A method and apparatus for calibrating an image of a specimen or subject obtained with an imaging modality or selecting a region of interest in the image. The apparatus comprises: a graduation support adapted for mounting on the specimen or subject； and one or more calibration graduations supported by the graduation support； the one or more calibration graduations are imagable with the imaging modality, and are distinguishable in the image from the graduation support and from the specimen or subject, and at least one of the calibration graduations have at least one characteristic of known value.
