Figure 3
Comparison of single-image evaluation scores in three anatomical regions. The box and whisker plots (upper row) show the median (line), mean (x), interquartile range (box) and internal fences (whiskers). The image processing technologies (DVA vs DSA) were compared by the Wilcoxon signed ranked test. whereas the non-inferiority of low-dose DVA images compared to normal dose DSA images (denoted by relation signs) was analysed by the one-sample Wilcoxon test (*p < 0.05, **p < 0.01, ***p < 0.001, = identical image quality, < superior image quality). The scatter plots (lower row) show the correlation of DSA100 and DVA30 scores with the Spearman correlation coefficients (rs). Each point represents the mean score of a normal dose DSA100 and the corresponding low-dose DVA30 image taken from the same patient and same position. Juxtaposed points show images with identical DSA and DVA scores. Open circles in the abdominal plot represent images obtained in the presence of large amount of intestinal gases (3 patients out of 30), rs’ is the correlation coefficient without these points. The diagonal line separates points with higher DSA100 (below the line) or higher DVA30 scores (above the line). DSA: Digital Subtraction Angiography; DVA: Digital Variance Angiography, n.s. not significant. The index shows the applied protocol, 100: normal dose (1.2 µGy/frame), 30: low-dose (0.36 µGy/frame).
