A method for reconstructing tomographic images of evoked neural activity with electrical impedance tomography using intracranial planar arrays.
A method is presented for reconstructing images of fast neural evoked activity in rat cerebral cortex recorded with electrical impedance tomography (EIT) and a 6 × 5 mm(2) epicortical planar 30 electrode array. A finite element model of the rat brain and inverse solution with Tikhonov regularization were optimized in order to improve spatial resolution and accuracy. The optimized FEM mesh had 7 M tetrahedral elements, with finer resolution (0.05 mm) near the electrodes. A novel noise-based image processing technique based on t-test significance improved depth localization accuracy from 0.5 to 0.1 mm. With the improvements, a simulated perturbation 0.5 mm in diameter could be localized in a region 4 × 5 mm(2) under the centre of the array to a depth of 1.4 mm, thus covering all six layers of the cerebral cortex with an accuracy of <0.1 mm. Simulated deep brain hippocampal or thalamic activity could be localized with an accuracy of 0.5 mm with a 256 electrode array covering the brain. Parallel studies have achieved a temporal resolution of 2 ms for imaging fast neural activity by EIT during evoked activity; this encourages the view that fast neural EIT can now resolve the propagation of depolarization-related fast impedance changes in cerebral cortex and deeper in the brain with a resolution equal or greater to the dimension of a cortical column.
Department of Medical Physics and Bioengineering, University College London, Malet Place Engineering Building, Gower Street, London WC1E 6BT, UK.
Kirill Y
KY
Aristovich
Gustavo Sato
GS
dos Santos
Brett C
BC
Packham
David S
DS
Holder
D000818:Animals; D001931:Brain Mapping; D003198:Computer Simulation; D017097:Electric Impedance; D004566:Electrodes; D006624:Hippocampus / Q000033:anatomy & histology / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D051381:Rats; D014054:Tomography / Q000295:instrumentation* / Q000379:methods*