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Radiation Therapy Mistakes Cost Lives
jmtpi recommends a long NY Times investigative report about how powerful medical linear accelerators have contributed to at least two deaths in the New York area. Although the mistakes were largely due to human error, buggy software also played a role. "...the records described 621 mistakes from 2001 to 2008... most were minor... The Times found that on 133 occasions, devices used to shape or modulate radiation beams... were left out, wrongly positioned, or otherwise misused. On 284 occasions, radiation missed all or part of its intended target or treated the wrong body part entirely. ... Another patient with stomach cancer was treated for prostate cancer. Fifty patients received radiation intended for someone else, including one brain cancer patient who received radiation intended for breast cancer."
Alternate title: Radiation Therapy Success Saves Lives
Blaming software isn't the answer(outside of specific software bugs); but blaming humans, while fun and morally satisfying, is also dubiously useful from the perspective of the system as a whole(this does not, of course, mean that you should feel any compunction about sacking egregious cases).
For instance: The radiation shield/guide setup. Yeah, the nurse should have installed it, and she fucked up. However, it is a basic fact of humans that all of them fuck up from time to time, some more than others, and more under some conditions than others. Unless that particular nurse has an atypically bad record for forgetting, it is unlikely that firing her will improve the quality of the system as a whole very much. Instead, such safety critical systems should be designed to take human error into account. Routine use of checklists, for instance, has been demonstrated to reduce human error. Or, for the more high tech approach, the Radiotherapy machine could have a few extra sensors(RFID and optointerrupters) and the shield and guide units could be RFID tagged. If the machine does not detect the presence of the correct guides in the correct locations, it alerts the operators and refuses to provide a beam.
Humans are flawed, often annoyingly so; but they are what we have to work with. Luckily, it is possible to systematically characterize the form of flawedness exhibited by humans(eg. limits of short and long term memory, probability of making an error on a procedure of given complexity as a function of experience, and so forth) and design systems that, as much as possible, are resistant to those errors. This requires a combination of organizational changes(eg. control of working hours, verification of nonimpairment for critical staff, enforced use of checklists and procedures, firing atypically unreliable staff) and technological changes(substitution of highly reliable barcodes/RFIDs for unreliable handwriting, automated sanity checking, marking patients before surgery, machines that refuse to operate unless their interlock conditions are met, etc.)
Some of this is just a matter of time, some of it will piss off doctors, and some of it will probably piss off patients; but building reliable systems is possible.