An EEG-NIRS Multimodal SoC for Accurate Anesthesia Depth Monitoring

Ha, Unsoo; Lee, Jae-Hyuk; Kim, Minseo; Roh, Taehwan; Choi, Sangsik; Yoo, Hoi‐Jun

doi:10.1109/jssc.2018.2810213

Cited by 66 publications

(24 citation statements)

References 13 publications

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“…The results showed that the system could capture the light intensity over a wide range. The dynamic optical range measured was higher than that of previously reported devices (i.e., 80 dB in [52], 55 dB in [53], and 60 dB in [54,55]). The device provided high SNR values for all the channels with different detector separations, and thus outperformed previously developed fNIRS devices (i.e., > 40 dB in [52], and max 19 dB in [56]).…”

Section: Discussioncontrasting

confidence: 68%

Compact, Portable, High-Density Functional Near-Infrared Spectroscopy System for Brain Imaging

2020

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Advancements in functional near-infrared spectroscopy (fNIRS) neuroimaging have extended its usage from clinical settings to real-life applications. We developed a wearable and wireless fNIRS-based neuroimaging system that can be applied for brain disease diagnostics and during daily life activities. We utilized 128 compact dual-wavelength LEDs of 735 nm and 850 nm and a silicon photodiode (SiPD). The LEDs and SiPD were closely assembled in a 3D-printed flexible configuration holder fitted in a soft neoprene cap. The developed configuration has 128 channels in a 7 × 7 cm area with source-detector separations ranging from 5 mm to 38 mm, which intends to provide a high-density device. The system acquires data from multiple brain depths to generate a 3D activation image. Short-separation channels provide the physiological noise in the superficial layer, which can be used to enhance fNIRS signals. The experimental data are stored in a USB flash disk attached to the device. We developed software that is connected to the device using Wi-Fi to display the oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) levels in real-time. The system architecture allows the selection of channels and the use of multiple devices simultaneously. The system was tested using a silicone phantom as well as human subjects. The LED intensity is dynamically calibrated within the safety range once the device is set up, so that every channel can acquire stable data. The system provided high-quality signals with a signal-to-noise ratio of more than 64 dB, high optical sensitivity, and dynamic optical range of 140 dB in the phantom test. A sampling rate of 30 Hz was achieved with all the channels used. The system exhibited valid HbO and HbR responses during the arterial occlusion test and a motor task. These results show that the developed system can provide precise, robust, and multi-depth measurements resulting in high-density images. With these novel characteristics, the system favors clinical usage and outdoor activities as well as brain-computer interface applications.

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Section: Discussioncontrasting

confidence: 68%

Compact, Portable, High-Density Functional Near-Infrared Spectroscopy System for Brain Imaging

2020

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“…The simulated f p1 value is 170 Hz. A maximum f hp of 340 Hz is expected according to (17). The simulated f hp value in the integrator mode and the setting mode is 0.4 and 180 Hz, respectively.…”

Section: Design Of the DC Servo Loopmentioning

confidence: 91%

“…A modified design is reported in [16] to reduce the silicon area, but sacrificing the IRN of the overall system by 6.7 uVrms (11.1×) in the band of 0.5-100 Hz, which is unacceptable for the application of LFP signal acquisition. The back-to-back pseudoresistor is widely used as an area-efficient method to create low highpass corner while achieving low noise [17], [18]. However, the value of the pseudoresistor is extremely sensitive to process-voltage-temperature (PVT) variations, which can be 0018-9200 © 2019 IEEE.…”

Section: Introductionmentioning

confidence: 99%

A Low-Noise Chopper Amplifier Designed for Multi-Channel Neural Signal Acquisition

Luo

Zhang

Wang

2019

IEEE J. Solid-State Circuits

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This paper proposed the design of a low-noise, low total harmonic distortion (THD) chopper amplifier for neural signal acquisition. A dc servo loop (DSL) based on active Gm-C integrator is proposed to reject the electrode-dcoffset (EDO). Architecture of a complementary input very lowtransconductance (VLT) operational transconductance amplifier (OTA) was proposed and integrated in the active Gm-C integrator to improve the linearity as well as to reduce the noise, featuring a transconductance ranging from 45 pS to a few nS. The proposed amplifier was fabricated in a TSMC 0.18-µm CMOS process, occupying an area of 0.2 mm 2 , featuring a power consumption of 3.24 µW/channel under a 1.8-V supply voltage. The THD for a 5-mV pp input is lower than −61 dB. An input-referred thermal noise power spectral density (PSD) of 39 nV/ √ Hz is measured. The measured input-referred noise is 0.65 µV rms in the 0.3-200-Hz frequency band and 2.14 µV rms in the 200-Hz-5-kHz frequency band, respectively, leading to a noise-efficiency factor of 2.37 (0.3-200 Hz) and 1.56 (0.2 k-5 kHz). In addition, the high-pass corner frequency can be precisely configured and linearly adjusted with the external bias current from 0.35 to 54.5 Hz.

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“…According to Table II, most research has achieved noise lower than 2 µV rms from 0.5 to 100 Hz. For example, in [95], the authors achieved 0.44 µV rms from 0.5 to 250 Hz, while their input impedance was 1 GΩ at 60 Hz. Their total power consumption was 5.4 µW.…”

Section: B Amplifier Noise-reduction Techniquesmentioning

confidence: 99%

Impedance and Noise of Passive and Active Dry EEG Electrodes: A Review

2020

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Dry electrodes are a promising solution for prolonged EEG signal acquisition, whereas wet electrodes may lose their signal quality in the same situation and require skin preparation for setup. Here, we review the impedance and noise of passive and active dry EEG electrodes. In addition, we compare noise and input impedance of the EEG amplifiers. As there are multiple definitions of impedance in each EEG system, they are all first defined. Electrodes must be compatible with amplifiers to accurately record EEG signals. This implies that their impedance plays a significant role in amplifier compatibility and affects total input-referred noise. Therefore, we review the impedance and noise of state-of-the-art amplifiers and electrodes. Furthermore, we compare the various structures and materials used and their final impedance to that of wet electrodes. Finally, we compare state-of-the-art electrodes and amplifiers to the standards of the IFCN and IEC80601-2-26. We investigate bottlenecks and propose a guideline for future work on passive and active dry electrodes, as well as EEG amplifiers.

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An EEG-NIRS Multimodal SoC for Accurate Anesthesia Depth Monitoring

Cited by 66 publications

References 13 publications

Compact, Portable, High-Density Functional Near-Infrared Spectroscopy System for Brain Imaging

Compact, Portable, High-Density Functional Near-Infrared Spectroscopy System for Brain Imaging

A Low-Noise Chopper Amplifier Designed for Multi-Channel Neural Signal Acquisition

Impedance and Noise of Passive and Active Dry EEG Electrodes: A Review

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