CT Scan "Reset Error" Gives 206 Patients Radiation Overdose 383
jeffb (2.718) writes "As the LA Times reports, 206 patients receiving CT scans at Cedar Sinai hospital received up to eight times the X-ray exposure doctors intended. (The FDA alert gives details about the doses involved.) A misunderstanding over an 'embedded default setting' appears to have led to the error, which occurred when the hospital 'began using a new protocol for a specialized type of scan used to diagnose strokes. Doctors believed it would provide them more useful data to analyze disruptions in the flow of blood to brain tissue.' Human-computer interaction classes from the late 1980s onward have pounded home the lesson of the Therac-25, the usability issues of which led to multiple deaths. Will we ever learn enough to make these errors truly uncommittable?"
Will errors ever go away? (Score:5, Insightful)
Re:Will errors ever go away? (Score:4, Insightful)
Re:Will errors ever go away? (Score:5, Funny)
The machine didn't build itself!
SPEAK FOR YOURSELF, MEATSACK!
Re:Will errors ever go away? (Score:5, Funny)
The machine didn't build itself!
SPEAK FOR YOURSELF, MEATSACK!
Oh, yeah?! Well who built your first model, you bucket o' bolts! And don't give me that FSM nonsense. Everyone knows that the Fantastical Spawning Machine was truly the work of humans, inspired by the intelligently designed schematics given to us by the noodley appendage of the true FSM.
Re:Will errors ever go away? (Score:5, Funny)
SPEAK FOR YOURSELF, MEATSACK!
Scanning with high intensity radiation reveals he is in fact about 60 percent water, 16 percent protein, 15 percent fat, and about 3 percent nitrogen... So, more of a stringy, greasy, slightly gassy water bag really.
Sorry about the high levels of radiation used to obtain the data, your armpits should stop smoking any minute now.
Re:Will errors ever go away? (Score:5, Funny)
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Or maybe just a simple display that tells you the amount of radiation exposure that the machine is currently set for?
Then the radiologist could take responsibility for noting it.
This is simple and things like this often exist in development versions but are taken out later by marketting. Why?
I once worked for an international company that had a billing system. It wasn't very user friendly and was often wrong.
On the other hand, we had a local billing system that was accurate and helpful. At some point, bills
Comment removed (Score:5, Insightful)
Re:It's About Automation (Score:5, Insightful)
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While its unfortunate that this error killed people
There is no mention of any deaths.
Even under normal circumstances, the procedure requires more radiation than most other types of CT scans. Radiation exposure increases the likelihood of cancer, though the risk is lower in older patients because they are likely to die of other causes first.
The median age of these patients is 70 years - and they are surely far more at risk of a second - more dibilitating - stroke than a cancer that might not manifest its
Re:It's About Automation (Score:4, Interesting)
This particular error is the kind that occurs when you simplify complex procedures in the interest of widespread use. It is the fault of specialization, which we typically embrace because it allows us to leverage human labor into increasingly complex areas of inquiry. It's more than just "human oversight" or "machine failure," it's the kind of problem that typically arises when people are trained to use machines without being trained to fully understand those machines.
A certain segment of society--that's mostly us geeks--strives against this tendency; we become technicians in various fields. But most people, including medical people, get trained by vendors to use a particular piece of software or hardware without reference to its underlying principles or inner workings. This is normal and usually beneficial for various reasons an economist could doubtless relate.
But one of the things that we geeks should be doing is looking at equipment like this in its overall system context, which includes the operator and which includes the training the operator has received. That's mandatory in the Aviation industry pretty much worldwide (my field); I don't know what the situation is for medical equipment in the USA. No, we will never make such mistakes "uncommittable" -- perfect safety is a myth. But we should be considering possible failure modes, and the likelihood and consequences of those failure modes, to ensure that the risk is tolerable.
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I don't know about the US, but in the UK the qualification you take to give CT scans these days is usually a degree - you'd be a diagnostic radiographer. How much more training do you want?
