1. A method comprising: acquiring, with a detector defining a field of view (FOV), emission imaging data of an object over the FOV; determining, with one or more processing units, a volume of interest (VOI) of the emission imaging data, wherein the VOI defines a volume smaller than an imaged volume of the object; performing, with the one or more processing units, a multivariate data analysis on the VOI to generate a waveform for the VOI; determining, with the one or more processing units, an amount of motion for at least the VOI based on the waveform; and displaying, on a display unit, at least one of information corresponding to the amount of motion or an image reconstructed based on the emission imaging data.