Therac-25

The Therac-25 was a computer-controlled radiation therapy machine produced by Atomic Energy of Canada Limited (AECL) in 1982 after the Therac-6 (neptune) and Therac-20 units (the earlier units had been produced in partnership with Compagnie générale de radiologie (CGR) of France). The Therac-25 was involved in at least six incident overdoses of radiation between 1985 and 1987, leading to patient death in what was described as "the worst series of radiation accidents in the 35-year history of medical accelerators". Because of concurrent programming errors (also known as race conditions), it sometimes gave its patients radiation doses that were up to 250 times higher than normal, resulting in death or serious injury. These accidents highlighted the dangers of software control of safety-critical systems. The Therac-25 has become a case study in health informatics, software engineering, and computer ethics. The incidents highlight the dangers of engineer overconfidence after the engineers dismissed end user reports, leading to severe consequences.

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