The problem isn't the qualification, it's the change in protocol. Someone thought it would be a good idea to override the machine's inbuilt safety cutout by resetting it part-way through the scan, proving that being highly qualified is no barrier to making dangerous decisions.
Re:It's About Automation (Score:5, Insightful)
I don't think being trained to fully understand the automobile will decrease the number of automobile related deaths.
Being trained to fully understand the laws of physics would certainly decrease automobile accidents.
Re:It's About Automation (Score:4, Funny)
Re:It's About Automation (Score:5, Insightful)
The person who reacts correctly to a slide is not doing so because he understands physics in general but because he has driving specific training. There's really no time to do math in that situation.
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Re:It's About Automation (Score:4, Funny)
Was that before or after your car hit the bottom of the ravine?
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Yes, because we all know that car accidents only kill stupid people...
I don't think the laws of physics cares how high your IQ is when you get t-boned by a drunk driver at an intersection.
Re:It's About Automation (Score:5, Insightful)
...But in that particular accident, the drunk is less likely to suffer severe or fatal injuries. The relaxant effect of alcohol makes their body more resilient to sudden shocks. Also, they're usually having a head-on collision, while they may be striking the other vehicle from the side; as head-on collisions are by far the most common, most of a car's safety features are geared toward mitigating them.
Re:It's About Automation (Score:5, Informative)
Woops, silly me, repeating what I learned in upper-division Transportation Engineering lecture from professors with decades of experience in the field of road design. Guess I should have checked Wikipedia first, because it never lies!
Got a cite for your critique?
It's true that the majority of people who die in alcohol-related crashes have a BAC of .08 or higher (67% according to this site [movetransport.com]). However, lower down, we see that 37% of single-car crashes involve a BAC of .08 or higher, which is higher than the 22% average rate. Since my point was about the comparative risks to the drunk driver and the sober driver in an accident, single-car crashes are irrelevant. That takes out 67% of the drunk driving crashes overall, and similarly lowers the fatality numbers considerably.
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The watchdog timer on the radiation module detects lack of input and shuts it down?
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Jesus, what must your code look like?
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As long as people are involved in some way, no.
Indeed. The problem here is that whenever you have to communicate something, there's no way to be 100% sure that 100% of your users will see what you intended, in the way that you intended it. You can explain everything perfectly clearly and concisely - but because humans don't read minds, all words and visual cues are subject to interpretation by indviduals.
Not the engineers fault (Score:5, Funny)
Re:Not the engineers fault (Score:5, Insightful)
Re:Not the engineers fault (Score:5, Insightful)
The machine's software should not be capable of triggering the release of that much radiation; any change in the radiation levels should require some kind of hardware interaction. Even an idiot who did not RTFM should not be able to cause harm with the machine.
I'm not sure what you mean by this? Most hardware is software these days.
Or are you talking about having a red button with a safety lock on it that has to be pushed in order to work?
Either way, people still bypass hardware solutions.
Re:Not the engineers fault (Score:5, Insightful)
Re:Not the engineers fault (Score:5, Insightful)
Don't even hard-wire it. Engineer it so that operating in the high-dose regime requires physical intervention, a "Kill Handle" with a lock and key. The machine should be physically incapable of generating an above-standard dose when the "Kill Handle" is not being held. Limit the power, or something. (The aformentioned Therac incident happened, in part, because such a hardware interlock did not exist.)
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In this particular case though, that particular dosage may have been appropriate to some uses, but not others. A "maximum allowed dose" can be in effect and still make a patient sick!
For some machines these doses are controlled mechanically; moving heavy lead and steel plates around, irises, etc. Hardwiring a maximum dosage in this case involves the interaction between many components.
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Ironically, earlier models of the Therac device *did* have hardware interlocks. These earlier models shared the same software defects as the Therac-25, but hardware interlocks prevented the overdose scenario.
I haven't RTFA, and I don't even pretend to assume that I could do things better (or even fully grasp the problem). That said, the struggle for efficiency and programmers' tendency to seek out a softw
Re:Not the engineers fault (Score:4, Funny)
Bet you can't circumvent that with just duct tape. Now, with an Arduino, some peripheral hardware and a few spare evenings....
