Method for pixel shift calculation in digital subtraction angiography and X-ray diagnostic imaging system for generating images in digital subtraction angiography

An X-ray diagnostic imaging system for generating images in digital subtraction angiography, in particular for conducting live fluoroscopic subtraction imaging, comprising:

• an X-ray source for directing X-ray radiation to a patient being examined;
• an X-ray imaging device positioned for receiving the X-ray radiation and acquiring images in response thereto;
• a processor arranged in communication with the X-ray source and X-ray imaging device to control acquisition of a mask image frame and live image frames, wherein one of the mask image frame and the live image frames is contrast-enhanced, to conduct a pixel shift vector calculation operation based on a region of interest (ROI) to realize a pixel shift vector to correct for motion between live image frames, to shift pixels comprising the mask image frame by pixel shift directions defined by the pixel shift vector, and to subtract the shifted mask image frame from the live image frames to realize improved images, in particular live roadmapping image frames;
• and
• a display for displaying the images,
• wherein the processor is configured to:
• assume possible shift vectors in the region of interest and calculating a scoring thereof, each possible shift vector being a difference vector between the mask image frame and a respective live image frame,
• determine the possible shift vector with the highest scoring and choosing it as an elected shift vector,
• calculate a likelihood p representing a quality value of the elected shift vector,
• calculate a modified shift vector depending on the elected shift vector and the likelihood p,
• shift the mask image frame with respect to the respective live image frame by the modified shift vector, and
• subtract the shifted mask image frame from the respective live image frame.