A method for assessing measurement quality in acquisition of an image of the interior of a medium (1) is provided. The method comprises the steps: subsequently irradiating the medium (1) with light from a plurality of different source positions (s) and, for each source position, detecting light emanating from the medium in a plurality of different detection positions (d) for acquisition of an image of the interior of the medium (1). The method further comprises the step: providing information about whether the measurement quality is deteriorated by exploiting signal symmetry under reversal of the light path.