Abstract
Objective
To provide organ and effective radiation doses for common pediatric imaging examinations, which may help clinicians understand site-specific cancer risk, compare exposure across imaging modalities, and make informed care decisions.
Study design
Within a large multicenter retrospective cohort, imaging utilization and associated radiation doses were estimated for children enrolled from birth into one of six US health care systems. Doses are described for examinations performed from 2012 to 2017. For computed tomography (CT), doses were estimated using examination-level technical parameters, patient height and weight, and Monte Carlo simulations. For fluoroscopy, angiography, nuclear medicine, and radiography, dose maps were developed by patient age, sex, size, and year through Monte Carlo simulations using technical parameters collected from patient examinations. The mean dose and standard deviation (SD) were calculated for each examination type, and each modality's contribution to the cohort's cumulative effective dose was calculated.
Results
Eight hundred thirty-five thousand six hundred forty-three imaging examinations in 278 909 patients are included. Radiographs were the most commonly performed exam but made up 6% of radiation dose exposure. CT exams made up 4% of imaging exams but accounted for 80% of exposure. Head CT was the most common CT exam (44% of all CT). For head CT, the average radiation dose to the bone marrow (associated with hematologic cancer risk) was 9.8 mGy (SD = 6.7) and to the brain (associated with brain cancer risk) was 39 mGy (SD = 14.8).
Conclusions
CT radiation doses to the bone marrow and brain fell within ranges associated with increased hematologic and brain cancer risk, and are highest in the youngest children.
Keywords: Organ dose; effective dose; pediatric imaging; pediatric radiology; computed tomography; fluoroscopy; angiography; nuclear medicine; radiography; x-ray
Radiation-based medical imaging offers invaluable diagnostic benefit to pediatric patients. Nevertheless, ionizing radiation is carcinogenic and several large epidemiology studies have observed excess hematologic and brain cancer risks associated with computed tomography (CT) in children.1, 2, 3, 4 Relative to adults, children and adolescents are at elevated risk owing to increased tissue radiosensitivity and longer life expectancy.5, 6, 7 Children with genetic conditions such as Down syndrome are more frequently imaged and have underlying cancer susceptibilities, putting them at increased risk from exposure.8,9 Furthermore, these risks are cumulative; thus children who undergo repeated imaging, such as those with chronic illness, face even higher radiation-induced cancer risk.10
Despite the rising use of magnetic resonance (MRI) and ultrasound imaging in children,11 radiation-based imaging with CT (a test of particular significance due to its relatively high radiation dose) has not decreased in the US over the past decade.12, 13, 14, 15, 16 Concerningly, low value CT use, such as when CT exams are obtained against the recommendations of evidence-based guidelines, frequently occur in the evaluation of common pediatric conditions.13, 14, 15, 16 Nevertheless, many patients, families, and clinicians have limited understanding of the radiation doses and cancer risks associated with different radiation-based imaging exams, which impedes them from accurately weighing the potential risks against benefits of their clinical care decisions.17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28 Thus, quantifying radiation doses and associated risks is of great importance to patients and caregivers alike.
While various metrics exist for quantifying radiation in imaging, organ dose (radiation deposited to an organ or tissue) is the most accurate way to estimate a patient's future risk of developing a site-specific cancer: for example, bone marrow dose most closely predicts hematologic cancer risk; brain dose predicts brain cancer risk. Effective dose reflects a whole-body, weighted summation of organ doses, and is appropriate to understand how the total dose from a particular exposure compares with other sources of radiation, such as other medical imaging or environmental exposures.29
This study provides organ and effective doses and contextualizes health risks for the most common radiation-based medical imaging examinations performed in children and adolescents <21 years of age in the US.30 This study aims to give referring pediatricians a reference for radiation doses so they can more accurately quantify radiation associated cancer risk for different imaging exams.
Methods
Study Population
The Risk of Pediatric and Adolescent Cancer Associated with Medical Imaging (RIC) Study is a National Institutes of Health–funded retrospective cohort study quantifying the relationship between cumulative radiation exposure from childhood medical imaging and subsequent cancer risk. The RIC cohort includes children enrolled from birth between 1996 and 2016 in one of six integrated US health care systems—Kaiser Permanente (KP) Northern California; KP Northwest (Oregon/Southwest Washington); KP Washington; KP Hawaii; Marshfield Clinic (Wisconsin); and Harvard Pilgrim Health Care (Massachusetts)—and in Ontario, Canada. Children were followed while continuously enrolled in the health care system until the earliest of age 21, health care system disenrollment, death, cancer diagnosis, or study end (December 31, 2017). Study design and cohort details have been previously published.30 Because radiation doses have decreased over time, and to reflect current practice, we limited this analysis to examinations performed from January 1, 2012, to January 31, 2017, in the US health care systems. The RIC study was approved with a waiver of informed consent by the institutional review boards at each participating health care system and the University of California at San Francisco and Davis.
