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Accident Accounts

Linda Knight: June 3,1985

61-year old Linda Knight had been receiving follow-up treatment at the Kennestone Regional Oncology Center (Marietta, GA) for the removal of a malignant breast tumor. On June 3, staff at Kennestone prepared Knight for electron treatment to the clavicle area, using the Therac-25 machine.

Knight had been through the process before, which was ordinarily uneventful. This time, when the machine was turned on, Knight felt a "tremendous force of heat… this red-hot sensation." When the technician re-entered the therapy room, Knight said, "you burned me." The technician replied that that was "not possible."

Back home, the skin above Knight's left breast began swelling. The pain was so great that she checked in at Atlanta's West Paces Ferry Hospital a few days after the Therac incident. For a week, doctors at West Paces Ferry continued to send Knight back to Kennestone for Therac treatment, but when the welt on her chest began to break down and lose layers of skin, Knight refused to undergo any more radiation treatment.

About two weeks later, the physicist at Kennestone noticed that Knight had a matching burn on her back, as though the burn had gone through her body. The swelling on her back had also begun to slough off skin. Knight was in great pain, and her shoulder had become immobile. These clues led the physicist to conclude that Knight had indeed suffered a major radiation burn. Knight had probably received one or two radiation doses in the 20,000-rad (radiation absorbed dose) range, well above the typical prescribed dosage of around 200-rads. The physicist called AECL and, without telling of the accident, asked questions about the likelihood of radiation overexposure from the Therac 25 machine: Could Therac 25 operate in electron mode without scanning to spread the beam? Three days later AECL engineers called back to say this was not possible.

Linda Knight was in constant pain, lost the use of her shoulder and arm, and her left breast had to be removed because of the radiation burns.