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1 Note: This copy is for your personal, non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at David B. Larson, MD, MBA Lara W. Johnson, MD, MHS Beverly M. Schnell, PhD Marilyn J. Goske, MD Shelia R. Salisbury, PhD Howard P. Forman, MD, MBA Rising Use of CT in Child Visits to the Emergency Department in the United States, Purpose: Materials and Methods: To describe nationwide trends and factors associated with the use of computed tomography (CT) in children visiting emergency departments (EDs) in the United States between 1995 and This study was exempt from institutional review board oversight. Data from the National Hospital Ambulatory Medical Care Survey were used to evaluate the number and percentage of visits associated with CT for patients younger than 18 years. A mean of 7375 visits were sampled each year. Data were subcategorized according to multiple patient and hospital characteristics. The Rao-Scott x 2 test was performed to determine whether CT use was similar across subpopulations. ORIGINAL RESEARCH n HEALTH POLICY AND PRACTICE Results: Conclusion: From 1995 to 2008, the number of pediatric ED visits that included CT examination increased from 0.33 to 1.65 million, a fivefold increase, with a compound annual growth rate of 13.2%. The percentage of visits associated with CT increased from 1.2% to 5.9%, a 4.8-fold increase, with a compound annual growth rate of 12.8%. The number of visits associated with CT at pediatric-focused and non pediatric-focused EDs increased from and , respectively, in 1995 to and , respectively, in By the end of the study period, top chief complaints among those undergoing CT included head injury, abdominal pain, and headache. Use of CT in children who visit the ED has increased substantially and occurs primarily at non pediatric-focused facilities. This underscores the need for special attention to this vulnerable population to ensure that imaging is appropriately ordered, performed, and interpreted. q RSNA, From the Department of Radiology (D.B.L., M.J.G.) and Division of Biostatistics and Epidemiology (B.M.S., S.R.S.), Cincinnati Children s Hospital Medical Center, 3333 Burnet Ave, MLC 5031, Cincinnati, OH 45229; Robert Wood Johnson Foundation Clinical Scholars Program (L.W.J.) and Department of Diagnostic Radiology (H.P.F.), Yale University School of Medicine, New Haven, Conn. Received October 6, 2010; revision requested November 26; revision received January 26, 2011; fi nal version accepted February 1. Address correspondence to D.B.L. ( ). q RSNA, 2011 Radiology: Volume 259: Number 3 June 2011 n radiology.rsna.org 793

2 Computed tomography (CT) has become a vital component of rapid diagnostic evaluation of children in the emergency department (ED). The advent of multidetector helical scanners has resulted in decreased scanning times and higher image quality, which are especially helpful in the pediatric setting ( 1 ). Scans that previously required several minutes now are completed in a few seconds, which eliminates the need for sedation in many instances ( 2,3 ). Not surprisingly, the use of CT in the United States has risen sharply in the general population in the decades since its introduction ( 4,5 ). The use of CT has similarly increased in children presenting at the ED ( 6,7 ). The rising use of CT has become a point of concern for providers ( 8 11 ) and regulators ( ) and is receiving increased attention in the medical literature and popular media ( ). In addition to the increasing expenditures dedicated to the modality, CT constitutes the largest source of medically related exposure to ionizing radiation in the United States ( 9,18,19 ). This is of special concern in pediatric patients, because the potential risk associated with radiation exposure is higher in children than in adults ( 20,21 ). In view of the higher susceptibility to potential effects from ionizing radiation in children than in adults, a broad assessment of pediatric CT use in EDs in the United States is warranted. The purpose of this study was to describe Advances in Knowledge n The fivefold increase in CT use in children visiting the emergency department (ED) from 1995 to 2008 mirrors the increase seen in the adult population. n Among pediatric visits to the ED that were associated with CT, 89.4% took place at non pediatric-focused facilities. n At non pediatric-focused facili- ties, children made up 11.7% of all visits associated with CT in 1995 and 8.1% of such visits in nationwide trends and factors associated with the use of CT in children visiting EDs in the United States between 1995 and Materials and Methods This study, based on the National Hospital Ambulatory Medical Care Survey (NHAMCS) public-use data set, met the criteria for exemption from institutional review board oversight under the Code of Federal Regulations Title 45, part (b)(4) ( 22 ). Sample The NHAMCS is a nationally representative stratified sample of ED encounters in the United States that is administered by the Centers for Disease Control and Prevention and the National Center for Health