MYCIN

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MYCIN

• Presented By
• Meenaxi Chandra
• Varun Kumar Sonker
• M.Tech IT(IS)- I Sem

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Topics

• What is MYCIN
• History
• Tasks Methods
• Rule based system MYCIN
• Certainty factor
• How MYCIN works
• Organisation of MYCIN
• MYCIN contains
• MYCIN dialogs
• MYCIN recommendations

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MYCIN(1970)

• MYCIN is an expert system that can recommend
  appropriate therapies for patients with bacterial
  infections.

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MYCIN

• MYCIN was developed at Stanford University in the
  mid-1970s.
• It was designed to aid physicians in the
  diagnosis and treatment of meningitis and
  bacteremia infections.
• MYCIN was the first large expert system to
  perform at the level of a human expert and to
• provide users with an explanation of its
  reasoning.

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MYCIN

• Task
• Diagnosis and prescription for bacterial
  infections of the blood (and later meningitis).
• Method
• Rule-based .
• Backward reasoning (from a specific goal back to
  known facts)
• Performs depth first, exhaustive search of all
  rules.
• Utilizes certainty factors

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Rule-Based Systems MYCIN

• IF (1) the stain of the organism is
  gram-positive, and
• (2) the morphology of the organism is coccus,
  and
• (3) the growth conformation of the organism is
  clumps.
• THEN
• there is suggestive evidence(0.7) that the
  identity of
• the organism is staphylococcus.
•  

• MYCIN used rules to compute certainty factors for
  hypotheses
• find rules whose conclusions match the hypothesis
• obtain CF's for premises (look up, use rules,
  ask, ) and compute the CF for the conclusion
• combine CF's obtained from all applicable rules.

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MYCIN Certainty Factors

• The skeleton in the MYCIN closet?
• What do certainty factors mean?
• How are they combined?
• Rules should be commutative and associative

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Certainty Factors

• several rules contribute to one hypothesis
• what is our belief in several propositions taken
  together?
• what is our belief in the result of rule
  chaining?

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Certainty Factors

• Measure of belief MBh,e
• Measure of disbelief MDh,e
• CFh,e MBh,e - MDh,e

Additional Evidence
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Certainty Factors
Combination of Hypothesis

• MBh1 ? h2,e min(MBh1,e ,MBh2,e )
• MBh1 ? h2,e maxMBh1,e ,MBh2,e )
• Disbelief computed analogously
• Needed for calculating the certainty factor of a
  rule antecedent with several clauses.

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Certainty Factors Example

• Measure of belief given two observations is
  measure of belief given one observation an
  increment.

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How Mycin Works

• Diagnose for infectious diseases.
• Identify infection that require therapy.
• What is the identity of the organism.
• primary, strilite, gram neg, morph rod, air
  aerobic.
• What are the potencially usefull drugs
  
• chloramphenicol (0.99)
• clindamycin (0.99)
• erthromycin (0.57)
• tetracycline (0.28)
• carbenicillin (0.27)
• 5. Which will be best ? (Uses Meta rule )

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Organization of MYCIN
MYCIN
PATIENT
RULE BASE
MEDICAL EXPERT
PATIENT DB
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Mycin contains
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MYCIN -- A typical consultation

• 1. Patients name (first - last)       UPENDRA
  HAGWAT .
• 2. sex                  M
• 3. Age                55
• 4. Are there any cultures for Upendra Hagwat
  which may be related to
• the present illness, and from which organisms
  have been grown successfully in the microbiology
  laboratory?
•                Y
•                     - - - CULTURE - 1 - - -
• 5. From what site was the specimen for CULTURE -
  1 taken?
•              BLOD                  BLOOD
• 6. Please give the date and time when CULTURE-1
  was obtained. (mo/da/yr time)
• JUN 20, 1977 The first organism isolated
  from the blood culture of 20-JUN-77 (CULTURE-1)
  will be referred to as   

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- - - ORGANISM - 1 - - -

• 7. Enter the laboratory - reported identity of
  ORGANISM-1                      UNKNOWN
• 8. The strain of ORGANISM-1         NEG
  (Preliminary lab results give some clues).
• 9. Is ORGANISM - 1 rod or coccus (etc.)
                       ROD
• 10. What is the form of the individual organisms
  (e.g. lancet-shaped for cocci, fusiform for rods,
  etc)?                      FUSIFORM
• .
• .
• .
• .
• .
• .
• .
• .

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Orgnasim1

• 23. What is the suspected portal of entry of the
  gramneg rod from the blood culture of 20-JUN-77
  (ORGANISM-1) into this site?
•                      GI (6)
• 24. Is Upendra Hagwat a burn patient?
                       N 25. Is Fred Braun a
  compromised host (e.g. alcoholic,
  sickle-cell-disease, immunosuppressed)?
                       N
• 25. Is Upendra Hagwat febrile?                
       Y

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RECOMMENDATION

•    1 - colistin                
                                                   
                                         2 -
  polymyxin                                       
                                                    
             3 - gentamicin          
                                                   
                                         4 -
  carbenicillin                                    
                                                    
            5 - sulfisoxazole         
• MYCIN selects drugs only on the basis of the
  identity of offending organisms.

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-Why mycin-

• Addresses the problems of reasoning.
• Provide clear and logical exp. Of reasoning.
• Explore how human experts make these rough (but
  important) guesses.
• Useful for junior or non-specialized doctors.
• Gave birth to EMYCIN - PUFF .
• Advanced mycin-NEOMYCIN .