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Injured Children Receive Twice the Radiation Dose at Nonpediatric Trauma Centers Compared With Pediatric Trauma Centers
ORIGINAL ARTICLE
Injured Children Receive Twice the Radiation Dose at Nonpediatric Trauma Centers Compared With Pediatric Trauma Centers Rosemary Nabaweesi, DrPH, MBChB, MPH a,b , Raghu H. Ramakrishnaiah, MD c, Mary E. Aitken, MD, MPH a,b, Mallikarjuna R. Rettiganti, PhD b, f, Chunqiao Luo, MS b, f, Robert T. Maxson, MD d, Charles M. Glasier, MD c, Phillip J. Kenney, MD e, James M. Robbins, PhD a,b Abstract Background: Use of cranial CT scans in children has been increasing, in part due to increased awareness of sports-related concussions. CT is the largest contributor to medical radiation exposure, a risk factor for cancer. Long-term cancer risks of CT scans can be two to three times higher for children than for adults because children are more radiosensitive and have a longer lifetime in which to accumulate exposure from multiple scans. Study Aim: To compare the radiation exposure injured children receive when imaged at nonpediatric hospitals (NPHs) versus pediatric hospitals. Methods: Injured children younger than 18 years who received a CT scan at a referring hospital during calendar years (CYs) 2010 and 2013 were included. Patient-level factors included demographics, mode of transportation, and Injury Severity Score, and hospital-level factors included region of state, radiology services, and hospital type and size. Our primary outcome of interest was the effective radiation dose. Results: Four hundred eighty-seven children were transferred to the pediatric trauma center during CYs 2010 and 2013, with a median age of 7.2 years (interquartile range 5-13). The median effective radiation dose received at NPHs was twice that received at the pediatric trauma center (3.8 versus 1.6 mSv, P < .001). Results were confirmed in independent and paired analyses, after controlling for mode of transportation, emergency department disposition, level of injury severity, and at the NPH trauma center level, hospital type, size, region, and radiology services location. Conclusion: NPHs have the potential to substantially reduce the medical radiation received by injured children. Pediatric CT protocols should be considered. Key Words: Effective radiation dose, nonpediatric hospitals, CT scan J Am Coll Radiol 2017;-:---. Copyright 2017 American College of Radiology
BACKGROUND CT use in children has increased, due in part to increasing concussion concerns, paralleled by emergency department (ED) visits [1-3]. During 2009 to 2010,
traumatic brain injury was evaluated in 4.8 million ED visits, and 82% of these evaluations included a CT scan [4]. Among injured children, head CT utilization is greater at hospitals with lower pediatric volumes, at
a Department of Pediatrics, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. b Arkansas Children’s Research Institute, Little Rock, Arkansas. c Department of Pediatric Radiology, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. d Department of Pediatric Surgery, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. e Department of Radiology, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. f Department of Biostatistics, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas.
Corresponding author and reprints: Rosemary Nabaweesi, DrPH, MBChB, MPH, University of Arkansas for Medical Sciences, College of Medicine, Arkansas Children’s Hospital Research Institute, 1 Children’s Way, Slot 512-26, Little Rock, AR 72202-3591; e-mail: [email protected]. Rosemary Nabaweesi was supported in part by the Arkansas Biosciences Institute, the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000, and the Marion B. Lyon Revocable Trust-New Scientist Development award. The authors have no conflicts of interest related to the material discussed in this article.
ª 2017 American College of Radiology 1546-1440/17/$36.00 n http://dx.doi.org/10.1016/j.jacr.2017.06.035
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community hospitals, and by providers without pediatric residency training [5]. Ionizing radiation from medical imaging now accounts for nearly half of the radiation exposure experienced by the US population [6,7]. CT scans are the greatest contributor to medical radiation exposure, which can increase cancer risk. Long-term cancer risks for children can be two to three times higher than for adults [8] because children are more sensitive to radiation and have a longer lifetime in which to accumulate exposure from multiple CT scans [6,9,10]. The ACR and American Association of Physicists for Medicine support the “as low as reasonably achievable” (ALARA) principle, which urges providers to use the minimum level of radiation needed in imaging examinations while maintaining diagnostic quality [11]. The use of optimized technical parameters focused on lowering tube current and tube voltage have demonstrated the reduction of radiation exposure in children by up to 65% [12-14]. Adoption of dose reduction imaging protocols has been variable with most success at pediatric hospitals and trauma centers [15]. The majority of pediatric trauma patients are managed at nonpediatric hospitals (NPHs), usually the nearest hospital after a traumatic event where children are transported for stabilization and evaluation. More seriously injured children are often transported to pediatric trauma centers (PTCs) for definitive care. It therefore follows that the majority of CT scans are performed at NPHs. In addition, results from our preliminary study demonstrated that a statewide image repository reduced the rate of CT scans repeated at a PTC by half [16]. Few studies have compared the radiation exposure between children imaged at NPHs and children imaged at pediatric facilities [5,10,16]. Most studies have used estimates for radiation dose [5,10]. We sought to use clinical radiology matrices, a more precise set of exposure metrics, to evaluate variability in CT scan exposure and to compare the CT scan radiation exposure of children imaged at NPHs and children imaged at a pediatric hospital using an optimal scanning protocol (OSP). We hypothesized that CT scans performed at NPHs would have higher radiation doses compared with CT scans performed at the children’s hospital.
METHODS Data Sources We conducted a cross-sectional study using administrative data from the pediatric trauma registry and clinical 2
data from the PACS. All children who met the state trauma system’s definition of a traumatic injury (trauma team activation, penetrating injuries, and ED deaths) were included in the registry. The trauma registry is housed at the only level I PTC in the state, which receives injured children from 64 accredited trauma system facilities. A dedicated trauma team manages the pediatric trauma registry to ensure the timeliness, accuracy, and completeness of the registry.
