1. A magnetic resonance imaging system, comprising: a user interface configured to receive a user input from a medical professional, the user input corresponding to one of a maximum imaging time, an overall reduction factor, or a minimum signal-to-noise ratio; at least one radio frequency coil with a plurality of coil elements configured to perform a scan of a subject; and at least one electronic processor programmed to: generate a plurality of sets of reduction factors along corresponding reduction directions from the received one of the maximum imaging time, the overall reduction factor, or the minimum signal-to-noise ratio, wherein the reduction directions correspond to at least one encoded direction; construct a signal map from the scan of the subject and a plurality of noise maps corresponding to the sets of reduction factors from the scan of the subject and the sets of reduction factors, wherein at least one of the noise maps optimizes signal-to-noise ratio and scanning speed; select one of the sets of reduction factors corresponding to one of the noise maps that optimizes the signal-to-noise ratio and the scanning speed; perform a magnetic resonance imaging scan of the subject based on the selected reduction factors.