Donna Gartner: July 26,1985Donna Gartner, a 40-year old cancer patient, was at the Ontario Cancer Foundation clinic in Hamilton, Ontario, Canada for her 24th Therac treatment for carcinoma of the cervix.
The Therac-25 operator activated the machine, but after 5 seconds, the
Therac-25 shut down and showed an "H-tilt" error message. The
computer screen indicated that no dose had been given, so the operator
hit the "P" key for the "proceed" command. The Therac
shut down in the same manner as before, reading "no dose," so
the operator repeated the process a total of four times after the initial
After the fifth try, a hospital service technician was called but found
no problems with the machine. Donna Gartner left the clinic and the Therac
was used with six other patients that day without any incidents. However,
despite the fact that the Therac had indicated that no radiation dose
had been given during Donna Gartner's five therapy attempts that day,
Gartner complained of a burning sensation she described as an "electric
tingling shock" in the treated area of her hip.
Gartner returned for treatment three days later, on July 29, and was
hospitalized for suspected radiation overexposure. She had considerable
burning, pain and swelling in the treatment region of her hip.
AECL reported to a range of stakeholders that there was a problem with
the operation of Therac 25. The FDA, the Canadian Radiation Protection
Board (the parallel Canadian agency to the FDA), and other Therac-25 users
were all notified. Users were instructed to visually confirm that the
Therac turntable was in the correct position for each use.
Because of the Hamilton accident, AECL issued a voluntary recall of the
Therac-25 machines and the FDA audited AECL's modifications to the Therac.
AECL could not reproduce the malfunction that had occurred but suspected
some hardware errors in a switch that monitored the turntable position.
A failure of this switch could result in the turntable being incorrectly
positioned, and an unmodified electron beam striking the patient. The
company redesigned the mechanism used to lock the turntable into place,
redesigned the switch to detect position and it accompanying software.
They then reported in November 1985 that this redesign was complete and
that, given their safety analyses, the machine was now at least 10,000
times safer than before.
Donna Gartner died on November 3, 1985 from cancer. An autopsy revealed that had the cancer not killed Gartner, a total hip replacement would have been necessary because of the radiation overexposure.