Patient and Variable Selection Our state trauma system comprises 64 trauma centers; these include 6 level I, 5 level II, 18 level III, and 35 level IV hospitals [12] served by 62 EDs. Among these are two PTCs and one burn center [17]. The second PTC is located in a neighboring state. All injured children under 18 years of age who met the trauma criteria, underwent CT imaging, and were transferred to the PTC from an outlying hospital during calendar year (CY) 2010 and CY 2013 were included. The image repository was created in July 2011, and we allowed for a year of full implementation across the state. All children transferred to the PTC arrived in the ED, where additional imaging, if required, is typically performed before the child is discharged to the intensive care unit, operating room, admitting floor, or home. Independent patient-level factors studied as potential covariates included age, race, gender, mode of transportation, Injury Severity Score (ISS), and ED disposition. ISS was categorized as mild (1-8), moderate (9-16), severe (17-25), and life-threatening (>26). Hospital-level factors studied included the region of the state, hospital type (urban, rural, critical care access, or community), hospital size (large, medium, and small), and location of radiology services (in-house or outsourced). Hospital size was based on the Healthcare Cost and Utilization Project definition and was nested in location and teaching status [18]. Our primary outcome of interest was the effective radiation dose (ERD). Optimal Scanning Protocols (OSPs) The CT scan protocols (referred to as OSPs) used at the PTC are institution-specific and partly based on the ACR protocols. Radiology clinicians in collaboration with equipment manufacturers developed the protocols through a quality improvement process. The protocols use dose modulation and iterative reconstruction. Additionally, the protocols require the following: (1) Radiologists’ approval is obtained for repeat scans if warranted Journal of the American College of Radiology Volume - n Number - n Month 2017
(eg, if original scan is degraded by motion artifact). (2) All head and cervical spine studies are performed without contrast, and all chest, abdomen, and pelvic scans are done with intravenous contrast. Contrast CT scans are not repeated in the same patient. (3) The thoracic and lumbar spines are reconstructed from the chest and abdominal scans, respectively; similarly, the maxillofacial scans are reconstructed from head CT when needed. (4) Arbitrary pan scanning is strictly controlled and avoided.
Statistical Analysis We summarized data using frequency and percentages for categorical variables and median (interquartile range) for continuous variables. Effective radiation dosage was calculated for each scan with dose length product (DLP) and age information using this formula, based on 16-cm diameter CT dosimetry phantom [19]: ERD ¼ DLP(16 cm) conversion coefficient(body region, age). At the CT scan-level analysis, ERD was stratified by body region (head, cervical spine, chest, and abdomen), race, age, gender, transportation, ED disposition, ISS, and trauma center level and was compared between NPH and the PTC using Mann-Whitney U tests. At the hospital-level analysis, we compared ERD using KruskalWallis tests. P values less than or equal to .05 were considered statistically significant. Statistical analysis was performed using the R software (R Core Team, Vienna, Austria). The study was approved by the Institutional Review Board of University of Arkansas for Medical Sciences. RESULTS Four hundred eighty-seven children were transferred to the PTC during the two study periods. Of those children, 78% were white, 14% were black, and 38% were female. The median age of an injured child was 7.2 years with an interquartile range (IQR) of 2.4 to 12.8. The median length of stay in the ED was 3 hours. The majority of children (58%) who received CT scans were transported by ground and had a relatively low acuity with a median ISS of 9 (IQR 5-13). (See Table 1.) Thirty-six percent of the study population was critically injured and received care in the operating room or intensive care unit. A total of 1,029 CT scans (all body regions) were received by the children in the study period. Fifty-three percent of the CT scans had DLP and age data points that were used to calculate the ERD. DLP was missing for only 6% of records at the pediatric hospital and 29% at the Journal of the American College of Radiology Nabaweesi et al n Radiation Exposure for Injured Children
Table 1. Demographic and clinical characteristics of children transferred to the pediatric trauma center at the children’s hospital Variable
N (%)
Total Race White Black Hispanic Other Gender Female Male Age (years), median (IQR) Transportation Ambulance Helicopter ED LOS in hours, median (IQR) ED disposition ICU or OR Other (home or floor) Injury Severity Score, median (IQR)
487 (100%) 379 (77.8%) 70 (14.4%) 22 (4.5%) 16 (3.3%) 186 (38%) 301 (62%) 7.2 (2.4, 12.8) 280 (58%) 205 (42%) 3.3 (2.2, 4.6) 173 (36%) 313 (64%) 9 (5, 13)
ED ¼ emergency department; ICU ¼ intensive care unit; IQR ¼ interquartile range; LOS ¼ length of stay; OR ¼ operating room.
NPHs. One thousand twenty (99.1%) of the CT scans had kilovoltage data, and 47% were missing CT dose index data (data not shown). The median ERD received at NPHs among black and white children was twice that received at the PTC (3.8 versus 1.6 mSv, P < .001). (See Table 2.) CT scans performed at NPHs had a median ERD at least twice as high as the ERD of scans performed using the OSPs among all children aged 1 year and older. Both male and female children were exposed to more than twice the ERD during CT scans conducted at NPHs as compared with the same body region scans performed using OSP. The doubling of ERD held across mode of transportation, ED disposition, level of injury severity, and trauma center level of transferring facility. Scans of the head involved twice the ERD when performed at NPHs than at the PTC. A second analysis matched CT scans done on the same patient at an NPH and repeated at the PTC. Eighty-eight children with 94 CT scan pairs were analyzed. (See Fig. 1 and Table 3.) The ERD for all CT scans conducted at NPHs was twice as high compared with CT scans performed at the PTC using OSP. The small cell sizes for CT cervical spine and abdomen did not yield stable ERD estimates. A third analysis evaluated the variability of ERD across NPHs and the PTC. The 61 (less 3, which are 3
Table 2. Comparison of effective radiation dose (millisieverts) between NPHs and PTC by demographic and clinical factors
Total Race White Black Hispanic Other Age (years) <1 1-4 5-9 10-14 >15 Gender Male Female Transportation Ambulance Helicopter ED disposition ICU or OR Other (home or floor) CT body region Head Cervical spine Chest Abdomen Injury Severity Score Mild Moderate Severe Life threatening Trauma center Level II Level III Level IV
n
NPH Median (Q1, Q3)
n
PTC Median (Q1, Q3)
P Value
415
3.8 (2.4, 5.8)
138
1.6 (1.3, 2.5)
<.001
335 48 19 13
3.8 (2.5, 6.0) 3.8 (2.0, 5.2) 3.9 (1.8, 6.8) 2.9 (2.0, 5.0)
109 19 5 5
1.6 (1.3, 2.5) 1.6 (1.0, 2.0) 2.1 (1.9, 2.3) 2.1 (1.6, 2.8)
<.001 <.001 NS NS
24 85 112 151 43
3.8 (2.8, 6.2) 3.3 (2.0, 4.7) 3.3 (1.8, 5.2) 4.2 (3.1, 8.0) 3.1 (2.5, 6.8)
11 37 31 38 21
2.5 (1.9, 2.6) 1.8 (1.5, 2.5) 1.4 (1.1, 1.6) 1.7 (1.3, 2.4) 1.6 (1.2, 7.5)
.006 <.001 <.001 <.001 NS
260 155
4 (2.6, 6.1) 3.4 (2.3, 5.1)
88 50
1.7 (1.2, 2.6) 1.6 (1.4, 2.3)
<.001 <.001
236 179
3.8 (2.6, 5.5) 3.8 (2.3, 6.9)
50 88
1.7 (1.3, 2.3) 1.6 (1.3, 2.5)
<.001 <.001
133 282
3.6 (2.5, 6.6) 3.9 (2.3, 5.6)
82 56
1.6 (1.3, 2.4) 1.8 (1.3, 2.5)
<.001 <.001
214 93 22 96
3.3 (2.4, 4.5) 3.1 (1.5, 4.6) 8.1 (5.2, 11.6) 7.3 (4.5, 11.6)
114 14 0 10
1.6 (1.2, 2.1) 5.4 (1.0, 7.0) — 7.7 (6.3, 15.7)
<.001 NS — NS
115 196 69 9
3.9 (2.1, 6.7) 3.7 (2.4, 5.2) 3.5 (2.6, 7.0) 4.6 (3.2, 7.5)
18 80 26 8
2 (1.3, 2.5) 1.6 (1.2, 2.1) 1.8 (1.4, 2.5) 2.1 (1.5, 2.6)
.004 <.001 <.001 .029
60 239 101
3.6 (2.6, 5.6) 3.7 (2.2, 5.8) 4 (2.5, 6.7)
23 72 29
1.8 (1.3, 2.7) 1.6 (1.3, 2.1) 1.6 (1.2, 2.5)
<.001 <.001 <.001
ED ¼ emergency department; ICU ¼ intensive care unit; NPH ¼ nonpediatric hospitals; NS ¼ not significant; OR ¼ operating room; PTC ¼ pediatric trauma center.
