the MRI artifact varies depending on the MRI sequence parameters, acquisition plane, phase encoding direction, and the implant"s extracranial trajectory. Clinical Relevance- Results will help researchers and clinicians to estimate the true location of DBS leads and contacts from postoperative MRI scans.
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Bhusal B, Jiang F, Kim D, Hong K, Monge MC, Webster G, Bonmassar G, Golestanirad L. The Position and Orientation of the Pulse Generator Affects MRI RF Heating of Epicardial Leads in Children. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:5000-5003. [PMID: 36086119 PMCID: PMC10843986 DOI: 10.1109/embc48229.2022.9871968] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Infants and children with congenital heart defects often receive a cardiac implantable electronic device (CIED). Because transvenous access to the heart is difficult in patients with small veins, the majority of young children receive epicardial CIEDs. Unfortunately, however, once an epicardial CIED is placed, patients are no longer eligible to receive magnetic resonance imaging (MRI) exams due to the unknown risk of MRI-induced radiofrequency (RF) heating of the device. Although many studies have assessed the role of device configuration in RF heating of endocardial CIEDs in adults, such case for epicardial devices in pediatric patients is relatively unexplored. In this study, we evaluated the variation in RF heating of an epicardial lead due to changes in the lateral position and orientation of the implantable pulse generator (IPG). We found that changing the orientation and position of the IPG resulted in a five-fold variation in the RF heating at the lead's tip. Maximum heating was observed when the IPG was moved to a left lateral abdominal position of patient, and minimum heating was observed when the IPG was positioned directly under the heart. Clinical Relevance- This study examines the role of device configuration on MRI-induced RF heating of an epicardial CIED in a pediatric phantom. Results could help pediatric cardiac surgeons to modify device implantation to reduce future risks of MRI in patients.
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25
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Lê TP, Gruetter R, Jorge J, Ipek Ö. Segmenting electroencephalography wires reduces radiofrequency shielding artifacts in simultaneous electroencephalography and functional magnetic resonance imaging at 7 T. Magn Reson Med 2022; 88:1450-1464. [PMID: 35575944 PMCID: PMC9323442 DOI: 10.1002/mrm.29298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 04/16/2022] [Accepted: 04/18/2022] [Indexed: 12/05/2022]
Abstract
Purpose Simultaneous scalp electroencephalography and functional magnetic resonance imaging (EEG‐fMRI) enable noninvasive assessment of brain function with high spatial and temporal resolution. However, at ultra‐high field, the data quality of both modalities is degraded by mutual interactions. Here, we thoroughly investigated the radiofrequency (RF) shielding artifact of a state‐of‐the‐art EEG‐fMRI setup, at 7 T, and design a practical solution to limit this issue. Methods Electromagnetic field simulations and MR measurements assessed the shielding effect of the EEG setup, more specifically the EEG wiring. The effectiveness of segmenting the wiring with resistors to reduce the transmit field disruption was evaluated on a wire‐only EEG model and a simulation model of the EEG cap. Results The EEG wiring was found to exert a dominant effect on the disruption of the transmit field, whose intensity varied periodically as a function of the wire length. Breaking the electrical continuity of the EEG wires into segments shorter than one quarter RF wavelength in air (25 cm at 7 T) reduced significantly the RF shielding artifacts. Simulations of the EEG cap with segmented wires indicated similar improvements for a moderate increase of the power deposition. Conclusion We demonstrated that segmenting the EEG wiring into shorter lengths using commercially available nonmagnetic resistors is effective at reducing RF shielding artifacts in simultaneous EEG‐fMRI. This prevents the formation of RF‐induced standing waves, without substantial specific absorption rate (SAR) penalties, and thereby enables benefiting from the functional sensitivity boosts achievable at ultra‐high field.
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Affiliation(s)
- Thanh Phong Lê
- Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Geneva School of Health Sciences, HES-SO University of Applied Sciences and Arts Western Switzerland, Geneva, Switzerland
| | - Rolf Gruetter
- Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - João Jorge
- Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.,CSEM - Swiss Center for Electronics and Microtechnology, Neuchâtel, Switzerland
| | - Özlem Ipek
- CIBM Center for Biomedical Imaging - Animal Imaging and Technology, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.,School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
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26
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Safety of Intracranial Electroencephalography During Functional Electromagnetic Resonance Imaging in Humans at 1.5 Tesla Using a Head Transmit RF Coil: Histopathological and Heat-Shock Immunohistochemistry Observations. Neuroimage 2022; 254:119129. [PMID: 35331868 DOI: 10.1016/j.neuroimage.2022.119129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 03/16/2022] [Accepted: 03/20/2022] [Indexed: 01/09/2023] Open
Abstract
OBJECTIVES Simultaneous intracranial EEG and functional MRI (icEEG-fMRI) recordings in humans, whereby EEG is recorded from electrodes implanted inside the cranium during fMRI scanning, were made possible following safety studies on test phantoms and our specification of a rigorous data acquisition protocol. In parallel with this work, other investigations in our laboratory revealed the damage caused by the EEG electrode implantation procedure at the cellular level. The purpose of this report is to further explore the safety of performing MRI, including simultaneous icEEG-fMRI data acquisitions, in the presence of implanted intra-cranial EEG electrodes, by presenting some histopathological and heat-shock immunopositive labelling observations in surgical tissue samples from patients who underwent the scanning procedure. METHODS We performed histopathology and heat shock protein expression analyses on surgical tissue samples from nine patients who had been implanted with icEEG electrodes. Three patients underwent icEEG-fMRI and structural MRI (sMRI); three underwent sMRI only, all at similar time points after icEEG implantation; and three who did not undergo functional or sMRI with icEEG electrodes. RESULTS The histopathological findings from the three patients who underwent icEEG-fMRI were similar to those who did not, in that they showed no evidence of additional damage in the vicinity of the electrodes, compared to cases who had no MRI with implanted icEEG electrodes. This finding was similar to our observations in patients who only underwent sMRI with implanted icEEG electrodes. CONCLUSION This work provides unique evidence on the safety of functional MRI in the presence of implanted EEG electrodes. In the cases studied, icEEG-fMRI performed in accordance with our protocol based on low-SAR (≤0.1 W/kg) sequences at 1.5T using a head-transmit RF coil, did not result in measurable additional damage to the brain tissue in the vicinity of implanted electrodes. Furthermore, while one cannot generalize the results of this study beyond the specific electrode implantation and scanning conditions described herein, we submit that our approach is a useful framework for the post-hoc safety assessment of MR scanning with brain implants.
