Figure 5. Time–signal intensity curves from dynamic contrast-enhanced MR imaging show faster and stronger enhancement and faster washout in prostate cancer (1) than in normal tissue (red curve, 2). The x-axis shows the number of series in MR imaging, and the y-axis shows the signal intensity in arbitrary units. The onset time (a) is the time at which signal intensity began to increase. The time to peak (b) is the period between the onset time and peak enhancement. The wash-in rate (c) represents the velocity of enhancement and is defined by d–c/b–a, where d represents the maximum (peak) enhancement, which is defined as the absolute maximum value of enhancement. Maximum (peak) relative enhancement is defined as the difference between the absolute maximum value of enhancement and the baseline signal intensity. The washout rate is defined as the velocity of enhancement loss. The shaded area represents the area under the time–signal intensity curve for prostate cancer.