Fig. 6. Comparison of vertical and horizontal diameters (mm) of puncture circles. The vertical and horizontal diameters were measured from five overlapping images, and the mean and standard deviations were calculated. The results were 1.49 ± 0.08 mm (mean ± SD, n = 5) for the vertical and 1.53 ± 0.06 mm (mean ± SD, n = 5) for the horizontal, with no significant statistical difference (P > 0.05). N, number; n.s., no significant; SD, standard deviation.