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27
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Nguyen BT, Bhusal B, Rahsepar AA, Fawcett K, Lin S, Marks DS, Passman R, Nieto D, Niemzcura R, Golestanirad L. Safety of MRI in patients with retained cardiac leads. Magn Reson Med 2021; 87:2464-2480. [PMID: 34958685 PMCID: PMC8919805 DOI: 10.1002/mrm.29116] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 11/18/2021] [Accepted: 11/20/2021] [Indexed: 11/17/2022]
Abstract
Purpose To evaluate the safety of MRI in patients with fragmented retained leads (FRLs) through numerical simulation and phantom experiments. Methods Electromagnetic and thermal simulations were performed to determine the worst‐case RF heating of 10 patient‐derived FRL models during MRI at 1.5 T and 3 T and at imaging landmarks corresponding to head, chest, and abdomen. RF heating measurements were performed in phantoms implanted with reconstructed FRL models that produced highest heating in numerical simulations. The potential for unintended tissue stimulation was assessed through a conservative estimation of the electric field induced in the tissue due to gradient‐induced voltages developed along the length of FRLs. Results In simulations under conservative approach, RF exposure at B1+ ≤ 2 µT generated cumulative equivalent minutes (CEM)43 < 40 at all imaging landmarks at both 1.5 T and 3 T, indicating no thermal damage for acquisition times (TAs) < 10 min. In experiments, the maximum temperature rise when FRLs were positioned at the location of maximum electric field exposure was measured to be 2.4°C at 3 T and 2.1°C at 1.5 T. Electric fields induced in the tissue due to gradient‐induced voltages remained below the threshold for cardiac tissue stimulation in all cases. Conclusions Simulation and experimental results indicate that patients with FRLs can be scanned safely at both 1.5 T and 3 T with most clinical pulse sequences.
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Affiliation(s)
- Bach T Nguyen
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Bhumi Bhusal
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Amir Ali Rahsepar
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Kate Fawcett
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Stella Lin
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Daniel S Marks
- Department of Electrophysiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Rod Passman
- Department of Electrophysiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Donny Nieto
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Richard Niemzcura
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Laleh Golestanirad
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.,Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA
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28
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Sanpitak P, Bhusal B, Nguyen BT, Vu J, Chow K, Bi X, Golestanirad L. On the accuracy of Tier 4 simulations to predict RF heating of wire implants during magnetic resonance imaging at 1.5 T. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:4982-4985. [PMID: 34892326 DOI: 10.1109/embc46164.2021.9630220] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Magnetic Resonance Imaging (MRI) access remains conditional to patients with conductive medical implants, as RF heating generated around the implant during scanning may cause tissue burns. Experiments have been traditionally used to assess this heating, but they are time-consuming and expensive, and in many cases cannot faithfully replicate the in-vivo scenario. Alternatively, ISO TS 10974 outlines a four-tier RF heating assessment approach based on a combination of experiments and full-wave electromagnetic (EM) simulations with varying degrees of complexity. From these, Tier 4 approach relies entirely on EM simulations. There are, however, very few studies validating such numerical models against direct thermal measurements. In this work, we evaluated the agreement between simulated and measured RF heating around wire implants during RF exposure at 63.6 MHz (proton imaging at 1.5 T). Heating was assessed around wire implants with 25 unique trajectories within an ASTM phantom. The root mean square percentage error (RMSPE) of simulated vs. measured RF heating remained <1.6% despite the wide range of observed heating (0.2 °C-53 °C). Our results suggest that good agreement can be achieved between experiments and simulations as long as important experimental features such as characteristics of the MRI RF coil, implant's geometry, position, and trajectory, as well as electric and thermal properties of gel are closely mimicked in simulations.Clinical Relevance- This work validates the application of full-wave EM simulations for modeling and predicting RF heating of conductive wires in an MRI environment, providing researchers with a validated tool to assess MRI safety in patients with implants.
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Nguyen BT, Bhusal B, Fawcett K, Golestanirad L. Radiofrequency heating of retained cardiac leads during magnetic resonance imaging at 1.5 T and 3 T. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:4986-4989. [PMID: 34892327 DOI: 10.1109/embc46164.2021.9629867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Patients with cardiovascular implantable electronic devices (CIEDs) are often prevented from receiving magnetic resonance imaging (MRI) due to risks associated with radiofrequency (RF) heating of tissue around the implanted leads. Although MR-conditional CIEDs are available, the safety labeling of such devices does not extend to patients with fragmented retained leads (FRLs), where segments of the leads are left in the tissue after the original device is extracted. Unlike intact and isolated leads of CIEDs, FRLs are often bare conductive lead fragments in direct contact with the tissue. No experimental work has been reported that assess RF heating of FRL during MRI thus far. In this work, we performed phantom experiments to measure RF heating of 4 patient-derived FRL models in a gel-based ASTM-like phantom during RF exposure at 64 MHz (proton imaging at 1.5 T) and 123 MHz (proton imaging at 3 T). We found FRL models to generate negligible temperature rise in the gel (∆T<1.84 °C) during a 10-minute scan at both 1.5 T and 3 T. These results are in agreement with previous simulation studies and suggest MRI may be performed safely in patients with fragmented retained leads.
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30
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Vu J, Bhusal B, Rosenow J, Pilitsis J, Golestanirad L. Modifying surgical implantation of deep brain stimulation leads significantly reduces RF-induced heating during 3 T MRI. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:4978-4981. [PMID: 34892325 DOI: 10.1109/embc46164.2021.9629553] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Radiofrequency (RF) heating of tissue during magnetic resonance imaging (MRI) is a known safety risk in the presence of active implantable medical devices (AIMDs). As a result, access to MRI is limited for patients with these implants including those with deep brain stimulation (DBS) systems. Numerous factors contribute to excessive RF tissue heating at the DBS lead-tip, most notable being the trajectory of the lead. Phantom studies have demonstrated that looping the extracranial portion of the DBS lead at the surgical burr hole reduces the heating at the lead-tip; however, clinical implementation of this technique is challenging due to surgical constraints. As such, the intended looped trajectory is usually different from what is implanted in patients. To date, no data is available to quantify the extent by which surgical trajectory modification reduces RF heating of DBS leads compared to the typical surgical approach. In this work, we measured RF heating of a commercial DBS system during 3 T MRI, where the trajectory of the lead and extension cable mimicked lead trajectories constructed from postoperative CT images of 13 patients undergoing modified DBS surgery and 2 patients with unmodified trajectories. Two manually created trajectories mimicking typical heating cases seen in the literature were also evaluated. We found that modified lead trajectories reduced the average heating by 3-folds compared to unmodified lead trajectories.Clinical Relevance- This study evaluates the performance of a surgical modification in the routing of DBS leads in reducing RF-induced heating during MRI at 3 T.