Statistics. The NHAMCS instrument samples visits to EDs and outpatient departments of noninstitutional general and short-stay hospitals in the 50 states and the District of Columbia, excluding federal, military, and Veterans Administration hospitals. A more detailed description of the NHAMCS is available at the Centers for Disease Control and Prevention Web sites (http: // /ahcd1.htm, /about/major/ahcd/nhamcsds.htm). We analyzed the ED component of the NHAMCS public-use data file in patients younger than 18 years during Implications for Patient Care n Because of the higher susceptibil- ity to potential effects from ionizing radiation in children compared with adults, the rapid rise in CT warrants further efforts to ensure appropriate use and dose optimization. n Because the large majority of pediatric CT is performed at non pediatric-focused EDs, collaborative approaches that align pediatric radiology departments and EDs with general radiology departments and EDs are needed. Included in the NHAMCS survey instrument is a response indicating whether the patient underwent CT or magnetic resonance (MR) imaging during the visit. For all years except , the NHAMCS survey instrument assessed CT use and MR imaging use as separate variables. However, for the years , the variables were assessed jointly, allowing only a single response for CT or MR imaging use. To estimate the number of visits associated with CT during , we calculated the mean percentage of visits involving CT among all visits with CT or MR imaging for and We multiplied this percentage by the number of visits with CT or MR imaging for The mean percentage of visits with CT was 97.9%, with a range from 94.0% to 100% and a standard deviation of 1.7%. High and low estimates of the number of visits with CT for these years were calculated for overall use of CT by using 6 2 standard deviations. The mean percentage of visits with CT (97.9%) was applied for estimates of CT use in all subcategories for We considered three patient characteristics: patient age (infant or toddler [, 2 years], preschool aged [2 years age, 6 years], school aged [6 age, 13 years], and adolescent [13 age, 18 years]), patient sex, and patient race (white, black, and other). We also included ED characteristics of ED Published online before print /radiol Radiology 2011; 259: Abbreviations: ED = emergency department NHAMCS = National Hospital Ambulatory Medical Care Survey Author contributions: Guarantor of integrity of entire study, D.B.L.; study concepts/study design or data acquisition or data analysis/ interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript fi nal version approval, all authors; literature research, D.B.L., L.W.J., M.J.G.; statistical analysis, D.B.L., L.W.J., B.M.S., S.R.S.; and manuscript editing, all authors Potential confl icts of interest are listed at the end of this article. 794 radiology.rsna.org n Radiology: Volume 259: Number 3 June 2011

3 teaching status and whether the ED had a pediatric focus. Teaching status was not directly assessed in the survey but was defined by the authors on the basis of the percentage of patient visits to the facility in which a resident or intern participated; Teaching EDs were defined as those in which at least 10% of visits involved trainee participation. The training status of the ordering physician was not assessed in the survey. Pediatric focus of the ED was not directly assessed in the survey but was defined on the basis of the mean patient age for the facility. The mean patient age for each facility was calculated for each year, and data for all years were aggregated into a single data set. On the basis of the resultant bimodal distribution, we determined a mean age threshold; EDs with a mean patient age below this threshold were considered to be focused on the care of children. We designated these facilities as EDs with a pediatric focus and the remaining facilities as nonpediatric focused. The numbers of visits associated with CT were estimated for both pediatric-focused and non pediatric-focused facili ties. Analysis of covariance was performed for the number of visits with CT by including the group-by-year interaction, where group was the type of ED (pediatric focused vs nonpedi atric focused). The analysis of covariance procedure was also performed for the percentage of visits with CT for pediatric-focused and non pediatric-focused facilities. The percentages of all visits with CT that were pediatric visits were calculated for non pediatric-focused facilities. The survey instrument allowed up to three reasons for a visit, stated in the patient s (or patient surrogate s) own words and coded into categories by survey staff. We treated the first reason for a visit as the chief complaint. Chief complaints most commonly associated with CT were determined by initially considering only visits in which CT was performed. Among these visits, the 10 most common chief complaints were identified for each year. On the basis of these results, a list of the three most common chief complaints over the course of all of the years was generated. (Estimates of