Time-domain diffuse optics
Time-domain diffuse optics or time-resolved functional near-infrared spectroscopy is a branch of functional near-Infrared spectroscopy which deals with light propagation in diffusive media. There are three main approaches to diffuse optics, namely continuous-wave (CW), frequency-domain (FD), and time-domain (TD).
Source: Wikipedia — Time-domain diffuse optics (CC BY-SA 4.0)