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Vu J, Nguyen BT, Bhusal B, Baraboo J, Rosenow J, Bagci U, Bright MG, Golestanirad L. Machine learning-based prediction of MRI-induced power absorption in the tissue in patients with simplified deep brain stimulation lead models. IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY 2021; 63:1757-1766. [PMID: 34898696 PMCID: PMC8654205 DOI: 10.1109/temc.2021.3106872] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Interaction of an active electronic implant such as a deep brain stimulation (DBS) system and MRI RF fields can induce excessive tissue heating, limiting MRI accessibility. Efforts to quantify RF heating mostly rely on electromagnetic (EM) simulations to assess individualized specific absorption rate (SAR), but such simulations require extensive computational resources. Here, we investigate if a predictive model using machine learning (ML) can predict the local SAR in the tissue around tips of implanted leads from the distribution of the tangential component of the MRI incident electric field, Etan. A dataset of 260 unique patient-derived and artificial DBS lead trajectories was constructed, and the 1 g-averaged SAR, 1gSARmax, at the lead-tip during 1.5 T MRI was determined by EM simulations. Etan values along each lead's trajectory and the simulated SAR values were used to train and test the ML algorithm. The resulting predictions of the ML algorithm indicated that the distribution of Etan could effectively predict 1gSARmax at the DBS lead-tip (R = 0.82). Our results indicate that ML has the potential to provide a fast method for predicting MR-induced power absorption in the tissue around tips of implanted leads such as those in active electronic medical devices.
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Affiliation(s)
- Jasmine Vu
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, USA
| | - Bach T Nguyen
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Bhumi Bhusal
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Justin Baraboo
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, USA
| | - Joshua Rosenow
- Department of Neurosurgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Ulas Bagci
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Molly G Bright
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, USA
| | - Laleh Golestanirad
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, USA
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Bhusal B, Stockmann J, Guerin B, Mareyam A, Kirsch J, Wald LL, Nolt MJ, Rosenow J, Lopez-Rosado R, Elahi B, Golestanirad L. Safety and image quality at 7T MRI for deep brain stimulation systems: Ex vivo study with lead-only and full-systems. PLoS One 2021; 16:e0257077. [PMID: 34492090 PMCID: PMC8423254 DOI: 10.1371/journal.pone.0257077] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 08/23/2021] [Indexed: 11/19/2022] Open
Abstract
Ultra-high field MRI at 7 T can produce much better visualization of sub-cortical structures compared to lower field, which can greatly help target verification as well as overall treatment monitoring for patients with deep brain stimulation (DBS) implants. However, use of 7 T MRI for such patients is currently contra-indicated by guidelines from the device manufacturers due to the safety issues. The aim of this study was to provide an assessment of safety and image quality of ultra-high field magnetic resonance imaging at 7 T in patients with deep brain stimulation implants. We performed experiments with both lead-only and complete DBS systems implanted in anthropomorphic phantoms. RF heating was measured for 43 unique patient-derived device configurations. Magnetic force measurements were performed according to ASTM F2052 test method, and device integrity was assessed before and after experiments. Finally, we assessed electrode artifact in a cadaveric brain implanted with an isolated DBS lead. RF heating remained below 2°C, similar to a fever, with the 95% confidence interval between 0.38°C-0.52°C. Magnetic forces were well below forces imposed by gravity, and thus not a source of concern. No device malfunctioning was observed due to interference from MRI fields. Electrode artifact was most noticeable on MPRAGE and T2*GRE sequences, while it was minimized on T2-TSE images. Our work provides the safety assessment of ultra-high field MRI at 7 T in patients with DBS implants. Our results suggest that 7 T MRI may be performed safely in patients with DBS implants for specific implant models and MRI hardware.
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Affiliation(s)
- Bhumi Bhusal
- Department of Radiology, Northwestern University, Chicago, IL, United States of America
| | - Jason Stockmann
- Department of Radiology, Harvard Medical School, Boston, MA, United States of America
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| | - Bastien Guerin
- Department of Radiology, Harvard Medical School, Boston, MA, United States of America
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| | - Azma Mareyam
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| | - John Kirsch
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| | - Lawrence L. Wald
- Department of Radiology, Harvard Medical School, Boston, MA, United States of America
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| | - Mark J. Nolt
- Department of Neurosurgery, Northwestern University, Chicago, IL, United States of America
| | - Joshua Rosenow
- Department of Neurosurgery, Northwestern University, Chicago, IL, United States of America
| | - Roberto Lopez-Rosado
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, United States of America
| | - Behzad Elahi
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, United States of America
| | - Laleh Golestanirad
- Department of Radiology, Northwestern University, Chicago, IL, United States of America
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, United States of America
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Wang Y, Zheng J, Guo R, Wang Q, Kainz W, Long S, Chen J. A technique for the reduction of RF-induced heating of active implantable medical devices during MRI. Magn Reson Med 2021; 87:349-364. [PMID: 34374457 DOI: 10.1002/mrm.28953] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 07/15/2021] [Accepted: 07/17/2021] [Indexed: 12/21/2022]
Abstract
PURPOSE The paper presents a novel method to reduce the RF-induced heating of active implantable medical devices during MRI. METHODS With the addition of an energy decoying and dissipating structure, RF energy can be redirected toward the dissipating rings through the decoying conductor. Three lead groups (45 cm-50 cm) and 4 (50 cm-100 cm) were studied in 1.5 Tesla MR systems by simulation and measurement, respectively. In vivo modeling was performed using human models to estimate the RF-induced heating of an active implantable medical device for spinal cord treatment. RESULT In the simulation study, it was shown that the peak 1g-averaged specific absorption rate near the lead-tips can be reduced by 70% to 80% compared to those from the control leads. In the experimental measurements during a 2-min exposure test in a 1.5 Telsa MR system, the temperature rises dropped from the original 18.3℃, 25.8℃, 8.1℃, and 16.1℃ (control leads 1-4) to 5.4℃, 6.9℃, 1.6℃, and 3.3℃ (leads 1-4 with the energy decoying and dissipation structure). The in vivo calculation results show that the maximum induced temperature rise among all cases can be substantially reduced (up to 80%) when the energy decoying and dissipating structures were used. CONCLUSION Our studies confirm the effectiveness of the novel technique for a variety of scanning scenarios. The results also indicate that the decoying conductor length, number of rings, and ring area must be carefully chosen and validated.
