Click to allow Flash. Software was adapted from earlier models It began development in In X-Ray mode a shield was needed due to the higher energy. In each mode bending magnets had to be set before it fired 6 Problems with Therac 25 Problems in the design process Software reuse management Failure of testing Failings of the risk assessments Irresponsible usage 7 Therac 25 design problems Attempted to combine functionality from previous versions for lower cost Apparently no consultation with stakeholders – such as medical technicians Over confidence in the previous designs resulting in complacency 8 Software Reuse Therac 25 borrowed heavily from previous Therac designs. Loop to delay until magnets set Appears to check for new data entry while waiting 5. Enter patient id, prescription, field size, gantry rotation and accessory info 6.
Computers reduce risk over mechanical systems. You can choose whether to allow people to download your original PowerPoint presentations and photo slideshows for a fee or free or not at all. Software Failures – ‘Those who cannot remember the past are condemned to repeat it’ Lots CSE , Wed-Fri, 12pm Therac Case PowerPoint Presentation. Do you have PowerPoint slides to share? Leave treatment room 5.
Software Safety Basics – a product performs predictably under normal and abnormal conditions, and Do you have PowerPoint slides to share? Or use it to upload your own PowerPoint slides so you can share them with your therca, class, students, bosses, employees, customers, potential investors or the world. The computer selects and implements an action without any human involvement.
PPT – Therac Case PowerPoint Presentation – ID
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Charles Kim Fall Webpage: Detects data entry 2. By elon Follow User. Download Presentation Connecting to Server. Help Preferences Sign up Log in. A patient has complained that he has received a radiation overdose during a treatment session caused by the malfunctioning of the Therac unit.
Software Safety Case Study Medical Devices : Therac 25 and beyond Matthew Dwyer. – ppt download
The computer tells the operator the options available and suggests one. What role do safety and risk play? It’s also worth putting extra effort stuvy getting the specification right, as it Software Failures – ‘Those who cannot remember the past are condemned to repeat it’ Lots Writing and Analyzing Ethics Cases in Business.
Therac 25 Lessons Engineering Computers provide greater reliability than the devices they replace. Leveson theraac al, 10 Failure of risk assessment AECL did not perform a proper risk assessment of Therac 25 Hardware would be the primary cause of failure Believed overdosing of patients was impossible 11 Software issues Used flags to synchronise processes Used 8-bit flags which were prone to overflowing Created race condition between magnet control and keyboard control The error messages were indecipherable to users technicians 12 Implications If the user entered any data while the gun was being set it did not react However the rest of the system did react, allowing unshielded X-Rays to be fired A race condition in a real-time system!
Therac 25 Incident – PowerPoint PPT Presentation
Pppt are all artistically enhanced with visually stunning color, shadow and lighting effects. Our new CrystalGraphics Chart and Diagram Slides for PowerPoint is a collection of over impressively designed data-driven chart and editable diagram s guaranteed to impress any audience. Reuters June 28, According to a study by the U. Therac 20 and Therac 6 relied on hardware safety systems Therac 25 removed the hardware safety Therac 25 software had the same bugs as found in Therac 20 9 Testing of Therac 25 As software came from Therac 20 it was assumed to be bug free AECL assumed only hardware failures were possible as software doesnt degrade syudy time AECL performed a safety analysis on the Therac and apparently excluded the software.
PowerPoint PPT presentation free to view. Loading SlideShow in 5 Seconds. Formal Verification of Computer Systems – Civil engineering. Malfunction 54but the system allows the operator to press a “proceed” key to retry the treatment.
Click to allow Flash. Introduction to Software Engineering and the Software Lifecycle