Depth dependent coherent hemodynamics during induced blood pressure oscillations

Angelo Sassaroli; Giles Blaney; Thao Pham; Sergio Fantini

doi:10.1117/12.2509861

1 March 2019 Depth dependent coherent hemodynamics during induced blood pressure oscillations

Angelo Sassaroli, Giles Blaney, Thao Pham, Sergio Fantini

Proceedings Volume 10874, Optical Tomography and Spectroscopy of Tissue XIII; 108742A (2019) https://doi.org/10.1117/12.2509861
Event: SPIE BiOS, 2019, San Francisco, California, United States

Abstract

We have compared different methods for analyzing dynamic changes of oxy- and deoxyhemoglobin concentrations oscillations, measured by near infrared spectroscopy (NIRS), during cyclic pneumatic thigh cuff occlusion and release at the frequency of 0.1 Hz. This protocol is usually adopted in coherence hemodynamics spectroscopy (CHS) to induce controlled arterial blood pressure perturbations which drive hemodynamic changes in the brain. It is a general problem of NIRS to differentiate hemodynamic signals originated in the brain from those in the extracerebral tissue layer. The purpose of this study is to gain some understanding about the spatial origin of the oscillating optical signals according to these five different methods of data analysis during the thigh cuff occlusion and release protocol. The results obtained on six human subjects show that similar qualitative behavior of oxy- and deoxyhemoglobin dynamic changes are found by using: (1) modified Beer-Lambert law at far source detector separations (d > 25 mm); (2) DC intensity slope method at d > 25 mm; (3) multi-distance method at d >25 mm; (4) Two-layer modified Beer-Lambert law (using d > 25 mm) when we consider dynamic changes in the second (deeper) layer. At short source-detector separations (d < 15 mm), the hemoglobin concentration changes obtained with the modified Beer-Lambert law are consistent with those obtained for the first (superficial) layer with the two-layer modified Beer-Lambert law. For more quantitative assessment of cerebral dynamic changes, we argue that DC slope or two-layer modified Beer-Lambert law should provide better estimates. We support this claim by comparing the sensitivity to layered absorption perturbations obtained by using the modified BeerLambert law and the DC slope methods.

Citation Download Citation

Angelo Sassaroli, Giles Blaney, Thao Pham, and Sergio Fantini "Depth dependent coherent hemodynamics during induced blood pressure oscillations", Proc. SPIE 10874, Optical Tomography and Spectroscopy of Tissue XIII, 108742A (1 March 2019); https://doi.org/10.1117/12.2509861

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