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Therac-25
The Therac-25 is a computer-controlled radiation therapy machine produced by Atomic Energy of Canada Limited (AECL) in 1982 after the Therac-6 (neptune) and Therac-20 units (the earlier units had been produced in partnership with Compagnie générale de radiologie (CGR) of France).
The Therac-25 was involved in at least six accidents between 1985 and 1987, in which some patients were given massive overdoses of radiation. Because of concurrent programming errors (also known as race conditions), it sometimes gave its patients radiation doses that were hundreds of times greater than normal, resulting in death or serious injury. These accidents highlighted the dangers of software control of safety-critical systems.
The Therac-25 has become a standard case study in health informatics, software engineering, and computer ethics. It highlights the dangers of engineer overconfidence after the engineers dismissed end user reports, leading to severe consequences.
The French company CGR, a subsidiary of Thomson-CSF, manufactured the Neptune and Sagittaire linear accelerators.
In the early 1970s, CGR and the Canadian public company Atomic Energy of Canada Limited (AECL) collaborated on the construction of linear accelerators controlled by a DEC PDP-11 minicomputer: the Therac-6, which produced X-rays of up to 6 MeV, and the Therac-20, which could produce X-rays or electrons of up to 20 MeV. The computer increased ease of use because the accelerator could operate without it.[clarification needed] CGR developed the software for the Therac-6 and reused some subroutines for the Therac-20.
In 1981, the two companies ended their collaboration agreement. AECL developed a new double pass concept for electron acceleration in a more confined space, changing its energy source from klystron to magnetron. In certain techniques, the electrons produced are used directly, while in others they are made to collide against a tungsten anode to produce X-ray beams. This dual accelerator concept was applied to the Therac-20 and Therac-25, with the latter being much more compact, versatile, and easy to use. It was also more economical for a hospital to have a dual machine that could apply treatments of electrons and X-rays, instead of two machines.
The Therac-25 was designed as a machine controlled by a computer, with some safety mechanisms switched from hardware to software as a result. AECL decided not to duplicate some safety mechanisms, and reused modules and code routines from the Therac-20 for the Therac-25.
The first prototype of the Therac-25 was built in 1976 and was put on the market in late 1982.
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Therac-25 AI simulator
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Therac-25
The Therac-25 is a computer-controlled radiation therapy machine produced by Atomic Energy of Canada Limited (AECL) in 1982 after the Therac-6 (neptune) and Therac-20 units (the earlier units had been produced in partnership with Compagnie générale de radiologie (CGR) of France).
The Therac-25 was involved in at least six accidents between 1985 and 1987, in which some patients were given massive overdoses of radiation. Because of concurrent programming errors (also known as race conditions), it sometimes gave its patients radiation doses that were hundreds of times greater than normal, resulting in death or serious injury. These accidents highlighted the dangers of software control of safety-critical systems.
The Therac-25 has become a standard case study in health informatics, software engineering, and computer ethics. It highlights the dangers of engineer overconfidence after the engineers dismissed end user reports, leading to severe consequences.
The French company CGR, a subsidiary of Thomson-CSF, manufactured the Neptune and Sagittaire linear accelerators.
In the early 1970s, CGR and the Canadian public company Atomic Energy of Canada Limited (AECL) collaborated on the construction of linear accelerators controlled by a DEC PDP-11 minicomputer: the Therac-6, which produced X-rays of up to 6 MeV, and the Therac-20, which could produce X-rays or electrons of up to 20 MeV. The computer increased ease of use because the accelerator could operate without it.[clarification needed] CGR developed the software for the Therac-6 and reused some subroutines for the Therac-20.
In 1981, the two companies ended their collaboration agreement. AECL developed a new double pass concept for electron acceleration in a more confined space, changing its energy source from klystron to magnetron. In certain techniques, the electrons produced are used directly, while in others they are made to collide against a tungsten anode to produce X-ray beams. This dual accelerator concept was applied to the Therac-20 and Therac-25, with the latter being much more compact, versatile, and easy to use. It was also more economical for a hospital to have a dual machine that could apply treatments of electrons and X-rays, instead of two machines.
The Therac-25 was designed as a machine controlled by a computer, with some safety mechanisms switched from hardware to software as a result. AECL decided not to duplicate some safety mechanisms, and reused modules and code routines from the Therac-20 for the Therac-25.
The first prototype of the Therac-25 was built in 1976 and was put on the market in late 1982.