1. Please read the below case and answer the following questions. (30 pts)

The Therac-25 machine was a state-of-the-art linear accelerator developed by the company Atomic Energy Canada Limited (AECL) to provide radiation treatment to cancer patients. The Therac-25 was the most computerized and sophisticated radiation therapy machine of its time. 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. AECL sold eleven Therac-25 machines that were used in the United States and Canada beginning in 1982.

Unfortunately, six accidents involving significant overdoses of radiation to patients resulting in death occurred between 1985 and 1987 (Leveson & Turner 1993). Patients reported being burned by the machine which some technicians reported, but the company thought was impossible. In the 35-year history of medical accelerators it was described as the worst series of radiation accidents. There was only one person doing the programming for this system, and he did all the tests to a great extent.

In particular, the operator must enter information into the treatment table and then re-enter the console in the control room. Operators complained; because it is extra work for them. Thus, protection removed. Error codes are reported on screen without any English description.

Example: Error 54 due to dose entry 2 reported. Technicians do not know if, input 2, means that the given dose is too high or too low! Failure after a non-critical error. Pause operator can ignore it by pressing P button.

1. Considering the above case, what kinds of problems do you see and how do you fix them? (15 pts)
2. If you were the CEO of AECL, what would you do now in order to fix your reputation in the industry? (15 pts)