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  • Privacy
    In order to accurately report on any accident sensitive medical data about individuals would need to be collected by treatment facilities and made available to national agencies These national agencies might in turn make this data available internationally In our case data about the accidents was shared by agencies of the Canadian and US governments It seems possible to make the data on patient records related to medical accidents anonymous

    Original URL path: http://computingcases.org/case_materials/therac/analysis/Privacy.html (2016-04-30)
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  • Equity and Access
    free market on the price of technology If AECL could make a less expensive but equally useful linear accelerator it would sell more of them and they would be more easily available to the public AECL would doubtless make money in the process This is Adam Smith s invisible hand at work decisions to make a better less expensive product are good both for the manufacturer and for the consumer

    Original URL path: http://computingcases.org/case_materials/therac/analysis/Access.html (2016-04-30)
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  • Honesty and Deception
    this information and are thus more dependent on the organization Engineers including software engineers have the capability of evaluating the claims though they may be allowed little time in which to do so Again we find a balance between the engineer s responsibilities to the company use time efficiently and to the consumer evaluate carefully claims made about the product Because of their special expertise it is precisely the role of a professional to balance these conflicting responsibilities and not to neglect responsibility to the consumer What organizational responsibilities might there be regarding claims of safety in medical devices AECL representatives in several instances made claims that no overdoses had occurred with the Therac 25 machine when there was clear evidence that someone at AECL must have heard of several previous accidents This suggests that there may have been some internal miscommunication within AECL Some portions of the organization may have known about the lawsuit regarding radiation harm but not have had the time or seen the need to inform other parts of the organization For instance those in the legal division hearing of the lawsuit may have assumed that the engineers were aware of the issue and that there

    Original URL path: http://computingcases.org/case_materials/therac/analysis/Honesty.html (2016-04-30)
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  • Analyzing Therac-25
    small sections of the case e g just the background early in a course and add information about the case as the course progresses Each of these approaches are likely to produce differences in the way the case is analyzed by students These differences help make it clear how important a comprehensive view of a case is Our modified paramedic ethic procedure consists of 4 phases The basic analysis consists of phases 1 and 2 in which the basic relationships among the important stakeholders in the case are outlined The phases that construct and judge the various alternative scenarios can be done as many times as you wish for each set of actions you think are important To make this go faster you might assign groups to construct and present their analysis of the duties and rights of each of the main stakeholders presented in the case AECL FDA hospitals operators and patients Gather data List the relevant stakeholders Start with some of the groups mentioned in the socio technical system page However do not end there Notice that our accident victims the patients are not included Other important groups may also be omitted e g the public The ImpactCS framework provides you with a useful guide to different levels of stakeholders that you might overlook Outline the duties and rights the stakeholders have toward each other This is best done with a drawing of each stakeholder with arrows indicating duties one owes to other and rights one has Duties always have targets one has duties to a particular person even to oneself Rights may appear to be free floating e g not to be harmed but they can often be translated into duties that others have toward the individual avoid harming X The ImpactCS framework provides a useful guide

    Original URL path: http://computingcases.org/case_materials/therac/exercises/analyzing_therac.html (2016-04-30)
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  • Computer Control Choices Exercise
    analysis The operator does everything The computer tells the operator the options available The computer tells the operator the options available and suggests one The computer suggests an action and implements it if asked The computer suggests an action informs the operator and implements the action if not stopped in time The computer selects and implements an action if not stopped in time and then informs the operator The computer selects and implements an action and tells the operator if asked The computer selects and implements an action and tells the operator if the designer decides the operator should be notified The computer selects and implements an action without any human involvement After students have explored the case have them decide at what level the Therac 25 system is targeted This may initially cause some confusion since one way of looking at the system is to think that the operator tells the computer what to do and then the computer does it Point out to them that this is true in the larger sense but that the computer clearly has sensors and information available to it to allow it to give error messages What do we know about the level in this control hierarchy at which those error messages are resolved What levels of computer control is the system using when an error message is given e g Malfunction 54 but the system allows the operator to press a proceed key to retry the treatment vs as required by the FDA the treatment is suspended after any error and all treatment data must be typed in over again or when the operator is required to visually check the settings on the treatment machine vs when the machine sets itself up based on the treatment data entered and then proceeds with

    Original URL path: http://computingcases.org/case_materials/therac/exercises/computer_control_exercise.html (2016-04-30)
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  • Tracing the Coding Errors to the Hazards
    system that resulted in overdoses to patients Have students trace each coding error from the problematic variable or operation e g a comparison to how this resulted in an overdose What items or sections in the code you have reviewed should be labeled safety critical Why How is it different from other sections of code What information is available in the design that the code is safety critical Assume you

    Original URL path: http://computingcases.org/case_materials/therac/exercises/coding_errors.html (2016-04-30)
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  • Software Safety Myths
    that of analog or electromechanical devices Software is easy to change Computers provide greater reliability than the devices they replace Increasing software reliability will increase safety Testing software and formal verification of software can remove all the errors Reusing software increases safety Computer reduce risk over mechanical systems After having the class explore the Therac 25 case ask students to evaluate the truth of each of these statements as they

    Original URL path: http://computingcases.org/case_materials/therac/exercises/safety_myths.html (2016-04-30)
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  • Designing a Reporting System
    office and to other sites and then getting resolutions of the problems communicated back to the sites In some cases AECL was only notified by lawsuit months after an incident In other cases information languished at the home office that might have been useful to sites where the machine was being used In this exercise you will ask your class to design a reporting system and to evaluate its impact on the various stakeholders in the case In her book Safeware System Safety and Computers p 88 Nancy Leveson lists four requirements of a successful reporting system Explicit delegation of responsibility for reporting Who should report accidents and to whom What about other errors or malfunctions What kind of deadlines and penalties should be imposed Whose responsibility should it be for imposing deadlines and penalties e g the company the FDA Protection and incentives for informants If hospitals or manufacturers are required to report errors incidents or accidents there is likely to be some resistance to reporting all errors because of liability issues What sort of protection and incentives might be given to increase accuracy Who else within the system other than an official representative might be a useful informant Procedures for analyzing incidents and identifying causal factors When an accident or error is reported who should investigate the facts How should the person or panel identify causal factors Procedures for using reports and generating corrective actions When causal factors have been identified who should be notified of the analysis What requirements and deadlines should there be for generating corrective actions Use these requirements to design a reporting system that might help to reduce the risk to patients Make sure to address all four points requirements in a successful system This exercise might be done as an in class exercise

    Original URL path: http://computingcases.org/case_materials/therac/exercises/reporting_system.html (2016-04-30)
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