The issue of accountability arises when a community expects its agents to stand up for the quality of their work. The FDA restructured its reporting requirements for radiation equipment after these incidents.Īs computers become more and more ubiquitous and control increasingly significant and complex systems, people are exposed to increasing harms and risks.
Furthermore, AECL had great difficulty reproducing the conditions under which the issues were experienced in the clinics. The premature assumption that the problem(s) was detected and corrected was unproven.
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The software was inadequately tested, and “patches” were used from earlier versions of the machine.
After this incident, Leveson and Turner (1993) compiled public information from AECL, the FDA, and various regulatory agencies and concluded that there was inadequate record keeping when the software was designed. Although the AECL was quick to state that a “fix” was in place, and the machines were now safer, that was not the case. On February 6, 1987, the FDA placed a shutdown on all machines until permanent repairs could be made. They relied primarily on hardware for safety controls, whereas the Therac-25 relied primarily on software. The Therac-6 and Therac-20 were clinically tested machines with an excellent safety record. There was some “base duplication” of the software used from the Therac-20 that carried over to the Therac-25. These units had built-in safety interlocks and positioning guides, and mechanical features that prevented radiation exposure if there was a positioning problem with the patient or with the components of the machine. The Therac-6 and Therac-20 units were built with a microcomputer that made the patient data entry more accessible, but the units were operational without an onboard computer. There were two earlier versions of the Therac-25 unit: the Therac-6 and the Therac-20, which were built from the CGR company’s other radiation units–Neptune and Sagittaire. The Food and Drug Administration (FDA) later found that there was an inadequate reporting structure in the company, to follow up with reported accidents. Lawsuits were filed, and no investigations took place. Reports to the manufacturer resulted in inadequate repairs to the system and assurances that the machines were safe. The machine was recalled in 1987 for an extensive redesign of safety features, software, and mechanical interlocks. Patients reported being “burned by the machine” which some technicians reported, but the company thought was impossible. Unfortunately, six accidents involving significant overdoses of radiation to patients resulting in death occurred between 19 (Leveson & Turner 1993). AECL sold eleven Therac-25 machines that were used in the United States and Canada beginning in 1982. With the aid of an onboard computer, the device could select multiple treatment table positions and select the type/strength of the energy selected by the operating technician. The Therac-25 was the most computerized and sophisticated radiation therapy machine of its time.
The Therac-25 machine was a state-of-the-art linear accelerator developed by the company Atomic Energy Canada Limited (AECL) and a French company CGR to provide radiation treatment to cancer patients.
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