located out of state) referring hospitals were evenly distributed across the seven state-designated regions of the state, with the southwest region having the most (18%) and the metro area having the fewest facilities (11.4%). (See Table 4.) Critical care access hospitals comprised the largest group (34%), and community hospitals were the fewest (7%). Also, 30% were urban and 32% rural or community hospitals. Large hospitals (rural with 75þ and urban nonteaching with 200þ beds, urban teaching with >500 beds) made up 46%; medium hospitals, 16%; and small hospitals, 38%. The 4
majority of the transferring hospitals had in-house radiology services (71%), 21% used an outside radiology group, and 8% used both in-house and outside services. Sixteen hospitals transferred at least 10 patients to the PTC during the study period (range ¼ 11-35). The hospitals were distributed more or less like all referring hospitals except being overrepresented by urban and large hospitals. Among these hospitals, scans with available data to calculate ERD ranged from 2 to 35. CT scans from all 16 NPHs were found to have higher median ERD than the PTC median of 1.6 mSv. Scans from five NPHs with Journal of the American College of Radiology Volume - n Number - n Month 2017
N=487 Children 1029 CT* Scans
NPH† 813 CT Scans
PTC‡ 216 CT Scans
Excluded 476 CT scans without DLP§ N=303 Children
415 CT Scans with DLP
138 CT Scans with DLP
Excluded 365 scans without a match at NPH & PTC N=88 Children
94 Matching CT Scan pairs Final dataset
* CT ‡ Pediatric Trauma Center
†Non Pediatric Hospitals § Dose Length Product
Fig 1. CT scan selection.
the lowest exposure had median ERD less than 3.0. Scans from four NPHs with the highest exposure had median ERD greater than 4.0. Hospitals reporting lower median ERD were distributed throughout the state, were predominantly rural (4 of 5), and had both in-house (3) and
outsourced (2) radiology services. Hospitals reporting the highest median ERD with the exception of one outlier (median ¼ 19.3) were also distributed throughout the state, were predominately urban (3 of 4), and had both inhouse (3) and outsourced (2) radiology services.
Table 3. Comparison of the median effective radiation dose (millisieverts) between NPHs and the PTC by body regions using paired analysis
Overall Head CT spine Abdomen
CT Scan Pairs
NPH
PTC
Difference
P Value
94 83 6 5
3.5 (2.6, 5.2) 3.4 (2.5, 4.8) 4.8 (4.1, 8.6) 9.0 (7.2, 10.2)
1.6 (1.2, 2.3) 1.6 (1.2, 2.0) 1.6 (0.9, 5.1) 8.0 (6.8, 17.7)
2.1 (0.8, 3.4) 2.1 (0.9, 3.3) 3.3 (3.2, 7.8) 2.1 (3.1, 1.1)
<.001 <.001 NS NS
NPH ¼ nonpediatric hospitals; PTC ¼ pediatric trauma center; NS ¼ not significant.
Journal of the American College of Radiology Nabaweesi et al n Radiation Exposure for Injured Children
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Table 4. Hospital Level Factors for Nonpediatric Hospitals Transferring Patients to Pediatric Trauma Center
Variable Region of state Arkansas Valley Metropolitan North Central Northeast Northwest Southeast Southwest Hospital type Urban Critical care access Rural Community Unknown Hospital size* Small Medium Large Radiology services In-house Outsourced Both
All Hospitals (n ¼ 61)
Hospitals With at Least 10 Transferred Patients (n ¼ 16)
9 (14.7%) 7 (11.4%) 9 (14.7%) 8 (13.1%) 8 (13.1%) 9 (14.7%) 11 (18.0%)
3 (18.7%) 3 (18.7%) 2 (12.5%) 1 (6.2%) 3 (18.7%) 1 (6.2%) 3 (18.7%)
18 (29.5%) 21 (34.4%)
11 (68.7%) 0 (0.0%)
15 (24.5%) 4 (6.5%) 3 (4.9%)
3 (4.9%) 1 (6.2%) 1 (6.2%)
23 (37.7%) 10 (16.4%) 28 (45.9%)
0 (0.0%) 1 (6.2%) 15 (93.8%)
43 (70.5%) 13 (21.3%) 5 (8.2%)
11 (69.0%) 3 (19.0%) 2 (12.0%)
*Hospital bed size is based on Healthcare Cost Utilization Project, embedded in location and teaching status.
