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?"
Re:Default setting... (Score:1, Informative)
As a user of GE machines I would have to say they are pretty well locked down. It's hard to change anything. That may sound good, but in practice it means if you *do* want to change something then you need to do some pretty nasty workarounds. E.g. you have to edit a text file on the scanner so that it does what you want it to do, however as far as the scanner software is concerned it is still running the original protocol.
I only hope GE don't decide they need to lock down the scanners even further. For "confident" users (see TFA) who want/need to try out different protocols it will only mean more dangerous hacking of the scanner settings. Confident users with NIH research grants should take note.
Re:Pretty narrow margin (Score:2, Informative)
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). They are definitely in some dangerous territory, but the article said the median age of the patients was 70. Couple that with the fact that they already had a stroke and it is safe to conclude that long term effects are unlikely to matter.
The machines were set for
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.
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.
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.
What is particularly appalling is that it took 18 months to catch this, and they only found out because a patient complained of hair falling out. The FDA recommendation is that doctors double-check that the machine is actually applying the correct dose.
It seems clear to me that this is a stop-gap that indicates a design flaw. It is not enough for the machine to display the actual dose: the procedures for using it must ensure that this is not missed. From the Therac-25 link:
This describes perfectly the recent incident. User-friendly defaults resulted in health professionals making unsafe assumptions. Blaming them does nothing to prevent such problems in the future. The system is broken.
Incidentally, I am not convinced by the lessons learned about Therac-25. It emphasizes proper software engineering practices and licensing. This may be necessary but insufficient.
This might not be enough. Initial testing of the machine had been of hardware only, though the problem was with software. Following the initial reports of an overdose, the company replaced a hardware component. If the real problems fall outside current engineering practices, they may be completely overlooked. In the recent case, the problem appears to include the practices of medical staff. These are part of the technical system, so they need to be treated as such by engineers. Ignoring that is very much like focusing on the hardware to the exclusion of the software. Technical systems are not clearly bounded, and are probably less so as time goes on. There always needs to be a broader view.
Therac-25 suffered suffered (among other things) from race conditions. The mere idea of having a deadly device that is even theoretically susceptible to race conditions terrifies me: if a race condition programming error is even potentially possible, I would want to make damned sure there's an independent hardware or software check to make sure failures will be caught. Problems like this can be incredibly subtle. I wonder if overconfidence in engineering might lead to complacency.
What really jumped out at me, however, was the role of the user community, which was formally excluded from the engineering. Following the discovery of one deadly software error, the company (AECL) fixed it and assumed the problem was solved: after which another patient died from a different bug. The users asked for access to the source code. This was denied. Unlike the company (and likely its engineers), the users clearly understood that they were part of the system.
Re:Medical Staff were a big part of the problem (Score:3, Informative)
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, there WAS an inquiry into what might have been happening but didn't come to light until Tyler's ill-fated mishaps occurred.
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:Not the engineers fault (Score:3, Informative)
I'm just going to ductape this authorized doctors finger and eyeball in place and drop an IV into him to keep him fed.
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
Re:It's About Automation (Score:3, Informative)
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 itself for another five, ten, or fifteen years.
Re:It's About Automation (Score:3, Informative)
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.
Re:HULK MAD! (Score:2, Informative)
Re:Some quantitative perspective (Score:2, Informative)