Imaging utilization was identified through administrative databases using Current Procedural Terminology, Healthcare Common Procedure Coding System, and International Classification of Diseases 9th and 10th revision procedure codes, each mapped to an anatomic area and imaging modality.12,30 Examinations performed both within and outside the health care systems (eg, in an emergency department unaffiliated with but billed to the health care system) were included.
Radiation Dose Estimation
Methods for estimating organ and effective doses varied by modality and have been reported.30 Additional details on dosimetry for CT, nuclear medicine, fluoroscopy, and radiography are provided in the Supplemental Materials.
Height and Weight
As radiation doses vary by patient size, all observed values of patients’ height and weight were extracted from the electronic medical records. If height or weight on the day of the exam were missing, they were imputed based on available values, or the cohort median for that age and sex if all values were missing.30
Computed Tomography
Patient-level technical parameters (including anatomic area imaged, peak kilovoltage, fixed or modulated tube current, pitch, collimation, scan length, tube rotation time, and volume CT dose index—the latter used only if tube current was not available) were abstracted for 25 301 CT examinations across all years of the RIC study.30 Using this examination-level data, together with height and weight, patient-dependent organ and effective doses were reconstructed through Monte Carlo radiation transport simulations—widely considered the most accurate method of modeling such doses—using the University of Florida/National Cancer Institute (UF/NCI) hybrid computational pediatric phantom library.31, 32, 33, 34, 35, 36 This library contains 168 pediatric male and female models representing a wide distribution of patient sizes.37,38 Using these 25 301 reconstructed doses, we developed a model to predict organ and effective doses for all CT examinations using random effects linear regression with predictors including anatomic area imaged, number of phases in the examination, health care system, facility, date, and patients’ age, sex, height, and weight.
Nuclear Medicine
Nuclear medicine examinations involve radiation emitted by radiopharmaceutical agents. For these studies, we developed a dose reference map based on age- and weight-specific International Commission on Radiological Protection reference biokinetic models for common diagnostic radiopharmaceuticals using estimated administered activities obtained from review of sample data from the largest health care system.30,39 Individual examinations were then mapped by patient age, sex, weight, and examination type to derive organ and effective doses.
Fluoroscopy and Angiography
Abstracted examination data, chart review, and clinician interviews were combined to generate procedure parameters for common pediatric fluoroscopy examinations at the largest health care system. Exam details partnered with machine-specific parameters were then applied in Monte Carlo simulations using the UF/NCI pediatric phantom library to develop a dose map covering males and females across an array of patient sizes for the most common examination types.40,41 Patients’ individual organ and effective doses were then calculated by linking each exam by age, sex, height, weight, and examination type to the reference map. For angiography, we used data from an unrelated contemporaneous study of pediatric angiography, which generated organ and effective doses using Monte Carlo simulations through the NCI dosimetry system based on individual abstracted data.10
Radiography
Radiography dose maps were generated through Monte Carlo simulations using the UF/NCI pediatric phantom library along with technical parameters from literature review and consultation with medical physicists.42 Children were mapped by age, sex, and examination type to radiography doses to determine patient-specific organ and effective doses.
Statistical Analysis
We summarized the number of examinations performed by modality and age group, for the most common examination types in the cohort. We calculated the mean and standard deviation (SD) examination-level organ and effective doses for each examination type, overall and by age group. There were negligible differences between males and females (results not shown). Effective doses are presented for all examination types, and organ doses are provided for the highest exposed organs in each examination type. We then estimated the percentage contribution of each modality to the total effective dose received by the study population overall and by age group. This included all imaging examinations performed from 2012 to 2017, not just the most common examination types presented in the tables.
Results
A total of 835 643 imaging examinations in 278 909 patients (47% female) are included, reflecting around 30% of the larger RIC US study cohort (n = 931 120 children). Radiography had the highest utilization, with wrist and chest imaging the most common examinations. The next most common modality was CT, and the distribution of examination types varied by age. Head examinations comprised 44% (13 305/30 413) of CT overall, although the percentage decreased with increasing age: from 76% (2240/2954) of CT in infants <1 year to 30% (2645/8742) in children 16-21 years, Table 1. Abdomen and pelvis CT was the next most common (23% of CT) and was more frequent in older children: increasing from 3% in infants <1 year to 31% of examinations in those aged 16-21 years.
Table 1.
