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Cui Q, Wang D, Zeng M, Dong J, Jin H, Hu Z, Zhang Y, Peng Y, Han R. Association of postoperative covert stroke and cognitive dysfunction among elderly patients undergoing non-cardiac surgery: protocol for a prospective cohort study (PRECISION study). BMJ Open 2020; 10:e034657. [PMID: 31911527 PMCID: PMC6955561 DOI: 10.1136/bmjopen-2019-034657] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
INTRODUCTION The incidence of covert stroke and cognitive dysfunction has gradually increased due to an ageing population. Recently, a prospective cohort study reported perioperative covert stroke was associated with an increased risk of postoperative cognitive dysfunction (POCD) 1 year after non-cardiac surgery. However, the mechanism remains unclear. METHODS AND ANALYSIS This is a prospective observational trial aiming to investigate the cumulative incidence of perioperative covert stroke and test the hypothesis that perioperative covert stroke associates with POCD in elderly patients undergoing non-cardiac and non-neurological surgery. Data on risk factors, brain MRI, cognitive function evaluation and serum immune-inflammatory cytokines will be collected and analysed. ETHICS AND DISSEMINATION Ethical approval has been granted by the Medical Ethics Committee of Beijing Tiantan Hospital, Capital Medical University (reference number: KY2017-027-02). The results of this study will be disseminated through presentations at scientific conferences and publication in scientific journals. TRIAL REGISTRATION NUMBER NCT03081429.
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Affiliation(s)
- Qianyu Cui
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Dexiang Wang
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Min Zeng
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Jia Dong
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Hailong Jin
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Zhengfang Hu
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Yuan Zhang
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Yuming Peng
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Ruquan Han
- Anesthesiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
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Hayashi N, Ogura A, Tsuchihashi T, Takahashi D, Matsuda T, Seino S, Doi T. Magnetization and demagnetization of magnetic dental attachments in a 3-T MRI system. Radiol Phys Technol 2017; 10:294-300. [DOI: 10.1007/s12194-017-0399-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 04/20/2017] [Accepted: 04/23/2017] [Indexed: 10/19/2022]
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Tsukimura I, Murakami H, Sasaki M, Endo H, Yamabe D, Oikawa R, Doita M. Assessment of magnetic field interactions and radiofrequency-radiation-induced heating of metallic spinal implants in 7 T field. J Orthop Res 2017; 35:1831-1837. [PMID: 27769107 PMCID: PMC5573950 DOI: 10.1002/jor.23464] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Accepted: 10/14/2016] [Indexed: 02/04/2023]
Abstract
The safety of metallic spinal implants in magnetic resonance imaging (MRI) performed using ultrahigh fields has not been established. Hence, we examined whether the displacement forces caused by a static magnetic field and the heating induced by radiofrequency radiation are substantial for spinal implants in a 7 T field. We investigated spinal rods of various lengths and materials, a screw, and a cross-linking bridge in accordance with the American Society for Testing and Materials guidelines. The displacement forces of the metallic implants in static 7 T and 3 T static magnetic fields were measured and compared. The temperature changes of the implants during 15-min-long fast spin-echo and balanced gradient-echo image acquisition sequences were measured in the 7 T field. The deflection angles of the metallic spinal materials in the 7 T field were 5.0-21.0° [median: 6.7°], significantly larger than those in the 3 T field (1.0-6.3° [2.2°]). Among the metallic rods, the cobalt-chrome rods had significantly larger deflection angles (17.8-21.0° [19.8°]) than the pure titanium and titanium alloy rods (5.0-7.7° [6.2°]). The temperature changes of the implants, including the cross-linked rods, were 0.7-1.0°C [0.8°C] and 0.6-1.0°C [0.7°C] during the fast spin-echo and balanced gradient-echo sequences, respectively; these changes were slightly larger than those of the controls (0.4-1.1°C [0.5°C] and 0.3-0.9°C [0.6°C], respectively). All of the metallic spinal implants exhibited small displacement forces and minimal heating, indicating that MRI examinations using 7 T fields may be performed safely on patients with these implants. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1831-1837, 2017.
