We describe the general principles and initial results of coherent hemodynamics spectroscopy (CHS), which is a new
technique for the quantitative assessment of cerebral hemodynamics on the basis of dynamic near-infrared spectroscopy
(NIRS) measurements. The two components of CHS are (1) dynamic measurements of coherent cerebral hemodynamics
in the form of oscillations at multiple frequencies (frequency domain) or temporal transients (time domain), and (2) their
quantitative analysis with a dynamic mathematical model that relates the concentration and oxygen saturation of
hemoglobin in tissue to cerebral blood volume (CBV), cerebral blood flow (CBF), and cerebral metabolic rate of oxygen
(CMRO2). In particular, CHS can provide absolute measurements and dynamic monitoring of CBF, and quantitative
measures of cerebral autoregulation. We report initial results of CBF measurements in hemodialysis patients, where we
found a lower CBF (54 ± 16 ml/(100 g-min)) compared to a group of healthy controls (95 ± 11 ml/(100 g-min)). We also
report CHS measurements of cerebral autoregulation, where a quantitative index of autoregulation (its cutoff frequency)
was found to be significantly greater in healthy subjects during hyperventilation (0.034 ± 0.005 Hz) than during normal
breathing (0.017 ± 0.002 Hz). We also present our approach to depth resolved CHS, based on multi-distance, frequency-domain
NIRS data and a two-layer diffusion model, to enhance sensitivity to cerebral tissue. CHS offers a potentially
powerful approach to the quantitative assessment and continuous monitoring of local brain perfusion at the
microcirculation level, with prospective brain mapping capabilities of research and clinical significance.
Sergio Fantini, Angelo Sassaroli, Jana M. Kainerstorfer, Kristen T. Tgavalekos, and Xuan Zang, "Non-invasive assessment of cerebral microcirculation with diffuse optics and coherent hemodynamics spectroscopy," Proc. SPIE 9690, Clinical and Translational Neurophotonics; Neural Imaging and Sensing; and Optogenetics and Optical Manipulation, 96900S (Presented at SPIE BiOS: February 15, 2016; Published: 9 March 2016); https://doi.org/10.1117/12.2213139.
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