Distribution of examination types overall and by age group, among the RIC cohort of children in the US who received medical imaging between 2012 and 2017
| Total number of exams by site | Overall |
< 1 y |
1-5 y |
6-10 y |
11-15 y |
16-21 y |
|---|---|---|---|---|---|---|
| N | N | N | N | N | N | |
| Harvard Pilgrim Health Care | 105 128 | 20 027 | 29 592 | 25 716 | 27 045 | 2748 |
| Kaiser Permanente Hawaii | 57 092 | 7463 | 12 781 | 12 013 | 15 587 | 9248 |
| Kaiser Permanente Northern California | 476 827 | 56 381 | 117 401 | 110 701 | 124 790 | 67 554 |
| Kaiser Permanente Northwest | 68 028 | 7455 | 15 700 | 14 995 | 17 860 | 12 018 |
| Kaiser Permanente Washington | 64 951 | 8480 | 15 589 | 14 226 | 16 235 | 10 421 |
| Marshfield | 63 617 | 6628 | 12 858 | 12 462 | 18 193 | 13 476 |
| Total exams | 835 643 | 106 434 | 203 921 | 190 113 | 219 710 | 115 465 |
| Total patients | 278 909 | 45 784 | 91 949 | 79 202 | 77 175 | 39 682 |
| Exams by modality | N (%) | N (%) | N (%) | N (%) | N (%) | N (%) |
| Computed tomography | ||||||
| Head/brain | 13 305 (44%) | 2240 (76%) | 3424 (63%) | 2381 (41%) | 2615 (35%) | 2645 (30%) |
| Abdomen and pelvis | 6969 (23%) | 82 (3%) | 534 (10%) | 1567 (27%) | 2043 (27%) | 2743 (31%) |
| Maxillofacial and sinus | 1868 (6%) | 54 (2%) | 115 (2%) | 439 (8%) | 634 (8%) | 626 (7%) |
| Chest | 1153 (4%) | 194 (7%) | 194 (4%) | 137 (2%) | 241 (3%) | 387 (4%) |
| Neck | 858 (3%) | 63 (2%) | 217 (4%) | 187 (3%) | 169 (2%) | 222 (3%) |
| Lower extremity | 737 (2%) | 11 (0%) | 10 (0%) | 74 (1%) | 384 (5%) | 258 (3%) |
| Cervical spine | 509 (2%) | 14 (0%) | 79 (1%) | 115 (2%) | 160 (2%) | 141 (2%) |
| Other | 5014 (16%) | 296 (10%) | 825 (15%) | 927 (16%) | 1246 (17%) | 1720 (20%) |
| Total exams | 30 413 | 2954 | 5398 | 5827 | 7492 | 8742 |
| Total patients | 24 467 | 2464 | 4565 | 5089 | 6437 | 6778 |
| Fluoroscopy | ||||||
| Voiding cystourethrogram | 7562 (45%) | 2041 (35%) | 1748 (46%) | 1578 (65%) | 1329 (61%) | 866 (35%) |
| Upper gastrointestinal study | 4296 (26%) | 1964 (33%) | 734 (19%) | 498 (20%) | 443 (20%) | 657 (27%) |
| Rehabilitation swallow | 1972 (12%) | 1069 (18%) | 696 (18%) | 122 (5%) | 53 (2%) | 32 (1%) |
| Lower gastrointestinal study | 1477 (9%) | 498 (8%) | 355 (9%) | 100 (4%) | 127 (6%) | 397 (16%) |
| Gastrostomy tube placement | 100 (1%) | 60 (1%) | 24 (1%) | 6 (0%) | 7 (0%) | 3 (0%) |
| Other | 1419 (8%) | 269 (5%) | 256 (7%) | 142 (6%) | 229 (10%) | 523 (21%) |
| Total exams | 16 826 | 5901 | 3813 | 2446 | 2188 | 2478 |
| Total patients | 12 046 | 4444 | 2889 | 1998 | 1709 | 1705 |
| Nuclear medicine | ||||||
| Renal functional imaging∗ | 862 (26%) | 426 (51%) | 240 (27%) | 92 (20%) | 52 (9%) | 52 (8%) |
| Bone scintigram† | 527 (16%) | 21 (3%) | 58 (7%) | 74 (16%) | 180 (33%) | 194 (31%) |
| Radionuclide cystogram‡ | 488 (15%) | 99 (12%) | 284 (32%) | 94 (21%) | 10 (2%) | 1 (0%) |
| Liver scintigram§ | 361 (11%) | 51 (6%) | 69 (8%) | 53 (12%) | 90 (16%) | 98 (15%) |
| Hepatobiliary scintigram¶ | 343 (10%) | 87 (10%) | 5 (1%) | 13 (3%) | 88 (16%) | 150 (24%) |