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Affiliation(s)
- Itsuko Tsukimura
- Department of Orthopedic SurgerySchool of MedicineIwate Medical University19‐1 UchimaruMorioka020‐8505Japan
| | - Hideki Murakami
- Department of Orthopedic SurgerySchool of MedicineIwate Medical University19‐1 UchimaruMorioka020‐8505Japan
| | - Makoto Sasaki
- Division of Ultrahigh Field MRIInstitute of Biomedical SciencesIwate Medical UniversityMoriokaJapan
| | - Hirooki Endo
- Department of Orthopedic SurgerySchool of MedicineIwate Medical University19‐1 UchimaruMorioka020‐8505Japan
| | - Daisuke Yamabe
- Department of Orthopedic SurgerySchool of MedicineIwate Medical University19‐1 UchimaruMorioka020‐8505Japan
| | - Ryosuke Oikawa
- Department of Orthopedic SurgerySchool of MedicineIwate Medical University19‐1 UchimaruMorioka020‐8505Japan
| | - Minoru Doita
- Department of Orthopedic SurgerySchool of MedicineIwate Medical University19‐1 UchimaruMorioka020‐8505Japan
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Golestanirad L, Iacono MI, Keil B, Angelone LM, Bonmassar G, Fox MD, Herrington T, Adalsteinsson E, LaPierre C, Mareyam A, Wald LL. Construction and modeling of a reconfigurable MRI coil for lowering SAR in patients with deep brain stimulation implants. Neuroimage 2016; 147:577-588. [PMID: 28011252 DOI: 10.1016/j.neuroimage.2016.12.056] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 11/13/2016] [Accepted: 12/19/2016] [Indexed: 10/20/2022] Open
Abstract
Post-operative MRI of patients with deep brain simulation (DBS) implants is useful to assess complications and diagnose comorbidities, however more than one third of medical centers do not perform MRIs on this patient population due to stringent safety restrictions and liability risks. A new system of reconfigurable magnetic resonance imaging head coil composed of a rotatable linearly-polarized birdcage transmitter and a close-fitting 32-channel receive array is presented for low-SAR imaging of patients with DBS implants. The novel system works by generating a region with low electric field magnitude and steering it to coincide with the DBS lead trajectory. We demonstrate that the new coil system substantially reduces the SAR amplification around DBS electrodes compared to commercially available circularly polarized coils in a cohort of 9 patient-derived realistic DBS lead trajectories. We also show that the optimal coil configuration can be reliably identified from the image artifact on B1+ field maps. Our preliminary results suggest that such a system may provide a viable solution for high-resolution imaging of DBS patients in the future. More data is needed to quantify safety limits and recommend imaging protocols before the novel coil system can be used on patients with DBS implants.
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Affiliation(s)
- Laleh Golestanirad
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
| | - Maria Ida Iacono
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, USA
| | - Boris Keil
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Institute of Medical Physics and Radiation Protection, THM, Life Science Engineering, Giessen, Germany
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, USA
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| | - Michael D Fox
- Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Todd Herrington
- Partners Neurology, Massachusetts General Hospital, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Elfar Adalsteinsson
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA
| | - Cristen LaPierre
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Azma Mareyam
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Lawrence L Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
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Golestanirad L, Angelone LM, Iacono MI, Katnani H, Wald LL, Bonmassar G. Local SAR near deep brain stimulation (DBS) electrodes at 64 and 127 MHz: A simulation study of the effect of extracranial loops. Magn Reson Med 2016; 78:1558-1565. [PMID: 27797157 DOI: 10.1002/mrm.26535] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 09/12/2016] [Accepted: 10/10/2016] [Indexed: 02/06/2023]
Abstract
PURPOSE MRI may cause brain tissue around deep brain stimulation (DBS) electrodes to become excessively hot, causing lesions. The presence of extracranial loops in the DBS lead trajectory has been shown to affect the specific absorption rate (SAR) of the radiofrequency energy at the electrode tip, but experimental studies have reported controversial results. The goal of this study was to perform a systematic numerical study to provide a better understanding of the effects of extracranial loops in DBS leads on the local SAR during MRI at 64 and 127 MHz. METHODS A total of 160 numerical simulations were performed on patient-derived data, in which relevant factors including lead length and trajectory, loop location and topology, and frequency of MRI radiofrequency (RF) transmitter were assessed. RESULTS Overall, the presence of extracranial loops reduced the local SAR in the tissue around the DBS tip compared with straight trajectories with the same length. SAR reduction was significantly larger at 127 MHz compared with 64 MHz. SAR reduction was significantly more sensitive to variable loop parameters (eg, topology and location) at 127 MHz compared with 64 MHz. CONCLUSION Lead management strategies could exist that significantly reduce the risks of 3 Tesla (T) MRI for DBS patients. Magn Reson Med 78:1558-1565, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Laleh Golestanirad
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Maria Ida Iacono
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Husam Katnani
