The Software Bug That Overdosed Six Cancer Patients | Therac-25

A radiation therapy machine delivered massive overdoses to at least six patients between 1985 and 1987. Two died within weeks. Every single time a hospital reported it, the manufacturer's answer was the same word: impossible. This is the story of the Therac-25, a cancer treatment machine that replaced the physical safety interlocks of its predecessors with software alone, and the two separate, unrelated bugs hiding in that software that nobody found until it was too late. Built from the primary academic investigation (Leveson & Turner, IEEE Computer, 1993), FDA correspondence, and lawsuit records, not the shorthand version of this story you may have heard before. CHAPTERS 0:00 Cold Open 0:55 A Machine Built On Trust 5:04 Removing the Safety Net 6:56 Three Accidents, Three Denials 10:33 The Flaw Nobody Would Believe 14:15 Tyler, Texas: The First Overdose 17:06 Three Weeks Later 19:57 A Second, Unrelated Bug 24:19 What It Took to Find the Truth 26:08 The Law That Changed After Therac 27:52 Closing SOURCES Nancy Leveson & Clark Turner, "An Investigation of the Therac-25 Accidents," IEEE Computer, July 1993 U.S. FDA correspondence and Corrective Action Plan records, 1986-1988 Failure Point covers engineering, architecture, and design failures, and corrects the popular version of each story against the primary record before telling it. #Therac25 #EngineeringFailure #SoftwareBug #MedicalDeviceSafety #TrueStory