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Affiliation(s)
- Yu Wang
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Jianfeng Zheng
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Ran Guo
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Qingyan Wang
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Wolfgang Kainz
- Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland, USA
| | - Stuart Long
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Ji Chen
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
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Derksen M, Rhemrev V, van der Veer M, Jolink L, Zuidinga B, Mulder T, Reneman L, Nederveen A, Feenstra M, Willuhn I, Denys D. Animal studies in clinical MRI scanners: A custom setup for combined fMRI and deep-brain stimulation in awake rats. J Neurosci Methods 2021; 360:109240. [PMID: 34097929 DOI: 10.1016/j.jneumeth.2021.109240] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 03/30/2021] [Accepted: 06/01/2021] [Indexed: 11/26/2022]
Abstract
BACKGROUND In humans, functional magnetic resonance imaging (fMRI) cannot be used to its full potential to study the effects of deep-brain stimulation (DBS) on the brain due to safety reasons. Application of DBS in small animals is an alternative, but was hampered by technical limitations thus far. NEW METHOD We present a novel setup that extends the range of available applications by studying animals in a clinical scanner. We used a 3 T-MRI scanner with a custom-designed receiver coil and a restrainer to measure brain activity in awake rats. DBS electrodes made of silver were used to minimize electromagnetic artifacts. Before scanning, rats were habituated to the restrainer. RESULTS Using our novel setup, we observed minor DBS-electrode artifacts, which did not interfere with brain-activity measurements significantly. Movement artifacts were also minimal and were not further reduced by restrainer habituation. Bilateral DBS in the dorsal part of the ventral striatum (dVS) resulted in detectable increases in brain activity around the electrodes tips. COMPARISON WITH EXISTING METHODS This novel setup offers a low-cost alternative to dedicated small-animal scanners. Moreover, it can be implemented in widely available clinical 3 T scanners. Although spatial and temporal resolution was lower than what is achieved in anesthetized rats in high-field small-animal scanners, we obtained scans in awake animals, thus, testing the effects of bilateral DBS of the dVS in a more physiological state. CONCLUSIONS With this new technical setup, the neurobiological mechanism of action of DBS can be explored in awake, restrained rats in a clinical 3 T-MRI scanner.
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Affiliation(s)
- Maik Derksen
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands; Department of Psychiatry, Amsterdam University Medical Centers (location AMC), University of Amsterdam, Amsterdam, the Netherlands
| | - Valerie Rhemrev
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands
| | - Marijke van der Veer
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands
| | - Linda Jolink
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands
| | - Birte Zuidinga
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands
| | - Tosca Mulder
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands
| | - Liesbeth Reneman
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers (location AMC), University of Amsterdam, Amsterdam, the Netherlands
| | - Aart Nederveen
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers (location AMC), University of Amsterdam, Amsterdam, the Netherlands
| | - Matthijs Feenstra
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands; Department of Psychiatry, Amsterdam University Medical Centers (location AMC), University of Amsterdam, Amsterdam, the Netherlands
| | - Ingo Willuhn
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands; Department of Psychiatry, Amsterdam University Medical Centers (location AMC), University of Amsterdam, Amsterdam, the Netherlands.
| | - Damiaan Denys
- The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, the Netherlands; Department of Psychiatry, Amsterdam University Medical Centers (location AMC), University of Amsterdam, Amsterdam, the Netherlands
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Kazemivalipour E, Bhusal B, Vu J, Lin S, Nguyen BT, Kirsch J, Nowac E, Pilitsis J, Rosenow J, Atalar E, Golestanirad L. Vertical open-bore MRI scanners generate significantly less radiofrequency heating around implanted leads: A study of deep brain stimulation implants in 1.2T OASIS scanners versus 1.5T horizontal systems. Magn Reson Med 2021; 86:1560-1572. [PMID: 33961301 DOI: 10.1002/mrm.28818] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Revised: 04/05/2021] [Accepted: 04/07/2021] [Indexed: 12/17/2022]
Abstract
PURPOSE Patients with active implants such as deep brain stimulation (DBS) devices are often denied access to MRI due to safety concerns associated with the radiofrequency (RF) heating of their electrodes. The majority of studies on RF heating of conductive implants have been performed in horizontal close-bore MRI scanners. Vertical MRI scanners which have a 90° rotated transmit coil generate fundamentally different electric and magnetic field distributions, yet very little is known about RF heating of implants in this class of scanners. We performed numerical simulations as well as phantom experiments to compare RF heating of DBS implants in a 1.2T vertical scanner (OASIS, Hitachi) compared to a 1.5T horizontal scanner (Aera, Siemens). METHODS Simulations were performed on 90 lead models created from post-operative CT images of patients with DBS implants. Experiments were performed with wires and commercial DBS devices implanted in an anthropomorphic phantom. RESULTS We found significant reduction of 0.1 g-averaged specific absorption rate (30-fold, P < 1 × 10-5 ) and RF heating (9-fold, P < .026) in the 1.2T vertical scanner compared to the 1.5T conventional scanner. CONCLUSION Vertical MRI scanners appear to generate lower RF heating around DBS leads, providing potentially heightened safety or the flexibility to use sequences with higher power levels than on conventional systems.
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Affiliation(s)
- Ehsan Kazemivalipour
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.,Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.,National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Bhumi Bhusal
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Jasmine Vu
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.,Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA
| | - Stella Lin
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Bach Thanh Nguyen
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - John Kirsch
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Elizabeth Nowac
- Department of Neurosurgery, Albany Medical Center, Albany, New York, USA
| | - Julie Pilitsis
- Illinois Bone and Joint Institute (IBJI), Wilmette, Illinois, USA
| | - Joshua Rosenow
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Ergin Atalar
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.,National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Laleh Golestanirad
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.,Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois, USA
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McGlynn E, Nabaei V, Ren E, Galeote‐Checa G, Das R, Curia G, Heidari H. The Future of Neuroscience: Flexible and Wireless Implantable Neural Electronics. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2002693. [PMID: 34026431 PMCID: PMC8132070 DOI: 10.1002/advs.202002693] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 01/15/2021] [Indexed: 05/04/2023]
Abstract
Neurological diseases are a prevalent cause of global mortality and are of growing concern when considering an ageing global population. Traditional treatments are accompanied by serious side effects including repeated treatment sessions, invasive surgeries, or infections. For example, in the case of deep brain stimulation, large, stiff, and battery powered neural probes recruit thousands of neurons with each pulse, and can invoke a vigorous immune response. This paper presents challenges in engineering and neuroscience in developing miniaturized and biointegrated alternatives, in the form of microelectrode probes. Progress in design and topology of neural implants has shifted the goal post toward highly specific recording and stimulation, targeting small groups of neurons and reducing the foreign body response with biomimetic design principles. Implantable device design recommendations, fabrication techniques, and clinical evaluation of the impact flexible, integrated probes will have on the treatment of neurological disorders are provided in this report. The choice of biocompatible material dictates fabrication techniques as novel methods reduce the complexity of manufacture. Wireless power, the final hurdle to truly implantable neural interfaces, is discussed. These aspects are the driving force behind continued research: significant breakthroughs in any one of these areas will revolutionize the treatment of neurological disorders.
