KEYWORDS: Head, Electrodes, Analog to digital converters, Skull, 3D modeling, Brain imaging, Analog electronics, Tomography, Medical image reconstruction, 3D image reconstruction, Electrical engineering
Electrical Impedance Tomography (EIT) is a medical imaging technique that reconstructs impedance distribution inside a target object by injecting electrical currents into pairs of electrodes and measuring induced voltages on the remaining electrodes. Since neural signals result from the activity of ion channels causing impedance changes in the cell membrane, EIT can image these neural activities for understanding brain function and medical purposes. In our research, our self-developed electronic prototype board was used to generate high-quality electrical current and collect the data on electrodes with a high sampling rate and bit-resolution. In image reconstruction, a preprocessing data analysis algorithm was newly developed and applied to improve the accuracy of our EIT imaging. The human head has complex anatomical geometry and non-uniform resistivity distribution along with the highly resistive skull, which makes brain-EIT remains challenging inaccurate image reconstruction. To mimic the human head, a multi-layered human head phantom was designed and tested to investigate the effect of the skull structure on imaging. In this presentation, comparison studies for measurements and simulation results will be introduced to discuss the source of errors and improve the accuracy and efficiency of our brain-EIT system.
KEYWORDS: Space reconnaissance, Particles, Animal model studies, Radiation effects, Prefrontal cortex, Nervous system, Light emitting diodes, In vivo imaging, Brain
A unique feature of the space radiation environment is the presence of high-energy charged (HZE) particles which may pose a health risk to astronauts. One of the greatest concerns is the possibility of radiation-induced deterioration of central nervous system (CNS) functions. Past research using rodent models has revealed that radiation exposure led to unexpected alterations in behavior where executive functions are compromised which are vital for facilitating the attainment of mission success. This research aims to study CNS-related damage on male and female animal models following radiation exposure. However, exposure to HZE particles will inevitably introduce radiation-induced artifacts during the in-vivo electrophysiological recording process. To accurately correlate altered neural activity observed with changes in behavior, the On-line Tool for the Assessment of Radiation in Space (OLTARIS) will confirm the materials needed to fabricate neural probes since they must be developed to withstand extreme, HZE environments. Successful results will help scientists to understand the effect radiation has on hippocampal and prefrontal cortex regions of the CNS to prove the onset of behavioral impairments by direct neural sensing. This will open new paths for developing shielding and pharmaceutical countermeasures against cosmic radiation effects detected during deep space exploration.
KEYWORDS: Electrodes, Polymers, Data modeling, Surgery, Signal to noise ratio, In vivo imaging, Dielectrics, Data acquisition, Circuit switching, Brain
This study involves implantable flexible polymer-based probes where these microelectrodes would then be used later for neural recordings in vivo, using rodents as test subjects. Neural electrodes are used for medical purposes to record action potential or local field potential that comes from brain activity. Flexible polymer-based probes are used in order to reduce the effects of glial scars that come from surgery, also the polymer has high mechanical strengths, high dielectric, and good biocompatibility. Fabricating and studying the effects of impedance is the key part of this experiment for data accusation of these electrodes. Impedance that has a good signal-to-noise ratio is the goal in this research. Later, the impedance data that is collected from the working electrode over a wide range of frequencies would then be fitted using a CH Instrument and/or ZSimWin to create an equivalent integrated circuit (IC) model that mimics the real experiment to get a deeper understanding on its electrical properties. For the preparation of polymer-based electrodes, Tungsten electrodes and Carbon electrodes were tested with Phosphate-buffered saline (PBS) solution which completed the circuit. By having to test two different electrodes, Data acquisition was the next step to see which electrode give the best result.
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