- Harvard Medical School, Boston, Massachusetts, USA.,Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Lawrence L Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
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Golestanirad L, Keil B, Angelone LM, Bonmassar G, Mareyam A, Wald LL. Feasibility of using linearly polarized rotating birdcage transmitters and close-fitting receive arrays in MRI to reduce SAR in the vicinity of deep brain simulation implants. Magn Reson Med 2016; 77:1701-1712. [PMID: 27059266 DOI: 10.1002/mrm.26220] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 02/02/2016] [Accepted: 02/24/2016] [Indexed: 11/07/2022]
Abstract
PURPOSE MRI of patients with deep brain stimulation (DBS) implants is strictly limited due to safety concerns, including high levels of local specific absorption rate (SAR) of radiofrequency (RF) fields near the implant and related RF-induced heating. This study demonstrates the feasibility of using a rotating linearly polarized birdcage transmitter and a 32-channel close-fit receive array to significantly reduce local SAR in MRI of DBS patients. METHODS Electromagnetic simulations and phantom experiments were performed with generic DBS lead geometries and implantation paths. The technique was based on mechanically rotating a linear birdcage transmitter to align its zero electric-field region with the implant while using a close-fit receive array to significantly increase signal to noise ratio of the images. RESULTS It was found that the zero electric-field region of the transmitter is thick enough at 1.5 Tesla to encompass DBS lead trajectories with wire segments that were up to 30 degrees out of plane, as well as leads with looped segments. Moreover, SAR reduction was not sensitive to tissue properties, and insertion of a close-fit 32-channel receive array did not degrade the SAR reduction performance. CONCLUSION The ensemble of rotating linear birdcage and 32-channel close-fit receive array introduces a promising technology for future improvement of imaging in patients with DBS implants. Magn Reson Med 77:1701-1712, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Laleh Golestanirad
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Boris Keil
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA.,Institute of Medical Physics and Radiation Protection, THM, Life Science Engineering, Giessen, Germany
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Azma Mareyam
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Lawrence L Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
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Practice advisory on anesthetic care for magnetic resonance imaging: an updated report by the american society of anesthesiologists task force on anesthetic care for magnetic resonance imaging. Anesthesiology 2015; 122:495-520. [PMID: 25383571 DOI: 10.1097/aln.0000000000000458] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Abstract
The American Society of Anesthesiologists Committee on Standards and Practice Parameters and the Task Force on Anesthetic Care for Magnetic Resonance Imaging presents an updated report of the Practice Advisory on Anesthetic Care for Magnetic Resonance Imaging.
Supplemental Digital Content is available in the text.
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Moens M, Droogmans S, Spapen H, De Smedt A, Brouns R, Van Schuerbeek P, Luypaert R, Poelaert J, Nuttin B. Feasibility of cerebral magnetic resonance imaging in patients with externalised spinal cord stimulator. Clin Neurol Neurosurg 2012; 114:135-41. [DOI: 10.1016/j.clineuro.2011.09.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2010] [Revised: 09/22/2011] [Accepted: 09/27/2011] [Indexed: 12/19/2022]
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Chermansky CJ, Krlin RM, Holley TD, Woo HH, Winters JC. Magnetic resonance imaging following InterStim®: an institutional experience with imaging safety and patient satisfaction. Neurourol Urodyn 2011; 30:1486-8. [PMID: 21780166 DOI: 10.1002/nau.21147] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 04/01/2011] [Indexed: 11/08/2022]
Abstract
AIMS We retrospectively assessed patient safety and satisfaction after magnetic resonance imaging (MRI) in patients with an InterStim® unit. METHODS The records of all patients implanted with InterStim® between 1998 and 2006 were reviewed. Nine of these patients underwent MRI following InterStim® implantation. The patients' neurologists requested the MRI exams for medical reasons. Both 0.6 Tesla (T) and 1.5 T machines were used. Patient safety, interference of implanted pulse generator (IPG) with radiological interpretation, and patient satisfaction were assessed in these patients. RESULTS The first patient in the series had IPG failure following MRI. For this patient, the voltage amplitude was set to zero, the IPG was turned off, and the IPG magnetic switch was left on. The patient underwent MRI uneventfully; however, the IPG did not function upon reprogramming. The IPG magnetic switch was turned off for the eight subsequent patients, all of whom underwent MRI safely. In addition, all of their IPGs functioned appropriately following reprogramming. Of the 15 MRIs performed, the lumbar spine was imaged in eight studies, the pelvis was imaged in one study, and the remaining examinations involved imaging the brain or cervical spine. Neither the IPG nor the sacral leads interfered with MRI interpretation. None of the eight patients perceived a change in perception or satisfaction following MRI. CONCLUSIONS Although we don't advocate the routine use of MRI following InterStim® implantation, our experience suggests MRI may be feasible under controlled conditions and without adverse events.