other chief complaints were limited by the sample size.) The percentage of visits with CT for each chief complaint for each year was calculated by dividing the national weighted estimate of the number of visits in which CT was performed for that chief complaint by the national weighted estimate of all visits for that chief complaint. Data Analysis Data analysis was performed with software (SAS, version 9.2; SAS Institute, Cary, NC). To estimate the total number of visits and the number of visits with CT among the subpopulations, domain analysis (also called subgroup analysis) was conducted by using Proc SURVEYFREQ (SAS) ( 23 ). The 95% confidence intervals were computed by using Proc SURVEYFREQ, which takes into account the sampling weights, stratification, and clustering. To test the null hypothesis that the percentage of CT use was similar across subpopulations (for example, between male and female subgroups), we used the Rao-Scott x 2 test, which is a design-adjusted version of the Pearson x 2 test. This test was conducted separately for each year. A P value less than.01 was considered to indicate a significant difference that is, for that year, the percentage of CT use was associated with the variable of interest and was therefore different across the categories of that variable. The compound annual growth rate (CAGR) for the study period was calculated by using the following equation: N CAGR 1, N 1995 where N 2008 and N 1995 are the numbers of visits with CT in 2008 and 1995, respectively. Results Sample Characteristics The number of ED visits in the samples ranged from a minimum of 5072 in 1999 to a maximum of 9725 in National 1 estimates of the number of ED visits represented by these samples ranged from a minimum of 24.3 million visits in 1997 to a maximum of 28.9 million visits in 2003 and The numbers of ED visits sampled and national estimates of the number of ED visits for each subpopulation are listed in Tables 1 and 2, respectively. Overall Use The numbers of ED visits in which CT was performed from 1995 to 2008 are illustrated in Figure 1. The number of visits increased by a factor of 5.0, corresponding to a compound annual growth rate of 13.2% and a doubling time of approximately every 5.6 years. By 2008, CT was performed in 1.7 million of a total of 27.9 million pediatric visits to the ED. The percentage of ED visits in which CT was performed from 1995 to 2008 is shown in Figure 2. The percentage of visits with CT increased by a factor of 4.8, corresponding to a compound annual growth rate of 12.8% and a doubling time of approximately every 5.8 years. By 2008, CT was performed in 5.9% of all pediatric visits to the ED. CT Use according to Patient Characteristics For each year of the study period, CT use in the ED was greater in adolescents and school-aged children than in preschool-aged children and infants or toddlers ( Table 3, Fig 3 ). Compound annual growth rates for the percentage of visits in which CT was performed for infants or toddlers, preschool-aged children, school-aged children, and adolescents were 16.2%, 11.7%, 12.0%, and 12.2%, respectively. The percentages of visits associated with CT for sex and race are listed in Table 3. There was no significant difference in CT use between male and female patients, except in There was no significant difference in CT use between patients of different races except in Chief Complaint For the patient visits in which CT was performed, the most common chief Radiology: Volume 259: Number 3 June 2011 n radiology.rsna.org 795

4 Table 1 NHAMCS Sample Characteristics according to Year Characteristic Overall No. of visits No. of visits with CT Sample percentage visits with CT Age (y) 0 age, age, age, age, Sex Male Female Race White Black Other ED teaching status Teaching Nonteaching Pediatric-focused facility status Pediatric focused Nonpediatric focused Chief complaint Head injury Headache Abdominal pain Note. All data except sample percentage of visits with CT are numbers of ED visits. complaint reported during the study period was head injury (1.94 million visits), followed by headache (1.39 million visits) and abdominal pain (0.97 million visits). Percentages of visits in which CT was performed for these chief complaints are listed in Table 3. In the last 4 years of the study period, CT was performed in these visits at a rate of approximately 20% 34%, 20% 28%, and 15% 21% for head injury, headache, and abdominal pain, respectively. The chief complaint for which the rate of imaging increased the most was abdominal pain, which was performed only rarely (less than 2% of visits) in the first 4 years of the study but was performed in 15% 21% of visits in the last 4 years. Other chief complaints for which CT was performed relatively commonly during the last 4 years included convulsions (18% 32%), syncope (25% 43%), and flank pain (20% 40%). More detailed evaluation on the basis of chief complaint was limited by the sample size. CT Use according to Hospital Characteristics The distribution of the mean patient age for the ED was bimodal; mean patient age was 10 years or younger in 