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Affiliation(s)
- Eve McGlynn
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Vahid Nabaei
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Elisa Ren
- Laboratory of Experimental Electroencephalography and NeurophysiologyDepartment of BiomedicalMetabolic and Neural SciencesUniversity of Modena and Reggio EmiliaModena41125Italy
| | - Gabriel Galeote‐Checa
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Rupam Das
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Giulia Curia
- Laboratory of Experimental Electroencephalography and NeurophysiologyDepartment of BiomedicalMetabolic and Neural SciencesUniversity of Modena and Reggio EmiliaModena41125Italy
| | - Hadi Heidari
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
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Davidson B, Tam F, Yang B, Meng Y, Hamani C, Graham SJ, Lipsman N. Three-Tesla Magnetic Resonance Imaging of Patients With Deep Brain Stimulators: Results From a Phantom Study and a Pilot Study in Patients. Neurosurgery 2021; 88:349-355. [PMID: 33045736 DOI: 10.1093/neuros/nyaa439] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 07/19/2020] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Deep brain stimulation (DBS) is a standard of care treatment for multiple neurologic disorders. Although 3-tesla (3T) magnetic resonance imaging (MRI) has become the gold-standard modality for structural and functional imaging, most centers refrain from 3T imaging in patients with DBS devices in place because of safety concerns. 3T MRI could be used not only for structural imaging, but also for functional MRI to study the effects of DBS on neurocircuitry and optimize programming. OBJECTIVE To use an anthropomorphic phantom design to perform temperature and voltage safety testing on an activated DBS device during 3T imaging. METHODS An anthropomorphic 3D-printed human phantom was constructed and used to perform temperature and voltage testing on a DBS device during 3T MRI. Based on the phantom assessment, a cohort study was conducted in which 6 human patients underwent MRI with their DBS device in an activated (ON) state. RESULTS During the phantom study, temperature rises were under 2°C during all sequences, with the DBS in both the deactivated and activated states. Radiofrequency pulses from the MRI appeared to modulate the electrical discharge from the DBS, resulting in slight fluctuations of voltage amplitude. Six human subjects underwent MRI with their DBS in an activated state without any serious adverse events. One patient experienced stimulation-related side effects during T1-MPRAGE scanning with the DBS in an ON state because of radiofrequency-induced modulation of voltage amplitude. CONCLUSION Following careful phantom-based safety testing, 3T structural and functional MRI can be safely performed in subjects with activated deep brain stimulators.
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Affiliation(s)
- Benjamin Davidson
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.,Harquail Centre for Neuromodulation, Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, Canada.,Sunnybrook Research Institute, Toronto, Canada
| | - Fred Tam
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
| | - Benson Yang
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
| | - Ying Meng
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.,Harquail Centre for Neuromodulation, Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, Canada.,Sunnybrook Research Institute, Toronto, Canada
| | - Clement Hamani
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.,Harquail Centre for Neuromodulation, Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, Canada.,Sunnybrook Research Institute, Toronto, Canada
| | - Simon J Graham
- Sunnybrook Research Institute, Toronto, Canada.,Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - Nir Lipsman
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.,Harquail Centre for Neuromodulation, Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, Canada.,Sunnybrook Research Institute, Toronto, Canada
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38
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Exposure levels of radiofrequency magnetic fields and static magnetic fields in 1.5 and 3.0 T MRI units. SN APPLIED SCIENCES 2021. [DOI: 10.1007/s42452-021-04178-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
AbstractMagnetic resonance imaging (MRI) staff is exposed to a complex mixture of electromagnetic fields from MRI units. Exposure to these fields results in the development of transient exposure-related symptoms. This study aimed to investigate the exposure levels of radiofrequency (RF) magnetic fields and static magnetic fields (SMFs) from 1.5 and 3.0 T MRI scanners in two public hospitals in the Mangaung Metropolitan region, South Africa. The exposure levels of SMFs and RF magnetic fields were measured using the THM1176 3-Axis hall magnetometer and TM-196 3 Axis RF field strength meter, respectively. Measurements were collected at a distance of 1 m (m) and 2 m from the gantry for SMFs when the brain, cervical spine and extremities were scanned. Measurements for RF magnetic fields were collected at a distance of 1 m with an average scan duration of six minutes. Friedman’s test was used to compared exposure mean values from two 1.5 T scanners, and Wilcoxon test with Bonferroni adjustment was used to identify where the difference between exist. The Shapiro–Wilk test was also used to test for normality between exposure levels in 1.5 and 3.0 T scanners. The measured peak values for SMFs from the 3.0 T scanner at hospital A were 1300 milliTesla (mT) and 726 mT from 1.5 T scanner in hospital B. The difference in terms of SMFs exposure levels was observed between two 1.5 T scanners at a distance of 2 m. The difference between 1.5 T scanners at 1 m was also observed during repeated measurements when brain, cervical spine and extremities scans were performed. Scanners’ configurations, magnet type, clinical setting and location were identified as factors that could influence different propagation of SMFs between scanners of the same nominal B0. The RF pulse design, sequence setting flip-angle and scans performed influenced the measured RF magnetic fields. Three scanners were complaint with occupational exposure guidelines stipulated by the ICNIRP; however, peak levels that exist at 1 m could be managed through adoption of occupational health and safety programs.
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Bhusal B, Keil B, Rosenow J, Kazemivalipour E, Golestanirad L. Patient's body composition can significantly affect RF power deposition in the tissue around DBS implants: ramifications for lead management strategies and MRI field-shaping techniques. Phys Med Biol 2021; 66:015008. [PMID: 33238247 DOI: 10.1088/1361-6560/abcde9] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Patients with active implants such as deep brain stimulation (DBS) devices have limited access to magnetic resonance imaging (MRI) due to risks associated with RF heating of implants in MRI environment. With an aging population and increased prevalence of neurodegenerative disease, the indication for MRI exams in patients with such implants increases as well. In response to this growing need, many groups have investigated strategies to mitigate RF heating of DBS implants during MRI. These efforts fall into two main categories: MRI field-shaping methods, where the electric field of the MRI RF coil is modified to reduce the interaction with implanted leads, and lead management techniques where surgical modifications in the trajectory reduces the coupling with RF fields. Studies that characterize these techniques, however, have relied either on simulations with homogenous body models, or experiments with box-shaped single-material phantoms. It is well established, however, that the shape and heterogeneity of human body affects the distribution of RF electric fields, which by proxy, alters the heating of an implant inside the body. In this contribution, we applied numerical simulations and phantom experiments to examine the degree to which variations in patient's body composition affects RF power deposition. We then assessed effectiveness of RF-heating mitigation strategies under variant patient body compositions. Our results demonstrated that patient's body composition substantially alters RF power deposition in the tissue around implanted leads. However, both techniques based on MRI field-shaping and DBS lead management performed well under variant body types.