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I'm just going to ductape this authorized doctors finger and eyeball in place and drop an IV into him to keep him fed.
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Well, the Therac-20 "worked fine" in the sense that the mechanical limit on the device prevented the software from delivering lethal doses. It doesn't mean that the Therac-20 was a "good" machine in any sense of the word.
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One of the system admins at school was trying out the latest and greatest such beast in his office before deploying it and thought it was a good idea to program F1 to send his userid and password. He also thought that the terminal would not retain the memory when he unplugged it to deploy the device to the public terminal room.
He learned that two stupid thought
Re:Not the engineers fault (Score:5, Informative)
Thank god you're not responsible for the design of complex, life-critical systems, like those commonly found on passenger jets, in nuclear power plants, in high-speed rail systems, etc. All of those systems incorporate fail-safe measures so that if something were to go wrong (like an operator losing control) the system would fallback on a safe state.
Sure, in an ideal world, every operator of a life-critical system would have total understanding of that system, know the value of every system setting at all times, never forget, never be tired, and have an IQ of 200. In the real world, operators are often overworked, susceptible to distractions, minimally qualified, and sometimes under-trained or even improperly trained. Even the most experienced and well-trained veteran airline pilots can lose focus and make deadly mistakes (which is why Cockpit Resource Management has been a major area of research in aviation psychology). You can base your system design on ideal conditions, or you can base it off of real-world conditions; either way, it's going to be operating in the later.
You also seem to be missing the main purpose of mechanization and automation, which is to simplify a task or make it easier to perform. When you buy a cappuccino machine, you don't want to understand the details of how it operates or be asked for input every step of the process to make a cup of coffee. Eliminating/minimizing the human factor in a particular process is another major advantage of automation. It provides more consistent results and helps to minimize human error. All of this helps to reduce the learning curve and skill level required to perform a task, which confers economic benefits. However, not every well-designed system can necessarily be operated by unskilled personnel—nor would you want a high school drop out to be operating most life-critical systems. Nonetheless, you still want mechanization/automation to simplify the task in these cases. That's because some tasks are so inherently complex and mentally demanding that, without automation, it simply can't be performed.
Flying a passenger jet is a perfect example of this. Even with all the sophisticated automation (including autopilot) on a modern airliner, it still takes a full cockpit crew (not to mention support personnel on the ground) to safely fly & land the plane. With all of the complex duties that airline pilots need to perform simultaneously, they don't have the time to monitor the status of every system component or manually adjust every actuator on the plane to control its flight surfaces. It may take 50 different mechanical actions to retract the landing gear on a plane, but why clutter the cockpit interface with 50 items when a single switch or button will do? Likewise, doctors and nurses are already required to undergo extensive medical training; they don't need to have to learn how to mechanically calibrate a CO2 laser or calculate the spectrum of an X-ray machine based on the anode material of its emitter and the voltage passed through it. Medical personnel should mainly be trained in medicine and only need to learn how to operate a particular medical device, not how to troubleshoot it or read its blueprints.
A simple and streamlined interface is much less distracting and more intuitive than a field of buttons and dials for a thousand different minute settings and system readings. Even with the utmost simplification, most industrial machinery and complex systems are still overwhelmingly difficult to operate by an untrained person. It's never just a single "magic button" for the operator to press. A nuclear power plant might take hundreds of different readings from multiple sensors and summarize it with a single status message or indicator light on a controller's console, but that message/light would likely be sitting next to a dozen other status indicators that each take hundreds of other readings. And although a complex process like lowering the reactor temperature might be simplified down to a single "magic button," the c
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Therein lies the problem. There should be a hardware mechanism that limits the maximum power the machine can operate at, despite what the software requests. If there is a reason to increase that limit, it should have to be done in hardware, using a mechanism that automatically resets after a single run. The process of overriding the hardware limit should be conspicuous: nobody should be able to do it without intending to do so. Preferably, it should be obvious
Re:Not the engineers fault (Score:5, Funny)
I see you are about to fry this patient like an egg (doseage set for multiples of normal protocol)
would you like me to
1 reset the machine to standard defaults
2 book you a flight to africa
3 call your lawyer now
4 forge the documents to show %person% did the treatment
or
You Are about to kill this patient [cancel] or [allow]
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Re:Not the engineers fault (Score:5, Insightful)
I'm willing to bet that the person that modified the machine has read, at least, the relevant parts of the manual.
