Patient Safety Tip of the Week
November 23, 2010
Focus on Cumulative Radiation Exposure
Earlier this year we chronicled several recent revelations about excessive patient exposure to radiation through various medical interventions (see our February 2, 2010 Patient Safety Tip of the Week “The Hazards of Radiation” and March 2010 What’s New in the Patient Safety World column “More on Radiation Safety”). In those we discussed not only the risk of radiation exposure from single studies but also the cumulative radiation exposure risk and the fact that currently no one is tracking that for our patients – not we as physicians, not health systems, and not the patients themselves.
While much of the previous discussion centered around imaging studies like CT scanning, a new paper (Einstein 2010) focused on another at-risk population: those receiving imaging studies for cardiovascular disorders. They looked at over 1000 consecutive patients who presented to Columbia University Medical Center for myocardial perfusion imaging and measured or estimated the total dose of ionizing radiation those patients received prior to and in the subsequent 2+ years. These nuclear isotope imaging studies are among those tests with the highest radiation burdens and are often followed by other studies with more radiation (eg. prolonged fluoroscopic exposure during cardiac catheterization, etc.). Moreover, many of these patients end up getting one or more followup perfusion imaging studies (20% had at least 3 such studies and 5% had 5 or more). They found that almost 40% of the patients had a cumulative radiation exposure higher than that seen in the large study of Japanese atomic bomb survivors. So clearly the radiation exposure here is of the magnitude known to be potentially carcinogenic (though keep in mind that many of these patients are older and have medical conditions that will shorten their lifespan so they may not live long enough to get cancer).
The authors point out that these were tests for which the patients had appropriate medical indications. However, they point out the need to consider the big picture when planning for evaluation and management of such patients. Specifically, both past and potential future radiation exposure need to be considered when deciding on ordering tests on these patients. There are alternative methods of testing in the chest pain patient that do not utilize ionizing radiation (eg. stress echocardiography, stress MRI, conventional treadmill exercise stress tests, etc.). Also, even more of a problem is layering of tests. For example, a chest pain patient may get a nuclear myocardial perfusion study, then a cardiac CT angiogram or PET scan, then a cardiac catheterization). In some cases, particularly in the highest risk patients, it makes more sense to go first with the most definitive test because it may result in the least cumulative radiation exposure (and may actually also be the least costly approach). National and specialty society guidelines need to do a better job of considering cumulative radiation dose when recommending algorithms for workup of various medical conditions.
Of even more concern is the cumulative radiation dose given to younger patients, particularly pediatric age group patients. The potential for cancer development as a result of radiation exposure is much greater over their longer lifetimes. Yet children presenting to emergency rooms or urgent care centers with abdominal pain frequently get CT scans to rule out appendicitis, when ultrasound examination (which does not use ionizing radiation) could suffice in many cases. Similarly CT scans of the head or X-rays of the ankle and knee are often done in the pediatric ER population that could be avoided if physicians applied well-validated clinical decision support rules that help sort out who should have a study and who should not. Most physicians think only about the radiation dose of the single study they are ordering and do not consider the radiation exposure that individual may get over a more prolonged period.
The numbers of CT scans have been rising at alarming rates over the past decade, often without a concomitant increase in diagnostic yield. A recent study on advanced imaging studies in emergency rooms (Korley 2010) showed that between 1998 and 2007 the rate of CT or MRI for injury-related conditions increased from 6% to 15% but the prevalence of life-threatening conditions increased only from 1.7% to 2.0%.
And in the Medicare population, the use of CT angiography of the head/neck rose 827% between 2002 and 2007 (Friedman 2010). And we are seeing more and more coronary CT angiograms in chest pain patients (though note that a negative coronary CT angiogram does have the potential to avoid the layering of testing noted above). Also becoming popular is the “triple rule out” CT (rule out coronary artery occlusion, aortic dissection, pulmonary embolus).
CT scanning in pediatrics remains a key issue. Though one study showed that CT utilization as a percentage of cross-sectional imaging studies has decreased steadily since 2003 in pediatric facilities across North America (Townsend 2010), studies presented at the Pediatric Academic Societies (PAS) 2010 Annual Meeting (Hoyle 2010) demonstrated that pediatric head CT scans for trauma continue to be overordered and that observation of children with head trauma who lack “red flags” can often result in avoidance of unnecessary CT scanning. Moreover, a significant number of pediatric trauma patients who receive CT scans at referring hospitals before transfer to a level I pediatric trauma center require duplicate scans of the same anatomical field(s) after transfer, exposing them to increase potential clinical risk and cost (Chwals 2008).
