1. A method for producing a time-resolved three-dimensional image of a subject, the method comprising the steps of: a) acquiring image data from the subject using a medical imaging system; b) generating a time-series of two-dimensional images from at least a portion of the acquired image data; c) reconstructing a three-dimensional image substantially without temporal resolution from at least a portion of the acquired image data; and d) producing a time-resolved three-dimensional image of the subject by selectively combining the three-dimensional image substantially without temporal resolution and the time-series of two-dimensional images.