Re:Not the engineers fault (Score:5, Insightful)
Re:Not the engineers fault (Score:5, Insightful)
Re:Not the engineers fault (Score:4, Insightful)
The machine's software should not be capable of triggering the release of that much radiation
That sentence, essentially, just said "The machine did something bad. It should have been designed so it isn't allowed to do that."
That's what qualifies as "insightful" these days????
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"Even an idiot who did not RTFM should not be able to cause harm with the machine."
But was this above that limit?
Different scans REQUIRE different amounts of radiation.
Nothing can be fool proof. I would bet that there is a limiter but this level could be below that limiter.
Re:Not the engineers fault (Score:5, Insightful)
Couldn't disagree more. Unfortunately, enforcing training and reading manuals would probably have little effect. In my 10+ years doing usability for missile systems, you have to build in the mechanisms to keep the users from doing bad things. Even if you force the user to read the *entire manual* before each use, people still have bad days, hangovers, fights with significant others. It has to be designed in.
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Couldn't disagree more. Unfortunately, enforcing training and reading manuals would probably have little effect. In my 10+ years doing usability for missile systems, you have to build in the mechanisms to keep the users from doing bad things. Even if you force the user to read the *entire manual* before each use, people still have bad days, hangovers, fights with significant others. It has to be designed in.
The story behind Murphy's Law [wikipedia.org] is pretty interesting and it ties in with this design philosophy.
Basically the story is that a technician incorrectly installed force sensors and in response, Murphy got pissed off and said "If that guy has any way of making a mistake, he will."
However, other people adapted that statement into "If anything can go wrong, it will," expressing the idea that if a system does not mechanically exclude the possibility of human error, human error can be expected to occur. This makes ac
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"You have to be pretty confident to think you know more than the guys who designed the equipment."
I think it speaks volumes. I don't think they would RTFM even if you threatened them it would be a conflict of their personality.
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The fact that nuclear medicine equipment continues to ship without an absolutely paranoid level of hardware safety interlocks 20+ years after the Therac-25 incidents is appalling.
Default setting... (Score:5, Insightful)
Better investigate "Hey, we got no picture" than "Hey, we got pictures, but everyone dies after that..."
Didn't RTFA.
Re:Default setting... (Score:5, Funny)
All I'm saying here is we shouldn't just dismiss this as a bad thing until we've fully explored the legislative and societal implications a team of crime-fighting mutants with superpowers would have.
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Didn't RTFA.
Well that explains why your comment makes no sense. The system was showing a correct dosage, but was delivering something different since they had been dorking with the protocol definitions. In the Therac-25 case, the error was due to the operators using the program in an undocumented manner and the system incorrectly calculating the required exposures as a result. Also the operator doesn't arbitrarily set a level. He picks a specific protocol from a menu which already has the scanning pattern, timing,
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They need to have some sort of sensor in-line with the radiation stream to audit the hardware and software output and confirm the human configurations are in line with expectations.
And what if it breaks between the "what is it emitting?" stage and the "OK, point it at the patient" stage?
If it breaks, it should emit zero.
HULK MAD! (Score:5, Funny)
Anyone else read this as David Banner?
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Hate this "immediately moderate when you select an option" feature. meant to mod funny... slip of the mouse goes to overrated... there should be a go/ok button next to the list imho.
wasted 3 mod points... oh well...
Pretty narrow margin (Score:2)
The error went unnoticed for the next 18 months, until this August, when a stroke patient informed the hospital that he had begun losing his hair after a scan.