| Lung ventilation perfusion∗∗ | 185 (6%) | 42 (5%) | 53 (6%) | 42 (9%) | 32 (6%) | 16 (3%) |
| Meckel diverticulum scintigram‡ | 122 (4%) | 22 (3%) | 46 (5%) | 20 (4%) | 18 (3%) | 16 (3%) |
| Positron emission tomography†† | 119 (4%) | 11 (1%) | 25 (3%) | 19 (4%) | 33 (6%) | 31 (5%) |
| Renal cortical imaging‡‡ | 54 (2%) | 43 (5%) | 11 (1%) | 0 (0%) | 0 (0%) | 0 (0%) |
| Thyroid uptake scan§§ | 31 (1%) | 5 (1%) | 0 (0%) | 2 (0%) | 12 (2%) | 12 (2%) |
| Myocardial perfusion scan¶¶ | 25 (1%) | 1 (0%) | 2 (0%) | 3 (1%) | 7 (1%) | 12 (2%) |
| Other | 236 (7%) | 30 (4%) | 83 (9%) | 41 (9%) | 29 (5%) | 53 (8%) |
| Total exams | 3353 | 838 | 876 | 453 | 551 | 635 |
| Total patients | 2555 | 723 | 644 | 363 | 458 | 516 |
| Angiography | ||||||
| Cardiac | 1171 (66%) | 292 (73%) | 315 (67%) | 205 (69%) | 165 (56%) | 194 (63%) |
| Other | 601 (34%) | 110 (27%) | 155 (33%) | 92 (31%) | 131 (44%) | 113 (37%) |
| Total exams | 1772 | 402 | 470 | 297 | 296 | 307 |
| Total patients | 813 | 246 | 228 | 160 | 138 | 129 |
| Radiography | ||||||
| Wrist | 153 355 (20%) | 1327 (1%) | 21 892 (11%) | 47 982 (26%) | 62 155 (30%) | 19 999 (19%) |
| Chest posteroanterior and lateral | 151 853 (19%) | 28,819 (30%) | 65 490 (34%) | 30 091 (17%) | 16,275 (8%) | 11 178 (11%) |
| Ankle | 111 765 (14%) | 926 (1%) | 20 058 (10%) | 25 351 (14%) | 44 362 (21%) | 21 068 (20%) |
| Elbow | 65 226 (8%) | 1008 (1%) | 19 579 (10%) | 24 409 (13%) | 15 702 (8%) | 4528 (4%) |
| Knees | 55 579 (7%) | 472 (0%) | 12 254 (6%) | 8898 (5%) | 20 466 (10%) | 13 489 (13%) |
| Abdomen | 49 317 (6%) | 8 397 (9%) | 13 464 (7%) | 15 553 (9%) | 8024 (4%) | 3 879 (4%) |
| Chest posteroanterior | 45 947 (6%) | 17 599 (18%) | 12 215 (6%) | 5915 (3%) | 5061 (2%) | 5157 (5%) |
| Pelvis | 24 480 (3%) | 3030 (3%) | 6678 (3%) | 4631 (3%) | 6299 (3%) | 3842 (4%) |
| Shoulder | 17 711 (2%) | 496 (1%) | 2919 (2%) | 3419 (2%) | 5965 (3%) | 4912 (5%) |
| Full spine | 12 782 (2%) | 1,426 (1%) | 3011 (2%) | 1502 (1%) | 4882 (2%) | 1961 (2%) |
| C-Spine | 11 221 (1%) | 879 (1%) | 3246 (2%) | 2753 (2%) | 2476 (1%) | 1867 (2%) |
| T-Spine | 10 576 (1%) | 55 (0%) | 430 (0%) | 1518 (1%) | 5896 (3%) | 2677 (3%) |
| Femur | 10 264 (1%) | 313 (0%) | 5623 (3%) | 1903 (1%) | 1637 (1%) | 788 (1%) |
| Skull posteroanterior | 9612 (1%) | 1007 (1%) | 2135 (1%) | 2418 (1%) | 2189 (1%) | 1863 (2%) |
| Whole body | 8600 (1%) | 8600 (9%) | . | . | . | . |
| L-Spine | 8424 (1%) | 118 (0%) | 552 (0%) | 1036 (1%) | 3404 (2%) | 3314 (3%) |
| Clavicle | 8169 (1%) | 487 (1%) | 1898 (1%) | 1638 (1%) | 2522 (1%) | 1624 (2%) |
| Skull lateral | 7879 (1%) | 1000 (1%) | 1781 (1%) | 2073 (1%) | 1868 (1%) | 1157 (1%) |
| Other | 20 519 (3%) | 20 380 (21%) | 139 (0%) | 0 (0%) | 0 (0%) | 0 (0%) |
| Total exams | 783 279 | 96 339 | 193 364 | 181 090 | 209 183 | 103 303 |
| Total patients | 270 844 | 42 930 | 89 166 | 76 876 | 75 379 | 37 969 |
Total patient counts in the total column reflect unique patients. Total patient counts within each age group add up to a greater sum than the overall total patients, as they include individuals who received imaging at different ages. Percentages reflect column percents.
