The Therac-25 Software Disaster Essay

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The Therac-25 Software Disaster

The Therac-25 is a computerized medical radiation therapy machine for cancer patients. During the time span of June 1985 to January 1987, it was the source of six fatal or near fatal overdoses. These incidents were a result of a combination of factors that can be viewed as unethical actions made through the ranks of hierarchy, from the manufactures to the FDA.
The Therac-25 is a medical dual-mode linear accelerator that is used to target the less sensitive cancer cells of patients. The Therac-25 was not the first generation of this product. The previous versions, Therac-6 and Therac-20, were very similar, however the Therac-25 used more advanced technology. Compared to the Therac-20, the Therac-25 is more
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However, with programming it better to start a new and create a clean design. In this case, the same flaws that were discovered in the Therac-25 were also existent in the Therac-20. The difference between the success of the Therac-20 and 25 is that the Therac-20’s use of hardware to do appropriate safety checks prevented these flaws from being exposed. When the use of hardware was discarded in the Therac-25, the flaws were revealed over time in a series of accidents (Leveson).
The programmer also failed to do any testing or specifications of the software. The company (Atomic Energy of Canada Limited, AECL) should have done equal testing on the software and the unit as a whole. AECL eventually admitted that the testing was marginal on the software and the majority of the testing was preformed on the whole integrated system. The only the testing of the software was during the use of the product. The testing only showed how the product would not deteriorate over time. They were able to prove that the Therac-25 was reliable, but this is not the same as being safe. A clear sign that there was inadequate testing is that when pressed by the FDA, AECL struggled to present a test plan. One reason for the lack of testing could be attributed to the software programming being overly complex. This complexity lead to the inability to properly test that it functioned without

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