Therac-25 - Factbites

Therac-25 - Factbites
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Topic: Therac-25

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	The Therac 25 page
		The Therac 25 was a development of an earlier model, the Therac 20, which had also featured computer-based control but only as a convenient supplement to purely mechanical control features; the Therac 20 could still be used without computer control.
		The Therac 25 was successfully used to treat thousands of patients but unfortunately, turned out to be unsafe.
		In the Therac 25, all the mechanical controls (including safety features) were incorporated into software.
	homepage.ntlworld.com /g.aydin/website/therac_25_page.htm (777 words)

	Therac-25 - Wikipedia, the free encyclopedia
		Soft X-ray therapy, which used X-rays derived from high energy (25 MeV) electron beam via a "target", a device which converts electron beams into X-rays.
		Direct electron-beam therapy, which used low (5 MeV) to high (25 MeV) doses of energy over short periods of time;
		When operating in direct electron-beam therapy mode, a low-powered electron beam was emitted directly from the machine, then spread to safe concentration using scanning magnets.
	en.wikipedia.org /wiki/Therac-25 (494 words)

	'twURLed World' Thumbnail: THERAC-25 ACCIDENTS
		THERAC - 25 ACCIDENTS 25 ACCIDENTS THERAC - 25 ACCIDENTS adapted from a proprietary report from the AECL Research Co..
		THERAC -25 ACCIDENTS adapted from a proprietary report from the AECL Research Co..
		The Therac -25 is a machine that uses radiation & It is stated...
	www.twurl.com /twurled_world/therac/URL_Details/URL_13.htm (181 words)

	Computer Risk
		The Therac 25 generated a dose that was more than 100 times larger then the typical treatment does.
		Therac 25 (Typical Therac 25 Facility), The Canadian-built linear accelerator, the radiation-therapy machine.
		It was later revealed that if an extremely fast-typing operator entered in a certain sequence of commands, can result the device appear to have made the correct adjustment but in fact had an improper setting so it focused electrons at full power to a tiny spot on the body.
	www.glue.umd.edu /~xiao/risk.html (343 words)

	An Investigation of Therac-25 Accidents - I
		On July 26, 1985, a 40-year-old patient came to the clinic for her 24th Therac-25 treatment for carcinoma of the cervix.
		As a result of the Hamilton accident, the head of advanced X-ray systems in the CRPB, Gordon Symonds, wrote a report that analyzed the design and performance characteristics of the Therac-25 with respect to radiation safety.
		Using this double-pass concept, AECL designed the Therac-25, a dual-mode linear accelerator that can deliver either photons at 25 MeV or electrons at various energy levels (see Figure 1.
	courses.cs.vt.edu /~cs3604/lib/Therac_25/Therac_1.html (3797 words)

	Seminars
		The Therac 25 came into use around 1985 and the case covers a two year period in which the casualties occurred and investigations were carried out.
		There were predecessors of the Therac 25 that had a clean safety record.
		Revisit the Therac 25 papers to see if this theory would help analyse that case.
	www.cse.unsw.edu.au /~se4921/Seminars/Seminars.html (1123 words)

	Sordid (well, not really) tales of Brian Harring, aka ferringb: March 2005 Archives
		They created the therac 20, and therac 25- both had a software bug, except the later lacked hardware safeties, allowing the software bug to cause some seriously bad mayhem.
		therac 25 linear accelerator and qa (history for the younguns)
		For example, the first case of the bug involed a patient getting in the range of 15,000 to 20,000 rads, when the avg rad dose was around 200.
	dev.gentoo.org /~ferringb/blog/archives/2005-03.html (3927 words)

	Therac-25 accidents
		The Therac 25 is designed so that the operator selects either X-ray or electron-beam treatment, as well as a series of other items, by typing on a keyboard and watching a video display screen for verification of the orders.
		The malfunctions occurred once last year and twice in March and April of this year in two of the Canadian-built linear accelerators, sold under the name Therac 25.
		It was revealed that if an extremely fast-typing operater inadvertently selected the X-ray mode, then used an editing key to correct the command and select the electron mode instead, it was possible for the computer to lag behind the orders.
	www.mrs.umn.edu /~mcphee/Courses/Readings/Therac_25_accidents.html (839 words)

