Table 1.
Overview of in vivo oral perfusion techniques.
| Imaging techniques | Mechanism | Signal source | Field of view/ROI | Penetration Depth | Primary outputs | ||
|---|---|---|---|---|---|---|---|
| RBC velocity | Capillary characters, such as morphology density/diameter | Composition/property, such as Oxygenation, Hb concentration | |||||
| Optical technology | |||||||
| Laser Doppler Flowmetry (LDF) | Detecting the Doppler shift of laser light scattered by Hemoglobin (Hb) in moving red blood cells (RBC) | Diode laser with light wavelength of 630, 780 or 830 nm | Generally, 1 mm diameter | Up to 1 mm | X | Laser Doppler Flowmetry (LDF) | Detecting the Doppler shift of laser light scattered by Hemoglobin (Hb) in moving red blood cells (RBC) |
| Laser Speckle Contrast Imaging (LSCI) | Measure speckles that are produced when coherent light is scattered back from Hb of RBCs | Diode laser with infrared light | Depends on zoom power, in general 10–40 mm | Up to 1 mm | X | Laser Speckle Contrast Imaging (LSCI) | Measure speckles that are produced when coherent light is scattered back from Hb of RBCs |
| Laser Doppler Spectrophotometry | Detecting the Doppler shift of laser light scattered by moving RBCs | Diode laser with wavelength of 630, 780, or 830 nm and white light (500–800 nm) | Generally, 1 mm diameter | Up to 1 mm | X | Laser Doppler Spectrophotometry | Detecting the Doppler shift of laser light scattered by moving RBCs |
| Diffuse Reflectance Spectral Imaging (DRS) | Measure reflection of light to analyze tissue composition | UV and visible light (180–800 nm) | 8 × 8 mm | Up to 1 mm | Diffuse Reflectance Spectral Imaging (DRS) | Measure reflection of light to analyze tissue composition | |
| Near-infrared spectroscopy (NIRS) | Measure near-infrared light reflection to measure tissue composition | NIR (780–2,500 nm) | Generally, a few mm | Few cm | Near-infrared spectroscopy (NIRS) | Measure near-infrared light reflection to measure tissue composition | |
| Sidestream Dark Field (SDF) | Measure LED absorption/reflection by Hemoglobin in capillary | LED (530 nm) | Depends on zoom power, in general 1 mm | 500 μm | X | Sidestream Dark Field (SDF) | Measure LED absorption/reflection by Hemoglobin in capillary |
| Orthogonal Spectral Polarization (OPS) | Measure green light absorption by Hemoglobin in capillary | Linearly polarized light (530 nm) | Depends on zoom power, in general 1 mm | Up to 1 mm | X | Orthogonal Spectral Polarization (OPS) | Measure green light absorption by Hemoglobin in capillary |
| Intravital Videomicroscopy (IVM) | Image cells illuminated by light under microscope | Visible spectrum plus ultra-violet and near-infrared wavelengths (∼300–1,100 nm) | Depends on zoom power, in general 1–3 mm | Up to 1 mm | X | Intravital Videomicroscopy (IVM) | Image cells illuminated by light under microscope |
| Video capillaroscopy (VC) | Image capillary illuminated by light under microscope | Visible spectrum (400–700 nm) | Depends on zoom power, in general 1–3 mm | Up to 1mm | X | Video capillaroscopy (VC) | Image capillary illuminated by light under microscope |
| Optical coherence tomography (OCT) and optical coherence angiography (OCTA) | Image blood vessels patterns and density by light waves | 1,310 nm wavelength and 110 nm bandwidth | 5.25 mm × 5.25 mm | Up to 2 mmm | X | Optical coherence tomography (OCT) and optical coherence angiography (OCTA) | |
| Real time optical vascular imaging technique (RTOVI) | Image microvascular features by green light | Wavelength (550 ± 10 nm) | 0.51 × 0.51 mm | Up to 1 mm | X | Real time optical vascular imaging technique (RTOVI) | |
| Narrowband imaging (NBI) | Image mucosal surfaces and microvasculature by optical filters with light | Wavelenght filters vary 500, 445, and 415 nm with ∼30 nm bandwidth | Depends on zoom power, in general up to 100X | 170–240 μm | X | ||
| Imaging techniques | |||||||
| Ultrasound | Measure sound frequency changes due to RBC movement | Sound of 12–25 MHz | Depends on probe size, in general 15–20 mm | Up to 15 mm | RBC velocity | ||