Technetium (Tc)-99m mercaptoacetyltriglycine (MAG3).
Technetium (Tc)-99m medronate.
Technetium (Tc)-99m pertechnetate.
Technetium (Tc)-99m sulfur colloid.
Technetium (Tc)-99m mebrofenin.
Technetium (Tc)-99m macroaggregated albumin (MAA) and Tc-99m diethylene-triamine-pentaacetate (DTPA) aerosol.
Fludeoxyglucose (FDG) F18.
Technetium (Tc)-99m dimercaptosuccinic acid (DMSA).
Iodine-123.
Technetium (Tc)-99m sestamibi.
Voiding cystourethrogram and upper gastrointestinal studies were the most common fluoroscopy examinations, comprising 45% (7562/16 826) and 26% (4296/16 826) of fluoroscopy, respectively. The most common nuclear medicine examinations were renal functional imaging (26%, 862/3353) with 51% among infants <1 declining to 8% in children 16-21 years, followed by bone scintigraphy (16%, 527/3353) which increased from 3% among infants <1 to 31% among children 16-21 years, Table 1.
Radiography Doses
Radiography examinations generally had very low effective and bone marrow doses, shown in units of microSv and microGy in Table 2. Doses were higher in trunk examinations (including the spine, chest, and abdomen) than in extremities, as exemplified in the two most common examination types: chest and wrist, each comprising 20% of radiography. Chest examinations had an effective dose of 13.6 microSv and bone marrow dose of 7.0 microGy, while wrist examinations had doses of 0.1 microSv and 0.0 microGy, respectively.
Table 2.
Average effective dose and bone marrow doses for radiography exams, by age group and examination type
| Exam type | Effective dose (microSv) |
Bone marrow dose (microGy) |
||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall |
<1 y |
1-5 y |
6-10 y |
11-15 y |
16-21 y |
Overall |
<1 y |
1-5 y |
6-10 y |
11-15 y |
16-21 y |
|||||||||||||
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | |||||||||||||
| Abdomen | 29.5 | (27.3) | 12.2 | (7.4) | 19.6 | (11.4) | 25.7 | (15.1) | 49.7 | (32.6) | 74.4 | (43.1) | 7.4 | (7.6) | 3.1 | (1.9) | 4.5 | (2.6) | 5.8 | (3.5) | 13.2 | (8.9) | 21.1 | (12.1) |
| Ankle | 0.2 | (0.1) | 0.1 | (0.0) | 0.2 | (0.1) | 0.2 | (0.2) | 0.2 | (0.1) | 0.3 | (0.1) | 0.1 | (0.2) | 0.2 | (0.1) | 0.3 | (0.1) | 0.2 | (0.3) | 0.1 | (0.0) | 0.0 | (0.0) |
| Chest lateral, chest PA | 13.6 | (6.7) | 20.6 | (2.8) | 15.4 | (6.8) | 7.3 | (0.6) | 8.7 | (0.3) | 8.7 | (0.5) | 7.0 | (3.4) | 11.0 | (1.3) | 7.2 | (3.8) | 4.1 | (0.6) | 5.6 | (0.3) | 5.9 | (0.3) |
| Chest PA | 6.0 | (3.4) | 8.4 | (1.6) | 7.5 | (3.0) | 2.1 | (0.5) | 2.4 | (0.7) | 2.2 | (0.6) | 3.0 | (1.0) | 3.8 | (0.6) | 2.8 | (0.9) | 1.7 | (0.5) | 2.4 | (0.7) | 2.5 | (0.7) |
| Clavicle | 9.2 | (1.4) | 8.5 | (1.0) | 8.4 | (1.3) | 7.6 | (0.9) | 10.0 | (0.5) | 10.7 | (0.4) | 4.1 | (1.0) | 3.7 | (0.0) | 3.1 | (0.4) | 3.3 | (0.5) | 4.8 | (0.3) | 5.2 | (0.3) |
| C-Spine | 13.4 | (3.6) | 11.5 | (2.2) | 15.9 | (2.8) | 15.3 | (3.6) | 10.3 | (1.6) | 11.1 | (1.7) | 16.8 | (7.0) | 20.6 | (2.1) | 24.0 | (2.7) | 18.8 | (5.7) | 9.4 | (1.4) | 9.7 | (1.4) |
