Functional MRI with active, fully implanted, deep brain stimulation systems: Safety and experimental confounds

Carmichael, David W.; Pinto, Serge; Limousin-Dowsey, Patricia; Thobois, Stéphane; Allen, Philip J.; Lemieux, Louis; Yousry, Tarek; Thornton, John S.

doi:10.1016/j.neuroimage.2007.04.058

Cited by 101 publications

(98 citation statements)

References 41 publications

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“…Different applications may require different levels of field accuracy in specific locations. An accurate assessment of the electromagnetic field inside the phantom is important when evaluating SAR levels as overall safety of the patient [9][10][11][12][13][14][15][16] or the RFinduced heating in patients with conductive medical devices that are fully implanted in the body [22] like deep brain stimulators [8,17,18] or pacemakers [1,20,21]. Conversely, an accurate representation of ||E ⃗ || in the space between the coil and the load is important when evaluating safety in patients with conductive medical devices that are partially implanted or in contact with the skin [7,23].…”

Section: Discussionmentioning

confidence: 99%

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Lucano

Liberti

Mendoza

et al. 2016

IEEE Trans. Biomed. Eng.

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Goal-This study aims at a systematic assessment of five computational models of a birdcage coil for magnetic resonance imaging (MRI) with respect to accuracy and computational cost.Methods-The models were implemented using the same geometrical model and numerical algorithm, but different driving methods (i.e., coil "defeaturing"). The defeatured models were labeled as: specific (S2), generic (G32, G16), and hybrid (H16, H16 fr-forced ). The accuracy of the models was evaluated using the "Symmetric Mean Absolute Percentage Error" ("SMAPE"), by comparison with measurements in terms of frequency response, as well as electric (||E ⃗ ||) and magnetic (||B ⃗ ||) field magnitude. HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author ManuscriptResults-All the models computed the ||B ⃗ || within 35 % of the measurements, only the S2, G32, and H16 were able to accurately model the ||E ⃗ || inside the phantom with a maximum SMAPE of 16 %. Outside the phantom, only the S2 showed a SMAPE lower than 11 %. Conclusions-Resultsshowed that assessing the accuracy of ||B ⃗ || based only on comparison along the central longitudinal line of the coil can be misleading. Generic or hybrid coils -when properly modeling the currents along the rings/rungs -were sufficient to accurately reproduce the fields inside a phantom while a specific model was needed to accurately model ||E ⃗ || in the space between coil and phantom.Significance-Computational modeling of birdcage body coils is extensively used in the evaluation of RF-induced heating during MRI. Experimental validation of numerical models is needed to determine if a model is an accurate representation of a physical coil.

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Section: Discussionmentioning

confidence: 99%

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Lucano

Liberti

Mendoza

et al. 2016

IEEE Trans. Biomed. Eng.

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“…A Perspex phantom, similar to one described previously [19,23], which broadly follows the ASTM standard for testing passive implants [34] was formed with a shape and dimensions approximating those of an adult human torso (Figure 1). This was filled to a depth of approximately 10cm with a semi-liquid gel comprising distilled water, poly-acrylic acid partial sodium salt (Aldrich Chemical) (8g/litre) and sodium chloride (0.70 g/litre) with electrical (conductivity of 0.26 Sm -1 ) and thermal characteristics (limited convection) similar to those of human tissue [34,35].…”

Section: Methodsmentioning

confidence: 99%

“…Combinations of these have been previously studied in the context of scalp EEGfMRI [18] and active deep brain stimulation (DBS) during MRI [19][20][21][22][23][24]. Depending on their frequency and amplitude, excessive currents in tissue may cause electro-motive forces, electrolysis, depolarisation and stimulation, burning, coagulation, and vaporisation which can all lead to cell damage and ultimately cell death [25][26][27].…”

