Fig 4.

Normal vessels: comparison of different matrix measurements. Graph shows differences in mean vessel measurements between the 512 matrix and the 256 and 256 ZIP matrices; the results for each observer are shown separately. Error bars indicate the standard deviation of the measurements. Compared with the 512 matrix, the 256 matrix consistently led to overestimation of the size of the vessel. With ZIP, however, a small but significant reduction in luminal diameter was noted for all observers; these results were not significantly different from those of the 512 matrix.