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Affiliation(s)
- Christopher J Chermansky
- Department of Urology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
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Muranaka H, Horiguchi T, Ueda Y, Usui S, Tanki N, Nakamura O. Evaluation of RF heating on hip joint implant in phantom during MRI examinations. Nihon Hoshasen Gijutsu Gakkai Zasshi 2010; 66:725-733. [PMID: 20702992 DOI: 10.6009/jjrt.66.725] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
PURPOSE We evaluate radiofrequency (RF) heating of two kinds of hip joint implants of different sizes, shapes and materials. Temperature rises at various positions of each implant are measured and compared with a computer simulation based on electromagnetic-field analysis. METHODS Two kinds of implants made of cobalt-chromium alloy and titanium alloy were embedded at a 2-cm depth of tissue-equivalent gel-phantom. The phantom was placed parallel to the static magnetic field of a 1.5 T MRI device. Scans were conducted at the specific absorption rate of 2.5 W/kg for 15 min, and temperatures were recorded with RF-transparent fiberoptic sensors. Temperatures of the implant surface were measured at 6 positions, from the tip to the head. Measured temperature rises were compared with the results of electromagnetic-field analysis. RESULTS The maximum temperature rise was observed at the tip of each implant, and it was 9.0 degrees C for the cobalt- chromium implant and 5.3 degrees C for the titanium implant. The simulated heating positions with electromagnetic-field analysis accorded with experimental results. However, a difference in temperature rise was seen with the titanium implant. CONCLUSION RF heating was confirmed to take place at both ends of the implants in spite of their different shapes. The maximum temperature rise was observed at the tip where there is large curvature. The value was found to depend on physical properties of the implant materials. The discrepancy between experimental and simulated temperature rises was presumed to be the result of an incomplete model for the titanium implant.
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Affiliation(s)
- Hiroyuki Muranaka
- Department of Radiology, Hiroshima City General Rehabilitation Center
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Graf H, Steidle G, Schick F. Heating of metallic implants and instruments induced by gradient switching in a 1.5-Tesla whole-body unit. J Magn Reson Imaging 2008; 26:1328-33. [PMID: 17969167 DOI: 10.1002/jmri.21157] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To examine gradient switching-induced heating of metallic parts. MATERIALS AND METHODS Copper and titanium frames and sheets ( approximately 50 x 50 mm(2), 1.5 mm thick, frame width = 3 mm) surrounded by air were positioned in the scanner perpendicular to the static field horizontally 20 cm off-center. During the execution of a sequence (three-dimensional [3D] true fast imaging with steady precession [True-FISP], TR = 6.4 msec) exploiting the gradient capabilities (maximum gradient = 40 mT/m, maximum slew rate = 200 T/m/second), heating was measured with an infrared camera. Radio frequency (RF) amplitude was set to zero volts. Heating of a copper frame with a narrowing to 1 mm over 20 mm at one side was examined in air and in addition surrounded by several liters of gelled saline using fiber-optic thermography. Further heating studies were performed using an artificial hip made of titanium, and an aluminum replica of the hip prosthesis with the same geometry. RESULTS For the copper specimens, considerable heating (>10 degrees C) in air and in gelled saline (>1.2 degrees C) could be observed. Heating of the titanium specimens was markedly less ( approximately 1 degrees C in air). For the titanium artificial hip no heating could be detected, while the rise in temperature for the aluminum replica was approximately 2.2 degrees C. CONCLUSION Heating of more than 10 degrees C solely due to gradient switching without any RF irradiation was demonstrated in isolated copper wire frames. Under specific conditions (high gradient duty cycle, metallic loop of sufficient inductance and low resistance, power matching) gradient switching-induced heating of conductive specimens must be considered.
