Patient Safety Tip of the Week


October 20, 2009

Radiology Again…But This Time It’s Really Radiology!


We’ve done multiple columns on the hazards of the radiology suite. But most of those have dealt with the errors and adverse events occurring in the radiology suite that are not related to radiology per se. Most of those have to do with things like medication errors, IV line mixups, running out of oxygen, and other events that are due to patients with complex medical problems being temporarily managed in “non-medical” areas of the hospital.


But this time we have a real issue directly related to radiology itself – the series of radiation overdoses occurring at Cedars-Sinai from CT brain perfusion imaging studies. On October 8, 2009 the FDA issued an alert about the issues involved. Over an 18-month period, 206 patients at Cedars-Sinai apparently received radiation doses eight times the expected level during brain CT perfusion imaging. The studies were being done in the acute diagnosis and management of patients with suspected stroke. The problem was only recognized after a patient complained of patchy hair loss after such a scan.


Though the FDA acknowledged this involved only one type of scan at one facility, the magnitude of the problem and the potential for occurrence at other facilities was so substantial that the alert was issued. The FDA encourages every facility performing CT to review its CT protocols and be aware of the dose indices that are displayed on the control panels. These indices should be checked for each protocol both before and after scanning and compared to the doses usually associated with that protocol.


Each type of CT study uses a protocol that is programmed into the system. Cedars-Sinai had apparently reprogrammed the protocol for only one type of scan, the brain perfusion scan, which is used for evaluation of patients with suspected acute stroke (LA Times October 14, 2009). That was done to enhance the ability of the radiologist to see cerebral blood flow changes. Apparently no other protocols were affected.


The radiation dose does apparently appear on the control display of most CT imaging studies. However, it is just one of a number of items appearing on those screens. The system in use, and apparently most CT systems, do not have any sort of flag (eg. display in a different color, audible alert, etc.) that alerts the CT technician or radiologist that the dose of radiation about to be administered is higher than the usual dose. Such flags should be “hard stops”, i.e. that the scan cannot proceed until the appropriate individual verifies that the higher dose is intended. This is analogous to having dose range limits programmed into a CPOE system that alerts physicians and/or pharmacists when a dose of a medication is higher (or lower) than most conventional doses.


Radiation doses also often appear with the images when the radiologist is reading the scans. But we bet that most radiologists probably never pay any attention to those numbers.


Cedars has apparently also instituted “double checks” when protocols are changed (ABC News October 13, 2009). The hospital has apparently created a chain of authority for making such reconfiguations and ensuring that they do not result in excessive radiation doses (LA Times October 16, 2009). They have also initiated further training for CT technicians.


Perhaps most bothersome is the fact that this went on for 18 months before it was detected. In the retrospective investigation, about 40% of affected patients had suffered patchy hair loss or skin redness or irritation (ABC News October 13, 2009).


To make matters worse, the issue of how and what the hospital told the affected patients has become an issue. Several patients who were contacted by personnel from the imaging department said they were asked multiple questions but never told that there had been an error nor told they had received excessive radiation doses (LA Times October 15, 2009). Candor and apology have become the accepted standards in patient safety. Sometimes early in an investigation you may be unaware that any error or adverse event has even occurred and you may need to contact patients as part of your investigation. However, once you have confirmed that the error or adverse event has taken place you should be very upfront and let the patient (or family in some cases) know what has happened and what you will be doing. In the current cases, since the average age of the patients was 70 years, there is less likelihood of long-term consequences of this radiation overdose. But for the younger patients affected, potential long-term consequences (eg. development of brain tumor) become more problematic. Such potential consequences should be explained clearly to the patient in all cases. See our June 16, 2009 Patient Safety Tip of the Week “Disclosing Errors That Affect Multiple Patients”.


The series of events also highlights more unintended consequences of technology. In highly computerized systems, a single error can be rapidly propogated to result in harm to multiple patients. The staff at Cedars may have thought the equipment defaulted back to the original standard protocol after each use. But the new (higher dose) protocol became the standard protocol that appeared each time a brain perfusion CT scan was done. Thus, the single change applied to the next 200+ patients receiving that type of scan.


