# Texture Analysis of Near-Infrared Vein Images During Reactive Hyperemia in Healthy Subjects
## 3 Results  
Table 3 presents the median and 95% confidence interval values for vein width and all calculated textural parameters across the different phases of the reactive hyperemia procedure. Figure 3 illustrates the temporal profile of each textural parameter throughout the procedure. Vein width increased significantly during occlusion (\(p<0.001\)). However, it did not fully return to baseline during the recovery phase, remaining significantly higher than at baseline (\(p=0.020\)). Conversely, most individual textural parameters, including contrast, energy, entropy, homogeneity, fractal dimension, and lacunarity, did not exhibit significant changes during occlusion. The exception was correlation, which increased significantly (\(p=0.023\)) and returned to baseline levels during recovery. Lacunarity demonstrated a progressive decline over time, reaching a value significantly lower than baseline during recovery (\(p=0.024\)). Among the composite indices, both entropy-to-width and correlation-to-width ratios decreased significantly with occlusion (\(p<0.001\) for both) and did not recover to baseline values. Conversely, total entropic content increased significantly with occlusion (\(p<0.001\)) and remained elevated during recovery.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & **Baseline** & **Occlusion** & **Recovery** & \multirow{2}{*}{\(p\)**-Value**} & \multirow{2}{*}{\(p\)**-Value**} \\  & **(Phase I)** & **(Phase II)** & **(Phase III)** & **(O vs. B)** & **(R vs. B)** \\ \hline Contrast & 0.021 (0.015; 0.025) & 0.020 (0.015; 0.024) & 0.021 (0.017; 0.025) & 0.397 & 0.737 \\ Correlation & 0.902 (0.882; 0.922) & 0.913 (0.900; 0.929) & 0.920 (0.914; 0.946) & 0.023 * & 0.074 \\ Energy & 0.699 (0.628; 0.786) & 0.661 (0.540; 0.716) & 0.696 (0.631; 0.795) & 0.600 & 0.157 \\ Homogeneity & 0.989 (0.987; 0.992) & 0.990 (0.988; 0.992) & 0.989 (0.987; 0.991) & 0.512 & 0.912 \\ Entropy & 4.25 (4.15; 4.42) & 4.16 (4.00; 4.34) & 4.18 (4.11; 4.42) & 0.198 & 0.083 \\ Fractal dimension & 12.462 (12.439; 12.480) & 12.463 (12.429; 12.63) & 12.463 (12.423; 12.485) & 0.060 & 0.319 \\ Lacunarity & 1.06 (0.95; 1.15) & 0.98 (0.72; 1.05) & 0.97 (0.79; 1.05) & 0.136 & 0.024 * \\ Vein width (mm) & 2.19 (2.12; 2.28) & 2.55 (2.34; 2.54) & 2.28 (2.14; 2.33) & \textless{}0.001 * & 0.020 * \\ Entropy-to-width & & & & & \\ ratio & 1.87 (1.69; 2.01) & 1.67 (1.57; 1.79) & 1.80 (1.67; 1.91) & \textless{}0.001 * & 0.228 \\ Correlation-to-width ratio & & & & & \\ width ratio & 0.403 (0.375; 0.420) & 0.368 (0.350; 0.388) & 0.404 (0.379; 0.412) & \textless{}0.001 * & 0.641 \\ Total entropic content & & & & & \\ Correlation-to-entropy ratio & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Median and 95% confidence interval values for the vein width and textural parameters in the different phases of the reactive hyperemia procedure (* \(p<0.05\)).  
Figure 2: NIRI image from a representative subject, showing a region of venous confluence on the dorsal hand. Three rectangular regions of interest are marked, corresponding to a superficial metacarpal vein and its two associated tributaries, which were selected for texture analysis.