Accidental Overdose In Medical Radiation


Engineering is, alongside very few, perhaps the most important profession in human history. The engineering systems designed and manufactured have a wide range of application avenues such as medicine, civil works and housing, agriculture and other relevant fields to people all over the world. As such, an intense code of ethics has been developed and implemented over the years to ensure that the engineering practice is monitored and freed from malice and malpractice contrary to the set code of ethics regarding the practice. Concurrent engineering developed in the latter 20th century makes use of computer design systems and software’s to create, design and manufacture new engineering related machinery and innovations. The use of computers in engineering systems do not necessarily create new ethical issues regarding the practice, they, however, create new ways in which ethical issues in engineering affect the practice.

Case study: The 1986 Therac-25 associated radiation therapy overdose

The Therac-25 radiation machine was a dual-mode linear accelerator designed to deliver X-ray photons at 25 MeV, or electrons over a given range of energies. The X-rays were used relatively on deeper tumors than the electrons relative to the skin surface.

The unique factor at the time regarding this machine was the fact that it was designed to be controlled by software only. It did not incorporate the level of hardware safety devices found in other earlier machines (Leveson and Turner, 1993).In Texas, 1986 to be exact, a particular therac-25 machine had been in use for 2 years and had treated about 500 patients. One particular patient was prescribed, around March, an 180 rads of 22MeV over a 170 cm2 area of her upper back. The machine malfunctioned, displaying the wrong dosage administration value as well as administering 16500 and 25000 rads on 1cm2 of the patient’s upper back. The result was complications resulting from radiation poisoning and subsequent death of the patient (Leveson and Turner, 1993).The investigation regarding the death of the patient indicates that a software malfunction; more so a lack of proper hardware and software time alignment in the execution of beam reset features in the machine. The software indicated the beam intensities had been reset while the beam itself needed time to process and execute the reset intensities. The result was higher doses being administered when the software displayed effective execution of the beam intensity changes (Leveson and Turner, 1993).

The time misalignment between the software and hardware was blamed on an exclusive over-reliance on the software without proper hardware features incorporated to prevent such occurrences and human errors as well as glitches in the software development with regards to inadequate documentation and testing (Leveson and Turner, 1993).

While many might argue that this is an exclusive software problem and hence the software developers should take the blame, the fact that there was an over-reliance on the software without fully incorporating hardware systems to prevent such occurrences is the ultimate sin, as far as engineering ethics is concerned. The machine is mostly an engineering innovation and therefore, operations on the same should be mostly engineering related. Software’s cannot be a good replacement for effective engineering judgment. The company responsible for the manufacture of the machine failed to incorporate all available engineering analysis systems and evaluations regarding the machine. Its failure seemed farfetched due to the perceived accuracy of the software but it was imminent due to lack of good engineering judgment.

The engineer who used the faulty software without proper assessment was also at fault, on the ethics scale.

The engineers’ codes of ethics put emphasis on the importance of engineers being on top of probable flaws regarding any engineering related innovation, even if the probable flaw is software related.The failure of the therac-25 was due to inadequate participation in the development and analysis of the machine. The engineers failed by not doing enough in researching on the probable malfunction of the machines or even being effectively involved in the project. It is primarily an engineering project, the software part of the project is secondary, therefore proper engineering evaluations should have been done.

The purpose of new designs is to make the old designs better. The new design, in my opinion, as well as the opinion of the attached professional engineer,  should not omit elements of the older design unless such elements are hazardous or better-streamlined elements replace the old element. The overall skeleton of the new system should be perfectly in line with the old one.

Proper analysis regarding the safety of the new system should be done before the design is released into the market. Safety should be the primary role of engineers.

As seen in this case study, hardware’s and software’s should be properly intertwined to ensure proper safety of a machine and its elements while in use. Software safety features like alert systems and quantity monitoring features within any machine should be accompanied by a hardware backup system of the same in the case of a system failure in the software. A backup manual hardware input should be available. When software’s experience failures and malfunctions, they should be adequately shut down and manual hardware input and control mechanisms put into play.


If the execution of the project/machine is primarily engineering related and isn’t directly affecting human life, the engineer should be at liberty to write and test the software, in the case of simple software. In the case of more complex software’s, a professional software expert should work alongside the engineer.In the case of delicate and life affecting projects, both professionals should work together and be fully involved in the development and testing of the software to avert cases like the one cited in this paper.In my opinion, engineering codes should be used in each and every engineering related project, even if it marries with other disciplines and are adequate in the evaluation of the case study because it is primarily an engineering project. The system analysis failure by the engineers resulted in the deaths of five other patients in the same situation. The fact that they could have done something to prevent the loss of lives but didn’t should be a clear indication of the ethical failures of the engineers involved.

It is the collective agreement between myself and the engineer I consulted regarding this case study that whenever engineering practice and software’s marry in any project an evaluation should be done to find out the role of both the engineer and the software developer in design, simulation and testing (finite element analysis) of the project. A failure of any software incorporated engineering project is more so the fault of the engineer rather than the software development. It is the duty of the engineer to be on top of such projects.



In order to avert potential hazards like the one cited in this paper, more should be done by engineers in accordance with the engineers’ codes of ethics in design, analysis, and testing of projects/ innovative machines developed in any engineering related industry.

Concurrent engineering allows for the simultaneous engineering related processes of design, manufacture and finite element analysis between professionals working on a project. The introduction of CAD/CAM in engineering has made the practice less complicated than before. There is, therefore, no excuse for an engineering project to fail, or put anyone in danger for that matter. In my opinion, stricter laws should be enacted, in accordance with the engineering codes of ethics to ensure lives are protected and preserved around the engineering practice.

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