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confidence: 99%

Feasibility of simultaneous intracranial EEG-fMRI in humans: A safety study

Carmichael¹,

Thornton

Rodionov³

et al. 2010

NeuroImage

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111

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In epilepsy patients who have electrodes implanted in their brains as part of their presurgical assessment, simultaneous intracranial EEG and fMRI (icEEG-fMRI) may provide important localising information and improve understanding of the underlying neuropathology. However, patient safety during icEEG-fMRI has not been addressed.Here the potential health hazards associated with icEEG-fMRI were evaluated theoretically and the main risks identified as: mechanical forces on electrodes from transient magnetic effects, tissue heating due to interaction with the pulsed RF fields and tissue stimulation due to interactions with the switched magnetic gradient fields.These potential hazards were examined experimentally in-vitro on a Siemens 3 T Trio, 1.5 T Avanto and a GE 3 T Signa Excite scanner using a Brain Products MR compatible EEG system. No electrode flexion was observed. Temperature measurements demonstrated thatheating well above guideline limits can occur. However heating could be kept within safe limits (<1.0°C) by using a head transmit RF coil, ensuring EEG cable placement to exit the RF coil along its central z-axis, using specific EEG cable lengths and limiting MRI sequence specific absorption rates (SARs). We found that the risk of tissue damage due to RF-induced heating is low provided implant and scanner specific SAR limits are observed with a safety margin used to account for uncertainties (e.g. in scanner-reported SAR). The observed scanner gradientswitching induced current (0.08mA) and charge density (0.2μC/cm 2 ) were well within safety limits (0.5mA and 30μC/cm 2 , respectively).3

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“…82 The study was performed at 1.5T and 3T by using head-transmit coils. The authors showed that for fMRI sequences with coil-averaged SARs Ͻ0.4 W/kg, MR imagingϪinduced temperatures were less than measurement sensitivity (0.1°C) at 1.5T and Ͻ0.5°C at 3T.…”

Section: 77mentioning

confidence: 99%

Neuroimaging and Deep Brain Stimulation

Dormont¹,

Seidenwurm²,

Galanaud³

et al. 2009

AJNR Am J Neuroradiol

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SUMMARY: Deep brain stimulation (DBS) is a new neurosurgical method principally used for the treatment of Parkinson disease (PD).Many new applications of DBS are under development, including the treatment of intractable psychiatric diseases. Brain imaging is used for the selection of patients for DBS, to localize the target nucleus, to detect complications, and to evaluate the final electrode contact position. In patients with implanted DBS systems, there is a risk of electrode heating when MR imaging is performed. This contraindicates MR imaging unless specific precautions are taken. Involvement of neuroradiologists in DBS procedures is essential to optimize presurgical evaluation, targeting, and postoperative anatomic results. The precision of the neuroradiologic correlation with anatomic data and clinical outcomes in DBS promises to yield significant basic science and clinical advances in the future. Chronic high-frequency stimulation of the ventral intermediate nucleus (VIM) of the thalamus was first described in the early 1990s by Benabid et al.1 These authors implanted chronic stimulating electrodes in the VIM connected to a subcutaneous pulse generator positioned in the thoracic region to treat disabling tremor in 26 patients with Parkinson disease (PD) and in 6 with essential tremor.1 They demonstrated the effectiveness of this technique and its ability to produce complete relief from tremor. Improvement was maintained for up to 29 months. This was the first clinical demonstration that chronic high-frequency stimulation of nuclei (deep brain stimulation [DBS]) could replace destructive lesion-producing functional neurosurgery such as thalamotomy. This new technique was reversible and led to a renaissance in functional neurosurgery.Next, the same team introduced bilateral DBS of the subthalamic nucleus (STN) in patients with disabling akineticrigid PD and severe motor fluctuations.2 This work extended data obtained in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine monkey model of PD showing that lesions and electric stimulation of the subthalamic nucleus reduced all of the major motor disturbances in this animal model. The results in patients with advanced PD were striking and were reproduced in many centers internationally. The US Food and Drug Administration approved the use of DBS for treatment of advanced PD with bilateral STN stimulation in 2002 and internal globus pallidus (GPi) stimulation in 2003. The main indication for DBS remains advanced PD, but numerous additional applications have been developed, ranging from dystonia to cluster headache, Tourette syndrome, and even psychiatric indications like obsessive-compulsive disorders (OCD) and major depression.DBS is a neurosurgical method, but the role of neuroimaging in successful DBS intervention is critical. Neuroimaging is used for the preoperative selection of patients who will have DBS and to localize the intended target nuclei. In the postoperative period, imaging detects complications that uncommonly accompany the procedure, confirms the pos...

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Functional MRI with active, fully implanted, deep brain stimulation systems: Safety and experimental confounds

Cited by 101 publications

References 41 publications

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Feasibility of simultaneous intracranial EEG-fMRI in humans: A safety study

Neuroimaging and Deep Brain Stimulation

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