Diffuse Optical Tomography and Its Applications To Epilepsy Research

Date(s) - 07/24/2015
12:30 pm

Tao Zhang, PhD candidate

Epilepsy is the second most common neurological disorder affecting millions of people worldwide. Diffuse optical tomography (DOT), as an emerging noninvasive and functional imaging modality, has the potential to become a powerful tool for epilepsy imaging. The goal of this study is to develop a dedicated DOT system that can be used for in vivo three-dimensional (3D) imaging of seizure dynamics, and then explore its applications to epilepsy study.

To achieve this goal, the hardware and software for a fast multispectral continuous-wave DOT system are developed. Fast data acquisition is realized through a time multiplexing approach based on a parallel lighting configuration. Parallelized GPU-based reconstruction algorithm is implemented using CUDA programming model with a 300x computational speedup. Our system can achieve up to 14Hz sampling rate and a real-time availability of the reconstructed images derived from hemodynamic changes. The system is validated using both static and dynamic tissue-like phantoms. In vivo experiments using acute focused seizure model are also presented.

In epilepsy it has been challenging to detect early changes in brain activity that occurs prior to seizure onset and to map their origin and evolution for possible intervention, especially when seizure experiments need to be conducted in awake animals, or in epilepsy patients. We demonstrate through a series of animal and human subject experiments that DOT is a promising tool to conquer these challenges.

Using a generalized epilepsy model, we demonstrate DOT provides a unique functional neuroimaging modality for noninvasively and continuously tracking brain activities with high spatiotemporal resolution, in both anesthetized and awake rats. We detected early hemodynamic responses with heterogeneous patterns several minutes preceding the electroencephalographic seizure onset. We also observed the decoupling between local hemodynamic and neural activities. We found widespread hemodynamic changes evolving from local regions to the entire brain, indicating that the onset of generalized seizures may originate locally.

Finally, we move the DOT system toward human applications by designing a head interface, and introducing 3D registration techniques. Expected brain activation pattern was mapped in both controls and epilepsy patients when performing motor tasks, and changed functional connectivity was observed in patients.