DISCUSSION The ALARA principle employs the following methods: (1) use weight-based protocols; (2) consider alternative nonradiating modalities; (3) when clinically appropriate, use focused or limited-view studies; and (4) dissuade repeat CT studies. Our results demonstrating that the centralized image repository halved the rate of repeat imaging in children transferred to the PTC are discussed elsewhere [16]. Use of newer-generation CT scanners, pediatric CT protocols, and head CT prediction rules as implemented by the PTC studied here are efforts to adhere to the ALARA principles. Anecdotal experience in Arkansas and a limited number of previous studies suggest that a large proportion of CT scans conducted at transferring facilities were obtained using higher tube voltage and tube current. Agarwal and colleagues demonstrated that children receive relatively higher tube voltage and tube current (radiation exposure) at NPHs, compared with pediatric hospitals [20]. 6
We set out to use available data to compare the radiation exposure when children undergo CT scans at NPHs to exposure at the pediatric hospital in a mostly rural state with a newly established trauma system and OSPs. Our findings using both independent and matched-pair analyses demonstrate a consistent pattern of twice the radiation dose when children undergo a CT scan at NPHs compared with the OSP used at the PTC. Our study confirmed that all 16 NPHs with sufficient numbers of CT scans to allow calculation of a stable median ERD subjected children to higher radiation exposure than the PTC. Five hospitals exposed children to relatively lower radiation. Four hospitals exposed children to relatively higher radiation. Our study affords an excellent opportunity to provide feedback to individual hospitals and to propose and implement standard CT scan policies across centers. This follow-up project is in development. The experience in our state is useful to inform other states with evolving trauma systems, particularly with large rural areas. Our study went beyond most current evidence by calculating ERD from tube voltage and tube current variation. Our finding that NPHs exposed children to twice the radiation dose of the PTC is in line with other studies that demonstrated lower radiation doses at pediatric institutions when compared with nonpediatric ones [5,20]. The head CT ERDs observed using the OSPs at the children’s hospital were lower than doses observed by Thomas and Wang at another large children’s hospital, across all age groups [19].
Limitations This study is a retrospective analysis and therefore was limited to the existing data. The majority of CT scans were performed on the head. Small numbers of scans performed on other body regions limit statistical power. The study compared several NPHs to a single children’s hospital. Although the children’s hospital has standardized protocols that are implemented institution-wide, there is likely wide variation among the NPHs. Equipment variation includes dose reduction software and age and type of CT scanners. However, we did not have access to the individual hospitals’ CT scanner inventory. We will collect these data in a planned quality improvement project. Missing data were a significant challenge with close to 50% of the DLP missing in CY 2010. With gradual adoption of newer radiation dose measures across hospitals, the amount of missing data declined over time. Journal of the American College of Radiology Volume - n Number - n Month 2017
Future studies using data collected more recently will likely limit the amount of missing data.
CONCLUSION Clinicians at NPHs have the potential to substantially reduce the medical radiation injured children receive by adopting OSPs similar to that used at PTCs. Careful analysis of patterns across a state trauma system affords an ideal opportunity to propose standardized scanning protocols based on real-world feedback delivered directly to hospitals and radiology staff. TAKE-HOME POINTS -
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The median ERD using OSPs at a PTC is half that at NPHs. Clinicians at NPHs have the potential to reduce the medical radiation injured children receive by adopting pediatric OSPs, which are consistently used at PTCs. Our state affords an ideal opportunity to implement standard dosing across trauma centers through audit and feedback, education, or policy change.
REFERENCES 1. Zonfrillo MR, Kim KH, Arbogast KB. Emergency department visits and head computed tomography utilization for concussion patients from 2006 to 2011. Acad Emerg Med 2015;22:872-7. 2. Kirsch TD, Hsieh YH, Horana L, Holtzclaw SG, Silverman M, Chanmugam A. Computed tomography scan utilization in emergency departments: a multi-state analysis. J Emerg Med 2011;41:302-9. 3. Kocher KE, Meurer WJ, Fazel R, Scott PA, Krumholz HM, Nallamothu BK. National trends in use of computed tomography in the emergency department. Ann Emerg Med 2011;58:452-62. 4. Korley FK, Kelen GD, Jones CM, Diaz-Arrastia R. Emergency department evaluation of traumatic brain injury in the United States, 2009-2010. J Head Trauma Rehabil 2015.
5. Graves JM, Kanal KM, Vavilala MS, Applegate KE, Jarvik JG, Rivara FP. Hospital-level factors associated with use of pediatric radiation dose reduction protocols for head CT: results from a national survey. J Am Coll Radiol 2014;11:717-24. 6. Linet MS, Kim K, Rajaraman P. Children’s exposure to diagnostic medical radiation and cancer risk: epidemiologic and dosimetric considerations. Pediatr Radiol 2009;39(Suppl 1):S4-26. 7. Wylie MC, Merritt C, Clark M, Garro AC, Rutman MS. Imaging of pediatric head injury in the emergency department. Pediatr Emerg Care 2014;30:680-5. 8. Kim PK, Gracias VH, Maidment AD, O’Shea M, Reilly PM, Schwab CW. Cumulative radiation dose caused by radiologic studies in critically ill trauma patients. J Trauma 2004;57:510-4. 9. Journy N, Roue T, Cardis E, et al. Childhood CT scans and cancer risk: impact of predisposing factors for cancer on the risk estimates. J Radiol Prot 2016;36:N1-7. 10. Kharbanda AB, Flood A, Blumberg K, Kreykes NS. Analysis of radiation exposure among pediatric trauma patients at national trauma centers. J Trauma Acute Care Surg 2013;74:907-11. 11. Goske MJ, Strauss KJ, Westra SJ, Frush DP. The Image Gently ALARA CT summit on new CT technologies for children. Pediatr Radiol 2014;44 Suppl 3:403. 12. Mahesh M, Fishman EK. CT dose reduction strategy: to modulate dose or not in certain patients? J Am Coll Radiol 2012;9:931-2. 13. Mahesh M. Advances in CT technology and application to pediatric imaging. Pediatr Radiol 2011;41 Suppl 2:493-7. 14. Strauss KJ, Goske MJ, Kaste SC, Bulas D, Frush DP, Butler P, et al. Image Gently: ten steps you can take to optimize image quality and lower CT dose for pediatric patients. AJR Am J Roentgenol 2010;194: 868-73. 15. Graves JM, Kanal KM, Rivara FP, Jarvik JG, Vavilala MS. Dose reduction efforts for pediatric head CT imaging in Washington State trauma centers: follow-up survey results. J Am Coll Radiol 2014;11:161-8. 16. Nabaweesi R, Ramakrishnaiah RH, Rettiganti MR, et al. The clinical impact of a Web-based image repository on radiation exposure in injured children. J Am Coll Radiol 2016. 17. Arkansas Department of Health. Designated trauma centers. 2016. Available at: http://www.healthy.arkansas.gov/programsServices/injury PreventionControl/TraumaticSystems/Pages/DesignatedTraumaCenters. aspx. Accessed November 2, 2016. 18. Agency for Research and Healthcare Quality. Healthcare Cost and Utilization Project. 2008. Available at: https://www.hcup-us.ahrq.gov/ db/vars/h_bedsz/nisnote.jsp. Accessed May 11, 2017. 19. Thomas KE, Wang B. Age-specific effective doses for pediatric MSCT examinations at a large children’s hospital using DLP conversion coefficients: a simple estimation method. Pediatr Radiol 2008;38:645-56. 20. Agarwal S, Jokerst C, Siegel MJ, Hildebolt C. Pediatric Emergency CT scans at a children’s hospital and at community hospitals: radiation technical factors are an important source of radiation exposure. AJR Am J Roentgenol 2015;205:409-13.
