The present invention concerns a method and an arrangement for reducing noise in a substance raw data image containing noise. The method may comprise following steps in any order for removing different noise signals contributions step-by-step in any order in a substance raw data image: reducing background radiation; reducing peak disturbance; locating the detection area within the search area; moving binary artifacts; removing unwanted areas of the detection area; and applying default detection area in noisy images). The present invention also relates to a method and an arrangement for determining a measure of at least one substance.