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

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buir.contributor.authorKazemivalipour, Ehsan
buir.contributor.authorAtalar, Ergin
buir.contributor.orcidKazemivalipour, Ehsan|0000-0003-4221-2397
buir.contributor.orcidAtalar, Ergin|0000-0002-6874-6103
dc.citation.epagee0280655-14en_US
dc.citation.issueNumber1
dc.citation.spagee0280655-1
dc.citation.volumeNumber18
dc.contributor.authorKazemivalipour, Ehsan
dc.contributor.authorSadeghi-Tarakameh, A.
dc.contributor.authorKeil, B.
dc.contributor.authorEryaman, Y.
dc.contributor.authorAtalar, Ergin
dc.contributor.authorGolestanirad, L.
dc.date.accessioned2024-03-12T12:40:32Z
dc.date.available2024-03-12T12:40:32Z
dc.date.issued2023-01-26
dc.departmentDepartment of Electrical and Electronics Engineering
dc.departmentNational Magnetic Resonance Research Center (UMRAM)
dc.description.abstractBackground 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.
dc.description.provenanceMade available in DSpace on 2024-03-12T12:40:32Z (GMT). No. of bitstreams: 1 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.pdf: 3986252 bytes, checksum: 129e47f9cabe2dcf99aa9276dc6840d5 (MD5) Previous issue date: 2023-01-26en
dc.identifier.doi10.1371/journal.pone.0280655
dc.identifier.eissn1932-6203
dc.identifier.urihttps://hdl.handle.net/11693/114605
dc.language.isoen
dc.publisherPublic Library of Science
dc.relation.isversionofhttps://dx.doi.org/10.1371/journal.pone.0280655
dc.rightsCC BY 4.0 DEED (Attribution 4.0 International)
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.source.titlePLoS One
dc.titleEffect 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
dc.typeArticle

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