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Affiliation(s)
- Bhumi Bhusal
- Department of Radiology, Northwestern University, Chicago, IL, United States of America
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40
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Jeong H, Ntolkeras G, Alhilani M, Atefi SR, Zöllei L, Fujimoto K, Pourvaziri A, Lev MH, Grant PE, Bonmassar G. Development, validation, and pilot MRI safety study of a high-resolution, open source, whole body pediatric numerical simulation model. PLoS One 2021; 16:e0241682. [PMID: 33439896 PMCID: PMC7806143 DOI: 10.1371/journal.pone.0241682] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 10/19/2020] [Indexed: 11/30/2022] Open
Abstract
Numerical body models of children are used for designing medical devices, including but not limited to optical imaging, ultrasound, CT, EEG/MEG, and MRI. These models are used in many clinical and neuroscience research applications, such as radiation safety dosimetric studies and source localization. Although several such adult models have been reported, there are few reports of full-body pediatric models, and those described have several limitations. Some, for example, are either morphed from older children or do not have detailed segmentations. Here, we introduce a 29-month-old male whole-body native numerical model, "MARTIN", that includes 28 head and 86 body tissue compartments, segmented directly from the high spatial resolution MRI and CT images. An advanced auto-segmentation tool was used for the deep-brain structures, whereas 3D Slicer was used to segment the non-brain structures and to refine the segmentation for all of the tissue compartments. Our MARTIN model was developed and validated using three separate approaches, through an iterative process, as follows. First, the calculated volumes, weights, and dimensions of selected structures were adjusted and confirmed to be within 6% of the literature values for the 2-3-year-old age-range. Second, all structural segmentations were adjusted and confirmed by two experienced, sub-specialty certified neuro-radiologists, also through an interactive process. Third, an additional validation was performed with a Bloch simulator to create synthetic MR image from our MARTIN model and compare the image contrast of the resulting synthetic image with that of the original MRI data; this resulted in a "structural resemblance" index of 0.97. Finally, we used our model to perform pilot MRI safety simulations of an Active Implantable Medical Device (AIMD) using a commercially available software platform (Sim4Life), incorporating the latest International Standards Organization guidelines. This model will be made available on the Athinoula A. Martinos Center for Biomedical Imaging website.
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Affiliation(s)
- Hongbae Jeong
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
| | - Georgios Ntolkeras
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States of America
| | - Michel Alhilani
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States of America
- Department of Medicine, Charing Cross Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Seyed Reza Atefi
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
| | - Lilla Zöllei
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
| | - Kyoko Fujimoto
- Center for Devices and Radiological Health, U. S. Food and Drug Administration, Silver Spring, MD, United States of America
| | - Ali Pourvaziri
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
| | - Michael H. Lev
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
| | - P. Ellen Grant
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States of America
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America
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Tian X, Lv Y, Fan Y, Wang Z, Yu B, Song C, Lu Q, Xi C, Pi L, Zhang X. Safety evaluation of mice exposed to 7.0-33.0 T high-static magnetic fields. J Magn Reson Imaging 2020; 53:1872-1884. [PMID: 33382516 DOI: 10.1002/jmri.27496] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 12/14/2020] [Accepted: 12/16/2020] [Indexed: 01/26/2023] Open
Abstract
Magnetic resonance imaging (MRI) of 7 T and higher can provide superior image resolution and capability. Clinical tests have been performed in 9.4 T MRI, and 21.1 T small-bore-size MRI has also been tested in rodents. Although the safety issue is a prerequisite for their future medical application, there are very few relevant studies for the safety of static magnetic fields (SMFs) of ≧20 T. The aim of this study was to assess the biological effects of 7.0-33.0 T SMFs in healthy adult mice. This was a prospective study, in which 104 healthy adult C57BL/6 mice were divided into control, sham control, and 7.0-33.0 T SMF-exposed groups.The sham control group and SMF group were handled identically, except for the electric current for producing SMF. A separate control group was placed outside the magnet and their data were used as normal range. After 1 h exposure, all mice were routinely fed for another 2 months while their body weight and food/water consumption were monitored. After 2 months, their complete blood count, blood biochemistry, key organ weight, and histomorphology were examined. All data are normally distributed. Differences between the sham and SMF-exposed groups were evaluated by unpaired t test. Most indicators did not show statistically significant changes or were still within the normal ranges, with only a few exceptions. For example, mono % in Group 2 (11.1 T) is 6.03 ± 1.43% while the normal range is 6.60-9.90% (p < 0.05). The cholesterol level in 33 T group is 3.38 ± 0.36 mmol/L while the normal range is 2.48-3.29 mmol/L (p < 0.05). The high-density lipoprotein cholesterol level in 33 T group is 2.54 ± 0.29 mmol/L while the normal reference range is 1.89-2.43 mmol/L (p < 0.01). Exposure to 7.0-33.0 T for 1 h did not have detrimental effects on normal adult mice. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 1.
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Affiliation(s)
- Xiaofei Tian
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Institutes of Physical Science and Information Technology, Anhui University, Hefei, China
| | - Yue Lv
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Science Island Branch of Graduate School, University of Science and Technology of China, Hefei, China
| | - Yixiang Fan
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Science Island Branch of Graduate School, University of Science and Technology of China, Hefei, China
| | - Ze Wang
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, China
| | - Biao Yu
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Science Island Branch of Graduate School, University of Science and Technology of China, Hefei, China
| | - Chao Song
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Science Island Branch of Graduate School, University of Science and Technology of China, Hefei, China
| | - Qingyou Lu
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, China.,Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, Hefei, China
| | - Chuanying Xi
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China
| | - Li Pi
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China
| | - Xin Zhang
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.,Science Island Branch of Graduate School, University of Science and Technology of China, Hefei, China.,Institutes of Physical Science and Information Technology, Anhui University, Hefei, China
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42
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Yaras YS, Yildirim DK, Herzka DA, Rogers T, Campbell-Washburn AE, Lederman RJ, Degertekin FL, Kocaturk O. Real-time device tracking under MRI using an acousto-optic active marker. Magn Reson Med 2020; 85:2904-2914. [PMID: 33347642 DOI: 10.1002/mrm.28625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 09/30/2020] [Accepted: 11/09/2020] [Indexed: 12/31/2022]
Abstract
PURPOSE This work aims to demonstrate the use of an "active" acousto-optic marker with enhanced visibility and reduced radiofrequency (RF) -induced heating for interventional MRI. METHODS The acousto-optic marker was fabricated using bulk piezoelectric crystal and π-phase shifted fiber Bragg grating (FBGs) and coupled to a distal receiver coil on an 8F catheter. The received MR signal is transmitted over an optical fiber to mitigate RF-induced heating. A photodetector converts the optical signal into electrical signal, which is used as the input signal to the MRI receiver plug. Acousto-optic markers were characterized in phantom studies. RF-induced heating risk was evaluated according to ASTM 2182 standard. In vivo real-time tracking capability was tested in an animal model under a 0.55T scanner. RESULTS Signal-to-noise ratio (SNR) levels suitable for real-time tracking were obtained by using high sensitivity FBG and piezoelectric transducer with resonance matched to Larmor frequency. Single and multiple marker coils integrated to 8F catheters were readout for position and orientation tracking by a single acousto-optic sensor. RF-induced heating was significantly reduced compared to a coax cable connected reference marker. Real-time distal tip tracking of an active device was demonstrated in an animal model with a standard real-time cardiac MR sequence. CONCLUSION Acousto-optic markers provide sufficient SNR with a simple structure for real-time device tracking. RF-induced heating is significantly reduced compared to conventional active markers. Also, multiple RF receiver coils connected on an acousto-optic modulator can be used on a single catheter for determining catheter orientation and shape.
