Biology subjects

Rosenow, J.

Publications and source records attributed to Rosenow, J..

5 recordsLinked to original sources

bioRxiv2025

Targeting intracranial electrical stimulation to network regions defined within individuals causes network-level effects

Intracranial electrical stimulation (ES) is routinely used therapeutically, diagnostically, and to provide causal evidence in neuroscience studies. However, our understanding of the brain network-level effects of ES remains limited. We applied precision functional mapping (PFM), based on functional magnetic resonance imaging (fMRI), to define large-scale networks within individual epilepsy patients. We show that single-pulse electrical stimulation (SPES) and high-frequency electrical stimulation (HFES) are more likely to evoke within-network responses and elicit network-related behavioral effects, respectively, when applied near to a PFM-defined network region. Network-level effects were more likely when stimulating sites in white matter, in close proximity to the targeted network, and within a region predominantly occupied by the targeted network. Further, network-specific modulation may be achievable by applying lower current intensities at these sites. Our findings support that modulation of specific networks is achievable by targeting ES to a functional anatomic "sweet spot" that can be identified using PFM.

neuroscience↗

bioRxiv2022

Artifacts can be deceiving: The actual location of deep brain stimulation electrodes differs from the artifact seen on magnetic resonance images

IntroductionDeep brain stimulation (DBS) is a common treatment for a variety of neurological and psychiatric disorders. Recent studies have highlighted the role of neuroimaging in localizing the position of electrode contacts relative to target brain areas in order to optimize DBS programming. Among different imaging methods, postoperative magnetic resonance imaging (MRI) has been widely used for DBS electrode localization; however, the geometrical distortion induced by the lead limits its accuracy. In this work, we investigated to what degree the difference between the actual location of the leads tip and the location of the tip estimated from the MRI artifact varies depending on the MRI sequence parameters such as acquisition plane and phase encoding direction, as well as the leads extracranial configuration. Accordingly, an imaging technique to increase the accuracy of lead localization was devised and discussed. MethodsWe designed and constructed an anthropomorphic phantom with an implanted DBS system following 18 clinically relevant configurations. The phantom was scanned at a Siemens 1.5 Tesla Aera scanner using a T1MPRAGE sequence optimized for clinical use and a T1TSE sequence optimized for research purposes. We varied slice acquisition plane and phase encoding direction and calculated the distance between the caudal tip of the DBS lead MRI artifact and the actual tip of the lead, as estimated from MRI reference markers. ResultsImaging parameters and lead configuration substantially altered the difference in the depth of the lead within its MRI artifact on the scale of several millimeters - with a difference as large as 4.99 millimeters. The actual tip of the DBS lead was found to be consistently more rostral than the tip estimated from the MR image artifact. The smallest difference between the tip of the DBS lead and the tip of the MRI artifact using the clinically relevant sequence (i.e., T1MPRAGE) was found with the sagittal acquisition plane and anterior-posterior phase encoding direction. Discussion/ConclusionThe actual tip of an implanted DBS lead is located up to several millimeters rostral to the tip of the leads artifact on postoperative MR images. This distance depends on the MRI sequence parameters and the DBS systems extracranial trajectory. MRI parameters may be altered to improve this localization.

neuroscience↗

bioRxiv2020

Application of Surgical Lead Management and Reconfigurable Coil Technology to Reduce RF Heating of DBS Implants during MRI at 3T Under Variant Body Compositions

Patients with active implants such as deep brain stimulation (DBS) devices, have limited access to magnetic resonance imaging (MRI) due to risks of RF heating. With an aging population, the prevalence of neurodegenerative and vascular disease increases; and so does the indication for MRI exams in patients with such implants. In response to this growing need for MRI, many groups have investigated strategies to mitigate the RF heating of the implants. These efforts, however, have relied either on simulations with homogenous body models or simplified phantom experiments (box shaped phantom with single tissue). It is well established, however, that the shape and heterogeneity of human body affects the distribution of MRI electric fields, which by proxy, alters the RF heating of an implant inside the body. In this contribution, we applied numerical simulations and phantom experiments to examine the effectiveness of RF heating mitigation strategies under variant patient body compositions, focusing on two recently proposed techniques: (a) surgical modification of DBS lead trajectories inside the body, and (b) use of a patient-adjustable reconfigurable MRI coil, both aiming to reduce the coupling of implanted leads and MRI electric fields. Our results demonstrated that both techniques perform well under variant body compositions.Competing Interest StatementThe authors have declared no competing interest.View Full Text

bioengineering↗

bioRxiv2020

The effect of device configuration and patient body composition on image artifact and RF heating of deep brain stimulation devices during MRI at 1.5T and 3T

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. PURPOSETo assess the effect of imaging landmark, DBS lead configuration, and patient body composition on RF heating of DBS leads during MRI at 1.5 T and 3T. STUDY TYPEPhantom 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 tips of DBS leads implanted in brain-mimicking gel. STATISTICAL TESTSNone. RESULTSWe observed substantial fluctuation in RF heating mainly affected by phantom composition and DBS lead configuration, ranging from 0.14{degrees}C to 23.73{degrees}C at 1.5 T, and from 0.10{degrees}C to 7.39{degrees}C at 3T. The presence of subcutaneous fat substantially altered RF heating at electrode tips (-3.06{degrees}C < {Delta}T < 19.05{degrees}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 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.

bioengineering↗

bioRxiv2019

RF heating of deep brain stimulation implants in open-bore vertical MRI systems

PurposePatients with deep brain stimulation (DBS) implants highly benefit from MRI, however access to MRI is restricted for these patients due to safety hazards associated with RF heating of the implant. To date, all MRI studies on RF heating of medical implants have been performed in horizontal closed-bore systems. Vertical MRI scanners have a fundamentally different distribution of electric and magnetic fields and are now available at 1.2T, capable of high-resolution structural and functional MRI. This work presents the first simulation study of RF heating of DBS implants in high-field vertical scanners.\n\nMethodsWe performed finite element electromagnetic simulations to calculate SAR at tips of DBS leads during MRI in a commercially available 1.2 T vertical coil compared to a 1.5 T horizontal scanner. Both isolated leads and fully implanted systems were included.\n\nResultsWe found 10-30-fold reduction in SAR implication at tips of isolated DBS leads, and up to 19-fold SAR reduction at tips of leads in fully implanted systems in vertical coils compared to horizontal birdcage coils.\n\nConclusionsIf confirmed in larger patient cohorts and verified experimentally, this result can open the door to plethora of structural and functional MRI applications to guide, interpret, and advance DBS therapy.

biophysics↗