The cases are also eerily similar to one described in what we think of as one of the first-ever patient safety books, Steven Casey’s “Set Phasers on Stun” (Casey 1993). That is a book about some of the adverse events related to design issues and the human-technology interface. In the lead case, a design flaw in the human-computer interface, plus several latent conditions, led to a cancer patient being inadvertently exposed to a fatal dose of radiation. The radiation machine had two output modes, a conventional one and a very high dose one, each activated by the technician entering a letter of the alphabet. However, when the technician entered the wrong letter, went back and edited to enter the desired letter, the machine did not recognize the sequence of keystrokes and delivered 25,000 rads to the patient. The computer screen then popped up an error code that led the technician to think no dose had been given so she actually delivered several more doses. Investigation in that case led to discovery of similar cases in at least 3 other cancer centers.


Design flaws are common in everything we interact with on a daily basis (see our prior columns on the work of Don Norman and John Grout and John Gosbee among others). But in medical equipment design we often fail to anticipate how humans will interact with the equipment, resulting in some very unintended consequences. In the above examples, the key question that should have been asked is “What is the worst thing this machine could do to a patient?”. Clearly the answer would be that it could deliver an unintentionally excessive dose of radiation. The design process should then do everything possible to prevent such an inadvertent consequence. That obviously should contain “hard stops” that would prevent a technician from delivering such a dose without getting approval for the override from some other authority. Simply putting the dose on the screen amongst numerous other parameters is not enough. A visual alarm (eg. color, flashing alert) or an audible alarm would be a start but is also not enough. The process should not be allowed to be overridden by a technician simply acknowledging that the warning was seen. After all, this is not Microsoft Word asking you if you want to save the changes you made to the document!!!! But the other key issue is that many (if not most) pieces of high tech equipment are designed away from actual user areas and the designers are often unaware of the ways in which healthcare workers are likely to interact with that equipment.


You should ask the question “Why should anyone be allowed to change the dose of radiation in the first place?”. Good question. Most of the recent changes in radiation doses have been in the downward direction. Protocols have been developed for certain types of imaging to allow lower doses yet allow adequate imaging of whatever is being imaged (see section below on cumulative radiation dose over a lifetime). That is a desirable goal. So there is a logical reason to allow users to change protocols. However, making it too easy to change a protocol can lead to the types of problems highlighted by the Cedars-Sinai events. Allowing the protocols to be changed should only take place under supervision of those who clearly understand all facets of the equipment (probably including the manufacturer).


The cases also again raise the issue of excessive use of imaging in our current healthcare system. As you can readily see, this has not only financial implications but clearly patient safety implications as well. The cumulative dose of radiation one gets over a lifetime from medical imaging studies now is considerably higher than for previous generations. We currently have no systems in place to track the cumulative dose of radiation patients receive. While one facility conceivably might keep track of the totals for studies done on a patient at their facility (but let us know if you actually find one!!!), patients typically have imaging studies done at multiple different facilities. Particularly as we move forward with electronic medical records, we should be able to begin to track lifetime cumulative radiation doses. Even if the exact radiation dose for each individual procedure is not captured in those EMR’s, it is pretty easy to set up a “counter” that would count the number of studies using radiation and multiply each by the “average” dose of radiation for that particular study. Just having a cumulative dose highlighted may defer someone from ordering another imaging study that may be of marginal necessity, particularly if a different diagnostic study not using radiation is available.


We hope you will be looking at all the sites in your organization that perform imaging studies and asking the key questions we’ve noted above. Don’t be surprised if you identify some vulnerabilities. The Cedars-Sinai events are ones that should make you all be asking “I wonder if that could happen here?”.






Safety Investigation of CT Brain Perfusion Scans: Initial Notification

Date Issued: October 8, 2009



Doctors 'Shocked' by Radiation Overexposure at Cedars-Sinai

Medical Scans Continue Increasing Our Exposure to Radiation, Experts Say

ABC News Medical Unit
Oct. 13, 2009



Cedars-Sinai head expresses regret for radiation overdoses

By Alan Zarembo

Los Angeles Times. October 16, 2009,0,3559559.story?track=rss



4 patients say Cedars-Sinai did not tell them they had received a radiation overdose

By Alan Zarembo

Los Angeles Times. October 15, 2009,0,2773125.story?track=rss



Cedars-Sinai radiation overdoses went unseen at several points

By Alan Zarembo

Los Angeles Times. October 14, 2009,0,5065886.story



Casey S. Set Phasers on Stun and Other True Tales of Design, Technology, and Human Error. Santa Barbara California: Aegean Publishing Company, 1998 (first published in 1993).










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