Statistical analysis
A Wilcoxon rank-sum test evaluated the difference between the HU of pre-contrast enhancement (HUpre) and that of post-contrast enhancement (HUpost). We compared the mean HU in the DDFT and palmar arteries at each site, calculating the difference between HUpre and HUpost(HUpost − HUpre) of the DDFT. Statistical analyses were performed using the non-parametric Kruskal− wallis rank-sum test and Spearman’s rank correlation analysis for assessing groups. A Wilcoxon rank-sum test was performed for the post-hoc test. The P value was adjusted using the Bonferroni method. Statistical significance was set at P < 0.05. All statistical analysis was processed using RStudio (RStudio, Boston, MA).