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

Abstract

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.

Applying antagonistic activation pattern to the single-trial classification of mental arithmetic

“…In this study, we successfully extracted features using VPA from 3 ROIs which have a close association with MA to improve the performance of classification. The proposed method is different from most other studies that used the average of all channels or a specific channel value and also does not employ the traditional HbO and HbR features [ 57 , 58 , 59 , 60 , 61 , 62 , 63 ]. This study shows classification accuracies are enhanced by using the novel method compared to the basic method.…”

Progress of near-infrared spectroscopy in cerebral blood oxygenation detection: A mini review

“…Table 3 lists different light sources and detectors that have been used in various NIRS systems over the last few years. Among them, Yaqub created a cutting-edge system with a 12bit successive-approximation analog-to-digital converter and used a silicon photodiode set up in the photoconductive mode to achieve a high sampling rate when processing significant amounts of NIRS data [28]. Additionally, a filter circuit was specifically included in this design to efficiently reduce high-frequency noise brought on by the high-voltage power supply.…”

Wearable functional near‐infrared spectroscopy for measuring dissociable activation dynamics of prefrontal cortex subregions during working memory

“…In cognitive research, fNIRS has been particularly useful in studies of patient populations and infants, due to its wearability and its robustness to motion artifacts (Baddeley, 2012; Obrig, 2014; Pinti et al, 2020; Quaresima et al, 2012; Wilcox & Biondi, 2015). The recent development of wireless systems with a high‐density array of channels and motion sensors (Frijia et al, 2021; Shin et al, 2017; Vidal‐Rosas et al, 2023; Yaqub et al, 2020) has made it possible to precisely localize the fNIRS signal to specific subregions of the brain, while maintaining a high temporal resolution that may be advantageous for tests of cognition. Leveraging such techniques could open new doors for neurocognitive research that can be applied in various naturalistic settings.…”