A method is provided for updating a uniformity map of a detector. The detector defines a detector surface area. The method includes positioning a flood on a sub-portion of the detector surface area of the detector. The flood defines a flood area that is smaller than the detector surface area. Also, the method includes collecting counts from the flood for the sub-portion of the detector surface area. Further, the method includes updating an adjustment portion of the uniformity map using the counts collected for the sub-portion of the detector surface area, wherein the adjustment portion corresponds to at least a part of the sub-portion of the detector surface area.