Date: 26 July 1985

Location: Ontario Cancer Foundation, Hamilton, Ontario, Canada

Type of event: radiotherapy accident

Description:

A defect in the computer program controlling the Therac-25 radiation therapy accelerator resulted in an overexposure to a patient. A 40-year old woman being treated for cancer received a localized dose of 13,000 to 17,000 rads and quickly reported pain. Operators did not recognize the accident until the woman returned to the clinic with radiation burns on 29 July. The patient died of the original cancer on 3 November 1985.

Consequences: 1 injury.

References:

• Leveson, Nancy, and Clark S. Turner, July 1993, "An investigation of the Therac-25 accidents," IEEE Computer, 26:18-41, on line at Computer Science at Virginia Tech [http://courses.cs.vt.edu/~cs3604/lib/Therac_25/Therac_1.html].

© 2004, 2007 by Wm. Robert Johnston.
Last modified 23 September 2007.
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