To understand the relationship between each tissue, we performed a cluster analysis of the nine tissues used in this study. Through the RRF-BP modeling process, we recorded the explanatory variable combinations producing the 10 lowest RMSE values. Based on this data, after normalization clustering was performed using the cluster hierarchy function of the SciPy package (ver. 1.7.3) in Python (ver. 3.7.10). A dendrogram was obtained from hierarchical clustering using Euclidian distance and Ward's method.