[Economic evaluation studies in diagnostic imaging: justification and critical reading]

First, this article describes the concepts and tools most widely used for economic evaluation in healthcare. Second, it discusses some elements that must be taken into account in the social decision about how much we are willing to spend to prolong a person's life by one year. Third, it describes the criteria recommended for the critical analysis of publications that evaluate the economic aspects of health interventions. Finally, several studies about ultrasound screening for aneurysms of the abdominal aorta are used as illustrative examples to show how these elements and criteria can be applied.