A method for automatically detecting the presence of contrast in an x-ray image includes acquiring an x-ray image prior to administration of contrast. A background image is estimated based on the x-ray image. The contrast is administered. A set of x-ray images is acquired. The background image is subtracted from the set of images. Image intensity is determined for each of the subtracted images. The subtracted images having highest image intensity are selected. A predefined shape model is fitted to the selected subtracted images. The fitting of the predefined shape model is used to fit the shape model to each of the subtracted images. A feature value is calculated for each image frame based on pixel intensities of each pixel fitted to the shape model for the corresponding subtracted image. An image frame of peak contrast is determined by selecting the image frame with the greatest feature value.