There's only a factor of 8 difference between a typical scan dose and one large enough to cause hair loss and skin damage? IIRC observable damage doesn't occur until the hundreds of mSv range. I'm pretty astonished that CT scans need such huge doses.
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There's only a factor of 8 difference between a typical scan dose and one large enough to cause hair loss and skin damage?
Yeh, that's what I was thinking. I thought that X ray machines were designed to stay well away from dangerous levels these days. I'll keep that in mind next time my doctor suggests a CT scan.
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You would expect that to require large, large doses to achieve.
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100s of mSv range
There are portions of the world that have a very high natural background in the 200 mSv range so you are not quite right with your estimates. In addition, you have to distinguish between whole body dose and localized dose. It is not uncommon to see tumor doses in the 40-50 Sv range.
.5 Gy (for xrays 1 Gy = 1 Sv) and got 3-4 Gy. A whole body dose of just above 4 Sv is a 50% death in 3-6 weeks (with no medical intervention). (remember that the CT was only to the brain). The
The machines were set for
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The high natural background areas deliver the 200 mSv over a period of a year though, not a matter of minutes.
There may be good medical reasons for using such enormous doses, but it still took me by surprise. The average dose of a nuclear worker is only a few mSv/year. Still, I guess a 1 in 40 chance of the radiation causing a fatal cancer isn't so bad if it stops you dying from a stroke in the meantime.
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but CT scan's aren't "typical" - you get xray'ed couple times a year so they are very low poweed, but a CT scan?? i think my last was? i might have had one 25 years ago when they cut my head open, for that they pump up the power to get it right.
Re:Pretty narrow margin (Score:5, Informative)
"chemo" refers to chemotherapy, where the patient is poisoned in the hopes that the poison will kill the cancer faster than it kills the patient. It is a different form of therapy than radiation therapy, in which the patient is subjected to intense doses of radiation in the hopes that the radiation will kill the cancer faster than it kills the patient. Often, people with cancer will receive both, one after the other, but they aren't the same thing.
Maybe testing it afterwards? (Score:4, Insightful)
Maybe next time they will test the damn thing before subjecting patients to it? It's a built in part of my job that I test/confirm a change after I make a change.. because often there's a likely hood of something unexpected or improperly explained that can cause an issue.
How hard would it have been to stick a dosimeter in the machine after the change and run it though a test?
(I realize that just a basic dosimeter might not be a sufficient measure.. but it would have been good to get a before/after.. and something like a 8-fold increase would have been easily detectable!)
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Maybe next time they will test the damn thing before subjecting patients to it? It's a built in part of my job that I test/confirm a change after I make a change.. because often there's a likely hood of something unexpected or improperly explained that can cause an issue.
So, what you're saying is, "Always mount a scratch human."
Re:Maybe testing it afterwards? (Score:5, Insightful)
'How hard would it have been to stick a dosimeter in the machine after the change and run it though a test'
Supposedly the actual dose would have been displayed on the machine's screen (I wonder how prominently?):
http://www.latimes.com/news/local/la-me-cedars-sinai14-2009oct14,0,5065886.story [latimes.com]
'"It's in your face on the screen," said Dr. Donald Rucker, chief medical officer for Siemens, a manufacturer of CT scanners.'
'CT technicians are trained to monitor dose levels, and some hospitals conduct checks before every scan..."There are other places where the techs might be operating more as button-pushers," said Dr. Geoffrey Rubin, a professor of radiology at Stanford University. "The user becomes a little blind to these numbers."'
Testing wouldn't catch it (Score:3, Informative)
The article is not very detailed, but my reading of it is that the default dose was not unsafe. If I am correct (hard to tell), what happened was that a doctor doing a specialized procedure programmed a custom dose. Then the machine defaulted to this new value for subsequent procedures, but the staff assumed it was using it's previous (safe) default.
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"Good job not reading TFA."
