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Background: Coil placement on the cerebellum lacks accuracy in targeting the intended lobules and limits the efficacy of cerebellar transcranial magnetic stimulation (TMS) in treating movement disorders. Objective: Develop a multiscale computational pipeline and method to rapidly predict the cellular response to cerebellar TMS and optimize the coil placement accordingly for lobule-specific activation. Methods: The pipeline integrates 3T T1/T2-weighted MRI scans of the human cerebellum, lobule parcellation, and finite element models of the TMS-induced electric (E-) fields for figure-of-eight coils (MagStim D70) and double-cone coils (Deymed 120BFV). A constrained optimization method is developed to estimate the fiber bundles from cerebellar cortices to deep nuclei and, for both coil types, find the coil placement and orientation that maximize the E-field intensity in a user-selected lobule. Multicompartmental Purkinje cell models with realistic axon geometries and Gaussian process regression are added to predict the recruitment in the Purkinje layer. Results: Our pipeline was tested in five individuals to target the left lobule VIII and resulted in normalized E-field intensities at the target 49.6±25.6% (D70) and 29.3±17.7% (120BFV) higher compared to standard coil positions (i.e., 3 cm left, 1 cm below the inion), mean±S.D. The minimum pulse intensity to recruit Purkinje cells on a 4 mm2-surface in the target decreased by 21.6% (range: 4.7-55.0%) and 10.7% (range: 7.9-18.2%), and the spillover to adjacent lobules decreased by 70.6±16.3% and 71.7±20.8% compared to standard positions (D70 and 120BFV, respectively). Conclusion: Our tools are effective at targeting specific lobules and pave the way toward patient-specific setups.
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This content will become publicly available on June 1, 2026
Projection-based numerical optimization of transcranial magnetic coil placement for nonconvex target surfaces and double-cone coil geometries
Abstract Objective.To develop a coil placement optimization pipeline for transcranial magnetic stimulation (TMS) that improves over existing solutions by guaranteeing the feasibility of the solution when double-cone coils are used and/or targets are placed over nonconvex scalp areas like the occipital region.Approach.Our proposed pipeline estimates feasible candidate coil locations by projecting the coil’s geometry over the scalp around the target site and optimizing the coil’s orientation to maximize scalp exposure to coil while avoiding coil-scalp collision. Then, the reciprocity principle is used to select the best position/orientation among candidates and maximize the average electric field (E-field) intensity at the target site. Our pipeline was tested on five magnetic resonance imaging-derived human head models for three different targets (motor cortex, lateral cerebellum, and cerebellar inion) and four coil models (planar coil: MagStim D70; double-cone coils: MagStim DCC, MagVenture Cool-D-B80, and Deymed 120BFV).Main results.Our pipeline returned several feasible solutions for any combination of anatomical target and coil, calculated and screened over 2000 candidates in minutes, and resulted in optimal locations that satisfy the minimum coil-scalp distance, whereas the direct method returned feasible candidates for just one combination of target and coil, i.e. planar coil and convex target over the motor cortex. We also found that, when the objective is to maximize the E-field magnitude, the target-to-scalp extension line is a better axis for coil translation compared to the normal vector at the scalp’s surface, which is commonly used in existing approaches.Significance.We expand the use of numerical optimization for coil placement to double-cone coils, which are rapidly diffusing in research and clinical settings, and novel application domains, e.g. cerebellar TMS and ataxia treatment.
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- Award ID(s):
- 1845348
- PAR ID:
- 10645008
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Neural Engineering
- Volume:
- 22
- Issue:
- 3
- ISSN:
- 1741-2560
- Page Range / eLocation ID:
- 036045
- Subject(s) / Keyword(s):
- Magnetic Resonance Imaging Equipment Design Cerebellum Scalp Motor Cortex Brain Cerebellar Stimulation Coil Placement Optimization Double-cone Coil Model Reciprocity Principle Transcranial Magnetic Stimulation
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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