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Journal of the American College of Radiology Nabaweesi et al n Radiation Exposure for Injured Children
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Injured Children Receive Twice the Radiation Dose at Nonpediatric Trauma Centers Compared With Pediatric Trauma Centers Rosemary Nabaweesi, DrPH, MBChB, MPH a,b , Raghu H. Ramakrishnaiah, MD c, Mary E. Aitken, MD, MPH a,b, Mallikarjuna R. Rettiganti, PhD b, f, Chunqiao Luo, MS b, f, Robert T. Maxson, MD d, Charles M. Glasier, MD c, Phillip J. Kenney, MD e, James M. Robbins, PhD a,b Abstract Background: Use of cranial CT scans in children has been increasing, in part due to increased awareness of sports-related concussions. CT is the largest contributor to medical radiation exposure, a risk factor for cancer. Long-term cancer risks of CT scans can be two to three times higher for children than for adults because children are more radiosensitive and have a longer lifetime in which to accumulate exposure from multiple scans. Study Aim: To compare the radiation exposure injured children receive when imaged at nonpediatric hospitals (NPHs) versus pediatric hospitals. Methods: Injured children younger than 18 years who received a CT scan at a referring hospital during calendar years (CYs) 2010 and 2013 were included. Patient-level factors included demographics, mode of transportation, and Injury Severity Score, and hospital-level factors included region of state, radiology services, and hospital type and size. Our primary outcome of interest was the effective radiation dose. Results: Four hundred eighty-seven children were transferred to the pediatric trauma center during CYs 2010 and 2013, with a median age of 7.2 years (interquartile range 5-13). The median effective radiation dose received at NPHs was twice that received at the pediatric trauma center (3.8 versus 1.6 mSv, P < .001). Results were confirmed in independent and paired analyses, after controlling for mode of transportation, emergency department disposition, level of injury severity, and at the NPH trauma center level, hospital type, size, region, and radiology services location. Conclusion: NPHs have the potential to substantially reduce the medical radiation received by injured children. Pediatric CT protocols should be considered. Key Words: Effective radiation dose, nonpediatric hospitals, CT scan J Am Coll Radiol 2017;-:---. Copyright 2017 American College of Radiology
BACKGROUND CT use in children has increased, due in part to increasing concussion concerns, paralleled by emergency department (ED) visits [1-3]. During 2009 to 2010,
traumatic brain injury was evaluated in 4.8 million ED visits, and 82% of these evaluations included a CT scan [4]. Among injured children, head CT utilization is greater at hospitals with lower pediatric volumes, at
a Department of Pediatrics, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. b Arkansas Children’s Research Institute, Little Rock, Arkansas. c Department of Pediatric Radiology, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. d Department of Pediatric Surgery, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. e Department of Radiology, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas. f Department of Biostatistics, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, Arkansas.
Corresponding author and reprints: Rosemary Nabaweesi, DrPH, MBChB, MPH, University of Arkansas for Medical Sciences, College of Medicine, Arkansas Children’s Hospital Research Institute, 1 Children’s Way, Slot 512-26, Little Rock, AR 72202-3591; e-mail: [email protected]. Rosemary Nabaweesi was supported in part by the Arkansas Biosciences Institute, the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000, and the Marion B. Lyon Revocable Trust-New Scientist Development award. The authors have no conflicts of interest related to the material discussed in this article.
ª 2017 American College of Radiology 1546-1440/17/$36.00 n http://dx.doi.org/10.1016/j.jacr.2017.06.035
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community hospitals, and by providers without pediatric residency training [5]. Ionizing radiation from medical imaging now accounts for nearly half of the radiation exposure experienced by the US population [6,7]. CT scans are the greatest contributor to medical radiation exposure, which can increase cancer risk. Long-term cancer risks for children can be two to three times higher than for adults [8] because children are more sensitive to radiation and have a longer lifetime in which to accumulate exposure from multiple CT scans [6,9,10]. The ACR and American Association of Physicists for Medicine support the “as low as reasonably achievable” (ALARA) principle, which urges providers to use the minimum level of radiation needed in imaging examinations while maintaining diagnostic quality [11]. The use of optimized technical parameters focused on lowering tube current and tube voltage have demonstrated the reduction of radiation exposure in children by up to 65% [12-14]. Adoption of dose reduction imaging protocols has been variable with most success at pediatric hospitals and trauma centers [15]. The majority of pediatric trauma patients are managed at nonpediatric hospitals (NPHs), usually the nearest hospital after a traumatic event where children are transported for stabilization and evaluation. More seriously injured children are often transported to pediatric trauma centers (PTCs) for definitive care. It therefore follows that the majority of CT scans are performed at NPHs. In addition, results from our preliminary study demonstrated that a statewide image repository reduced the rate of CT scans repeated at a PTC by half [16]. Few studies have compared the radiation exposure between children imaged at NPHs and children imaged at pediatric facilities [5,10,16]. Most studies have used estimates for radiation dose [5,10]. We sought to use clinical radiology matrices, a more precise set of exposure metrics, to evaluate variability in CT scan exposure and to compare the CT scan radiation exposure of children imaged at NPHs and children imaged at a pediatric hospital using an optimal scanning protocol (OSP). We hypothesized that CT scans performed at NPHs would have higher radiation doses compared with CT scans performed at the children’s hospital.
METHODS Data Sources We conducted a cross-sectional study using administrative data from the pediatric trauma registry and clinical 2
data from the PACS. All children who met the state trauma system’s definition of a traumatic injury (trauma team activation, penetrating injuries, and ED deaths) were included in the registry. The trauma registry is housed at the only level I PTC in the state, which receives injured children from 64 accredited trauma system facilities. A dedicated trauma team manages the pediatric trauma registry to ensure the timeliness, accuracy, and completeness of the registry.
