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

Hamilton radiotherapy accident, 1985

compiled by Wm. Robert Johnston
last modified 23 September 2007

Date: 26 July 1985

Location: Ontario Cancer Foundation, Hamilton, Ontario, Canada

Type of event: radiotherapy accident


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.


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