Wyser Dominik, Lambercy Olivier, Scholkmann Felix, Wolf Martin, Gassert Roger
ETH Zurich, Rehabilitation Engineering Laboratory, Department of Health Sciences and Technology, Zurich, Switzerland.
University Hospital of Zurich, Biomedical Optics Research Laboratory, Department of Neonatology, Zurich, Switzerland.
Neurophotonics. 2017 Oct;4(4):041413. doi: 10.1117/1.NPh.4.4.041413. Epub 2017 Aug 18.
With the aim of transitioning functional near-infrared spectroscopy (fNIRS) technology from the laboratory environment to everyday applications, the field has seen a recent push toward the development of wearable/miniaturized, multiwavelength, multidistance, and modular instruments. However, it is challenging to unite all these requirements in a precision instrument with low noise, low drift, and fast sampling characteristics. We present the concept and development of a wearable fNIRS instrument that combines all these key features with the goal of reliably and accurately capturing brain hemodynamics. The proposed instrument consists of a modular network of miniaturized optode modules that include a four-wavelength light source and a highly sensitive silicon photomultiplier detector. Simultaneous measurements with short-separation (7.5 mm; containing predominantly extracerebral signals) and long-separation (20 mm or more; containing both extracerebral and cerebral information) channels are used with short-channel regression filtering methods to increase robustness of fNIRS measurements. Performance of the instrument was characterized with phantom measurements and further validated in human measurements, demonstrating the good raw signal quality (signal-to-noise ratio of 64 dB for short channels; robust measurements up to 50 mm; dynamic optical range larger than 160 dB), the valid estimation of concentration changes (oxy- and deoxyhemoglobin, and cytochrome-c-oxidase) in muscle and brain, and the detection of task-evoked brain activity. The results of our preliminary tests suggest that the presented fNIRS instrument outperforms existing instruments in many aspects and bears high potential for real-time single-trial fNIRS applications as required for wearable brain-computer interfaces.
为了将功能近红外光谱（fNIRS）技术从实验室环境过渡到日常应用，该领域最近一直在推动可穿戴/小型化、多波长、多距离和模块化仪器的开发。然而，要将所有这些要求统一到一台具有低噪声、低漂移和快速采样特性的精密仪器中具有挑战性。我们提出了一种可穿戴fNIRS仪器的概念和开发方案，该仪器结合了所有这些关键特性，目标是可靠、准确地捕捉脑血流动力学。所提出的仪器由一个模块化网络组成，该网络包含小型化的光探测器模块，其中包括一个四波长光源和一个高灵敏度的硅光电倍增管探测器。使用短间距（7.5毫米；主要包含脑外信号）和长间距（20毫米或更长；包含脑外和脑内信息）通道的同时测量，并结合短通道回归滤波方法，以提高fNIRS测量的稳健性。该仪器的性能通过模型测量进行了表征，并在人体测量中进一步得到验证，结果表明该仪器具有良好的原始信号质量（短通道的信噪比为64分贝；在长达50毫米的距离内测量稳健；动态光学范围大于160分贝），能够有效估计肌肉和大脑中的浓度变化（氧合血红蛋白、脱氧血红蛋白和细胞色素c氧化酶），并能检测任务诱发的脑活动。我们初步测试的结果表明，所提出的fNIRS仪器在许多方面优于现有仪器，并且对于可穿戴脑机接口所需的实时单次试验fNIRS应用具有很高的潜力。
