. 2023 Jun 30;10(2):023522. doi: 10.1117/1.NPh.10.2.023522

Table 1.

Comparison of different NIRS methods and related technologies.

NIRS modality	Principles used	Information provided	Applications/advantages	Disadvantages
CW-NIRS	Constant illumination	Relative changes in [HbO] and [HbR]	Continuous monitoring for relative changes in CBF in response to discrete clinical events/interventions	Only relative changes
	Measures changes in NIR absorption of HbO and HbR using MBLL			Susceptible to background light contamination
			Commercial devices available for clinical use
			Easily portable
FD-NIRS	Intensity-modulated illumination	Absolute [HbO], [HbR], and ${rSO}_{2}$	Compare absolute hemodynamic and oxygenation changes,	Bulky size/expensive
	Intensity-modulated illumination		Compare absolute hemodynamic and oxygenation changes,	Lack of commercial devices
	Phase-resolved detection		Make comparisons within patients over time and between patients
	Measures the average intensity of the detected light as well as fluctuating intensity and phase shift		Less susceptible to background light artifact
TD-NIRS	Extremely short, pulsed illumination	Absolute [HbO], [HbR], and ${rSO}_{2}$	Compare absolute hemodynamic and oxygenation changes	Bulky/expensive
	Extremely short, pulsed illumination	Absolute [HbO], [HbR], and ${rSO}_{2}$	Compare absolute hemodynamic and oxygenation changes	Lack of commercial devices
	Time-resolved detection of emerging photons (time of flight [TOF])	Detailed assessment of the tissue’s optical properties	Make comparisons within and between-patients	Lack of commercial devices
DCS	Coherent NIR-range light	Relative changes in CBF	Detecting changes in CBF and cerebral ischemia	Can only measure relative changes
	Detects fluctuations in light intensity over time produced by scattering particles			Can only measure relative changes
				Susceptible to motion and background light artifacts
				Paucity of commercially available devices
DCS/NIRS	Hybrid of DCS and NIRS	Concurrent CBF, [HbO], [HbR], and ${rSO}_{2}$	Detection of cerebral ischemia	Repeated calibration with tracer injection if using CW-NIRS
			Can detect absolute changes in CBF if using contrast enhanced NIRS	Repeated calibration with tracer injection if using CW-NIRS
			Can monitor cerebral oxygen metabolism	Bulky/expensive
			Can monitor cerebral oxygen metabolism	Lack of commercially available devices
DCT	Analyzes CBF data from DCS using many source-detector pairs and a wide FOV	Dynamic, 3D imaging of CBF	Obtaining spatial information in focal injuries	Susceptible to noise, artifacts
DCT		Dynamic, 3D imaging of CBF	Obtaining spatial information in focal injuries	Decreased penetration to deeper tissues