Table 3.
Optical techniques for perfusion monitoring of the gastric wall after gastrectomy.
| Methods | Optical Principle | Evaluation Unit | Physiological Evaluation | Depth of Imaging | Demand for Fluorescent | Vantages | Drawbacks | Future Prospects |
|---|---|---|---|---|---|---|---|---|
| LSCI | Laser scattering pattern | Laser Spot Perfusion Unit (LSPU) | Scatter contrast inversely proportional to flow rate | 700–1000 μm | No | 1. Continuous and real-time assessment 2. Combining with ICG for physiologic imaging 3. Spatio-temporal precision and accuracy |
1. Evaluation limited to the serosal layer 2. High angle and space requirements |
Exploring applications in minimally invasive surgery |
| TI | Temperature of the tissue surface | Anastomotic Viability Index (AVI) |
AVI = L-GEAa × TRra(AVI ≤0.61 suggests high leak risk) | 2000 μm | No | 1. Direct measurement of blood flow distribution 2. Repeatable measurement 3. Suitable for minimally invasive surgery |
1. Only still photos can be observed 2. Inability to clearly visualize vascular structures 3. Narrow application scope, requiring frequent algorithm changes |
Software development and algorithm expansion are needed to broaden the scope of suitable surgical applications |
| HSI | Analysis of light interactions (absorption, reflection) on tissue surfaces, reflecting various intrinsic biochemical properties of the tissue. | oxygen saturation (StO2), near-infrared perfusion index (NIR), hemoglobin index (THI), and tissue water index (TWI) et al. | StO2 in HSI dataset reflects tissue perfusion | 6 mm | No | 1. Providing rich and fine spectral characterization 2. Simultaneous provision of two-dimensional spatial information 3. Complementary advantages with fluorescence imaging 4. Repeatable observations 5. Easy selection of areas of interest |
1. Still images only 2. Inability to provide information in small spaces (meaning difficult to assess after reconstruction) 3. Lack of real biological parameters to confirm the accuracy of HSI |
1. Translating HSI technology into virtual reality, and Visualization of spatial data 2. Minimally invasive HSI |
| LDH & VLS | Laser, Doppler shift and the absorption spectra | rHba，StO2 | Decrease in StO2 and increase in rHb, reflecting inadequate tissue perfusion and increased venous venous congestion | 500 μm | No | 1. Fast, less invasive and highly reproducible. 2. Measurements are done through microcatheters, suitable for laparoscopic surgery. 3. Easy operation |
1. Need for quantitative values from a wider range of samples to improve reliability 2. Tissue structure and perfusion cannot be visualized |
Results from a large number of more extensive studies are needed to standardize the way microcirculation is assessed for clinical use. |
a
L-GEA:length ratio of the gastroepiploic artery. TRr: temperature retain rate. rHb:relative hemoglobin amount.