Chain of Events. Cause and Effect. We analyse what went right and what went wrong as we discover that many outcomes can be predicted, planned for and even prevented.


episode 39: Therac-25

The successor to the Therac-6 and Therac-20 RadioTherapy machines would integrate the powerful DEC PDP-11 mini-computer to control all of the Therac-25s functions, including the safety interlocks, for the first time. In two years the 11 machines in service would overdose six people across two countries, killing three of them before they figured out why.
With John Chidgey.

This show is Podcasting 2.0 Enhanced

Reports into the Incidents:

  • An Investigation of the Therac-25 Accidents
  • ?Medical Devices: The Therac-25
  • The Therac-25: 30 Years Later
  • A Usage-Model Based Approach to Test Therac-25
  • Good Computing: A Virtue Approach To Computer Ethics: Chapter 6

Links of Potential Interest:

  • Therac-25
  • The PDP-11 Assembly Language
  • PDP-11
  • Digital Equipment Corporation
  • Programmed Data Processor
  • Rad (unit)
  • Order of Magnitude
  • Myelitis
  • Collimator
  • Fatal Dose: Radiation Deaths linked to AECL Computer Errors
  • Reactor Accidents: The Human Fallout
  • An Overview on Radiotherapy: From Its History to Its Current Applications in Dermatology
  • In MedTech History: Mammography
  • The programmer behind the THERAC-25 Fiasco was never found
  • AMA: My professor investigated the Therac-25 incident
  • How history, principles and standards led to the safety PLC

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Episode Gold Producers: 'r' and Chip Salzenberg.
Episode Silver Producers: Mitch Biegler, John Whitlow, Kevin Koch, Oliver Steele, Lesley Law Chan, Hafthor and Shane O'Neill.