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Affiliation(s)
- Yusuf S Yaras
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Micromachined Sensors and Transducers Group, Atlanta, Georgia, USA
| | - Dursun Korel Yildirim
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | - Daniel A Herzka
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | - Toby Rogers
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | | | - Robert J Lederman
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | - F Levent Degertekin
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Micromachined Sensors and Transducers Group, Atlanta, Georgia, USA
| | - Ozgur Kocaturk
- Institute of Biomedical Engineering, Bogazici University, Kandilli Kampus, Istanbul, Turkey
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Nguyen BT, Pilitsis J, Golestanirad L. The effect of simulation strategies on prediction of power deposition in the tissue around electronic implants during magnetic resonance imaging. ACTA ACUST UNITED AC 2020; 65:185007. [DOI: 10.1088/1361-6560/abac9f] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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44
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Bhusal B, Nguyen BT, Sanpitak PP, Vu J, Elahi B, Rosenow J, Nolt MJ, Lopez‐Rosado R, Pilitsis J, DiMarzio M, Golestanirad L. Effect of Device Configuration and Patient's Body Composition on the
RF
Heating and Nonsusceptibility Artifact of Deep Brain Stimulation Implants During
MRI
at 1.5T and 3T. J Magn Reson Imaging 2020; 53:599-610. [DOI: 10.1002/jmri.27346] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 08/12/2020] [Accepted: 08/13/2020] [Indexed: 12/13/2022] Open
Affiliation(s)
- Bhumi Bhusal
- Department of Radiology Northwestern University Chicago Illinois USA
| | - Bach T. Nguyen
- Department of Radiology Northwestern University Chicago Illinois USA
| | - Pia P. Sanpitak
- Department of Biomedical Engineering Northwestern University Chicago Illinois USA
| | - Jasmine Vu
- Department of Radiology Northwestern University Chicago Illinois USA
- Department of Biomedical Engineering Northwestern University Chicago Illinois USA
| | - Behzad Elahi
- Department of Physical Therapy and Human Movement Sciences Northwestern University Chicago Illinois USA
| | - Joshua Rosenow
- Department of Neurosurgery Northwestern University Chicago Illinois USA
| | - Mark J. Nolt
- Department of Neurosurgery Northwestern University Chicago Illinois USA
| | - Roberto Lopez‐Rosado
- Department of Physical Therapy and Human Movement Sciences Northwestern University Chicago Illinois USA
| | - Julie Pilitsis
- Department of Neurosciences and Experimental Therapeutics Albany Medical College Albany New York USA
| | - Marisa DiMarzio
- Department of Neurosciences and Experimental Therapeutics Albany Medical College Albany New York USA
| | - Laleh Golestanirad
- Department of Radiology Northwestern University Chicago Illinois USA
- Department of Biomedical Engineering Northwestern University Chicago Illinois USA
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Green AL, Paterson DJ. Using Deep Brain Stimulation to Unravel the Mysteries of Cardiorespiratory Control. Compr Physiol 2020; 10:1085-1104. [PMID: 32941690 DOI: 10.1002/cphy.c190039] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This article charts the history of deep brain stimulation (DBS) as applied to alleviate a number of neurological disorders, while in parallel mapping the electrophysiological circuits involved in generating and integrating neural signals driving the cardiorespiratory system during exercise. With the advent of improved neuroimaging techniques, neurosurgeons can place small electrodes into deep brain structures with a high degree accuracy to treat a number of neurological disorders, such as movement impairment associated with Parkinson's disease and neuropathic pain. As well as stimulating discrete nuclei and monitoring autonomic outflow, local field potentials can also assess how the neurocircuitry responds to exercise. This technique has provided an opportunity to validate in humans putative circuits previously identified in animal models. The central autonomic network consists of multiple sites from the spinal cord to the cortex involved in autonomic control. Important areas exist at multiple evolutionary levels, which include the anterior cingulate cortex (telencephalon), hypothalamus (diencephalon), periaqueductal grey (midbrain), parabrachial nucleus and nucleus of the tractus solitaries (brainstem), and the intermediolateral column of the spinal cord. These areas receive afferent input from all over the body and provide a site for integration, resulting in a coordinated efferent autonomic (sympathetic and parasympathetic) response. In particular, emerging evidence from DBS studies have identified the basal ganglia as a major sub-cortical cognitive integrator of both higher center and peripheral afferent feedback. These circuits in the basal ganglia appear to be central in coupling movement to the cardiorespiratory motor program. © 2020 American Physiological Society. Compr Physiol 10:1085-1104, 2020.
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Affiliation(s)
- Alexander L Green
- Division of Medical Sciences, Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - David J Paterson
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, UK
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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. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 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] [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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Kazemivalipour E, Vu J, Lin S, Bhusal B, Thanh Nguyen B, Kirsch J, Elahi B, Rosenow J, Atalar E, Golestanirad L. RF heating of deep brain stimulation implants during MRI in 1.2 T vertical scanners versus 1.5 T horizontal systems: A simulation study with realistic lead configurations. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:6143-6146. [PMID: 33019373 PMCID: PMC10882580 DOI: 10.1109/embc44109.2020.9175737] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Patients with deep brain stimulation (DBS) implants are often denied access to magnetic resonance imaging (MRI) due to safety concerns associated with RF heating of implants. Although MR-conditional DBS devices are available, complying with manufacturer guidelines has proved to be difficult as pulse sequences that optimally visualize DBS target structures tend to have much higher specific absorption rate (SAR) of radiofrequency energy than current guidelines allow. The MR-labeling of DBS devices, as well as the majority of studies on RF heating of conductive implants have been limited to horizontal close-bore MRI scanners. Vertical MRI scanners, originally introduced as open low-field MRI systems, are now available at 1.2 T field strength, capable of high-resolution structural and functional imaging. No literature exists on DBS SAR in this class of scanners which have a 90° rotated transmit coil and thus, generate a fundamentally different electric and magnetic field distributions. Here we present a simulation study of RF heating in a cohort of forty patient-derived DBS lead models during MRI in a commercially available vertical openbore MRI system (1.2 T OASIS, Hitachi) and a standard horizontal 1.5 T birdcage coil. Simulations were performed at two major imaging landmarks representing head and chest imaging. We calculated the maximum of 0.1g-averaged SAR (0.1g-SARMax) around DBS lead tips when a B1+ = 4 µT was generated on an axial plane passing through patients body. For head landmark, 0.1g-SARMax reached 220±188 W/kg in the 1.5 T birdcage coil, but only 14±11 W/kg in the OASIS coil. For chest landmark, 0.1g-SARMax was 24±17 W/kg in the 1.5 T birdcage coil and 3±2 W/kg in the OASIS coil. A paired two-tail t-test revealed a significant reduction in SAR with a large effect-size during head MRI (p < 1.5×10-8, Cohen's d = 1.5) as well as chest MRI (p < 6.5×10-10, Cohen's d = 1.7) in 1.2 T Hitachi OASIS coil compared to a standard 1.5 T birdcage transmitter. Our findings suggest that open-bore vertical scanners may offer an untapped opportunity for MRI of patients with DBS implants.
