[The "right choice" in medical imaging studies: the radiologist's viewpoint--application to lumbosciatic pain]

These past few years, very efficient imaging technologies, which are not traumatic for the patient, but often quite expensive, have been developed. Within the context of budgetary restrictions, these progress require a carefully planned strategy on the choice of investigations. First of all basic rules are defined: "the most simple act", "the direct way", "the direct exploitation of results", "the therapeutic relevance", "the multidisciplinary integration". Several erroneous types of behaviour are also described: "the most comprehensive set of examinations", "the examination in fashion", "the exaggerated medico-legal fear". Finally, these principles apply to a common clinical situation: lumbosciatic pain. Relevant examinations are first spotted: standard examination, myelography, discography, CT scan, MRI. A synthetic diagnostic approach is then suggested. The latter rules out any complementary study in the case of non-chronic common lombosciatic pain and in the absence of certain revealing signs. In the other cases, the correct combination of conventional radiology, nuclear medicine, CT and MRI is suggested, according to the clinical context.