Depth dependence of coherent hemodynamics in the human head

Kosar Khaksari; Giles Blaney; Angelo Sassaroli; Nishanth Krishnamurthy; Thao Pham; Sergio Fantini

doi:10.1117/1.JBO.23.12.121615

15 November 2018 Depth dependence of coherent hemodynamics in the human head

Kosar Khaksari, Giles Blaney, Angelo Sassaroli, Nishanth Krishnamurthy, Thao Pham, Sergio Fantini

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Journal of Biomedical Optics, Vol. 23, Issue 12, 121615 (November 2018). https://doi.org/10.1117/1.JBO.23.12.121615

Abstract

We report a near-infrared spectroscopy (NIRS) study of coherent hemodynamic oscillations measured on the human forehead at multiple source–detector distances (1 to 4 cm). The physiological source of the coherent hemodynamics is arterial blood pressure oscillations at a frequency of 0.1 Hz, induced by cyclic inflation (to a pressure of 200 mmHg) and deflation of two thigh cuffs wrapped around the subject’s thighs. To interpret our results, we use a recently developed hemodynamic model and a phasor representation of the oscillations of oxyhemoglobin, deoxyhemoglobin, and total hemoglobin concentrations in the tissue (phasors O, D, and T, respectively). The increase in the phase angle between D and O at larger source–detector separations is assigned to greater flow versus volume contributions and to a stronger blood flow autoregulation in deeper tissue (brain cortex) with respect to superficial tissue (scalp and skull). The relatively constant phase lag of T versus arterial blood pressure oscillations at all source–detector distances was assigned to competing effects from stronger autoregulation and smaller arterial-to-venous contributions in deeper tissue with respect to superficial tissue. We demonstrate the application of a hemodynamic model to interpret coherent hemodynamics measured with NIRS and to assess the different nature of shallow (extracerebral) versus deep (cerebral) tissue hemodynamics.

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Kosar Khaksari, Giles Blaney, Angelo Sassaroli, Nishanth Krishnamurthy, Thao Pham, and Sergio Fantini "Depth dependence of coherent hemodynamics in the human head," Journal of Biomedical Optics 23(12), 121615 (15 November 2018). https://doi.org/10.1117/1.JBO.23.12.121615

Received: 2 August 2018; Accepted: 29 October 2018; Published: 15 November 2018

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