Dimitrios Christias Robert Lyon Andreas Petrou Dimitrios Christias Robert Lyon Andreas Petrou

 Therac-25 is a computer-controlled radiation therapy machine that was designed by Atomic Energy of Canada Limited (AECL).  It was used in medical institutions to destroy tumors.  Operates in a dual-mode.  Depends more on software routines to ensure safety.  Evolution of Software  Several accidents of radiation overdose happened between 1985 and 1987 using the Therac-25 due to software issues. Therac-6 Therac-25 Therac-20

 Concurrency problems - Therac-25 has a software system that allows concurrent access to shared memory. - The fundamental design of the system was flawed, as it lacked synchronization  Lack of safety - Therac-25 relied only on its software to ensure safety measures and handling errors  Lack of documentation - The system has been developed to display cryptic error messages - The user manuals did not indicate the danger of those malfunctions for the patient health.  Lack of testing - Limited and poor test coverage  The user centred design - User centred design concerns seemed to override patient safety  The role of Government - No information of the development, management and quality control procedures is available  Ignorance of the incidents - system users were unconcerned about the fact that Therac-25 was causing harm through its use

Adhere to basic principles of software engineering Proper testing Extensive documentation Re-using code Arrogance in the assumption that the software is safe Unrealistic risk assessment Interface design that focused on usability rather than safety

 Bozdag, E., Therac-25 and the security of the computer controlled equipment. [online], Ethics of Science and Technology. Available at [Accessed 01 October 2011].  Leveson, N., Medical Devices: The Therac-25. [online], University of Washington. Available at [Accessed 01 October 2011].  Lim, J., An Engineering Disaster: Therac-25. [online], Available at [Accessed 01 October 2011].