Threshold contrasts of four digital subtraction angiography (DSA) systems were compared using a contrast-detail (C-D) phantom which can be used for the measurement of quantitative C-D diagrams. The C-D diagrams were determined form an observer performance study and were plotted on log-log curves for comparison of threshold contrast of the simulated vessels. The results indicated that the threshold contrast of DSA systems decreased by increasing the incident exposure to the image intensifier (I.I.). The slopes of the curves for three DSA systems were similar. However, one DSA system indicated a different slope. This is assumed that the artifacts in the subtracted image disturbed the appearance of the simulated vessels.
