1. A method for producing a time-resolved three-dimensional image of a subject, the method comprising: acquiring image projection data from the subject using a medical imaging system during a single contrast injection, the medical imaging system including a single source/single detector system; generating a time-series of two-dimensional images from at least a portion of the acquired image projection data; reconstructing a three-dimensional image substantially without temporal resolution from at least a portion of the acquired image projection data; and producing a time-resolved three-dimensional image having a signal-to-noise ratio substantially higher than a signal-noise-ratio of the acquired image projection data by selectively combining the three-dimensional image substantially without temporal resolution and the time-series of two-dimensional images.