An imaging system (10) comprises a data device (30), which controls radiation data acquisition from a subject positioned in an examination region (18) for an examination. A rebinning processor (40) bins the acquired data periodically into a histogram (42). A transform (70) transforms the histogram (42) into individual independent or uncorrelated components, each component including a signal content and a noise content. A stopping determining device (52) compares an aspect of at least one selected component to a predetermined threshold (TH) and, based on the comparison, terminates the data acquisition.