Table 1.
Summary of each endoscopic diagnostic technology
| Technique | Excitation spectra | Frame rate (Hz) | Achievable spatial resolution (μm) |
Penetration depth (mm) | Functional information | Real morphologic image | Whether the probe is in direct contact with the tissue surface while operating | ||
|---|---|---|---|---|---|---|---|---|---|
| HSI | Visible & Near-IR | > 30 | < 250 | 1 | ✔ | ✔ | – | ||
| FLIM | UV-Blue | 20–120 | < 50 | < 0.1 | ✔ | ✔ | Non-contact | ||
| PAE | Visible & Near-IR | 2–5 | 10 | > 1 | ✔ | ✔ | Contact | ||
| OCT | Near-IR | < 50 | < 3 | 2–4 | ✘ | ✔ | Non-contact | ||
| CARS | Near-IR | 0.01–0.2 | < 3 | > 1 | ✔ | ✔ | Non-contact | ||
|
TPEF/ SHG |
Near-IR | 1–8 | < 1 | 0.2–0.3 | ✔ | ✔ | Contact or non-contact | ||
|
3PEF/ THG |
Near-IR | 0.05–0.1 | 1 | 0.2–0.7 | ✔ | ✔ | Contact or non-contact | ||
| DRS | Visible | 0.02–2 | – | < 1 | ✘ | ✘ | Contact | ||
| LSS | Visible | 0.02–0.05 | – | < 1 | ✘ | ✘ | Non-contact | ||
| a/LCI | Near-IR | 1–4 | – | < 0.5 | ✘ | ✘ | Contact | ||
| RS | Near-IR | 0.1–10 | – | > 1 | ✔ | ✘ | Contact | ||
HSI: hyperspectral imaging; FLIM: fluorescence lifetime imaging microscopy; PAE: photoacoustic endoscopy; OCT: optical coherent tomography; CARS: coherent anti-Stokes Raman scattering; TPEF: two-photon excited fluorescence; 3PEF: three-photon excited fluorescence; SHG: second-harmonic generations; THG: third-harmonic generations; DRS: diffuse reflectance spectroscopy; LSS: light-scattering spectroscopy; a/LCI: angle-resolved low coherence interferometry; RS: Raman spectroscopy