| Elbow | 0.3 | (0.1) | 0.2 | (0.1) | 0.2 | (0.1) | 0.3 | (0.1) | 0.4 | (0.1) | 0.5 | (0.1) | 0.2 | (0.1) | 0.1 | (0.1) | 0.2 | (0.1) | 0.3 | (0.1) | 0.2 | (0.1) | 0.1 | (0.0) |
| Femur | 7.3 | (7.8) | 1.5 | (0.7) | 2.7 | (2.3) | 8.4 | (4.0) | 16.4 | (7.4) | 21.1 | (8.0) | 2.3 | (2.4) | 0.4 | (0.1) | 0.7 | (0.6) | 2.5 | (0.7) | 5.5 | (1.7) | 7.0 | (2.0) |
| Full spine | 91.5 | (49.6) | 36.7 | (7.1) | 47.7 | (8.8) | 83.9 | (29.7) | 121.1 | (41.6) | 130.7 | (45.1) | 42.6 | (22.6) | 19.6 | (3.7) | 23.0 | (3.9) | 36.3 | (13.0) | 55.8 | (19.2) | 61.4 | (21.2) |
| Knees | 1.0 | (0.8) | 0.2 | (0.1) | 0.5 | (0.3) | 0.9 | (1.6) | 1.2 | (0.5) | 1.4 | (0.5) | 0.7 | (1.1) | 0.2 | (0.1) | 0.7 | (0.5) | 1.4 | (2.4) | 0.7 | (0.5) | 0.2 | (0.1) |
| L-Spine | 44.9 | (21.7) | 8.9 | (0.1) | 13.6 | (3.9) | 26.2 | (8.7) | 45.9 | (17.8) | 56.3 | (19.8) | 21.9 | (11.0) | 4.4 | (0.0) | 5.5 | (1.2) | 11.3 | (4.1) | 22.5 | (8.8) | 28.0 | (9.8) |
| Pelvis | 18.8 | (12.4) | 7.4 | (4.7) | 11.8 | (5.1) | 16.8 | (7.2) | 24.7 | (11.7) | 32.4 | (14.0) | 7.4 | (6.0) | 2.2 | (1.4) | 3.2 | (1.3) | 5.4 | (2.4) | 11.0 | (5.2) | 15.1 | (6.4) |
| Shoulder | 23.0 | (10.0) | 3.7 | (1.6) | 9.8 | (4.8) | 20.4 | (5.5) | 27.0 | (7.4) | 29.9 | (7.0) | 9.3 | (4.0) | 2.3 | (0.9) | 4.1 | (1.7) | 8.0 | (2.2) | 10.8 | (3.0) | 12.1 | (2.8) |
| Skull lateral | 8.0 | (3.1) | 13.4 | (2.3) | 9.1 | (2.5) | 7.7 | (1.6) | 6.3 | (1.7) | 5.1 | (1.7) | 14.9 | (8.8) | 31.3 | (5.2) | 20.1 | (6.0) | 13.1 | (3.1) | 8.6 | (2.2) | 6.5 | (1.6) |
| Skull PA | 7.0 | (2.9) | 11.6 | (2.6) | 9.3 | (2.6) | 6.6 | (1.5) | 5.1 | (1.0) | 4.6 | (0.9) | 15.7 | (8.0) | 29.4 | (5.6) | 22.4 | (6.5) | 14.5 | (3.6) | 10.0 | (2.1) | 9.0 | (2.0) |
| T-Spine | 48.4 | (13.5) | 13.2 | (1.5) | 18.3 | (3.4) | 31.7 | (5.6) | 49.8 | (7.7) | 60.5 | (9.4) | 28.8 | (9.1) | 7.9 | (0.9) | 9.3 | (1.3) | 16.7 | (3.4) | 29.7 | (5.2) | 37.4 | (5.7) |
| Whole body | 15.8 | (0.6) | 15.8 | (0.6) | . | . | . | . | . | . | . | . | 9.6 | (1.1) | 9.6 | (1.1) | . | . | . | . | . | . | . | . |
| Wrist | 0.1 | (0.0) | 0.1 | (0.0) | 0.1 | (0.0) | 0.1 | (0.0) | 0.1 | (0.0) | 0.1 | (0.0) | 0.04 | (0.0) | 0.1 | (0.1) | 0.1 | (0.0) | 0.1 | (0.0) | 0.03 | (0.0) | 0.02 | (0.0) |
Computed Tomography Doses
Head examinations had a lower overall effective dose (2.9 millisievert (mSv), SD = 2.8) than most other CT examination types, Table 3; however, bone marrow, brain, and eye lens doses tended to be higher in head CT than in other anatomic areas. The mean bone marrow dose for head CT was 9.8 milliGray (mGy) (SD = 6.7), which was more than double that of any other CT examination type. The bone marrow dose was highest in the youngest children (14.1 mGy [SD = 8.1]), and decreased with age. The mean brain dose for head CT was 39.0 mGy (SD = 14.8) overall and increased with age, from 35.6 mGy (SD = 18.6) in infants <1 to 43.4 mGy (SD = 10.3) in children 16-21 years. The mean radiation dose to the eye lens ranged from 37.0 mGy (SD = 17.3) in 1-5–year-olds to 47.8 mGy (SD = 11.5) in 16-21–year-olds. Thyroid doses in head CT were highest in the youngest children (18.8 mGy, SD = 30.8) and declined with age.
