Fig. 1. Three types of optical transmission

Fig. 2. Three imaging modalities of diffuse optics, and $I_{\mathrm{0}}$ is incident light signal, $I$ is transmitted light signal, ${\mu }_{\mathrm{a}}$ is absorption coefficient, ${\mu }_{\mathrm{s}}^{\mathrm{\text{'}}}$ is reduced scattering coefficient. (a) Illustration of diffuse optical light transmission; (b) continuous wave mode; (c) frequency domain mode; (d) time domain mode

Fig. 3. Absorption spectra of oxyhemoglobin and deoxyhemoglobin^[6]

Fig. 4. Light absorption profile through issue detected by pulse oximetry^[7]

Fig. 5. Schematic of pulse oximetry in two modes ^[4]. (a) Transmission mode; (b) reflection mode

Fig. 6. Fundus images acquired by the oxymap system using dual-wavelength approach^[30]. (a) Color-coded oximetry vessel map, where different colors represent oxygen saturation levels; (b) (c) retinal images acquired at 570 nm and 600 nm, respectively

Fig. 7. Flowchart of DOS ^[35]

Fig. 8. Schematic of DOS and DOT^[35]. (a) DOS; (b) DOT

Fig. 9. Subject measurement with the DOS instrument ^[46]

Fig. 10. Distribution of sources and detectors of DOT system

Fig. 11. Schematic of parallel plate diffuse optical tomography instrument^[56]

Fig. 12. Chromophore concentration maps in the breasts of a patient with tumor in the right breast ^[35]

Fig. 13. Evaluation of brain function ^[59]. (a) Imaging cap structure of DOT system, subject position, and audiovisual stimuli; (b) schematic of source and detector locations, where blue represents the detector and other colors represent light sources in different areas; (c)‒(f) evaluation of distributed brain function mapping by imaging hierarchical language processing

Fig. 14. Functional imaging of neonatal brain^[60]. (a) A newborn infant wearing the DOT system; (b) source-detector channels; (c) source positions and detector positions shown on the scalp surface of the head model

Fig. 15. Hemodynamics monitoring of visual cortex ^[61]. (a) Schematic of imaging area; (b) image slice in the axial direction; (c) distribution of oxyhemoglobin at different time; (d) concentration changes of oxyhemoglobin (red), deoxyhemoglobin (blue), and total hemoglobin (green)

Fig. 16. Measurement device^[62]. (a) Instrument setup; (b) optical fiber holder (front); (c) optical fiber holder (back); (d) schematic of imaging

Fig. 17. FMT systems^[72-73]. (a) FMT system based on fiber coupling; (b) temporal-domain FMT system

Fig. 18. FMT of small animal tumor models ^[78]. (a) FMT for small animal imaging; (b) imaging of mouse tumor models using FMT

Fig. 19. FMT of breast cancer in humans^[79]. (a) FMT system for breast cancer detection; (b) 2D cross-section images acquired by FMT, including total hemoglobin concentration, oxygen saturation, reduced scattering coefficient, and ICG concentration; (c) 3D reconstruction using FMT

Fig. 20. ICG imaging in mice using FMT ^[83]

Fig. 21. Diagram of SFDI system^[115]

Fig. 22. SFDI monitoring of burn wounds in pork model^[120]

Fig. 23. Spatial frequency domain oxygenation imaging system ^[122]

Fig. 24. Cervical carcinoma screening^[123]. (a) Photograph of cervical carcinoma tissue specimen; (b) reduced scattering coefficient map; (c) backscattering probability map; (d) light spreading length map; (e)‒(h) stained histological images of the highlighted regions in Fig.24 (a)‒(d)

Fig. 25. ROC curves using two and six parameters, respectively ^[124]

Fig. 26. Comparison of fluorescence imaging in tumor models^[125]

Fig. 27. Tumor growth and treatment monitored by with spatial frequency domain imaging^[132]

Fig. 28. Spatial frequency domain imaging for apple tissue measurement ^[133]