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Affiliation(s)
- Hansjörg Graf
- Section on Experimental Radiology, Department of Diagnostic Radiology, University Hospital Tübingen, Tübingen, Germany
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D'Avenio G, Canese R, Podo F, Grigioni M. A novel method for measuring the torque on implantable cardiovascular devices in MR static fields. J Magn Reson Imaging 2007; 26:1368-74. [PMID: 17969137 DOI: 10.1002/jmri.21146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To propose a novel quantitative method for measuring the torque acting on mechanical heart valve prostheses subjected to a high static magnetic field in a MR scanner. MATERIALS AND METHODS Torque measurements were performed with a torsion balance, implemented with a copper wire. The reaction torque exerted by the static magnetic field on the device was measured optically from the deflection angle of a laser beam spot on a graduate scale. Three different types of mechanical valves (two bileaflet and one monoleaflet) were tested at different locations of a small bore 4.7 tesla system. RESULTS The method proved to be particularly sensitive (detectability limit lower than 10(-6) N x m), reliable and yielded quantitative reproducible results. The equivalent force of the torque measured for the three valves was at least 10(3)-fold lower than the force exerted by the beating heart. CONCLUSION The proposed method provides a quantitative evaluation of the torque induced on prosthetic device by a MR scanner operating at high magnetic field.
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Affiliation(s)
- Giuseppe D'Avenio
- Department of Technology and Health, Istituto Superiore di Sanità, Rome, Italy
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Levin G, Ortiz AO, Katz DS. Noncardiac Implantable Pacemakers and Stimulators: Current Role and Radiographic Appearance. AJR Am J Roentgenol 2007; 188:984-91. [PMID: 17377034 DOI: 10.2214/ajr.05.1281] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The purpose of this pictorial essay is to familiarize radiologists with the clinical functioning, proper anatomic positioning, appearance on radiographs and CT scans, potential complications, and MRI safety issues of several implantable noncardiac pacemaker and stimulator devices. CONCLUSIONS The use of noncardiac pacemakers and stimulators is rapidly increasing because of the utility of these devices in the management of surgically and medically refractory conditions. Unlike cardiac pacemakers, electrical stimulators are MRI compatible under certain circumstances.
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Affiliation(s)
- Galina Levin
- Department of Radiology, Winthrop-University Hospital, 259 First St., Mineola, NY 11501, USA.
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Graf H, Lauer UA, Schick F. Eddy-current induction in extended metallic parts as a source of considerable torsional moment. J Magn Reson Imaging 2006; 23:585-90. [PMID: 16534754 DOI: 10.1002/jmri.20539] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To examine eddy-current-provoked torque on conductive parts due to current induction from movement through the fringe field of the MR scanner and from gradient switching. MATERIALS AND METHODS For both cases, torque was calculated for frames of copper, aluminum, and titanium, inclined to 45 degrees to B0 (maximum torque case). Conditions were analyzed in which torque from gravity (legal limit, ASTM F2213-02) was exceeded. Experiments were carried out on a 1.5 T and a 3 T scanner for copper and titanium frames and plates (approximately 50 x 50 mm2). Movement-induced torque was measured at patient table velocity (20 cm/second). Alternating torque from gradient switching was investigated by holding the specimens in different locations in the scanner while executing sequences that exploited the gradient capabilities (40 mT/m). RESULTS The calculations predicted that movement-induced torque could exceed torque from gravity (depending on the part size, electric resistance, and velocity). Two experiments on moving conductive frames in the fringe fields of the scanners confirmed the calculations. For maximum torque case parameters, gradient-switching-induced torque was calculated to be nearly 100 times greater than the movement-induced torque. Well-conducting metal parts located off center vibrated significantly due to impulse-like fast alternating torque characteristics. CONCLUSION Torque on metal parts from movement in the fringe field is weak under standard conditions, but for larger parts the acceptable limit can be reached with a high static field and increased velocity. Vibrations due to gradient switching were confirmed and may explain the sensations occasionally reported by patients with implants.