3.0% of facilities and 18 years or older in approximately 97.0% ( Fig 4 ). Only 0.3% of facilities had a mean patient age older than 10 years and younger than 18 years. Pediatric-focused EDs were defined as those in which the mean patient age was 10 years or younger. The number of child visits associated with CT was much higher at non pediatric-focused EDs than at pediatricfocused EDs ( Table 2 ). Among the 376 million ED visits during the study period, 47.6 million (12.7%) were to pediatricfocused EDs and 328 million (87.3%) were to non pediatric-focused EDs. Among the 12.3 million visits associated with CT during the study period, 1.31 million (10.6%) were to pediatricfocused EDs and million (89.4%) were to non pediatric-focused EDs. The increase in the number of visits with CT was greater at pediatric-focused EDs than non pediatric-focused EDs ( P,.0001). Differences in the percentage of visits in which CT was performed at pediatricfocused versus non pediatric-focused EDs did not reach statistical significance during the study period, although the relatively small sample size limits the statistical power. Visits by children made up a decreasing percentage of all visits with CT at nonpediatric facilities, decreasing from 11.7% in 1995 to 8.1% in 2008 ( Fig 5 ). 796 radiology.rsna.org n Radiology: Volume 259: Number 3 June 2011

5 Table 2 National Estimates of Number of ED Visits (in Millions) according to Patient and Hospital Characteristics Characteristic Overall no. of visits Age (y) 0 age, age, age, age, Sex Male Female Race White Black Other ED teaching status Teaching Nonteaching Pediatric-focused facility status Pediatric focused Nonpediatric focused Chief complaint Head injury Headache Abdominal pain Note. Data are numbers of ED visits (in millions). Data for were derived from estimates of CT or MR imaging use. Figure 1 Figure 2 Figure 1: Graph illustrates number of ED visits with CT from 1995 to 2008 in patients younger than 18 years. Data points = national estimates of the number of annual ED visits. Error bars = 95% confi dence intervals. Data for were derived from estimates of CT use or MR imaging use. High and low estimates of these values (thick horizontal lines) for these years are indicated. Figure 2: Graph illustrates percentages of ED visits with CT from 1995 to 2008 in patients younger than 18 years. Data points = national estimates of the number of ED visits with CT divided by the number of all ED visits. Error bars = 95% confi dence intervals. Radiology: Volume 259: Number 3 June 2011 n radiology.rsna.org 797

6 Table 3 CT Use according to Patient and Hospital Characteristics Characteristic Overall No. of visits (in millions) No. of visits with CT (in millions) Percentage of visits with CT Age (y) 0 age,2 0.4 * * * 1.7 * 1.9 * 1.6 * 1.4 * 2.4 * 2.5 * 1.7 * 2.3 * 3.1 * 2 age,6 0.8 * * * 1.6 * 2.0 * 1.5 * 2.0 * 2.2 * 2.9 * 3.5 * 2.0 * 3.4 * 6 age, * * * 4.5 * 3.4 * 2.8 * 3.8 * 5.3 * 5.4 * 6.0 * 6.2 * 6.5 * 13 age, * * * 5.3 * 4.8 * 5.4 * 6.1 * 7.4 * 8.0 * 7.4 * 10.4 * 10.5 * Sex Male * Female * Race White * 6.4 Black * 4.5 Other * 6.4 ED teaching status Teaching * Nonteaching * Pediatric-focused facility status Pediatric focused Nonpediatric focused Chief complaint Head injury Headache Abdominal pain Note. Unless otherwise indicated, data are national estimates of percentages of ED visits with CT. National estimates of percentage of ED visits with CT represent the weighted percentages of ED visits that were associated with CT within each category. Data for were derived from estimates of CT or MR imaging use. * P,.01. Figure 3 Figure 3: Graph illustrates percentages of ED visits with CT according to patient age. Percentages are national estimates of the number of ED visits with CT divided by the number of all ED visits for each age group. P,.01 for all years, except 1996 and Discussion We found that the growth in the use of CT in children who visit EDs in the United States was substantial and relatively sustained during the 14-year study period. The compound annual growth rate for the overall number of visits in which CT was performed in children visiting the ED (13.2%) was comparable to the 15.9% growth rate in the use of CT in patients of all ages during a similar period, as described elsewhere ( 7 ). The growth in the use of CT is explained by increasing frequency of use, not by an increase in the number of pediatric visits to the ED, because the number of pediatric visits remained relatively constant during the study period. The compound annual growth rate for the percentage of visits in 798 radiology.rsna.org n Radiology: Volume 259: Number 3 June 2011

