[The heuristics of expert systems in radiodiagnosis]

In the practice of creating expert systems, the radiologist and his team are considered as "the expert" who leads the job of the "cognitian or cognitician". Different kinds of expert systems can be imagined. The author describes the main characteristics of heuristics in redefining semiology, semantics and rules of picture reading. Finally it is the experience of the couple "expert and cognitician" which will in the future grant for the success of expert systems in radiology.