# Time-Domain Near-Infrared Spectroscopy and Imaging: A Review
## 7 Summary
\begin{table}
\begin{tabular}{c c c} \hline
**Year** & **Event** & **Ref.** \\ \hline
1983 & Monte Carlo method applied to photon migration & [22] \\ \hline
1988 & TD measurement of optical pathlength & [34] \\ \cline{2-3}  & TD-NIRS of hemoglobin and myoglobin in muscle & [36] \\ \hline
1989 & Analytical solutions of the TD-DE for semi-infinite and slab media & [18] \\ \hline
1991-1995 & TD sensitivity functions & [26; 27; 28; 29] \\ \hline
1991, 1993 & Method of TD-DOT image reconstruction including forward and inverse models & [69; 164] \\ \hline
1992 & Analytical solutions of the TD-DE for various simple geometries & [19] \\ \cline{2-3}  & Monte Carlo code for multi-layered tissue, MCML & [23] \\ \hline
1993, 1995 & TOF and absorbance imaging of biological media and neonates & [156; 181] \\ \hline
1994 & Mathematical model for TD-FT & [197] \\ \hline
1994, 2006 & Diffusion coefficient independent of the absorption coefficient & [8; 17] \\ \hline
1996 & TD imaging based on the perturbation model & [87] \\ \hline
1996, 1998 & Perturbation Monte Carlo simulation & [105; 107] \\ \hline
1997 & Light propagation in a model of the adult head & [126] \\ \cline{2-3}  & TD-FT using early-arriving photons & [205] \\ \hline
1998 & TR reflectance from two-layered media & [98] \\ \cline{2-3}  & Simultaneous MR and TD-NIRS mammography & [191] \\ \hline
2000, 2014 & Open source software for TD-DOT: TOAST and TOAST++ & [49; 165] \\ \hline
2001 & TD-DOT of human forearm & [193] \\ \cline{2-3}  & Photon path distribution based on the microscopic Beer–Lambert law & [9] \\ \hline
2002 & GPST and full TR algorithms for TD-DOT & [170; 171] \\ \cline{2-3}  & 3D TD-DOT of premature infant brain & [185] \\ \hline  & Perturbation model for layered media & [91] \\ \cline{2-3}  & TR reflectance at null space SD distance & [131] \\ \cline{2-3}  & Measurements of optical properties in neonates using a commercial TD-NIRS system: & [222] \\ \cline{2-3}  & TRS-10 & [222] \\ \hline
2010 & (Monograph) Light propagation through biological tissue & [32] \\ \hline
2014 & Hybrid TD-RTE and TD-DE & [119; 120] \\ \hline
2014, 2016 & Estimate of tissue composition in breasts using TR reflectance at 7 wavelengths & [54; 139] \\ \hline \end{tabular}
\end{table} 
Table 2: Chronology of major events in theories, methods and applications of TD-NIRS. The reputation of being cumbersome, bulky, and very expensive has prevented TD-NIRS systems from being used widely in clinical applications, while the theoretical studies of TD-NIRS have antecedently developed many features toward clinical applications. Figure 19: Schematic view of the chronological development of the TD-NIRS instruments classifying the sources, detectors, and systems, indicating incorporation of the sources and detectors into the systems by vertical arrows (abbreviation: pLD—pulsed laser diode). Figure 20: Schematic view of the chronological development of TD-NIRS theories, methods, and applications, indicating their relationship with vertical arrows. In this situation, slow but steady progresses in TD-NIRS systems over the conventional TD-NIRS techniques have recently shown the possibility and feasibility of solving the drawbacks. As described in Section 3.3, many new systems without using the PMTs have been developed such as the compact, low-power consuming and dual-channel or dual-wavelength TD-NIRS systems using the SiPMs (MPPCs) [55; 56], the systems incorporating fast-gated SPADs [58; 60; 61], the systems based on a spread spectrum approach using laser diodes with pseudo-random-bit sequences [63; 64], the systems using time-gated ICCD cameras [65; 66], the system incorporating a low-cost commercially available optical transceiver module widely used in telecommunications [3], the system using a supercontinuum laser [67], and the system using state-of-the-art SPAD camera chips [62]. In particular, the SiPM (MPPC) that is a new photon counting semiconductor device may replace the conventional PMTs.