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Affiliation(s)
- Hansjörg Graf
- Section on Experimental Radiology, Department of Diagnostic Radiology, University Hospital Tübingen, Tübingen, Germany.
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Shellock FG, Fieno DS, Thomson LJ, Talavage TM, Berman DS. Cardiac pacemaker: in vitro assessment at 1.5 T. Am Heart J 2006; 151:436-43. [PMID: 16442911 DOI: 10.1016/j.ahj.2005.04.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2004] [Accepted: 04/07/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND In vitro testing is used to determine safe parameters before performing magnetic resonance imaging (MRI) on a patient with an implant. Therefore, the objective of this study was to evaluate a cardiac pacemaker using a 1.5-T magnetic resonance (MR) system. METHODS A modern cardiac pacemaker (INSIGNIA I PLUS, Model 1298, and FINELINE II, Model 4471, pacing leads; Guidant Corporation, St Paul, MN) was evaluated for magnetic field interactions at 1.5 T. Magnetic resonance imaging-related heating was assessed using 3 different 1.5-T scanners operating at various levels of radio-frequency power and imaging conditions. Functional aspects of the pacemaker were evaluated immediately before and after MRI (9 different pulse sequences). Artifacts were also characterized. RESULTS Magnetic field interactions for the pacemaker were minor. Temperature changes measured in vitro were at levels that are not expected to pose a risk for specific MR conditions (< 4.0 degrees C). The function of the pacemaker was unaffected by MRI. Artifacts were minor for the leads and relatively large for the implantable pulse generator. CONCLUSION The findings indicated that this pacemaker exhibited acceptable safety features relative to the use of a 1.5-T MR system. If induced currents do not occur for this device, it may be safe for a patient to undergo MRI by following specific conditions. The results are specific to the pacemaker tested, the MR systems, and conditions used in this evaluation.
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Affiliation(s)
- Frank G Shellock
- Department of Radiology, Keck School of Medicine, University of Southern California, Institute for Magnetic Resonance Safety, Education, and Research, Los Angeles, CA, USA.
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Baker KB, Tkach JA, Nyenhuis JA, Phillips M, Shellock FG, Gonzalez-Martinez J, Rezai AR. Evaluation of specific absorption rate as a dosimeter of MRI-related implant heating. J Magn Reson Imaging 2004; 20:315-20. [PMID: 15269959 DOI: 10.1002/jmri.20103] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To compare the magnetic resonance imaging (MRI)-related heating per unit of whole body averaged specific absorption rate (SAR) of a conductive implant exposed to two different 1.5-Tesla/64 MHz MR systems. MATERIALS AND METHODS Temperature changes at the electrode contacts of a deep brain stimulation lead were measured using fluoroptic thermometry. The leads were placed in a typical surgical implant configuration within a gel-filled phantom of the human head and torso. MRI was performed using two different transmit/receive body coils on two different generation 1.5-Tesla MR systems from the same manufacturer. Temperature changes were normalized to whole body averaged SAR values and compared between the two scanners. RESULTS Depending on the landmark location, the normalized temperature change for the implant was significantly higher on one MR system compared to the other (P < 0.001). CONCLUSION The findings revealed marked differences across two MR systems in the level of radiofrequency (RF)-induced temperature changes per unit of whole body SAR for a conductive implant. Thus, these data suggest that using SAR to guide MR safety recommendations for neurostimulation systems or other similar implants across different MR systems is unreliable and, therefore, potentially dangerous. Better, more universal, measures are required in order to ensure patient safety.
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Affiliation(s)
- Kenneth B Baker
- Department of Neurology, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Desk S-90, Cleveland, OH 44195, USA.
