EEG technology has advanced substantially with respect to digital processing capability during the past 20 years. However, the process of transducing the very small cerebral electrical signals at the scalp surface remains difficult, requiring very low and balanced contact impedances to achieve acceptable levels of line frequency (e.g. 60 Hz) noise. Preparation of scalp sites using solvents, abrasives and syringe needles to match amplifier system input requirements is time consuming, costly and especially burdensome in neonatal and critical care patients. The use of """"""""electrode caps"""""""" of various designs reduced the time required to apply the electrodes at anatomically correct locations but scalp contact impedances are typically high and unbalanced with these due to the small contact area. A preparation-free EEG technology is proposed that would entirely eliminate scalp site preparation with solvents, abrasive and needles, etc. Setup time for clinical and experimental protocols would be reduced to the time required to make contact. In addition to time savings, it would eliminate patient irritation and the risk of infection from scalp puncture during abrasion. Two implementations of the technology would be developed: one to serve as a small, fully automated, in-line modular retrofit to existing EEG/Evoked potential systems and the second would serve as the sole amplifier interface to electrically isolated notebook and desktop PC's equipped with a universal serial bus (USB) port. As a retrofit, it will enable the uncomplicated use of electrode caps and for most EEG amplifier systems, substantially improve overall signal-to-noise performance. This new technology would greatly reduce application requirements of """"""""high resolution"""""""" EEG procedures requiring >32 channels. Key elements of this technology are: active common mode cancellation (CMC) circuitry; high performance instrumentation amplifiers; driven """"""""microcoaxial"""""""" shielding on each lead wire and extremely high ground isolation. In Phase l, a prototype device will be evaluated in benchtop tests and in a clinical sample at the University of California, Irvine, Department of Neurology. Preliminary production cost estimation supports price ranges of $2,000 for the ETM and $4,000 for the ESM.
The proposed new technology would find application in both routine clinical acquisition of EEG and evoked potentials as well as experimental protocols. The ETM device is designed to be compatible with all existing EEG/EP recording systems. The very high tolerance of the ETM and ESM for high and unbalanced electrode impedances in electrically noisy environments recommends their application in critical care and operating room environments. Both devices would also find immediate application in """"""""high resolution"""""""" EEG applications calling for 32, 64, 128-channels.