Table 3.
Average effective dose and select organ doses for computed tomography, by age group and examination type
| Examination type |
Effective dose (mSv) |
Organ dose (mGy) |
|||||
|---|---|---|---|---|---|---|---|
| Bone marrow |
Brain |
Eye lens |
Thyroid |
||||
| Overall and by age | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | ||
| Head/brain | 2.9 (2.8) | 9.8 (6.7) | 39.0 (14.8) | 41.7 (17.0) | 6.3 (18.0) | ||
| <1 y | 4.7 (4.5) | 14.1 (8.1) | 35.6 (18.6) | 37.7 (21.2) | 18.8 (30.8) | ||
| 1-5 y | 3.6 (2.3) | 13.3 (6.1) | 35.5 (15.3) | 37.0 (17.3) | 7.0 (13.0) | ||
| 6-10 y | 2.6 (1.5) | 9.8 (4.5) | 39.1 (13.1) | 41.0 (14.9) | 3.2 (8.2) | ||
| 11-15 y | 1.9 (0.8) | 6.2 (2.4) | 42.5 (12.9) | 46.4 (15.0) | 1.9 (1.4) | ||
| 16-21 y | 1.7 (0.6) | 4.9 (1.5) | 43.4 (10.3) | 47.8 (11.5) | 1.4 (1.2) | ||
| Maxillofacial/sinus | 0.5 (1.7) | 1.3 (4.6) | 5.9 (17.7) | 8.3 (22.1) | 1.8 (8.7) | ||
| <1 y | 1.6 (2.0) | 5.2 (3.7) | 11.0 (11.0) | 16.4 (12.0) | 11.8 (20.5) | ||
| 1-5 y | 0.9 (2.2) | 3.4 (6.4) | 8.5 (17.3) | 11.0 (19.0) | 3.9 (14.3) | ||
| 6-10 y | 0.5 (2.0) | 1.6 (6.4) | 6.6 (21.9) | 8.8 (24.4) | 1.4 (4.6) | ||
| 11-15 y | 0.5 (1.7) | 1.1 (3.4) | 6.6 (20.9) | 9.3 (27.6) | 1.5 (5.7) | ||
| 16-21 y | 0.3 (0.8) | 0.6 (1.3) | 3.8 (8.3) | 5.7 (12.1) | 1.0 (6.1) | ||
| Neck | 6.5 (3.7) | 4.1 (2.8) | 1.0 (2.3) | 0.8 (2.7) | 32.1 (17.2) | ||
| <1 y | 7.4 (5.1) | 6.2 (4.0) | 1.0 (1.2) | 1.1 (2.5) | 24.1 (9.7) | ||
| 1-5 y | 6.0 (3.4) | 4.0 (2.5) | 0.9 (1.0) | 0.7 (1.3) | 23.9 (11.6) | ||
| 6-10 y | 5.3 (1.8) | 2.7 (0.8) | 0.6 (0.2) | 0.4 (0.1) | 23.7 (6.8) | ||
| 11-15 y | 6.9 (3.9) | 3.7 (2.0) | 0.8 (0.5) | 0.5 (0.4) | 38.9 (19.0) | ||
| 16-21 y | 7.4 (3.2) | 5.0 (2.0) | 1.6 (5.7) | 1.2 (6.4) | 45.6 (20.1) | ||
| Cervical spine | 3.0 (6.6) | 3.0 (7.0) | 5.7 (10.0) | 7.5 (12.5) | 13.7 (22.0) | ||
| <1 y | 7.9 (34.3) | 12.3 (39.3) | 15.0 (52.0) | 14.2 (49.3) | 29.6 (84.7) | ||
| 1-5 y | 3.2 (3.7) | 3.4 (3.7) | 5.3 (5.6) | 6.5 (7.6) | 11.0 (11.3) | ||
| 6-10 y | 2.9 (5.5) | 2.9 (4.3) | 5.3 (7.9) | 7.7 (14.5) | 14.3 (25.8) | ||
| 11-15 y | 2.5 (2.5) | 2.1 (2.2) | 4.9 (6.3) | 6.4 (9.4) | 11.8 (11.4) | ||
| 16-21 y | 3.0 (1.9) | 2.8 (1.6) | 6.4 (3.9) | 8.6 (4.8) | 15.6 (15.5) | ||
| Bone marrow | Breast | Lung | Thyroid | ||||
|---|---|---|---|---|---|---|---|
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | ||||
| Chest | 4.9 (4.0) | 2.8 (2.3) | 6.9 (6.6) | 7.6 (6.6) | 7.7 (6.2) | ||