Patient and Variable Selection Our state trauma system comprises 64 trauma centers; these include 6 level I, 5 level II, 18 level III, and 35 level IV hospitals [12] served by 62 EDs. Among these are two PTCs and one burn center [17]. The second PTC is located in a neighboring state. All injured children under 18 years of age who met the trauma criteria, underwent CT imaging, and were transferred to the PTC from an outlying hospital during calendar year (CY) 2010 and CY 2013 were included. The image repository was created in July 2011, and we allowed for a year of full implementation across the state. All children transferred to the PTC arrived in the ED, where additional imaging, if required, is typically performed before the child is discharged to the intensive care unit, operating room, admitting floor, or home. Independent patient-level factors studied as potential covariates included age, race, gender, mode of transportation, Injury Severity Score (ISS), and ED disposition. ISS was categorized as mild (1-8), moderate (9-16), severe (17-25), and life-threatening (>26). Hospital-level factors studied included the region of the state, hospital type (urban, rural, critical care access, or community), hospital size (large, medium, and small), and location of radiology services (in-house or outsourced). Hospital size was based on the Healthcare Cost and Utilization Project definition and was nested in location and teaching status [18]. Our primary outcome of interest was the effective radiation dose (ERD). Optimal Scanning Protocols (OSPs) The CT scan protocols (referred to as OSPs) used at the PTC are institution-specific and partly based on the ACR protocols. Radiology clinicians in collaboration with equipment manufacturers developed the protocols through a quality improvement process. The protocols use dose modulation and iterative reconstruction. Additionally, the protocols require the following: (1) Radiologists’ approval is obtained for repeat scans if warranted Journal of the American College of Radiology Volume - n Number - n Month 2017
(eg, if original scan is degraded by motion artifact). (2) All head and cervical spine studies are performed without contrast, and all chest, abdomen, and pelvic scans are done with intravenous contrast. Contrast CT scans are not repeated in the same patient. (3) The thoracic and lumbar spines are reconstructed from the chest and abdominal scans, respectively; similarly, the maxillofacial scans are reconstructed from head CT when needed. (4) Arbitrary pan scanning is strictly controlled and avoided.
Statistical Analysis We summarized data using frequency and percentages for categorical variables and median (interquartile range) for continuous variables. Effective radiation dosage was calculated for each scan with dose length product (DLP) and age information using this formula, based on 16-cm diameter CT dosimetry phantom [19]: ERD ¼ DLP(16 cm) conversion coefficient(body region, age). At the CT scan-level analysis, ERD was stratified by body region (head, cervical spine, chest, and abdomen), race, age, gender, transportation, ED disposition, ISS, and trauma center level and was compared between NPH and the PTC using Mann-Whitney U tests. At the hospital-level analysis, we compared ERD using KruskalWallis tests. P values less than or equal to .05 were considered statistically significant. Statistical analysis was performed using the R software (R Core Team, Vienna, Austria). The study was approved by the Institutional Review Board of University of Arkansas for Medical Sciences. RESULTS Four hundred eighty-seven children were transferred to the PTC during the two study periods. Of those children, 78% were white, 14% were black, and 38% were female. The median age of an injured child was 7.2 years with an interquartile range (IQR) of 2.4 to 12.8. The median length of stay in the ED was 3 hours. The majority of children (58%) who received CT scans were transported by ground and had a relatively low acuity with a median ISS of 9 (IQR 5-13). (See Table 1.) Thirty-six percent of the study population was critically injured and received care in the operating room or intensive care unit. A total of 1,029 CT scans (all body regions) were received by the children in the study period. Fifty-three percent of the CT scans had DLP and age data points that were used to calculate the ERD. DLP was missing for only 6% of records at the pediatric hospital and 29% at the Journal of the American College of Radiology Nabaweesi et al n Radiation Exposure for Injured Children
Table 1. Demographic and clinical characteristics of children transferred to the pediatric trauma center at the children’s hospital Variable
N (%)
Total Race White Black Hispanic Other Gender Female Male Age (years), median (IQR) Transportation Ambulance Helicopter ED LOS in hours, median (IQR) ED disposition ICU or OR Other (home or floor) Injury Severity Score, median (IQR)
487 (100%) 379 (77.8%) 70 (14.4%) 22 (4.5%) 16 (3.3%) 186 (38%) 301 (62%) 7.2 (2.4, 12.8) 280 (58%) 205 (42%) 3.3 (2.2, 4.6) 173 (36%) 313 (64%) 9 (5, 13)
ED ¼ emergency department; ICU ¼ intensive care unit; IQR ¼ interquartile range; LOS ¼ length of stay; OR ¼ operating room.
NPHs. One thousand twenty (99.1%) of the CT scans had kilovoltage data, and 47% were missing CT dose index data (data not shown). The median ERD received at NPHs among black and white children was twice that received at the PTC (3.8 versus 1.6 mSv, P < .001). (See Table 2.) CT scans performed at NPHs had a median ERD at least twice as high as the ERD of scans performed using the OSPs among all children aged 1 year and older. Both male and female children were exposed to more than twice the ERD during CT scans conducted at NPHs as compared with the same body region scans performed using OSP. The doubling of ERD held across mode of transportation, ED disposition, level of injury severity, and trauma center level of transferring facility. Scans of the head involved twice the ERD when performed at NPHs than at the PTC. A second analysis matched CT scans done on the same patient at an NPH and repeated at the PTC. Eighty-eight children with 94 CT scan pairs were analyzed. (See Fig. 1 and Table 3.) The ERD for all CT scans conducted at NPHs was twice as high compared with CT scans performed at the PTC using OSP. The small cell sizes for CT cervical spine and abdomen did not yield stable ERD estimates. A third analysis evaluated the variability of ERD across NPHs and the PTC. The 61 (less 3, which are 3
Table 2. Comparison of effective radiation dose (millisieverts) between NPHs and PTC by demographic and clinical factors
Total Race White Black Hispanic Other Age (years) <1 1-4 5-9 10-14 >15 Gender Male Female Transportation Ambulance Helicopter ED disposition ICU or OR Other (home or floor) CT body region Head Cervical spine Chest Abdomen Injury Severity Score Mild Moderate Severe Life threatening Trauma center Level II Level III Level IV
n
NPH Median (Q1, Q3)
n
PTC Median (Q1, Q3)
P Value
415
3.8 (2.4, 5.8)
138
1.6 (1.3, 2.5)
<.001
335 48 19 13
3.8 (2.5, 6.0) 3.8 (2.0, 5.2) 3.9 (1.8, 6.8) 2.9 (2.0, 5.0)
109 19 5 5
1.6 (1.3, 2.5) 1.6 (1.0, 2.0) 2.1 (1.9, 2.3) 2.1 (1.6, 2.8)
<.001 <.001 NS NS
24 85 112 151 43
3.8 (2.8, 6.2) 3.3 (2.0, 4.7) 3.3 (1.8, 5.2) 4.2 (3.1, 8.0) 3.1 (2.5, 6.8)
11 37 31 38 21
2.5 (1.9, 2.6) 1.8 (1.5, 2.5) 1.4 (1.1, 1.6) 1.7 (1.3, 2.4) 1.6 (1.2, 7.5)
.006 <.001 <.001 <.001 NS
260 155
4 (2.6, 6.1) 3.4 (2.3, 5.1)
88 50
1.7 (1.2, 2.6) 1.6 (1.4, 2.3)
<.001 <.001
236 179
3.8 (2.6, 5.5) 3.8 (2.3, 6.9)
50 88
1.7 (1.3, 2.3) 1.6 (1.3, 2.5)
<.001 <.001
133 282
3.6 (2.5, 6.6) 3.9 (2.3, 5.6)
82 56
1.6 (1.3, 2.4) 1.8 (1.3, 2.5)
<.001 <.001
214 93 22 96
3.3 (2.4, 4.5) 3.1 (1.5, 4.6) 8.1 (5.2, 11.6) 7.3 (4.5, 11.6)
114 14 0 10
1.6 (1.2, 2.1) 5.4 (1.0, 7.0) — 7.7 (6.3, 15.7)
<.001 NS — NS
115 196 69 9
3.9 (2.1, 6.7) 3.7 (2.4, 5.2) 3.5 (2.6, 7.0) 4.6 (3.2, 7.5)
18 80 26 8
2 (1.3, 2.5) 1.6 (1.2, 2.1) 1.8 (1.4, 2.5) 2.1 (1.5, 2.6)
.004 <.001 <.001 .029
60 239 101
3.6 (2.6, 5.6) 3.7 (2.2, 5.8) 4 (2.5, 6.7)
23 72 29
1.8 (1.3, 2.7) 1.6 (1.3, 2.1) 1.6 (1.2, 2.5)
<.001 <.001 <.001
ED ¼ emergency department; ICU ¼ intensive care unit; NPH ¼ nonpediatric hospitals; NS ¼ not significant; OR ¼ operating room; PTC ¼ pediatric trauma center.
