Carolina Ciumas1, Gregor Schaefers2, Sandrine Bouvard3, Emmeline Tailhades4, Emmanuel Perrin4, Jean-Christophe Comte5, Emmanuelle Canet-Soulas6, Chantal Bonnet7, Danielle Ibarrola8, Gustavo Polo9, Jose Moya10, Olivier Beuf4, Philippe Ryvlin11. 1. Translational and Integrative Group in Epilepsy Research (TIGER), INSERM, France; U1028, CNRS UMR 5292, Centre de Recherche en Neuroscience de Lyon, Lyon, France. Electronic address: carolina.ciumas@inserm.fr. 2. MR:comp GmbH, Testing Services for MR Safety & Compatibility, Gelsenkirchen, Germany. 3. Translational and Integrative Group in Epilepsy Research (TIGER), INSERM, France; U1028, CNRS UMR 5292, Centre de Recherche en Neuroscience de Lyon, Lyon, France; CERMEP - Imagerie du Vivant, Lyon, France. 4. CREATIS, CNRS UMR 5220, Inserm U1044, INSA-Lyon, Université Lyon 1, Villeurbanne, France. 5. U1028, CNRS UMR 5292, Centre de Recherche en Neuroscience de Lyon, Lyon, France. 6. CarMeN, INSERM U1060, INSA de Lyon, Université de Lyon, Villeurbanne, France. 7. Translational and Integrative Group in Epilepsy Research (TIGER), INSERM, France; U1028, CNRS UMR 5292, Centre de Recherche en Neuroscience de Lyon, Lyon, France. 8. CERMEP - Imagerie du Vivant, Lyon, France. 9. Department of Functional Neurosurgery, Hospices Civils de Lyon, Lyon, France. 10. DIXI, Besançon, France. 11. Translational and Integrative Group in Epilepsy Research (TIGER), INSERM, France; U1028, CNRS UMR 5292, Centre de Recherche en Neuroscience de Lyon, Lyon, France; CERMEP - Imagerie du Vivant, Lyon, France; Department of Functional Neurology and Epileptology, Hospices Civils de Lyon, Lyon, France. Electronic address: ryvlin@cermep.fr.
Abstract
BACKGROUND: MRI is routinely used in patients undergoing intracerebral electroencephalography (icEEG) in order to precisely locate the position of intracerebral electrodes. In contrast, fMRI has been considered unsafe due to suspected greater risk of radiofrequency-induced (RF) tissue heating at the vicinity of intracerebral electrodes. We determined the possible temperature change at the tip of such electrodes during fMRI sessions in phantom and animals. METHODS: A human-shaped torso phantom and MRI-compatible intracerebral electrodes approved for icEEG in humans were used to mimic a patient with four intracerebral electrodes (one parasagittal and three coronal). Six rabbits were implanted with one or two coronal electrodes. MRI-induced temperature changes at the tip of electrodes were measured using a fibre-optic thermometer. All experiments were performed on Siemens Sonata 1.5T scanner. RESULTS: For coronally implanted electrodes with wires pulled posteriorly to the magnetic bore, temperature increase recorded during EPI sequences reached a maximum of 0.6°C and 0.9°C in phantom and animals, respectively. These maximal figures were decreased to 0.2°C and 0.5°C, when electrode wires were connected to cables and amplifier. When electrode wires were pulled anteriorly to the magnetic bore, temperature increased up to 1.3°C in both phantom and animals. Greater temperature increases were recorded for the single electrode implanted parasagitally in the phantom. CONCLUSION: Variation of the temperature depends on the electrode and wire position relative to the transmit body coil and orientation of the constant magnetic field (B0). EPI sequence with intracerebral electrodes appears as safe as standard T1 and T2 sequence for implanted electrodes placed perpendicular to the z-axis of the magnetic bore, using a 1.5T MRI system, with the free-end wires moving posteriorly, in phantom and animals.
BACKGROUND: MRI is routinely used in patients undergoing intracerebral electroencephalography (icEEG) in order to precisely locate the position of intracerebral electrodes. In contrast, fMRI has been considered unsafe due to suspected greater risk of radiofrequency-induced (RF) tissue heating at the vicinity of intracerebral electrodes. We determined the possible temperature change at the tip of such electrodes during fMRI sessions in phantom and animals. METHODS: A human-shaped torso phantom and MRI-compatible intracerebral electrodes approved for icEEG in humans were used to mimic a patient with four intracerebral electrodes (one parasagittal and three coronal). Six rabbits were implanted with one or two coronal electrodes. MRI-induced temperature changes at the tip of electrodes were measured using a fibre-optic thermometer. All experiments were performed on Siemens Sonata 1.5T scanner. RESULTS: For coronally implanted electrodes with wires pulled posteriorly to the magnetic bore, temperature increase recorded during EPI sequences reached a maximum of 0.6°C and 0.9°C in phantom and animals, respectively. These maximal figures were decreased to 0.2°C and 0.5°C, when electrode wires were connected to cables and amplifier. When electrode wires were pulled anteriorly to the magnetic bore, temperature increased up to 1.3°C in both phantom and animals. Greater temperature increases were recorded for the single electrode implanted parasagitally in the phantom. CONCLUSION: Variation of the temperature depends on the electrode and wire position relative to the transmit body coil and orientation of the constant magnetic field (B0). EPI sequence with intracerebral electrodes appears as safe as standard T1 and T2 sequence for implanted electrodes placed perpendicular to the z-axis of the magnetic bore, using a 1.5T MRI system, with the free-end wires moving posteriorly, in phantom and animals.
Keywords:
ASTM; American Society of Testing and Materials; BOLD; EPI; Epilepsy; FOV; HFO; MR; MRI; RF; RF heating; SAR; bold oxygenation level dependency; echo-planar imaging; fMRI; field of view; functional magnetic resonance imaging; high frequency oscillation; icEEG; icEEG/fMRI; intracerebral electroencephalography; magnetic resonance; magnetic resonance imaging; radiofrequency; specific absorption rate
Authors: Johannes B Erhardt; Thomas Lottner; Jessica Martinez; Ali C Özen; Martin Schuettler; Thomas Stieglitz; Daniel B Ennis; Michael Bock Journal: Neuroimage Date: 2019-03-29 Impact factor: 6.556
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