Angiographic data is obtained by injecting a chemical contrast agent intravascularly, and imaging passage of the contrast as a function of time, thereby generating a sequence of images. To correct error from uncalibrated timestamps embedded in the image metadata, radio-opaque markers are used to generate a watermark embedding timestamp data in obtained images. The radio-opaque markers cause opacification on the x-ray images in the form of dynamic watermarks that encode timestamps. The positions of the markers in the watermark (cast from the radio-opaque markers) are then processed and analyzed to generate an accurate timestamp for the image. By generating an accurate timestamp, synchronized calculations of the images with other data sources are provided.
