Essay --

INTRODUCTION Nowadays. Information technology (IT) is a familiar term for the people and the expert. This technology is developing rapidly and introducing in all social fields as well as influencing on all sciences and being affected by the other sciences. All processes and steps of remedial –healthy cares have been depended heavily on management information and its transfer. Information technology is also used increasingly for new medical practices, effective and active management of health cares and medical profession knowledge. In medical profession is necessarily required the informed scientists and intelligent expert having enough knowledge of related matters, comprehensive knowledge of medical devices and its technology as well as information and communication technologies. Medical informatics (data processing ) science which is developing and growing rapidly includes decision making based on the information, therapy display, systematic management, information saving and its retainin g, management system, model identifying and image and signal processing. Expert system is a subdivision of artificial intelligence and an expert system is the one having expertise within a special field and may be applied to that field for decision making and/or helping the expert people for decision making [1]. Expert system is a component of the process for intelligently automation of the processes regarded as artificial intelligence. Once John MC charty created Lisp language in masachoset institute of technology in 1960, it was as the initial step toward an expert system . from that date onward, a variety of expert systems have been developed and applied like CMS, XI-PLUS, ROSIE, OPS5, EMYCIN, EXPERT and so on. An expert system is comprised o... ... beyond the studying of direct relationship and subject not found among the nodes. Maybe the most important problem in giving the network and the most important interests in processing rule were needed to be identified gradually and this need was related to both the knowledge and cognition of small zone parts and the alignment of experts sharing in this study. since the expert did not use these cases for autopsy and interpreting , their clinical reasoning, asking them to say whatever they know was completely vain. Nevertheless, discussing with some special patients with severe diseases and encouraging our colleagues in interpreting the trends and their decisions, some of them who were n’t expert in a field got information about a piece of knowledge of applied environment, that is, personal inferencial realities which an expert regards them in solving the problem[2].