Correct.. I did not read the (included for historical and anecdotal purposes, but otherwise not relevant to this incident), Therac-25 article.. Instead I read the LATimes article that this story is about, and the FDA recommendation.. neither which had "One example cited that a machine operator who ran through the dosage screen too quickly caused a race and a resultant incorrect dosage."
Good job reading the wrong article :]
The personal jab aside, you're correct in that you cannot t
not idiot proof enough (Score:2, Interesting)
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Silver lining (Score:2)
"Unwilling to admit"? Hardly. (Score:2)
I think doctors, machine designers, and everyone else involved are aware of the increased radiation associated with CT scans. But if you've got someone presenting with stroke symptoms, you're balancing "additional 1 in 10,000 lifetime risk of cancer" against "irreversible brain damage increasing in severity with each passing minute". If I'm ever in that situation, I'd tell them "cook me as hard and fast as you like, and I'll deal with the side effects at my leisure."
No, there will always be risk (Score:2, Interesting)
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Life is brutal, but that doesn't mean we should give up on trying to make it less so. Asking whether CT scanners can be redesigned to make this not happen, and whether it's worthwhile to do so, is very valid.
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It is heartening to note that at least the new GE Brightstars's print out the radiation exposure given with each study as part of the ro
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And while this may or may not apply to your particular comment (depending on your meaning), if we didn't work to remove unnecessary risk from the world, there would be no fire, no stick clubs, and we would all be living in trees trying to hide from tigers and lions--when they didn'
Medical Staff were a big part of the problem (Score:5, Interesting)
Along with the usability issues with the design of the Therac-25 it's obvious that the attitude of the medical staff contributed greatly to the problem. Patients complained of being burned, but their complaints were essentially ignored. Meanwhile, they were sent back for multiple treatments. Overwhelming evidence of radiation burns was ignored or given only cursory investigation because medical personal or manufacturer reps claimed that it was impossible for the Therac-25 to be responsible for the burns.
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If you read the history...about half of the deaths were due to one-shot incidents where the patent received a lethal dose out of the machine on the first treatment. To be sure, some of the incidents should have been dealt with differently as you indicate- but what about the Tyler, TX incidents, for example?
Yes... Medical Staff are a big part. But so was the manufacturer of the device- had you read all the evasiveness on AECL's part when the problems started coming in. In the case of the first incident,
8 times intended != fatal (Score:2, Insightful)
For comparison remember more people are killed by vending machines and by falling off the roof putting up the christmas lights.
Meh... (Score:2, Funny)
What's a few hundred rem among friends?
The errorless machine... (Score:5, Insightful)
There is and never will be such a thing as a machine without the possibility for error. And you'll never get around the old adage/rule - If it can happen, it will. How often it occurs it the key; and while we should always aim to make an error-less machine, it is an impossibility and we can only achieve it by make the occurrence of such errors as few and far between as possible.
After all, an error-prone human must be involved to make the machine; even if that machine made another machine a human was still involved at some point to make the original. Thus there will always be the possibility for errors. Even if, as demonstrated by the Matrix, iRobot, and many others, the machines make that error on purpose to save humanity - it is still an error.
Film badges? (Score:3, Interesting)
IRBs for devices (Score:2)
Perhaps having the equivalent of IRB review over any changes to devices of this sort would help prevent such problems. It makes sense for devices to be reconfigurable, and it makes sense for devices to try to warn people away from doing stupid things. In this case, they overrode the safeguards, and their judgement happened to be worse than that embodied in said safeguard. That is not always the case - the problem is when people make changes with potantially lethal consequence and there are not enough eyes o
Feedback? (Score:5, Interesting)
Will we ever learn enough to make these errors truly uncommittable?"
No. As long as correctness can't be proven and operators are permitted to create unanalyzed conditions by altering protocols there will always be risk. There are probably other mis-configured CT scanners out there in use right now that have been overdosing patients for years.
CT scans use X-rays; an easily detected frequency of light. Why not require that scanners incorporate an independent detector that measures the amount X-ray energy? If that is possible then create an interlock that can shut down the emitter when the net energy gets out of bounds and require that any such incident be NRC reportable. If the detector excluded from alteration by the operators then software bugs, misunderstandings, etc. can be detected even years after the last engineer had contact with the system, either before harm is done or at least before hundreds of patients are literally burned.