located out of state) referring hospitals were evenly distributed across the seven state-designated regions of the state, with the southwest region having the most (18%) and the metro area having the fewest facilities (11.4%). (See Table 4.) Critical care access hospitals comprised the largest group (34%), and community hospitals were the fewest (7%). Also, 30% were urban and 32% rural or community hospitals. Large hospitals (rural with 75þ and urban nonteaching with 200þ beds, urban teaching with >500 beds) made up 46%; medium hospitals, 16%; and small hospitals, 38%. The 4
majority of the transferring hospitals had in-house radiology services (71%), 21% used an outside radiology group, and 8% used both in-house and outside services. Sixteen hospitals transferred at least 10 patients to the PTC during the study period (range ¼ 11-35). The hospitals were distributed more or less like all referring hospitals except being overrepresented by urban and large hospitals. Among these hospitals, scans with available data to calculate ERD ranged from 2 to 35. CT scans from all 16 NPHs were found to have higher median ERD than the PTC median of 1.6 mSv. Scans from five NPHs with Journal of the American College of Radiology Volume - n Number - n Month 2017
N=487 Children 1029 CT* Scans
NPH† 813 CT Scans
PTC‡ 216 CT Scans
Excluded 476 CT scans without DLP§ N=303 Children
415 CT Scans with DLP
138 CT Scans with DLP
Excluded 365 scans without a match at NPH & PTC N=88 Children
94 Matching CT Scan pairs Final dataset
* CT ‡ Pediatric Trauma Center
†Non Pediatric Hospitals § Dose Length Product
Fig 1. CT scan selection.
the lowest exposure had median ERD less than 3.0. Scans from four NPHs with the highest exposure had median ERD greater than 4.0. Hospitals reporting lower median ERD were distributed throughout the state, were predominantly rural (4 of 5), and had both in-house (3) and
outsourced (2) radiology services. Hospitals reporting the highest median ERD with the exception of one outlier (median ¼ 19.3) were also distributed throughout the state, were predominately urban (3 of 4), and had both inhouse (3) and outsourced (2) radiology services.
Table 3. Comparison of the median effective radiation dose (millisieverts) between NPHs and the PTC by body regions using paired analysis
Overall Head CT spine Abdomen
CT Scan Pairs
NPH
PTC
Difference
P Value
94 83 6 5
3.5 (2.6, 5.2) 3.4 (2.5, 4.8) 4.8 (4.1, 8.6) 9.0 (7.2, 10.2)
1.6 (1.2, 2.3) 1.6 (1.2, 2.0) 1.6 (0.9, 5.1) 8.0 (6.8, 17.7)
2.1 (0.8, 3.4) 2.1 (0.9, 3.3) 3.3 (3.2, 7.8) 2.1 (3.1, 1.1)
<.001 <.001 NS NS
NPH ¼ nonpediatric hospitals; PTC ¼ pediatric trauma center; NS ¼ not significant.
Journal of the American College of Radiology Nabaweesi et al n Radiation Exposure for Injured Children
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Table 4. Hospital Level Factors for Nonpediatric Hospitals Transferring Patients to Pediatric Trauma Center
Variable Region of state Arkansas Valley Metropolitan North Central Northeast Northwest Southeast Southwest Hospital type Urban Critical care access Rural Community Unknown Hospital size* Small Medium Large Radiology services In-house Outsourced Both
All Hospitals (n ¼ 61)
Hospitals With at Least 10 Transferred Patients (n ¼ 16)
9 (14.7%) 7 (11.4%) 9 (14.7%) 8 (13.1%) 8 (13.1%) 9 (14.7%) 11 (18.0%)
3 (18.7%) 3 (18.7%) 2 (12.5%) 1 (6.2%) 3 (18.7%) 1 (6.2%) 3 (18.7%)
18 (29.5%) 21 (34.4%)
11 (68.7%) 0 (0.0%)
15 (24.5%) 4 (6.5%) 3 (4.9%)
3 (4.9%) 1 (6.2%) 1 (6.2%)
23 (37.7%) 10 (16.4%) 28 (45.9%)
0 (0.0%) 1 (6.2%) 15 (93.8%)
43 (70.5%) 13 (21.3%) 5 (8.2%)
11 (69.0%) 3 (19.0%) 2 (12.0%)
*Hospital bed size is based on Healthcare Cost Utilization Project, embedded in location and teaching status.
DISCUSSION The ALARA principle employs the following methods: (1) use weight-based protocols; (2) consider alternative nonradiating modalities; (3) when clinically appropriate, use focused or limited-view studies; and (4) dissuade repeat CT studies. Our results demonstrating that the centralized image repository halved the rate of repeat imaging in children transferred to the PTC are discussed elsewhere [16]. Use of newer-generation CT scanners, pediatric CT protocols, and head CT prediction rules as implemented by the PTC studied here are efforts to adhere to the ALARA principles. Anecdotal experience in Arkansas and a limited number of previous studies suggest that a large proportion of CT scans conducted at transferring facilities were obtained using higher tube voltage and tube current. Agarwal and colleagues demonstrated that children receive relatively higher tube voltage and tube current (radiation exposure) at NPHs, compared with pediatric hospitals [20]. 6
We set out to use available data to compare the radiation exposure when children undergo CT scans at NPHs to exposure at the pediatric hospital in a mostly rural state with a newly established trauma system and OSPs. Our findings using both independent and matched-pair analyses demonstrate a consistent pattern of twice the radiation dose when children undergo a CT scan at NPHs compared with the OSP used at the PTC. Our study confirmed that all 16 NPHs with sufficient numbers of CT scans to allow calculation of a stable median ERD subjected children to higher radiation exposure than the PTC. Five hospitals exposed children to relatively lower radiation. Four hospitals exposed children to relatively higher radiation. Our study affords an excellent opportunity to provide feedback to individual hospitals and to propose and implement standard CT scan policies across centers. This follow-up project is in development. The experience in our state is useful to inform other states with evolving trauma systems, particularly with large rural areas. Our study went beyond most current evidence by calculating ERD from tube voltage and tube current variation. Our finding that NPHs exposed children to twice the radiation dose of the PTC is in line with other studies that demonstrated lower radiation doses at pediatric institutions when compared with nonpediatric ones [5,20]. The head CT ERDs observed using the OSPs at the children’s hospital were lower than doses observed by Thomas and Wang at another large children’s hospital, across all age groups [19].
