## 3 Results  
The demographic and clinical data of all patients are summarized in Table 1. A total of 18 acne patients were enrolled in this study. Among them, ten patients were male and eight patients were female. Their mean age was 22.7 years. All patients were between 16 and 35 years old. All 18 patients completed this study. Five patients were taking oral antibiotics for acne: doxycycline and minocycline. There were no patients who had been treated with systemic retinoids and had a high probability of becoming pregnant or a propensity for keloids or immunosuppression. Figure 2: Evaluation of the number of lesions exceeding the erythema threshold (NET) and summation of the area exceeding the erythema threshold (Pixel %) using a skin color analysis system. (**a**) SpyderCUBE® and SpyderChkecker® for correction of white balance, exposure color, and black and white values. (**b**) Facial region extraction with the Viola–Jones algorithm before (**c**) and after (**d**) converting into a CIELAB image. (**e**) A* channel images. (**f**,**g**) Area higher than the threshold-specific erythema value from A* channel images to evaluate the number of lesions exceeding the erythema threshold (NET) and the summation of the area exceeding the erythema threshold (pixel %). Tables 2 and 3 summarize the clinical results. Almost all patients experienced decreases in the number and area of lesions. The mean number of NET (the number of lesions exceeding the erythema threshold) was significantly decreased from the first visit to the final visit (forehead, \(p\) = 0.039; left malar, \(p\) = 0.031; and right malar, \(p\) = 0.012). The mean number of Pixels % (summation of the area exceeding the erythema threshold) was significantly decreased from the first visit to the final visit for the left malar (\(p\) = 0.007) and the right malar (\(p\) = 0.002), but not for the forehead (\(p\) = 0.181). The forehead Pixel % showed no statistically significant difference after treatment. Additionally, a comparison was conducted between adjacent visits. Tables 4 and 5 summarize the clinical results. NET (number of lesions exceeding the erythema threshold) on the forehead was significantly different between visits 1 and 2 (\(p\) = 0.015). Pixel % \begin{table}
\begin{tabular}{l c} \hline \hline
**Patient Information** & **No (\%)** \\ \hline Sex, \(n\) (\%) & 10 (55.6\%) \\ Male & 8 (44.4\%) \\ Female & 8 (44.4\%) \\ \hline Age (years) & Mean age 22.7 (16–35) \\
11–20 & 6 (33.3\%) \\
21–30 & 11 (61.1\%) \\
31–40 & 1 (5.6\%) \\ \hline Oral Medication & 5 (27.8\%) \\ \hline Total & 18 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Demographic data of acne vulgaris patients. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Area** & **V1** & **V2** & **V3** & **V4** \\ \hline \hline \multicolumn{5}{c}{NET (number of lesions exceeding the erythema threshold)} & \multicolumn{1}{c}{\(p\)-value} \\ \hline Forehead & 1.83 & 0.33 & 0.11 & 0.33 & 0.039 \\ Left malar & 49.72 & 26.61 & 14.94 & 17.83 & 0.031 \\ Right malar & 49.00 & 24.50 & 12.00 & 15.44 & 0.012 \\ \hline \multicolumn{5}{c}{Pixel \% (summation of the area exceeding the erythema threshold)} & \multicolumn{1}{c}{\(p\)-value} \\ \hline Forehead & 0.0623 & 0.0203 & 0.0039 & 0.0053 & 0.181 \\ Left malar & 1.1191 & 0.5532 & 0.2639 & 0.3041 & 0.007 \\ Right malar & 1.5382 & 0.7496 & 0.3476 & 0.3186 & 0.002 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mean NET (number of lesions exceeding the erythema threshold) and Pixel % (summation of the area exceeding the erythema threshold) and Pixel % (summation of the area exceeding the erythema threshold) of acne vulgaris patients at each visit, suggested [median, IQR].