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A hardware X-Ray "circuit breaker" that would physically trip the power to the CT scanner if levels are exceeded? Not a bad idea. I would also require a monthly/quarterly test of the equipment by intentionally running it slightly over it's rated threshold.
What is amazing (Score:2)
Approximately 90 people over 18 months suffered hair loss and/or burns on their head, and not one of them reported it.
Patients need to wake up and realize doctors and the medical establishment try to do their best, but they are only human and a vast majority of what they do is simply educated guessing.
The patient is ultimately responsible for his/her own health care, so drill the doctors and do not let them get away with brushing
Put a dosimeter in there with the patient (Score:2, Insightful)
Failsafe anyone? (Score:2)
There are very strict regulations on what radiation is acceptable. Why did the not add a failsafe or critical warning, something like a big red blinking message "What you are gonna do is probably stupid" or so?! Just to give the therapist a hint that something is wrong. I mean, implementing this kind of failsafe should not pose that much of a problem, would it?
Dev is behind schedule! Forget testing.... (Score:2)
Sound familiar to anybody? Hope you enjoy that next doctor visit, plane ride, etc.
Hey, I hear they want to make a smart grid! Any takers on reliability? Anybody?
Oh great (Score:3, Funny)
Now there are 206 hulks running around.
Just don't make them angry.
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a rational question (Score:2)
soft error (Score:2)
Add a dialog box... (Score:3, Funny)
That pops up for the operator to respond to....
Are you sure you want to kill this patient?
Yes No Retry
Some quantitative perspective (Score:5, Informative)
Typical normal CT scan dose: 1-2 rem
Faulty CT scan overdose: 8-16 rem
1950s shoe-salesman's fluoroscope: 10 rem
Typical normal Therac-25 dose: 200 rem
Malfunctioning Therac-25 dose: 15-20,000 rem
Come on, seriously people. Yes, this is a mistake that needs to be fixed, but millions of kids in the '50s got their feet nuked with this much radiation and lived to become healthy normal adults with normal feet.
The Therac-25 cooked straight through people, leaving a hole of rotting meat behind. This is not even remotely in the same league.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/Radiation.html [rcn.com]
http://chestjournal.chestpubs.org/content/107/1/113.full.pdf [chestpubs.org]
http://www.ccnr.org/fatal_dose.html [ccnr.org]
http://www.orau.org/ptp/collection/shoefittingfluor/shoe.htm [orau.org]
Re:Don't be such a wuss (Score:4, Informative)
In 1895, Thomas Edison investigated materials' ability to fluoresce when exposed to X-rays, and found that calcium tungstate was the most effective substance. Around March 1896, the fluoroscope he developed became the standard for medical X-ray examinations. Nevertheless, Edison dropped X-ray research around 1903 after the death of Clarence Madison Dally, one of his glassblowers. Dally had a habit of testing X-ray tubes on his hands, and acquired a cancer in them so tenacious that both arms were amputated in a futile attempt to save his life.
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Actually, Hulk turns green right now. So says Peter David.
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The problem is that even those safeguards are ignored or not always wanted. The vendors actually have a lot to do with it too. They want to sell as much systems as possible for the lowest cost. A lot of the safeguards are thus implemented in software and the same software is shipped to both research sites (where you might want to overdose eg. a mouse) as medical sites (where you don't want to overdose). The only warning you get for most (even dangerous) levels is a pop-up box asking 'are you sure'.
Another p
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Don't blame the UI designers. Blame whoever designed the display to leave out two digits.
It makes sense, in a way. After all, you rarely turn your oven much over 600 degrees, so a 4-digit display makes little sense. 5 digits? You cook what over 9,999 degrees?
From then on, all other decisions are compromised.
Sometimes, the interface is hamstrung by the device. The Therac-25 might also be such a case. Safety shutters and all...