RF heating of deep brain stimulation implants in open‐bore vertical MRI systems: A simulation study with realistic device configurations

Golestanirad, Laleh; Kazemivalipour, Ehsan; Lampman, David A; Habara, Hideta; Atalar, Ergin; Rosenow, Joshua M.; Pilitsis, Julie G.; Kirsch, John E.

doi:10.1002/mrm.28049

Cited by 30 publications

(24 citation statements)

References 38 publications

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“…This oversimplified approach to MRI safety assessment is concerning for two reasons. First, as RF heating is highly sensitive to implant's configuration and its orientation with respect to MRI electric field (14)(15)(16)(17)(18)(19)(20)(21)(22), and as trajectory of DBS leads is substantially variant among patients (23), basing safety inferences on few tested configurations can expose a large number of patients to undue risk. Second, conclusions drawn from studies in single-material box-shaped phantoms may not apply to the realistic cases, as the distribution of electromagnetic fields depend upon the geometry and composition of the sample.…”

Section: Resultsmentioning

confidence: 99%

The effect of device configuration and patient’s body composition on image artifact and RF heating of deep brain stimulation devices during MRI at 1.5T and 3T

Bhusal¹,

Nguyen²,

Vu³

et al. 2020

Preprint

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BACKGROUNDPatients with deep brain stimulation (DBS) implants have limited access to MRI due to safety concerns associated with RF-induced heating. Currently, MRI in these patients is allowed only in 1.5T horizontal scanners and with pulse sequences with reduced power.Nevertheless, off-label use of MRI at 3T is increasingly reported based on limited safety assessments. Here we present results of systematic RF heating measurements for two commercially available DBS systems during MRI at 1.5T and 3T. from 0.10℃ to 7.39℃ at 3T. The presence of subcutaneous fat substantially altered RF heating at electrode tips (-3.06℃ < ∆ < 19.05℃). Introducing concentric loops in the extracranial portion of the lead at the surgical burr hole reduced RF heating by up to 89% at 1.5T and up to 98% at 3T compared to worst case heating scenarios. DATA CONCLUSIONDevice configuration and patient body composition significantly altered the RF heating of DBS leads during MRI at 1.5T and 3T. Interestingly, certain lead trajectories consistently reduced RF heating and image artifact over different imaging landmarks, RF frequencies, and phantom compositions. Such trajectories could be implemented in patients with minimal disruption to the surgical workflow.

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Section: Resultsmentioning

confidence: 99%

The effect of device configuration and patient’s body composition on image artifact and RF heating of deep brain stimulation devices during MRI at 1.5T and 3T

Bhusal¹,

Nguyen²,

Vu³

et al. 2020

Preprint

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“…Such off‐label studies have relied on in‐home safety assessments mostly performed in ASTM‐like phantoms (ie, the box‐shaped phantom filled with a single material), and with a limited number of DBS device configurations 14,15 . This oversimplified approach to MRI safety assessment is concerning for two reasons: First, RF heating is highly sensitive to the configuration of an implant and its orientation with respect to MRI electric field 10,16–20 . As trajectories of DBS leads are substantially variant among patients, basing safety inferences on a few tested configurations can expose a large number of patients to undue risk 21 .…”

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confidence: 99%

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

Bhusal

Nguyen

Sanpitak

et al. 2020

Magnetic Resonance Imaging

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BackgroundPatients with deep brain stimulation (DBS) implants have limited access to MRI due to safety concerns associated with RF‐induced heating. Currently, MRI in these patients is allowed in 1.5T horizontal bore scanners utilizing pulse sequences with reduced power. However, the use of 3T MRI in such patients is increasingly reported based on limited safety assessments. Here we present the results of comprehensive RF heating measurements for two commercially available DBS systems during MRI at 1.5T and 3T.PurposeTo assess the effect of imaging landmark, DBS lead configuration, and patient's body composition on RF heating of DBS leads during MRI at 1.5T and 3T.Study TypePhantom and ex vivo study.Population/Subjects/Phantom/Specimen/Animal ModelGel phantoms and cadaver brain.Field Strength/Sequence1.5T and 3T, T1‐weighted turbo spin echo.AssessmentRF heating was measured at the tips of DBS leads implanted in brain‐mimicking gel. Image artifact was assessed in a cadaver brain implanted with an isolated DBS lead.Statistical TestsDescriptive.ResultsWe observed substantial fluctuation in RF heating, mainly affected by phantom composition and DBS lead configuration, ranging from 0.14°C to 23.73°C at 1.5T, and from 0.10°C to 7.39°C at 3T. The presence of subcutaneous fat substantially altered RF heating at the electrode tips (3.06°C < ∆T < 19.05° C). Introducing concentric loops in the extracranial portion of the lead at the surgical burr hole reduced RF heating by up to 89% at 1.5T and up to 98% at 3T compared to worst‐case heating scenarios.Data ConclusionDevice configuration and patient's body composition substantially altered the RF heating of DBS leads during MRI. Interestingly, certain lead trajectories consistently reduced RF heating and image artifact.Level of Evidence 1Technical Efficacy Stage 1J. MAGN. RESON. IMAGING 2021;53:599–610.

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“…As the orientation and phase of MRI incident electric field along the trajectory of an elongated implant has a substantial effect on the local SAR at the electrode tips [1,[3][4][5][6][7][8], we hypothesized that vertical scanners generate a statistically different RF heating compared to horizontal systems. Our hypothesis is based on a preliminary study of RF heating of DBS implants in three (3) realistic patient models which showed 4-to 14-fold reduction in the maximum local SAR around DBS electrodes in a vertical 1.2 T coil compared to a horizontal 1.5 T coil [2]. Here we extend our previous work to include a cohort of 20 patient models with bilateral DBS leads (40 lead models in total) with realistic trajectories.…”

Section: Introductionmentioning

confidence: 84%

“…Vertical scanners, originally introduced as low-field open-bore systems, are now available at high field strength capable of high-resolution structural and functional studies. No literature (except our recent work [2]) exists on RF heating of DBS implants inside this class of scanners which have a 90 rotated transmit coil and thus generate a fundamentally different distribution of electric and magnetic fields inside patient's body. As the orientation and phase of MRI incident electric field along the trajectory of an elongated implant has a substantial effect on the local SAR at the electrode tips [1,[3][4][5][6][7][8], we hypothesized that vertical scanners generate a statistically different RF heating compared to horizontal systems.…”

Section: Introductionmentioning

confidence: 99%

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

Kazemivalipour

Lin

et al. 2020

2020 42nd Annual International Conference of the IEEE Engineering in Medicine &Amp; Biology Society (EMBC)

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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 T 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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RF heating of deep brain stimulation implants in open‐bore vertical MRI systems: A simulation study with realistic device configurations

Cited by 30 publications

References 38 publications

The effect of device configuration and patient’s body composition on image artifact and RF heating of deep brain stimulation devices during MRI at 1.5T and 3T

The effect of device configuration and patient’s body composition on image artifact and RF heating of deep brain stimulation devices during MRI at 1.5T and 3T

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

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

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