To understand the biophysical basis of the diffusion MR signal, Uri Nevo has successfully constructed and tested an experimental system for interrogating organotypic cultured brain slices using diffusion MRI methods. This work has already shown promising results relating changes in the measured diffusion coefficient map to changes in environmental conditions to which the cultured tissue is subjected. A theoretical aspect of this work is the development of model systems in which we can demonstrate how microscopic flows manifest themselves as """"""""pseudo-diffusion"""""""", resulting in additional signal loss in diffusion weighted MRI experiments. In the area of Transcranial Magnetic Stimulation (TMS), Pedro Miranda and his group in Lisbon, in association with STBB, has performed detailed calculations using finite element methods (FEM), to predict the electric field and current density distributions induced in the brain during TMS. Previously, we found that both tissue heterogeneity and anisotropy of the electrical conductivity (i.e., the conductivity tensor field) contribute significantly to distort the induced fields, and even to create excitatory or inhibitory hot spots in some regions. These phenomena could have significant clinical consequences both in interpreting or inferring the region or locus of excitation and in determining the source of nerve excitation. More recently, we have focussed on determining the dominant physical mechanisms responsible for cortical excitation. A longer term goal is to marry our macroscopic models of TMS with microscopic models of nerve excitability in the CNS. More detailed FEM models of TMS in the cortex are under development.

Project Start
Project End
Budget Start
Budget End
Support Year
12
Fiscal Year
2009
Total Cost
$70,104
Indirect Cost
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State
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Bai, Ruiliang; Stewart, Craig V; Plenz, Dietmar et al. (2016) Assessing the sensitivity of diffusion MRI to detect neuronal activity directly. Proc Natl Acad Sci U S A 113:E1728-37
Benjamini, Dan; Komlosh, Michal E; Holtzclaw, Lynne A et al. (2016) White matter microstructure from nonparametric axon diameter distribution mapping. Neuroimage 135:333-44
Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J et al. (2016) Improving Tumor Treating Fields Treatment Efficacy in Patients With Glioblastoma Using Personalized Array Layouts. Int J Radiat Oncol Biol Phys 94:1137-43
Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J et al. (2015) The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study. Phys Med Biol 60:7339-57
Fields, R Douglas; Woo, Dong Ho; Basser, Peter J (2015) Glial Regulation of the Neuronal Connectome through Local and Long-Distant Communication. Neuron 86:374-86
Miranda, Pedro C; Mekonnen, Abeye; Salvador, Ricardo et al. (2014) Predicting the electric field distribution in the brain for the treatment of glioblastoma. Phys Med Biol 59:4137-47
Pajevic, S; Basser, P J; Fields, R D (2014) Role of myelin plasticity in oscillations and synchrony of neuronal activity. Neuroscience 276:135-47
Bai, Ruiliang; Koay, Cheng Guan; Hutchinson, Elizabeth et al. (2014) A framework for accurate determination of the T? distribution from multiple echo magnitude MRI images. J Magn Reson 244:53-63
Bai, Ruiliang; Basser, Peter J; Briber, Robert M et al. (2014) NMR Water Self-Diffusion and Relaxation Studies on Sodium Polyacrylate Solutions and Gels in Physiologic Ionic Solutions. J Appl Polym Sci 131:
Salvador, R; Silva, S; Basser, P J et al. (2011) Determining which mechanisms lead to activation in the motor cortex: a modeling study of transcranial magnetic stimulation using realistic stimulus waveforms and sulcal geometry. Clin Neurophysiol 122:748-58

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