The present invention relates to detection of contrast agent arrival in X-ray imaging. In order to provide an improved way of detecting contrast agent arrival in X-ray imaging for reducing the delay in the detection, a temporal sequence of X-ray image data is provided (102) comprising a plurality of frames with a field of view of an anatomy of interest and an inserted catheter for delivery of contrast agent, wherein, in the field of view, contrast agent is injected with the catheter during the temporal sequence. At least one location for measuring contrast in each of the frames is determined (104), wherein the at least one location for measuring contrast pertains to a portion of the catheter in the field of view in the image data. Contrast is measured (106) at the at least one location for each of the frames at least in the image part pertaining to the portion of the catheter. A change of the measured contrast along time at the at least one location pertaining to the portion of the catheter is determined (108). Further, an instant of contrast agent arrival in the field of view of the anatomy of interest is provided (110) as a function of the instant along time with the change of contrast.
