Dynamic measurements of absolute cerebral blood flow with coherent hemodynamics spectroscopy

We used coherent hemodynamics spectroscopy (CHS) and near-infrared spectroscopy (NIRS) for dynamic measurements of absolute cerebral blood flow (CBF) in one healthy subject over the prefrontal cortex. Temporal transients in mean arterial pressure (MAP) and CBF were induced by rapid deflation of pneumatic thigh cuffs following a sustained 2-minute occlusion at a super-systolic pressure. We studied the sensitivity of relative and absolute measurements of CBF with NIRS-CHS (CBF_NIRS-CHS) to the physiological parameters in the CHS model. The temporal dynamics of CBF_NIRS-CHS were compared with co-localized NIRS measurements of hemoglobin difference ([HbD] = [HbO₂]−[Hb]), and with diffuse correlation spectroscopy (DCS) measurements of relative CBF. We demonstrated that NIRS-CHS provides quantitative measurements of absolute baseline CBF, and corrects [HbD] estimations of CBF dynamics for blood volume contributions and for blood transit times in the microvasculature resulting in a better agreement with CBF dynamics measured by DCS.