Nationally, the “Image Gently” campaign has focused both on reducing the frequency of unnecessary exposures to ionizing radiation in children and to using lower doses of radiation when such studies must be done. In New York, as part of the “Image Gently” campaign, the Department of Health has made available an informational pamphlet for parents on imaging in their child and a medical imaging record card. We find that brochures like these also helps address some of the “consumer demand” for CT scans. When a physician provides a family with these as he/she is discussing the benefits and risks of various imaging modalities (or the benefits and risk of simply observing without imaging), families tend to be more understanding of approaches that do not involve CT scanning.
The FDA completed its investigation of last year’s rash of radiation overdoses from brain perfusion CT scans and concluded there was no equipment malfunction but rather that improper use of the systems had led to the overdoses. Nevertheless, they are working with the imaging manufacturing industry to improve design and functionality of imaging equipment, including development of adequate warnings for techs and radiologists when a patient is being exposed to higher than normal levels of radiation.
Tracking of cumulative radiation dosage is an equally important goal. As we develop electronic medical records, particularly with interoperability so that data can be exchanged across multiple hospital systems, free standing units and offices, a longitudinal record of a patient’s cumulative radiation exposure may be possible. An article just out (Cook 2010) describes a methodology for extracting radiation dose from those systems where dose is stored in an image-based dose sheet. Such might be used to get at least a partial cumulative dose record for patients as we wait for more proactive solutions in the future.
One of the most important strategies in reducing the frequency of unnecessary CT scans is letting your physicians know how often they order them (audit and feedback). Typically, when we provide this data we see considerable variation in ordering rates by individual provider. When they see how they compare to their peers and discuss the issue at departmental QI meetings, we usually see a subsequent reduction in unnecessary testing. One report noted that pediatric emergency room physicians were more likely to order CT scans on children than adult emergency room physicians (Sullivan 2008), a somewhat unexpected finding.
Making providers aware of the radiation dose exposure of individual tests as well as cumulative dosing may also be helpful. There are a couple web-based tools available for calculating radiation risk and/or radiation dose. One is http://www.xrayrisk.com/. The other is a pediatric CT Effective Dose and Cancer Risk Estimator developed by Alessi and Phillips (Alessi 2010). An excellent commentary on how to discuss the radiation hazard of CT scanning with patients (and our obligation to do so) was recently published in JAMA (Baerlocher 2010).
Use of clinical decision support rules is a good way to minimize the number of unnecessary CT scans. In our March 2010 What’s New in the Patient Safety World column “CATCH: New Clinical Decision Rule for CT in Pediatric Head Trauma” we discussed several “rules” that aid the decision about performing CT scans of the head in patients with minor head trauma. These include the Canadian CT Head Rule (Stiell 2001), the New Orleans Criteria (Haydel 2000) and the CHIP Prediction Rule (Smits 2007) for adults and CATCH (the Canadian Assessment of Tomography for Childhood Head Injury), for children with minor head injury (Osmond et al 2010). A recent cost-effectiveness analysis for use of these rules in minor head injury (Smits 2010) showed that use of these rules can produce substantial cost savings.
In our August 2009 What’s New in the Patient Safety World column “Imaging for Acute Abdominal Pain” we discussed multiple issues regarding imaging for acute abdominal pain and noted that a conditional strategy (ultrasound followed by CT only if the ultrasound is negative) could cut CT use by up to 50% and appears to be quite accurate, safe, efficient and economical and avoids some of the potential adverse effects of CT scanning.
And always keep in mind that there are risks to imaging beyond the radiation danger. Any time IV contrast is utilized there is a danger of contrast-induced nephropathy. In fact, a recent study (see Joelving 2010 reporting on a study by Mitchell et al.) noted that with spiral CT scanning to rule out pulmonary emboli, you are actually more likely to cause contrast-induced renal damage than to diagnose pulmonary emboli. In that prospective study of 175 ED patients who had CT for suspected pulmonary embolism, 9% were diagnosed with pulmonary embolism and received anticoagulation but 15% developed contrast-induced nephropathy.
The other significant risk often seen in CT scanning, particularly in pediatrics, is that related to sedation administered for the scan. We discussed that extensively in our May 25, 2010 Patient Safety Tip of the Week “Propofol Issues”.