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Abstract
The technology used for magnetic resonance (MR) procedures has evolved continuously during the past 20 years, yielding MR systems with stronger static magnetic fields, faster and stronger gradient magnetic fields, and more powerful radiofrequency transmission coils. Most reported cases of MR-related injuries and the few fatalities that have occurred have apparently been the result of failure to follow safety guidelines or of use of inappropriate or outdated information related to the safety aspects of biomedical implants and devices. To prevent accidents in the MR environment, therefore, it is necessary to revise information on biologic effects and safety according to changes that have occurred in MR technology and with regard to current guidelines for biomedical implants and devices. This review provides an overview of and update on MR biologic effects, discusses new or controversial MR safety topics and issues, presents evidence-based guidelines to ensure safety for patients and staff, and describes safety information for various implants and devices that have recently undergone evaluation.
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Affiliation(s)
- Frank G Shellock
- Keck School of Medicine, University of Southern California, USA.
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Georgi JC, Stippich C, Tronnier VM, Heiland S. Active deep brain stimulation during MRI: a feasibility study. Magn Reson Med 2004; 51:380-8. [PMID: 14755664 DOI: 10.1002/mrm.10699] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The goal of this study was to evaluate the feasibility of active deep brain stimulation (DBS) during the application of standard clinical sequences for functional MRI (fMRI) in phantom measurements. During active DBS, we investigated induced voltage, temperature at the electrode tips and lead, forces on the electrode and lead, consequences of defective leads and loose connections, proper operation of the neurostimulator, and image quality. Sequences for diffusion- and perfusion-weighted imaging, fMRI, and morphologic MRI were used. The DBS electrode and lead were placed in a NaCl solution-filled phantom. The results indicate that there are severe potential hazards for patients. Strong heating, high induced voltage, and even sparking at defects in the connecting cable could be observed. However, it was demonstrated that under certain conditions, safe MR examinations during active DBS are feasible. Certain safety precautions are recommended in this report.
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Affiliation(s)
- J-C Georgi
- Division of Neuroradiology, Department of Neurology, University of Heidelberg Medical Center, Heidelberg, Germany.
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Martin ET, Coman JA, Shellock FG, Pulling CC, Fair R, Jenkins K. Magnetic resonance imaging and cardiac pacemaker safety at 1.5-Tesla. J Am Coll Cardiol 2004; 43:1315-24. [PMID: 15063447 DOI: 10.1016/j.jacc.2003.12.016] [Citation(s) in RCA: 257] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OBJECTIVES The study was done to determine whether patients with pacemakers could safely undergo magnetic resonance imaging (MRI) at 1.5-Tesla (T). BACKGROUND Because of theoretical risks, it is an absolute contraindication for a patient with a pacemaker to undergo MRI. However, there are times when an MRI is needed to provide valuable clinical information. METHODS Fifty-four patients underwent a total of 62 MRI examinations at 1.5-T. The type of MRI examination was not limited and included cardiac, vascular, and general MRI studies using various whole-body averaged specific absorption rate (SAR) of radiofrequency power. Restrictions were not placed on the type of pacemaker present in the patient. All pacemakers were interrogated immediately before and after MRI scanning, and patients were continuously monitored. Before and after MRI, interrogation was done, and pacing and sensing thresholds, as well as lead impedances, were all measured. RESULTS A total of 107 leads and 61 pulse generators were evaluated. No adverse events occurred. Forty (37%) of the leads underwent changes, whereas 10 (9.4%) leads underwent a significant change. Only 2 of the 107 (1.9%) leads required a change in programmed output. Threshold changes were unrelated to cardiac chamber, anatomical location, peak SAR, and time from lead implant to the MRI examination. Electrocardiographic changes and patient symptoms were minor and did not require cessation of MRI. CONCLUSIONS Safety was demonstrated in this series of patients with pacemakers at 1.5-T.
