# Assessment and Feasibility Study of Lemon Ripening Using X-ray Image of Information Visualization
## 4 Discussion  
The theory behind radiography is related to the linear attenuation coefficients of ionizing radiation through substances of uneven densities. The linear attenuation coefficients of X-ray through substances are proportioned to substance densities [42]. The imagining grayscale value of each pixel represents the image converted from the pixel element density [43]. In the fields of food and agriculture, the radiography technique is only used for quality control based on visual differences. For example, in the food industry, the technique based on visual differences of radiography has been widely used [44] and the thresholding of image segmentation technique has been applied with DR to explore the influences of quality loss in fruits caused by plant diseases and insect pests [45]. As for the application of radiography in this study, besides using visual differences for quality control, the DICOM standard was also used to produce monochrome grayscale images, combined with the quantified statistical methods, to analyze the quality and freshness of fruits [24; 46]. The standard errors of the means of the grayscale values and the 95% CIs were all under one, meaning the X-ray output exposure quality and the linear attenuation of the substances of uneven densities were quite stable, proven by the accuracies of the results obtained using the quantified statistical method with the grayscale values, as shown in Table 1 [47]. Figure 5: (**A,B**) represent two different phases. The images show the quantified statistical analysis results of (1) fresh, (2) mature, and (3) overripe lemons based on the four-layer stratification of lemon, peel, fiber, and pulp. The \(p\) values less than 0.05 are summarized with one asterisk. According to Table 1, the SEM results showed that the variations of the means of the grayscale values of the grayscale images were rather low, and the corresponding 95% CI results were consistent. The linear regression results are shown in Figure 6. The stratified analysis results of the (A) median-plane and (B) axial-plane images of the lemons showed that the coefficients of determination R\({}^{2}\) of the lemon, fiber, and pulp layers were all higher than 0.8 [48]. The coefficients dropped with freshness of the lemon and pulp layers, and increased of the fiber layer. Only the peel layer did not exhibit any consistent trend. This finding is consistent with the study on the citrus growth [49], verifying the feasibility of applying the non-destructive radiography grayscale imaging and statistical methods on analyzing lemon ripening. The results indicate that the pulp layer is the best region for statistical analyses to determine the lemon ripening, as the averaged gray values at the layer have a significant change with the increase of lemon ripening. The primary limitation of the study lies in a limited number of lemons for evaluation, although the scope of the study is to evaluate the feasibility of lemon ripening evaluation based on the image quantification of X-ray radiological images. Our preliminary results are promising, and additionally, cirtuses have a similar structure to lemons. Further work should be made to collect more lemons and other cirtuses for advanced analysis and