1. A method of medical image processing comprising: capturing a plurality of time separated images of a target region of interest of a patient, wherein the plurality of time separated images capture a time-varying behavior of said target region of interest; selecting a plurality of imaging units from each of the plurality of captured time separated images, wherein the selected plurality of imaging units are at the same location within each of the plurality of captured time separated images; representing each of the selected plurality of imaging units by a value; for each imaging unit location, using the corresponding values to determine a temporal difference for the selected imaging units; selecting temporal differences above a threshold limit; and constructing a noise reduced image based on the selected temporal differences.