7 Figure 4 Figure 4: Graph illustrates distribution of mean patient age for ED according to the NHAMCS. Pediatric-focused EDs were considered to be those with a mean age of 10 years or younger (vertical line). Figure 5 Figure 5: Graph illustrates percentage of all visits with CT by children at non pediatricfocused EDs. Percentages are number of visits with CT (children) divided by number of visits with CT (all ages). which CT was performed in children in the ED (12.8%) was comparable to the 14.2% growth rate in the percentage of visits with CT in patients of all ages. Therefore, while CT was performed in a lower percentage of ED visits in children than in adults ( 7 ), its use in children continued to rise at a rate comparable to that of adults. Our reported growth rates of CT use in children in the ED were similar to the previously published growth rate of CT in the ED of 10.5% in a single children s hospital between 2000 and 2006 ( 6 ). Our finding that CT use was higher in older children than in younger children corresponds to that reported by other authors ( 6,24 ). Other authors have reported that the use of CT may have begun to decline at children s hospitals ( 25 ). Our findings suggested that this may indeed have been the case at pediatric-focused EDs during a similar time period ( ). However, this downward trend did not appear to continue in The chief complaints for which children most commonly undergo CT are similar to those of adults, although CT is performed at rates roughly percentage points lower for the same indications in children than in adults ( 7 ). CT use in the setting of abdominal pain increased much more than in the setting of head injury and headache. This suggests that the radiation dose likely increased at an even higher rate than the rate of increase in the percentage of visits in which CT was performed, given that CT of the abdomen and pelvis is typically associated with effective doses of radiation of up to seven times that of head CT ( 26,27 ). This is of particular importance in children whose tissues are more radiosensitive. During the study period, we found that only 10.6% of the 12.3 million pediatric visits with CT occurred at pediatricfocused EDs. This is supported by reports that only 7% of hospitals in the United States have a dedicated pediatric ED ( 28 ). This has several important implications. The performance of CT in children requires special oversight, especially in regard to the selection of size-based CT scanning parameters and sedation techniques ( 29 ). It is possible that non pediatric-focused radiology departments may be less likely to consistently tailor the CT technique to the body size of the pediatric patient. For example, in their 2001 study of mostly communitybased hospitals, Paterson et al ( 21 ) found that CT radiation doses were not typically adjusted for children s smaller body size. To our knowledge, no follow-up studies have been performed in this same population to determine if this situation has improved over time. This is in contradistinction to a study by Arch and Frush ( 30 ), who found that CT protocols supervised by pediatric radiologists Radiology: Volume 259: Number 3 June 2011 n radiology.rsna.org 799

8 have improved with routine adjustments of scanning techniques for children. Other studies have shown that the number of pediatric radiologists in private practice is less than the number at children s hospitals ( ) and that most pediatric radiologists in private practice spend only a fraction of their time practicing pediatric radiology sometimes a very small fraction ( 33,34 ). Our findings that the large majority of ED visits associated with CT in children occur at non pediatric-focused facilities (89.4%) indicates that most CT examinations performed in the ED in children likely are interpreted by radiologists who are not subspecialty trained in pediatric radiology. At the same time, children made up a decreasing percentage of all visits with CT at nonpediatric facilities. This implies that while the overwhelming majority of CT examinations in children visiting the ED are performed in non pediatric-focused EDs, most of the attention of such facilities and personnel continues to be occupied by adult patients, at least from the standpoint of the volume of ED CT examinations. We recognize that some EDs have dedicated pediatric facilities and specialists who are separate from or work within an adult facility, which may not be accurately reflected in our analysis. However, Athey et al ( 28 ) found that this is relatively uncommon; 76% of U.S. hospitals care for pediatric emergencies in an adult-pediatric combined ED and 18% care for children in an adult ED. Our study had several other limitations. Because of the lack of oversampling of the pediatric population, the data obtained from the NHAMCS are less precise when focused on children than when accounting for patients of all ages. The NHAMCS instrument does not acquire detailed clinical data; therefore, our findings cannot be used to match CT use to clinical criteria and should be used with caution in establishing benchmarks for individual ED pediatric CT utilization rates. Possible external causes driving increased use, such as increasing ED patient acuity and clinical referral to the ED specifically for CT, are not captured by this survey. Furthermore, the NHAMCS instrument samples patient visits but does not track individual patients over time; it is impossible to know how many of the visits associated with CT represent repeat imaging of the same patient. The estimates for are