Application of computer-based expert systems to diagnostic medical problems has been described in many areas including clinical diagnosis and radiology. Expert systems are computer programs that contain encoded expert knowledge to provide expert advice. A modified observer-performance study was done comparing the efficacy of the Radiology Image Interpretation System (RIIS), ah expert system that diagnoses focal bone abnormalities, and radiology residents on a known set of 44 abnormal and 10 normal cases. Modified receiver operating characteristic curves for four inexperienced residents, five experienced residents, and RIIS were generated using the set of known radiographs. The true-positive rates of RIIS and the residents at false-positive rates of 0.05, 0.15, and 0.20 were estimated using the modified receiver operating characteristics curve and were compared using a paired t test. On the average, the RIIS system was less accurate when compared with experienced and inexperienced residents but the difference was only significant for experienced residents at a false-positive rate of 0.05. RIIS performed better than inexperienced residents when RIIS was used by experienced residents but this difference was not significant.
Copyright 9 1991 by W.B. Saunders CompanyKEY WORDS: ROC, observer.performer, expert system, diagnoses, image.
EXPERT SYSTEMS have been applied to a wide variety of medical problems including clinical diagnosis, radiology, laboratory test interpretation, and chemotherapy protocols. 1 Expert systems ate computer programs that contain encoded knowledge obtained from an expert in a speci¡ field. These programs use simple inference techniques and the encoded knowledge to produce expert advice for the user in the specific field. Several investigators have been studying the application of expert systems to radiographic image interpretation and consultation. 24 These systems have been used asa cognitive aid in their areas of expertise. Lodwick et al 4 produced a program for computer-aided diagnosis of primary bone tumors using an approach based on Bayes' formula of inverse probability. This type of program can estimate conditional probabilities, but may not be as useful asa cognitive aid as expert systems. A probability matrix was estimated using a large number of known cases. This program correctly predicted the pathological diagnosis in 77% of selected cases taken from the group on which the conditional probability matrix was based. 4RIIS was developed to study the application of expert systems to diagnosing bone tumors and other focal bone abnormalities. Knowledge is encoded in Radiology Image Interpretation System (RIIS) in two ways: (1) "if-then" rules and (2) a knowledge base of diseases and findings associated with those diseases. The "if-then" rules are used to make conclusions from specific information. When the "IF" portion of the rule is true then RIIS will conclude that the "THEN" portion of the rule is also true. Multiple "if-then" rules can be concluded sequentiaUy allowing complex analysi...