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Bhusal B, Nguyen BT, Vu J, Elahi B, Rosenow J, Nolt MJ, Pilitsis J, DiMarzio M, Golestanirad L. Device Configuration and Patient's Body Composition Significantly Affect RF Heating of Deep Brain Stimulation Implants During MRI: An Experimental Study at 1.5T and 3T. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:5192-5197. [PMID: 33019155 PMCID: PMC10900233 DOI: 10.1109/embc44109.2020.9175833] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Patients with deep brain stimulation (DBS) devices have limited access to magnetic resonance imaging (MRI) due to safety concerns associated with RF heating generated around the implant. The problem of predicting RF heating of conductive leads is complex with a large parameter space and several interplaying factors. Recently however, off-label use of MRI in patients with DBS devices has been reported based on limited safety assessments, raising the concern that potentially dangerous scenarios may have been overlooked. In this work, we present results of a systematic assessment of RF heating of a commercial DBS device during MRI at 1.5T and 3T, taking into account the effect of device configuration, imaging landmark, and patient's body composition. Ninety-six (96) RF heating measurements were performed using anthropomorphic phantoms implanted with a full DBS system. We evaluated eight clinically relevant device configurations, implanted in phantoms with different material compositions, and imaged at three different landmarks (head, shoulder, and lower chest) in 1.5 T and 3T scanners. We observed a substantial fluctuation in the RF heating depending on phantom's composition and device configuration. RF heating in the brain-mimicking gel varied from 0.1°C to 12°C during 1.5 T MRI and from <0.1°C to 4.5°C during 3T MRI. We also observed that certain device configurations consistently reduced RF heating across different phantom compositions, imaging landmarks, and MRI transmit frequencies.
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Vu J, Bhusal B, Nguyen BT, Golestanirad L. Evaluating Accuracy of Numerical Simulations in Predicting Heating of Wire Implants During MRI at 1.5 T. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:6107-6110. [PMID: 33019364 PMCID: PMC10900227 DOI: 10.1109/embc44109.2020.9175724] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Patients with long conductive implants such as deep brain stimulation (DBS) leads are often denied access to magnetic resonance imaging (MRI) exams due to safety concerns associated with radiofrequency (RF) heating of implants. Experimental temperature measurements in tissue-mimicking gel phantoms under MRI RF exposure conditions are common practices to predict in-vivo heating in the tissue surrounding wire implants. Such experiments are both expensive-as they require access to MRI units-and time-consuming due to complex implant setups. Recently, full-wave numerical simulations, which include realistic MRI RF coil models and human phantoms, are suggested as an alternative to experiments. There is however, little literature available on the accuracy of such numerical models against direct thermal measurements. This study aimed to evaluate the agreement between simulations and measurements of temperature rise at the tips of wire implants exposed to RF exposure at 64 MHz (1.5 T) for different implant trajectories typically encountered in patients with DBS leads. Heating was assessed in seven patient-derived lead configurations using both simulations and RF heating measurements during imaging of an anthropomorphic head phantom with implanted wires. We found substantial variation in RF heating as a function of lead trajectory; there was a 9.5-fold and 9-fold increase in temperature rise from ID1 to ID7 during simulations and experimental measurements, respectively. There was a strong correlation (r2 = 0.74) between simulated and measured temperatures for different lead trajectories. The maximum difference between simulated and measured temperature was 0.26 °C with simulations overestimating the temperature rise.
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50
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Boutet A, Chow CT, Narang K, Elias GJB, Neudorfer C, Germann J, Ranjan M, Loh A, Martin AJ, Kucharczyk W, Steele CJ, Hancu I, Rezai AR, Lozano AM. Improving Safety of MRI in Patients with Deep Brain Stimulation Devices. Radiology 2020; 296:250-262. [PMID: 32573388 DOI: 10.1148/radiol.2020192291] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
MRI is a valuable clinical and research tool for patients undergoing deep brain stimulation (DBS). However, risks associated with imaging DBS devices have led to stringent regulations, limiting the clinical and research utility of MRI in these patients. The main risks in patients with DBS devices undergoing MRI are heating at the electrode tips, induced currents, implantable pulse generator dysfunction, and mechanical forces. Phantom model studies indicate that electrode tip heating remains the most serious risk for modern DBS devices. The absence of adverse events in patients imaged under DBS vendor guidelines for MRI demonstrates the general safety of MRI for patients with DBS devices. Moreover, recent work indicates that-given adequate safety data-patients may be imaged outside these guidelines. At present, investigators are primarily focused on improving DBS device and MRI safety through the development of tools, including safety simulation models. Existing guidelines provide a standardized framework for performing safe MRI in patients with DBS devices. It also highlights the possibility of expanding MRI as a tool for research and clinical care in these patients going forward.
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Affiliation(s)
- Alexandre Boutet
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Clement T Chow
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Keshav Narang
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Gavin J B Elias
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Clemens Neudorfer
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Jürgen Germann
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Manish Ranjan
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Aaron Loh
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Alastair J Martin
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Walter Kucharczyk
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Christopher J Steele
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Ileana Hancu
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Ali R Rezai
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
| | - Andres M Lozano
- From the University Health Network, Toronto, Canada (A.B., C.T.C., K.N., G.J.B.E., C.N., J.G., A.L., W.K., A.M.L.); Joint Department of Medical Imaging, University of Toronto, Toronto, Canada (A.B., W.K.); Department of Neurosurgery, West Virginia University, Morgantown, WVa (M.R., A.R.R.); Department of Neurosurgery, Rockefeller Neuroscience Institute, Morgantown, WVa (M.R., A.R.R.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, Calif (A.J.M.); Department of Psychology, Concordia University, Montreal, Canada (C.J.S.); Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany (C.J.S.); Center for Scientific Review, National Institutes of Health, Bethesda, Md (I.H.); and Division of Neurosurgery, Department of Surgery, Toronto Western Hospital and University of Toronto, 399 Bathurst St, WW 4-437, Toronto, ON, Canada M5T 2S8 (A.M.L.)
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