A method and a system for monitoring a bolus value are disclosed. The method includes contrast-agent-assisted test recording of a time series of test images of a region under examination, wherein one bolus value is determined in each of the respective test images, together with the change in the bolus values between at least two test images. The method includes regulating the time interval between the recordings of individual test images as a function of the change in the bolus values, thereby enabling the temporal resolution for determining the bolus value to be selected in such a way that it corresponds to the change in the bolus values. In this way the temporal resolution in the monitoring of bolus values is improved with a view to avoiding both too high and too low a recording rate for the test images.