A reconstruction processor(24) reconstructs diagnostic data from a diagnostic imaging device, such as a CT scanner(10), starting before a contrast agent reaches a region of interest(50), as the concentration of contrast agent in the region of interest builds(52), and at a contrast agent peak(56). The plurality of images generated while the contrast agent concentration is building are aligned(78). A change map is generated indicative of a rate-of-change(62) gradient or a time-to-peak(64) for corresponding pixels or voxels of the images generated during the time the contrast agent is building to the peak. A segmentation processor(70) uses the change map in segmenting the diagnostic images generated without contrast agent or at the contrast agent concentration peak. |