A low-cost multichannel NIRS oximeter for monitoring systemic low-frequency oscillations
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ORIGINAL ARTICLE
A low-cost multichannel NIRS oximeter for monitoring systemic low-frequency oscillations Yingwei Li1,2 • Yunfei Ma1 Blaise deB Frederick2,4
•
Shaoqing Ma1
•
Lia Maria Hocke2,4
•
Yunjie Tong3
•
Received: 21 December 2019 / Accepted: 25 March 2020 Ó Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Systemic low-frequency oscillations (sLFOs) are non-neuronal oscillations at 0.01–0.15 Hz. These sLFOs travel through the entire body and the brain with symmetrical (across the midline of the body) and highly predictable delays, where they can be observed with functional near-infrared spectroscopy (fNIRS) and blood oxygen level-dependent functional magnetic resonance imaging. Their characteristics may serve as useful biomarkers for detecting and monitoring circulatory dysfunction. Pure sLFOs can be collected in the periphery (e.g., fingers, toes, earlobes). Here we present a 7-channel NIRS oximeter [MNO] for sLFOs detection and analysis in the periphery, which we named concurrent continuous wave fNIRS system (CON-CW fNIRS). Our CON-CW fNIRS is small (10 9 10 9 20 cm3), highly portable, has low-power consumption and is highly cost-effective (below $300). We show that our device is highly reliable and can reproduce values acquired with a commercial fNIRS device with direct comparison (rmax = 0.908 D[HbO] and rmax = 0.841 D[Hb]) and when compared to previously published data. Keywords fNIRS Circulation Systemic low-frequency oscillations MSP430
1 Introduction Low-frequency oscillations (LFOs: 0.01–0.15 Hz) are slow, spontaneous variations in hemodynamic parameters commonly observed in functional near-infrared spectroscopy (fNIRS) studies, where they are often interpreted as indicative of neuronal activity [1–6]. However, part of these LFOs is non-neuronal [1, 7, 8]. The origins and functions of these LFOs are complex and not fully & Yingwei Li [email protected] & Blaise deB Frederick [email protected] 1
School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China
2
McLean Imaging Center, McLean Hospital, Belmont, MA 02478, USA
3
Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47906, USA
4
Department of Psychiatry, Harvard Medical School, Boston, MA 02115, USA
understood [1]. In order to distinguish them from the neuronal LFOs, we refer to these physiological fluctuations as systemic LFOs (sLFOs). sLFOs with no neuronal components can be collected in the periphery at the fingers, toes and earlobes [9]. Frederick et al. have demonstrated strong correlations between the sLFOs collected in the periphery (NIRS) and in the brain (BOLD fMRI), with varying time delays [1]. These delays were symmetric across the body midline and demonstrate that some portion of sLFOs actually reflects systemic physiological circulatory effects. Furthermore, these sLFOs, and their temporal delays within the body and brain, can be reliably and consistently measured in hea
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