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Accident Accounts

Janis Tilman: December 1985

Janis Tilman was being treated with the Therac-25 machine at the Yakima Valley Memorial Hospital in Yakima, Washington. After one treatment in December 1985, her skin in the treatment area, her right hip, began to redden in a parallel striped pattern. The reddening did not immediately follow treatment with the Therac-25 because it generally takes at least several days before the skin reddens and/or swells from a radiation overexposure.

Tilman continued Therac treatment until January 6, 1986 despite the reddening, since it was not determined that the reddening was an abnormal reaction. Hospital staff monitored the skin reaction and searched unsuccessfully for possible causes for the striped marks.

The hospital sent a letter to AECL and spoke on the phone with AECL's technical support supervisor, who later sent a written response stating, "After careful consideration, we are of the opinion that this damage could not have been produced by any malfunction of the Therac-25 or by any operator error." The hospital staff dismissed the skin/tissue problem as "cause unknown," partly due to the response from AECL, and partly because they knew AECL had already installed additional safety devices to their Therac-25 machine in September 1985.

Upon investigation in February 1987, the Yakima staff found Tilman to have a chronic skin ulcer, dead tissue, and constant pain in her hip, providing further evidence for a radiation overexposure. Tilman underwent surgery and skin grafts, and overcame the incident with minor disability and some scarring related to the overdose.