	The University of Michigan Health Physics Web Site: Brief Chronology Continued
		Therac 25 gives a Malfunction 54 software error which delivers an estimated 25,000 rad dose.
		1986 (April) Vernon Kidd, 66, receives a fatal overdose (estimated 25,000 rad) from a Therac 25 medical linear accelerator at the East Texas Cancer Center in Tyler, Texas.
		1987 (Jan 17) A patient at Yakima Valley Memorial Hospital, Yakima, Washington, receives approximately 11,000 rad overdose from a Therac 25 medical linear accelerator due to a software error.
	www.umich.edu /~radinfo/introduction/chrono5.htm (4286 words)

	Eye - Diagnosis: not maudlin - 05.09.02
		Examined from all angles, Therac 25 is a remarkable play, and not simply because this two-hander is beautifully written (by Adam Pettle of Zadie's Shoes fame), compassionately acted (Pettle again with Patricia Fagan) and delicately directed (by Adam's brother Jordan Pettle).
		Based on journals Adam Pettle wrote while under treatment for thyroid cancer in the early '90s, Therac 25 -- a remount of his 1997 SummerWorks hit -- follows Allan and Moira as they meet and forge a relationship in and outside of the hospital.
		With a running time of just under 50 minutes, it seems the creative team behind Therac 25 is aware of the potential pitfalls.
	www.eye.net /eye/issue/issue_05.09.02/arts/onstage.html (982 words)

	TheracSituation.htm
		The machine's linear accelerator produces a high‑energy electron beam (25 million electron volts) that is dangerous.
		Patients are not to be exposed to the raw beam.
		The type of beam to be used depends oil the tumor being treated.
	crystal.uta.edu /~cse1111/cse1111/TheracSituation.htm (2500 words)

	ICSR8 - Madrid (Spain), July 5-9, 2004
		Much of the negative view of reuse is based on the failure of the Therac-25 medical system which resulted in the deaths of several patients (Leveson and Clark, 1993).
		One of the sources of failure is believed to be reusable software carried over from previous versions of the Therac system.
		The case against reuse in the Ariane 5 system is made in (Jézéquel and Meyer.
	icsr8.cs.rug.nl /panel.html (286 words)

	Safety-Critical Computing
		In the Therac- 25, however, both target position and beam intensity were controlled solely by the computer.
		The Therac accidents were only the worst examples of a trend that the FDA had been tracking for several years: computer-related problems in medical devices were on the increase.
		The Therac accidents remain the best-known examples in the public record of computer-related deaths and injuries.
	staff.washington.edu /jon/pubs/safety-critical.html (10034 words)

	SE441 - Unit 1 Questions
		Suggest material that the Therac developers should have studied before developing the system, and outline how they might have applied this material.
		There were two specific defects in the Therac software that caused the accidents discussed in Leveson's report.
		Engineering process issues also contributed to the Therac accidents.
	www.se.rit.edu /~se441/UnitActivities/Unit1-Questions.htm (802 words)

	therac-ariane
		25 was technically due to a software design error that did not process user input correctly under a certain
		The overall reason for the system’s failure was the poor software-engineering practices
	www.cs.virginia.edu /~ami4v/cs685/therac-ariane.html (409 words)

	SENG621 Week1 Notes: Introduction
		AECL developed the Therac-25, capable of delivering photons at 25 MeV or electrons at various energy levels.
		Initial cost estimate for the AAS was estimated at 2.5 billion dollars in 1983.
		Initial estimate for code to be developed was 1.5 million lines of code (LOC).
	sern.ucalgary.ca /courses/seng/621/W98/Al-notes621.html (4652 words)

	THERAC-25
		The Therac-25 was the third system created under the Therac name by the Atomic Energy of Canada Limited (AECL).
		It was believed that the new Therac-25 was much more efficient than Therac-6 and Therac-20.
		The number that goes along with the word Therac stands for the maximum amount of mega electron volts (MeV) the machine can dispense.
	neptune.netcomp.monash.edu.au /cpe9001/assets/readings/www_uguelph_ca_~tgallagh_~tgallagh.html (1322 words)

	Therac 25 tickets - Therac 25 information - Canada
		Therac 25 is a simple and beautiful play that tackles themes of fear, trust and courage with wry humour.
		Therac 25 tickets - Therac 25 information - Canada
		Their friendship deepens even as they endure painful treatments and, against the odds, friendship turns to love.
	www.theatermania.com /content/show.cfm/show/15075 (142 words)

	Therac-25 - III
		He placed a film in the Therac's beam and ran two exposures of X-ray parameters with the turntable in field-light position.
		On May 2, 1986, the FDA declared the Therac defective, demanded a CAP, and required renotification of all the Therac customers.
		The software turned on the full 25 MeV without the target in place and without scanning.
	courses.cs.vt.edu /~cs3604/lib/Therac_25/Therac_3.html (3856 words)

