Date: September 1985-January 1986

Location: Yakima Valley Memorial Hospital, Yakima, Washington, USA

Type of event: radiotherapy accident

Description:

A defect in the computer program controlling the Therac-25 radiation therapy accelerator resulted in overexposures to patients. A woman who received several treatments from September 1985 to 6 January 1986 developed radiation burns which were not recognized as radiation injuries until another injury occurred in 1987.

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_2.html].

© 2004 by Wm. Robert Johnston.
Last modified 13 June 2004.
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