Database of radiological incidents and related events--Johnston's Archive

Tyler radiotherapy accident, 1986

compiled by Wm. Robert Johnston
last modified 11 May 2005

Date: 21 March-11 April 1986

Location: East Texas Cancer Center, Tyler, Texas, USA

Type of event: radiotherapy accident


A defect in the computer program controlling the Therac-25 radiation therapy accelerator resulted in overexposures to two patients. One male patient was overexposed on 21 March, immediately experiencing pain from an estimated 16,500 to 25,000 rad localized dose. Various radiation injuries developed over the next few weeks and the patient died 5 months after the accident. The second patient, also male, received an overexposure to the face on 11 April which produced immediate skin burns. The patient eventually went into a coma and died 1 May of radiation injury to the brain and brain stem. An ETCC physicist eventually identified the nature of the software program that caused this and similar accidents with the Therac-25.

Consequences: 2 fatalities.


© 2004, 2005 by Wm. Robert Johnston.
Last modified 11 May 2005.
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