also limited in that CT and MR imaging was assessed jointly, although this effect is likely small given the consistently high percentage of CT in the years that both CT and MR imaging use was measured. While appropriate use of CT is important in all populations, it is of special concern in the pediatric population in that (a) in terms of the risk of developing radiation-induced cancer, children s organs are more radiosensitive than adults ( 20 ), (b) children have a longer remaining life expectancy in which cancer may potentially form, (c) radiation settings are often not adjusted to match children s smaller sizes ( 21 ), and (d) with the recent advent and growth in use of CT ( 4 ), individuals who are currently children are likely to eventually receive a higher cumulative lifetime dose of medically related radiation than those who are currently adults. We find it noteworthy that, while the overwhelming majority of pediatric CT examinations are performed at non pediatric-focused EDs, pediatric CT makes up a diminishing percentage of the studies that are performed at those facilities. In other words, the evidence suggests that, at least when it comes to the provision of CT in children visiting the ED, results of pediatric imaging are less likely to be interpreted by a pediatric radiologist than in the past. This finding is supported by Smith et al ( 35 ) who found a 31% decrease in the percentage of radiologists whose main subspecialty was pediatric radiology between 2003 and Interestingly, Smith et al found evidence of a decreased number of subspecialists in only two radiology subspecialties: pediatric imaging and ultrasonography; otherwise, subspecialization in radiology appears to be increasing. This apparent shift, whereby subspecialty imaging apparently is increasingly interpreted by generalists, stands in contradistinction to the model of increasing specialization prevalent in modern medicine ( 36,37 ), as well as trends that have been predicted in radiology for many years ( ). From a technical standpoint, radiology is in a unique position to overcome the logistic barriers to subspecialization through the use of electronic communication systems ( 41,42 ). Such systems are technically capable of instantly distributing studies to subspecialists regardless of locale, facilitating support to general radiologists through subspecialty consultation and enabling subspecialty oversight of imaging utilization and performance ( 43 ). Furthermore, this can theoretically be done at no increased marginal cost, because radiology subspecialists are typically not compensated at a higher rate than general radiologists ( 44 ). However, we find little evidence that pediatric- and non pediatric-focused facilities have begun to engage in this kind of cooperation. On the contrary, it has been found that performance of CT at an institution that is preparing to transfer a child is a primary factor in the delay of transfer to a level I pediatric trauma center in the setting of severe pediatric injury ( 45,46 ). While increased subspecializaton of pediatric imaging may be highly achievable from technical and cost standpoints, the trend toward decreased subspecialized oversight of pediatric imaging is likely to continue as long as current reimbursement and organizational structures are maintained. Our finding of a substantial increase in the use of CT in children who visit EDs in the United States underscores the need for special attention to this vulnerable population to ensure that imaging is appropriately ordered, performed, and interpreted. It is the professional obligation of all radiologists who perform pediatric CT to invest the required time and effort in developing the expertise to ensure that this occurs consistently for children. Adult-focused facilities may have many competing priorities; focus on pediatric CT may be hard to achieve because of the relatively small volume that pediatric CT represents at such institutions. Because the large majority of pediatric CT is performed at such facilities, collaborative 800 radiology.rsna.org n Radiology: Volume 259: Number 3 June 2011

9 approaches that align pediatric radiology departments and EDs with general radiology departments and EDs are needed. Disclosures of Potential Conflicts of Interest: D.B.L. No potential conflicts of interest to disclose. L.W.J. No potential conflicts of interest to disclose. B.M.S. No potential conflicts of interest to disclose. M.J.G. No potential conflicts of interest to disclose. S.R.S. Financial activities related to the present article: none to disclose. Financial activities not related to the present article: institution receives money from Toshiba Medical Systems for Toshiba Aquilion Dosimetry Study, author is biostatistician for study. Other relationships: none to disclose. H.P.F. No potential conflicts of interest to disclose. References 1. Donnelly LF. Reducing radiation dose associated with pediatric CT by decreasing unnecessary examinations. AJR Am J Roentgenol 2005 ; 184 ( 2 ): Pappas JN, Donnelly LF, Frush DP. 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