Table 2.
Overview of the advancements and shortcomings of clinically available endoscopic imaging techniques.
| Technique | Advancements | Shortcomings |
|---|---|---|
| 4K/8K UHD | (i) Improving imaging resolution which makes it easier to distinguish minute blood vessels, lymph vessels, nerves, etc. (ii) Shooting with a wider range |
Realized in rigid laparoscopy or sinuscopy only |
| CF | (i) A higher resolving power (ii) Decreasing the minimum visible length to 2 mm |
— |
| Zoom | Enhance surface detail such as pit patterns and vascular detail | The durability of the mechanical zoom system needs further tests |
| NBI | Improving vascular contrast of capillaries and submucosal vessels based on narrow band light which corresponds to the main and secondary hemoglobin absorption peaks (415 and 540 nm) | The illumination intensity of the 1st generation NBI system is poor |
| RDI | Enhancing the visibility of blood vessels and bleeding sources in deeper tissue by using narrow band light at two center wavelengths (600 and 630 nm) in the red band | Lacking of further practical clinical experience and data since it has been officially put into clinical use for a very short time |
| BLI | (i) Highlighting the contrast between blood vessels and surrounding tissues (ii) Enhancing the visualization of relatively distant targets by changing the intensity ratio between blue and violet light (iii) Durable LED light source |
Unable to enhance the contrast of submucosal vessels, comparing with NBI |
| FICE | (i) Providing customized structural and vascular enhancement imaging presets based on spectral image processing algorithm (ii) Better analysis of the pit pattern and the normal-pathological mucosal junction |
(i) It is difficult to find the best FICE channels according to different clinical situations (ii) Unstable performance in detecting lesions |
| SPIES | Five imaging modes are proposed to be candidates according to various clinical situations | Few reports on clinical practice |
| I-scan OE | Integrating both digital algorithms and optical filters to enhance vascular and mucosal pattern characterization | The technique has just released soon; thus, well-designed clinical trials are warranted and highly anticipated |
| LCI | (i) Differentiating red color tones more effectively than white-light imaging between the malignant lesion and the surrounding area (ii) Originally red/white regions are represented redder/whiter |
Further validation for the diagnosis of malignant lesions is needed |
| AFI | Detecting neoplastic lesions by exciting endogenous fluorophores such as collagen and flavins in the tissue | (i) Imaging resolution is lower than WLE due to frame averaging, which is utilized to increase the quality of the autofluorescence image (ii) The intensity-based contrast is often not sufficiently specific |
| IRI, NIR/ICG | Enhancing contrast images of the vessels deep in the mucosa (up to 10 mm) | The false-positive rate of examinations may reach 40%–50% because the cirrhotic nodules and inflammatory hyperplasia can also emit fluorescence |
| PDD | Improving detection of hardly visible cancer based on the abnormal metabolism of tumor cells in the process of heme synthesis | (i) Phototoxicity of exogenous fluorophores (ii) The validation of the new effective PDD exogenous fluorophores is needed |
| EC | Visualizing mucosal microstructures in cellular level with high-frame-rate video (30 Hz) | (i) Unable to detect lesions under the mucosal surface (ii) Vital staining is relatively poor (iii) The durability of the ultra-zoom system |
| CLE | (i) Challenging in-vitro biopsy by identifying structures with cellular and subcellular resolution (ii) Optical sectioning ability |
(i) Relatively low frame rate (ii) The interpretation of the acquired image is challenging (iii) Limited lifespan |