Chiarelli A M, Giaconia G C, Perpetuini D, Greco G, Mistretta L, Rizzo R, Vinciguerra V, Romeo M F, Merla A, Fallica P G
Annu Int Conf IEEE Eng Med Biol Soc. 2019 Jul;2019:60-66. doi: 10.1109/EMBC.2019.8857206.
Development and in-vivo validation of a Continuous Wave (CW) functional Near Infrared Spectroscopy (fNIRS) system is presented. The system is wearable, fiber-less, multi-channel (16×16, 256 channels) and expandable and it relies on silicon photomultipliers (SiPMs) for light detection. SiPMs are inexpensive, low voltage and resilient semiconductor light detectors, whose performances are analogous to photomultiplier tubes (PMTs). The advantage of SiPMs with respect to PMTs is that they allow direct contact with the scalp and avoidance of optical fibers. In fact, the coupling of SiPMs and light emitting diodes (LEDs) allows the transfer of the analog signals to and from the scalp through thin electric cables that greatly increase the system flexibility. Moreover, the optical probes, mechanically resembling electroencephalographic electrodes, are robust against motion artifacts. In order to increase the signal-to-noise-ratio (SNR) of the fNIRS acquisition and to decrease ambient noise contamination, a digital lock-in technique was implemented through LEDs modulation and SiPMs signal processing chain. In-vivo validation proved the system capabilities of detecting functional brain activity in the sensorimotor cortices. When compared to other state-of-the-art wearable fNIRS systems, the single photon sensitivity and dynamic range of SiPMs can exploit the long and variable interoptode distances needed for estimation of brain functional hemodynamics using CW-fNIRS.
本文介绍了一种连续波（CW）功能近红外光谱（fNIRS）系统的开发及其体内验证。该系统可穿戴、无光纤、多通道（16×16，256个通道）且可扩展，依靠硅光电倍增管（SiPM）进行光检测。SiPM是廉价、低电压且耐用的半导体光探测器，其性能类似于光电倍增管（PMT）。SiPM相对于PMT的优势在于它们可直接与头皮接触并避免使用光纤。实际上，SiPM与发光二极管（LED）的耦合使得模拟信号能够通过细电缆在头皮与外界之间传输，这极大地提高了系统的灵活性。此外，光学探头在机械结构上类似于脑电图电极，对运动伪影具有鲁棒性。为了提高fNIRS采集的信噪比（SNR）并减少环境噪声污染，通过LED调制和SiPM信号处理链实现了数字锁相技术。体内验证证明了该系统在检测感觉运动皮层中大脑功能活动方面的能力。与其他现有可穿戴fNIRS系统相比，SiPM的单光子灵敏度和动态范围能够利用连续波fNIRS估计脑功能血液动力学所需的长且可变的探测器间距离。
