Improved Sensing Pulses for Increased Human Head Depth Measurement Sensitivity With Electrical Impedance Spectroscopy

Abstract

This paper describes an improved electrical impedance spectroscopy (EIS) stimulus paradigm, based on dual-energy pulses using the stochastic Gabor function (SGF) that may more sensitively assess deep brain tissue impedance than current single-pulse paradigms. The SGF is a uniformly distributed noise, modulated by a Gaussian envelope, with a wide-frequency spectrum representation regardless of the stimuli energy, and is least compact in the sample frequency phase plane. Numerical results obtained using a realistic human head model confirm that two sequential SGF pulses at different energies can improve EIS depth sensitivity when used in a dual-energy subtraction scheme. Specifically, although the two SGF pulses exhibit different tissue current distributions, they maintain the broadband sensing pulse characteristics needed to generate all the frequencies of interest. Moreover, finite-difference time domain simulations show that this dual-energy excitation scheme is capable of reducing the amplitude of weighted current densities surface directly underneath the electrodes by approximately 3 million times versus single stimulation pulses, while maintaining an acceptable tissue conductivity distribution at depth. This increased sensitivity for the detection of small, deep impedance changes might be of value in potential future EIS applications, such as the portable, point-of-care detection of deep brain hemorrhage or infarction.

Classification of Hemorrhage Using Priori Information of Electrode Arrangement With Electrical Impedance Tomography

“…Comparatively, electrical impedance tomography (EIT) is a safe, low cost, reliable and fast method that has been successfully applied in various fields of medical imaging [7][8][9][10]. In the brain imaging, conductivity variation caused by hemorrhage can be also recovered by EIT [11][12][13]. It is known that conductivity distribution in the measured region can be reconstructed by processing voltage measurement with EIT imaging methods.…”

Aluminum Thin Film Nanostructure Traces in Pediatric EEG Net for MRI and CT Artifact Reduction

“…The major strengths of the NeoNet lie in the ease of application of the net compared to single electrodes in fragile patients such as neonates and children, and its compatibility with MRI environments, not needing to remove electrodes prior to the recording and re-apply them after the exam. Finally, other potential applications of the NeoNet include electrical impedance spectroscopy (EIS) in children [3]. The aluminum thin films and alloys comprise most of the interconnections used in semiconductor chips [5].…”

“…In all of these situations, high-density EEG (HD-EEG) is preferred as it provides the best signal-to-noise ratio (SNR), dynamic range, and sampling rate compared to the older 10–20 EEG. Furthermore, HD-EEG has enhanced artifact removal and can automatically detect seizures [ 3 ] (see also Supplementary Material S1 ). Typically, however, EEG nets must be removed prior to MRI and CT imaging, as they can pose a safety hazard in the MRI environment and can severely impact the image quality.…”