Limitations This study is a retrospective analysis and therefore was limited to the existing data. The majority of CT scans were performed on the head. Small numbers of scans performed on other body regions limit statistical power. The study compared several NPHs to a single children’s hospital. Although the children’s hospital has standardized protocols that are implemented institution-wide, there is likely wide variation among the NPHs. Equipment variation includes dose reduction software and age and type of CT scanners. However, we did not have access to the individual hospitals’ CT scanner inventory. We will collect these data in a planned quality improvement project. Missing data were a significant challenge with close to 50% of the DLP missing in CY 2010. With gradual adoption of newer radiation dose measures across hospitals, the amount of missing data declined over time. Journal of the American College of Radiology Volume - n Number - n Month 2017
Future studies using data collected more recently will likely limit the amount of missing data.
CONCLUSION Clinicians at NPHs have the potential to substantially reduce the medical radiation injured children receive by adopting OSPs similar to that used at PTCs. Careful analysis of patterns across a state trauma system affords an ideal opportunity to propose standardized scanning protocols based on real-world feedback delivered directly to hospitals and radiology staff. TAKE-HOME POINTS -
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The median ERD using OSPs at a PTC is half that at NPHs. Clinicians at NPHs have the potential to reduce the medical radiation injured children receive by adopting pediatric OSPs, which are consistently used at PTCs. Our state affords an ideal opportunity to implement standard dosing across trauma centers through audit and feedback, education, or policy change.
REFERENCES 1. Zonfrillo MR, Kim KH, Arbogast KB. Emergency department visits and head computed tomography utilization for concussion patients from 2006 to 2011. Acad Emerg Med 2015;22:872-7. 2. Kirsch TD, Hsieh YH, Horana L, Holtzclaw SG, Silverman M, Chanmugam A. Computed tomography scan utilization in emergency departments: a multi-state analysis. J Emerg Med 2011;41:302-9. 3. Kocher KE, Meurer WJ, Fazel R, Scott PA, Krumholz HM, Nallamothu BK. National trends in use of computed tomography in the emergency department. Ann Emerg Med 2011;58:452-62. 4. Korley FK, Kelen GD, Jones CM, Diaz-Arrastia R. Emergency department evaluation of traumatic brain injury in the United States, 2009-2010. J Head Trauma Rehabil 2015.
5. Graves JM, Kanal KM, Vavilala MS, Applegate KE, Jarvik JG, Rivara FP. Hospital-level factors associated with use of pediatric radiation dose reduction protocols for head CT: results from a national survey. J Am Coll Radiol 2014;11:717-24. 6. Linet MS, Kim K, Rajaraman P. Children’s exposure to diagnostic medical radiation and cancer risk: epidemiologic and dosimetric considerations. Pediatr Radiol 2009;39(Suppl 1):S4-26. 7. Wylie MC, Merritt C, Clark M, Garro AC, Rutman MS. Imaging of pediatric head injury in the emergency department. Pediatr Emerg Care 2014;30:680-5. 8. Kim PK, Gracias VH, Maidment AD, O’Shea M, Reilly PM, Schwab CW. Cumulative radiation dose caused by radiologic studies in critically ill trauma patients. J Trauma 2004;57:510-4. 9. Journy N, Roue T, Cardis E, et al. Childhood CT scans and cancer risk: impact of predisposing factors for cancer on the risk estimates. J Radiol Prot 2016;36:N1-7. 10. Kharbanda AB, Flood A, Blumberg K, Kreykes NS. Analysis of radiation exposure among pediatric trauma patients at national trauma centers. J Trauma Acute Care Surg 2013;74:907-11. 11. Goske MJ, Strauss KJ, Westra SJ, Frush DP. The Image Gently ALARA CT summit on new CT technologies for children. Pediatr Radiol 2014;44 Suppl 3:403. 12. Mahesh M, Fishman EK. CT dose reduction strategy: to modulate dose or not in certain patients? J Am Coll Radiol 2012;9:931-2. 13. Mahesh M. Advances in CT technology and application to pediatric imaging. Pediatr Radiol 2011;41 Suppl 2:493-7. 14. Strauss KJ, Goske MJ, Kaste SC, Bulas D, Frush DP, Butler P, et al. Image Gently: ten steps you can take to optimize image quality and lower CT dose for pediatric patients. AJR Am J Roentgenol 2010;194: 868-73. 15. Graves JM, Kanal KM, Rivara FP, Jarvik JG, Vavilala MS. Dose reduction efforts for pediatric head CT imaging in Washington State trauma centers: follow-up survey results. J Am Coll Radiol 2014;11:161-8. 16. Nabaweesi R, Ramakrishnaiah RH, Rettiganti MR, et al. The clinical impact of a Web-based image repository on radiation exposure in injured children. J Am Coll Radiol 2016. 17. Arkansas Department of Health. Designated trauma centers. 2016. Available at: http://www.healthy.arkansas.gov/programsServices/injury PreventionControl/TraumaticSystems/Pages/DesignatedTraumaCenters. aspx. Accessed November 2, 2016. 18. Agency for Research and Healthcare Quality. Healthcare Cost and Utilization Project. 2008. Available at: https://www.hcup-us.ahrq.gov/ db/vars/h_bedsz/nisnote.jsp. Accessed May 11, 2017. 19. Thomas KE, Wang B. Age-specific effective doses for pediatric MSCT examinations at a large children’s hospital using DLP conversion coefficients: a simple estimation method. Pediatr Radiol 2008;38:645-56. 20. Agarwal S, Jokerst C, Siegel MJ, Hildebolt C. Pediatric Emergency CT scans at a children’s hospital and at community hospitals: radiation technical factors are an important source of radiation exposure. AJR Am J Roentgenol 2015;205:409-13.
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