So what should your organization be doing? We recommend the following as a start:
- Audit and feedback (part of your QI program, you should be tracking imaging studies and who is ordering them)
- Use evidence-based clinical decision support tools to help guide the appropriate ordering of imaging studies
- Provide “Image Gently” pamphlets and imaging record cards to families of your pediatric patients
- Alert your providers to the web-based tools for calculating radiation risk
- Implement low-dose protocols where recommended by radiology and other specialty societies
- See if you can calculate cumulative radiation dosage for individual patients (on studies done at your facilities)
- Make sure you have available alternatives to ionizing radiation-based studies where applicable (eg. ultrasound)
References:
Einstein AJ, Weiner SD, Bernheim A, et al. Multiple Testing, Cumulative Radiation Dose, and Clinical Indications in Patients Undergoing Myocardial Perfusion Imaging. JAMA. published online Nov 15, 2010; (doi:10.1001/jama.2010.1664)
http://jama.ama-assn.org/cgi/reprint/jama.2010.1664v1
Korley FK, Pham JC, Kirsch TD. Use of Advanced Radiology During Visits to US Emergency Departments for Injury-Related Conditions, 1998-2007. JAMA 2010; 304(13): 1465-1471
http://jama.ama-assn.org/cgi/content/abstract/304/13/1465
Friedman DP, Levin DC, Rao VM. Trends in the Utilization of CT Angiography and MR Angiography of the Head and Neck in the Medicare Population.. J Amer Coll Rad 2010; 7(11): 854-858
http://www.jacr.org/article/S1546-1440%2810%2900261-9/abstract
Townsend BA, Callahan MJ, Zurakowski D, Taylor GA. Has Pediatric CT at Children's Hospitals Reached Its Peak? Am. J. Roentgenol., May 2010; 194: 1194 – 1196
Hoyle B. CT Scans Overused in Emergency Assessment of Pediatric Head Trauma? Medscape Medical News. May 12, 2010
http://www.medscape.com/viewarticle/721689
Chwals WJ, Robinson, AV, Sivit CJ, et al. Computed tomography before transfer to a level I pediatric trauma center risks duplication with associated increased radiation exposure. J Pediatr Surg 2008; 43(12): 2268-2272
http://www.jpedsurg.org/article/S0022-3468%2808%2900760-4/abstract
The Image Gently Campaign.
http://www.pedrad.org/associations/5364/ig/
NYSDOH. What Parents Should Know About CT Scans for Children: Medical Radiation Safety
My Child’s Medical Imaging Record
Cook TS, Zimmerman S, Maidment ADA, et al. Automated Extraction of Radiation Dose Information for CT Examinations. J Amer Coll Rad 2010; 7(11): 871-877
http://www.jacr.org/article/S1546-1440%2810%2900377-7/abstract
Sullivan MG. Pediatric Physicians More Likely to Order Head CT Scans. ACEP News. August 2008
http://www.acep.org/publications.aspx?id=40708
xrayrisk.com
CT Effective Dose and Cancer Risk Estimator
http://faculty.washington.edu/aalessio/doserisk2/
Alessi A, Phillips GS. A pediatric CT dose and risk estimator. Pediatric Radiology 2010; 40(11): 1816-1821
http://www.springerlink.com/content/a7466344628627lg/fulltext.pdf
Baerlocher MO, Detsky AS. Discussing Radiation Risks Associated With CT Scans With Patients. JAMA. 2010;304(19):2170-2171. doi:10.1001/jama.2010.1591
http://jama.ama-assn.org/cgi/content/short/304/19/2170
Stiell IG, Wells GA,Vandemheen K, et al for the CCC Study Group. The Canadian CT Head Rule for patients with minor head injury. Lancet 2001; 357: 1391–96
http://www.mcgill.ca/files/emergency/CCHR.pdf
Haydel MJ, Preston CA, Mills TJ, et al. Indications for Computed Tomography in Patients with Minor Head Injury. N Engl J Med 2000; 343: 100-5
http://content.nejm.org/cgi/reprint/343/2/100.pdf
Smits M, Dippel DWJ, Steyerberg EW, et al.Predicting Intracranial Traumatic Findings on Computed Tomography in Patients with Minor Head Injury: The CHIP Prediction Rule. Ann Intern Med. 2007; 146: 397-405
http://www.annals.org/content/146/6/397.full.pdf+html
Smits M, Dippel DWJ, Nederkoorn PJ. Minor Head Injury: CT-based Strategies for Management—A Cost-effectiveness Analysis. Radiology 2010; 254: 532-540
http://radiology.rsna.org/content/254/2/532.abstract
Osmond MH, Klassen TP, Wells GA, et al. CATCH: a clinical decision rule for the use of computed tomography in children with minor head injury. Can. Med. Assoc. J., Feb 2010; early release published February 8, 2010 doi:10.1503/cmaj.091421
Joelving F. Contrast-induced nephropathy may be common after chest CT. By Reuters Health October 1, 2010
http://www.auntminnie.com/index.asp?Sec=sup&Sub=cto&Pag=dis&ItemId=92220
http://www.patientsafetysolutions.com
Patient
Safety Tip of the Week Archive
What’s New in the Patient Safety World Archive