Fig 3. Comparison of measured volume using three-dimensional ultrasound and estimated volume from 2D diameters $\left(\text{V=}\frac{\pi }{6}abc\right)$ with the true volume of tumor phantoms.

A-C) Plots of difference between the volume measurement and estimation against the true volume. The 95% limits of agreement (mean difference ± 1.96 SD) calculated using the Bland and Altman method were indicated as dashed line.