Table 7.

Advantages and limitations of the perfusion assessment techniques.

Perfusion technique	Laser Doppler flowmetry (LDF)	Laser speckle contrast imaging (LCSI)	Spectral imaging methods (LDS, DRSI, NIRS)	Ultrasound (US)	Sidestream dark field (SDF) Orthogonal spectral polarization (OSP) Real-time optical vascular imaging (RTOVI)	Intravital microscopy (IVM), Video capillaroscopy, Optical coherence tomography angiography (OCTA), Narrow band imaging (NBI)
Advantages	Non-contact Relatively easy to perform	Non-contact Wide field of view (can up to cover few teeth) Provide anatomical images and perfusion data	Allow evaluation of tissue composition/property, such as oxygenation, hemoglobin concentration, and water content	Cross-sectional (good penetration depth than the other optical-based techniques) Provide anatomical images, vessel distribution, perfusion direction, and velocity/volume of blood flow	Non-contact High spatial resolution Visualize capillaries True blood velocity measurements	Non-contact High spatial resolution Visualize capillaries True blood velocity measurements
Disadvantages	Arbitrary tissue perfusion units provided No anatomical images Limited penetration depth	Arbitrary tissue perfusion units provided Limited penetration depth Large sensor (molars are hard to image)	Limited penetration depth Lower sensitivity Generally, no anatomical images provided	Surrogate tissue perfusion Need contact via coupling agent	Limited penetration depth Sensitive to motion Limited field of view	Very limited penetration depth Very sensitive to motion Limited field of view Standardization challenge Time-consuming data analysis Dye needed for IVM High cost