Bulletin Spring‧Summer 1997

by fuzzy sets in the form of 11 numbers, which denote different degrees on an imaginery conceptual continuum. Fuzzy numbers are used to store fuzzy certainty factors ranging between -1.0 and 1.0, with negative factors reflecting disconfirmation. Built in a PC environment, Z-III can handle both exact and inexact reasoning. Example: Rule: If height is tall and sex is male, then weight is heavy. Certainty factor is 0.7. (Both 'tair and 'heavy' are fuzzy concepts.) Data Input: Height is 'very t a l l ' . Sex is 'male'. Certainty factor is 0.9. Inference: Weight is ' very heavy'. Certainty factor is 0.63. Three Medical Ex pert Systems From Z-III, three medical expert systems called ABVAB, INDUCE36, and ESROM have been developed. ABVAB can diagnose the cause of abnormal vaginal bleeding from the past history and physical examination results of a patient. While medical knowledge is represented as expert rules, imprecise medical concepts are represented by fuzzy types such as 'freshness of blood: Certainty factors indicate the degree of confirmation for the individual diagnoses. The expert system gives more than one possible diagnosis, in order of preference, and the first preference has the highest certainty factor. A consultation with ABVAB involves making numerous inferences using the expert rules stored in the knowledge base and the information stored in the medical data base, which can be accessed by the users during a consultation. A sample diagnostic conclusion of the possible causes of abnormal bleeding in a patient, in preference order, is shown in Table 1. Forty-four real patient cases were used to verify the accuracy of ABVAB, and the results were satisfactory. (Table 2) Ta ble 1 'Diagnoses Made by ABVAB It is extremely certain (0.97) that the diagnosis should be dysfunctional uterine bleeding. It is very certain (0.95) that the diagnosis should be pelvic infection. It is very certain (0.94) that the diagnosis should be malignant genital tumour. It is indeed certain (very close to 0.92) that the diagnosis should be benign genital tumour. It is pretty certain (0.8) that the diagnosis should be complications of pregnancy. It is quite certain (0.72) that the diagnosis should be hormone induced. It is almost certain (0.6) that the diagnosis should be a foreign body in the vagina. It is somewhat certain (0.58) that the diagnosis should be endometriosis. It is somewhat certain (0.53) that the diagnosis should be genital injury. It is little certain (0.32) that the diagnosis should be an intrauterine contraceptive device. Ta bl e 2 Correct D iagnoses Made by ABVAB P e r c e n t a g e As the first choice 68 As the first three choices 90 Listed 100 Chinese University Bulletin Spring . Summer 1997 38