	25 report - infos
		Education World presents 25 ideas for you to use or adapt.
		From: Rodney K. Short DCP 25 1 SR.
		Last major update issued on November 25, 2004 at 04:30 UTC.
	www.angelfire.com /alt2/ang1/2/25-report.html (164 words)

	Chuck Huff: Classes
		The case is one of those available on www.ComputingCases.org, namely the Therac 25 case.
		This web page will send you to a series of pages that describe a case that Deborah Johnson and Keith Miller will discuss at the workshop.
		The introduction below is taken from the description of that case on the site.
	www.stolaf.edu /people/huff/classes/CEcase.html (441 words)

	Citations: An Investigation of the Therac-25 Accidents - Leveson, Turner (ResearchIndex)
		A well known example where such mechanisms were not effective is the Therac 25 radiation therapy machine where several fatal radiation overdoses occurred due to an obscure malfunction of the equipment, the first of its type produced by the company involved to include software
		Expensive and catastrophic experiences have however shown that it is not so simple: Ariane 5, and Therac 25.
		report on the Therac incidents, where software uncertainties were deemed impossible and therefore were not considered by the manufacturer of a medical radiation device.
	citeseer.ist.psu.edu /context/96007/0 (1804 words)

	Fatal Dose - Radiation Deaths linked to AECL Computer Errors
		AECL faxed me a statement approved by their lawyers that was to be their definitive answer to questions about the Therac- 25 accidents.
		Just as technicians leave the room to operate x-ray equipment in hospitals and dentists' offices, operators ran the Therac-25 from a computer console outside the treatment area.
		And the Therac-25 was controlled principally by software.
	www.ccnr.org /fatal_dose.html (5034 words)

	CSC 301 Paper: Computers & Liability
		Earlier Theracs used PDP-11s as control computers, but they served as little more than front ends for existing radiotherapy equipment.
		With the Therac-6 and Therac-20, the computers merely made operating the equipment more convenient.
	salfter.dyndns.org /cs301.html (1538 words)

	sci.engr.* FAQ on Failures: THERAC-25
		Those steps evidently outraced the THERAC computer's duty cycle, retracting a protective tungsten target plate and resetting the mode from the technician's point of view, but leaving the power setting to maximum.
		Investigators later learned that AECL engineers didn't realize that steps 1-8 could be performed within eight seconds.
	www.tcnj.edu /~rgraham/failures/THERAC25.html (286 words)

	An Investigation of the Therac-25 Accidents
		[4] J.A. Rawlinson, "Report on the Therac- 25," OCTRF/OCI Physicists Meeting, Kingston, Ont., Canada, May 7, 1987.
	csdl2.computer.org /persagen/DLAbsToc.jsp?resourcePath=/dl/mags/co/&toc=comp/mags/co/1993/07/r7toc.xml&DOI=10.1109/MC.1993.274940 (346 words)

	spm3: July 2004
		It has been proven that in therac 25 case the AECL reusing the therac 6 package when they built the therac 25 software, because by reusing the software that has been proven safe to be used it will increase the safety, and when the AECL using therac 6 they didnât found any problem.
		Therac 25 is reliable software the system works very smoothly and also makes the recovery machine to be a combination of 2 machines into 1 machine.
		In Therac 25, one of the errors that are not detected in the testing time is the using of the up-key.
	spm3.blogspot.com /2004_07_01_spm3_archive.html (346 words)

	spm4: July 2004
		Therac 25 is tested 2700 hours, but still cause errors exist, this is because the Therac 25 lack of documentation on software specification and software test plan.
		Therac 6 and Therac 20 are noted to have less damaging errors than it is in Therac 25.
		The case in Therac 25 is that, they were over confident with their software and did not check and test on the software.
	spm4.blogspot.com /2004_07_01_spm4_archive.html (346 words)

	spm1: 07/01/2004 - 07/31/2004
		Therac 25 which controlled by computer is not reliable.
		As i know after read the article about Therac 25, I found that after therac -25 was introduced, there are six known accidents involved massive overdoses by the Therac-25 -- with resultant deaths and serious injuries between June 1985 and January 1987.
		For example the software for the therac 6 and therac 20 are no suitable for the therac 25.
	spm1.blogspot.com /2004_07_01_spm1_archive.html (346 words)

	Therac-25 - Network Live
		The Therac - 25 was the third system created under the Therac name by the Atomic...
		Therac - 25 was released on the market in 1983.
		Therac - 25 was a medical linear accelerator, a device used to treat cancer.
	therac-25.networklive.org (346 words)

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