Indexing cerebrovascular health using near-infrared spectroscopy.

Near-infrared spectroscopy (NiRS) is a relatively new technology of brain imaging with its potential in the assessment of cerebrovascular health only recently discovered. Encouraging early results suggest that NiRS can be used as an inexpensive and portable cerebrovascular health tracking device using a recently proposed pulse relaxation function (PReFx). In this paper, we propose a new NiRS timing index, [Formula: see text], of cerebrovascular health. [Formula: see text] is a novel use of the NiRS technology. [Formula: see text] is motivated by the previously proved relationship of the timing of the reflected wave with vascular resistance and compliance in the context of pressure waveforms. We correlated both [Formula: see text] and PReFx against age, a non-exercise cardiorespiratory fitness (CRF) index, and two existing indices of cerebrovascular health, namely transcranial Doppler (TCD) augmentation index, [Formula: see text], and magnetic resonance imaging (MRI) blood flow pulsatility index, [Formula: see text]. The [Formula: see text] correlations with Age, CRF, [Formula: see text] and [Formula: see text] all are significant, i.e., [Formula: see text] ([Formula: see text]), [Formula: see text] ([Formula: see text]), [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]), respectively. PReFx, however, did not have significant correlations with any of the vascular health factors. The proposed timing index is a reliable indicator of cerebrovascular aging factors in the NiRS waveform.