OBJECTIVE: MRI-guided real-time transcranial magnetic stimulation (TMS) navigators that apply electromagnetic modeling have improved the utility of TMS. However, their accuracy and speed depends on the assumed volume conductor geometry. Spherical models found in present navigators are computationally fast but may be inaccurate in some areas. Realistically shaped boundary-element models (BEMs) could increase accuracy at a moderate computational cost, but it is unknown which model features have the largest influence on accuracy. Thus, we compared different types of spherical models and BEMs. METHODS: Globally and locally fitted spherical models and different BEMs with either one or three compartments and with different skull-to-brain conductivity ratios (1/1-1/80) were compared against a reference BEM. RESULTS: The one-compartment BEM at inner skull surface was almost as accurate as the reference BEM. Skull/brain conductivity ratio in the range 1/10-1/80 had only a minor influence. BEMs were superior to spherical models especially in frontal and temporal areas (up to 20mm localization and 40% intensity improvement); in motor cortex all models provided similar results. CONCLUSIONS: One-compartment BEMs offer a good balance between accuracy and computational cost. SIGNIFICANCE: Realistically shaped BEMs may increase TMS navigation accuracy in several brain areas, such as in prefrontal regions often targeted in clinical applications.
OBJECTIVE: MRI-guided real-time transcranial magnetic stimulation (TMS) navigators that apply electromagnetic modeling have improved the utility of TMS. However, their accuracy and speed depends on the assumed volume conductor geometry. Spherical models found in present navigators are computationally fast but may be inaccurate in some areas. Realistically shaped boundary-element models (BEMs) could increase accuracy at a moderate computational cost, but it is unknown which model features have the largest influence on accuracy. Thus, we compared different types of spherical models and BEMs. METHODS: Globally and locally fitted spherical models and different BEMs with either one or three compartments and with different skull-to-brain conductivity ratios (1/1-1/80) were compared against a reference BEM. RESULTS: The one-compartment BEM at inner skull surface was almost as accurate as the reference BEM. Skull/brain conductivity ratio in the range 1/10-1/80 had only a minor influence. BEMs were superior to spherical models especially in frontal and temporal areas (up to 20mm localization and 40% intensity improvement); in motor cortex all models provided similar results. CONCLUSIONS: One-compartment BEMs offer a good balance between accuracy and computational cost. SIGNIFICANCE: Realistically shaped BEMs may increase TMS navigation accuracy in several brain areas, such as in prefrontal regions often targeted in clinical applications.
Authors: Brian Harris Kopell; Jerry Halverson; Christopher R Butson; Mercedes Dickinson; Julie Bobholz; Harold Harsch; Charles Rainey; Douglas Kondziolka; Robert Howland; Emad Eskandar; Karleyton C Evans; Darin D Dougherty Journal: Neurosurgery Date: 2011-11 Impact factor: 4.654
Authors: Aung Thu Htet; Guilherme B Saturnino; Edward H Burnham; Gregory M Noetscher; Aapo Nummenmaa; Sergey N Makarov Journal: J Neural Eng Date: 2019-01-03 Impact factor: 5.379
Authors: Aapo Nummenmaa; Jennifer A McNab; Peter Savadjiev; Yoshio Okada; Matti S Hämäläinen; Ruopeng Wang; Lawrence L Wald; Alvaro Pascual-Leone; Van J Wedeen; Tommi Raij Journal: Brain Stimul Date: 2013-10-16 Impact factor: 8.955
Authors: Max M Klein; Roi Treister; Tommi Raij; Alvaro Pascual-Leone; Lawrence Park; Turo Nurmikko; Fred Lenz; Jean-Pascal Lefaucheur; Magdalena Lang; Mark Hallett; Michael Fox; Merit Cudkowicz; Ann Costello; Daniel B Carr; Samar S Ayache; Anne Louise Oaklander Journal: Pain Date: 2015-09 Impact factor: 7.926