VISUAL INTERPRETATION KEYS
Keys that provide useful reference of refresher materials and valuable trainingaids for novice interpreters are called image interpretation keys. These image interpretation keys are very much useful for the interpretation of complex imageries or photographs. These keys provide a method of organising the information in a consistent manner and provide guidance about the correct identification of features or conditions on the images. Ideally, it consists of two basic parts' (i) a collection of annotated or captioned images (stereopalrs) illustrative of the features or conditions to be identified, and (ii) a graphic or word description that sets forth in some systematic fashion the image recognition characteristics of those features or conditions. There are two types of keys: selective key and elimination key.
Selective key is also called reference key which contains numerous examples images with supporting text. The interpreter select one example image that most nearly resembles the fracture or condition found on the image under study.
elimination key is arranged so that interpretation process step by step from
general to specific, and leads to the elimination of all features of conditions
except the one being identified. Eliminationkeys are also called
dichotomous keys where the interpreter makes a series of choices between two
alternatives and progressively eliminates all but one possible answer.