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Shellock FG. Biomedical implants and devices: assessment of magnetic field interactions with a 3.0-Tesla MR system. J Magn Reson Imaging 2002; 16:721-32. [PMID: 12451586 DOI: 10.1002/jmri.10207] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To evaluate magnetic field interactions for 109 different biomedical implants and devices in association with exposure to a 3.0-Tesla magnetic resonance (MR) system. MATERIALS AND METHODS A total of 109 implants and devices (aneurysm clips, 32; clips, fasteners, and staples, 10; coils and stents, 10; heart valve prostheses and annuloplasty rings, 12; orthopedic implants, five; suture materials, 13; vascular access ports and accessories, 13; miscellaneous implants and devices, 14) were tested for magnetic field interactions at 3.0-Tesla using previously-described, standardized techniques to assess magnetic field translational attraction and torque. RESULTS The deflection angles and torque measurements ranged, respectively, from 0 to 16 degrees and 0 to +2 for the aneurysm clips; 0 to 90 degrees and 0 to +4 for the clips, fasteners, and staples; 0 to 47 degrees and 0 to +4 for the coils and stents; 0 to 4 degrees and 0 to +1 for the heart valve prostheses and annuloplasty rings; 0 to 12 degrees and 0 to +2 for the orthopedic implants; 0 to 13 degrees and 0 to +2 for the suture materials; 0 to 52 degrees and 0 to +4 for the vascular access ports and accessories; and 0 to 28 degrees and 0 to +3 for the miscellaneous implants and devices. CONCLUSION Of the 109 implants and devices assessed for magnetic field interactions at 3.0-Tesla, four (4%) are potentially unsafe based on deflection angle criteria. The implications of these results for patients undergoing MR procedures at 3.0-Tesla is discussed. Notably, these results are specific to the 3.0-Tesla MR system used for this evaluation.
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Affiliation(s)
- Frank G Shellock
- University of Southern California, Keck School of Medicine, Los Angeles, California, USA.
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Abstract
The preservation of a safe magnetic resonance (MR) environment requires constant vigilance by MR healthcare professionals, particularly with regard to the management of patients with metallic biomedical implants or devices. The variety and complexity of implants and devices constantly changes, requiring continuous attention and diligence with regard to obtaining the most current and accurate information about these objects relative to the MR environment. This review article discusses MR safety and MR compatibility issues and presents important information for a variety of implants and devices, with an emphasis on those objects that have recently undergone evaluation or that require additional consideration because of existing controversy or confusion.
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Affiliation(s)
- Frank G Shellock
- Institute for Magnetic Resonance Safety, Education, and Research, Los Angeles, California, USA.
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Rezai AR, Finelli D, Nyenhuis JA, Hrdlicka G, Tkach J, Sharan A, Rugieri P, Stypulkowski PH, Shellock FG. Neurostimulation systems for deep brain stimulation: in vitro evaluation of magnetic resonance imaging-related heating at 1.5 tesla. J Magn Reson Imaging 2002; 15:241-50. [PMID: 11891968 DOI: 10.1002/jmri.10069] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
PURPOSE To assess magnetic resonance imaging (MRI)-related heating for a neurostimulation system (Activa Tremor Control System, Medtronic, Minneapolis, MN) used for chronic deep brain stimulation (DBS). MATERIALS AND METHODS Different configurations were evaluated for bilateral neurostimulators (Soletra Model 7426), extensions, and leads to assess worst-case and clinically relevant positioning scenarios. In vitro testing was performed using a 1.5-T/64-MHz MR system and a gel-filled phantom designed to approximate the head and upper torso of a human subject. MRI was conducted using the transmit/receive body and transmit/receive head radio frequency (RF) coils. Various levels of RF energy were applied with the transmit/receive body (whole-body averaged specific absorption rate (SAR); range, 0.98-3.90 W/kg) and transmit/receive head (whole-body averaged SAR; range, 0.07-0.24 W/kg) coils. A fluoroptic thermometry system was used to record temperatures at multiple locations before (1 minute) and during (15 minutes) MRI. RESULTS Using the body RF coil, the highest temperature changes ranged from 2.5 degrees-25.3 degrees C. Using the head RF coil, the highest temperature changes ranged from 2.3 degrees-7.1 degrees C.Thus, these findings indicated that substantial heating occurs under certain conditions, while others produce relatively minor, physiologically inconsequential temperature increases. CONCLUSION The temperature increases were dependent on the type of RF coil, level of SAR used, and how the lead wires were positioned. Notably, the use of clinically relevant positioning techniques for the neurostimulation system and low SARs commonly used for imaging the brain generated little heating. Based on this information, MR safety guidelines are provided. These observations are restricted to the tested neurostimulation system.
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Affiliation(s)
- Ali R Rezai
- Section of Stereotactic and Functional Neurosurgery, Department of Neurosurgery, Cleveland Clinic Foundation, Cleveland, Ohio, USA
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