| <1 y | 2.6 (2.0) | 2.0 (1.8) | 3.3 (2.9) | 4.0 (3.5) | 5.1 (4.5) | ||
| 1-5 y | 3.4 (3.2) | 2.4 (2.6) | 4.2 (3.9) | 5.2 (4.6) | 6.7 (6.1) | ||
| 6-10 y | 3.8 (3.3) | 2.1 (1.6) | 5.0 (5.2) | 5.6 (4.6) | 6.7 (4.9) | ||
| 11-15 y | 4.8 (3.8) | 2.6 (1.9) | 7.3 (7.8) | 8.3 (8.3) | 8.4 (6.6) | ||
| 16-21 y | 7.2 (4.5) | 3.9 (2.5) | 10.5 (7.1) | 11.1 (6.3) | 9.4 (5.9) |
| Bone marrow | Colon | Kidney | Liver | Ovaries | Testes | ||
|---|---|---|---|---|---|---|---|
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | ||
| Abdomen and pelvis | 4.7 (3.1) | 3.4 (2.2) | 6.2 (5.8) | 6.3 (5.3) | 5.9 (4.4) | 5.5 (4.9) | 5.8 (6.1) |
| <1 y | 2.8 (3.9) | 1.4 (2.3) | 4.6 (6.7) | 3.6 (6.0) | 2.8 (4.4) | 5.1 (0.1) | 4.4 (8.0) |
| 1-5 y | 3.8 (2.2) | 1.9 (1.1) | 5.2 (3.5) | 5.2 (3.3) | 5.0 (3.2) | 4.4 (3.6) | 4.4 (3.4) |
| 6-10 y | 3.6 (1.8) | 2.2 (1.0) | 3.5 (3.9) | 3.9 (3.7) | 4.3 (2.9) | 2.4 (3.1) | 2.7 (4.2) |
| 11-15 y | 4.3 (2.6) | 3.2 (1.9) | 4.4 (5.3) | 4.8 (4.8) | 5.1 (3.6) | 3.9 (4.6) | 3.3 (7.2) |
| 16-21 y | 6.0 (4.0) | 4.5 (2.7) | 9.5 (6.7) | 9.2 (6.2) | 7.9 (5.5) | 8.3 (5.3) | 10.6 (6.5) |
| Lower extremity | 0.1 (0.7) | 0.1 (0.7) | |||||
| <1 y | 0.94 | 0.47 | |||||
| 1-5 y | 0.22 (0.1) | 0.15 (0.0) | |||||
| 6-10 y | 0.12 (0.5) | 0.15 (0.5) | |||||
| 11-15 y | 0.07 (0.5) | 0.08 (0.3) | |||||
| 16-21 y | 0.06 (1.1) | 0.10 (1.2) |
mGy, milliGray; mSv, milliSievert.
Abdomen and pelvis, the next most common CT examination type (23%, 6969/30 413), had higher effective doses than head CT for all but the youngest age group. Effective (mean 4.7 mGy, SD = 3.1, across all age groups), bone marrow (mean = 3.4 mGy, SD = 2.2), colon (mean = 6.2 mGy, SD = 5.8), kidney (mean = 6.3 mGy, SD = 5.3), liver (mean = 5.9 mGy, SD = 4.4), ovary (mean = 5.5 mGy, SD = 4.9), and testes (mean = 5.8 mGy, SD = 6.1) doses generally increased with age and were consistently highest in the oldest children, aged 16-21 years. The highest organ dose was observed in the testes in males 16-21 years old (10.6 mGy, SD = 6.5).
Neck examinations had the highest effective and thyroid doses of all CT examination types, overall and by age group. Thyroid doses for neck examinations ranged from 23.7 to 45.6 mGy in children 6-10 and 16-21 years, respectively.
Fluoroscopy and Angiography Doses
Fluoroscopy delivered less radiation than CT for most examination types, with overall effective and organ doses at 0.7 mSv and 1.4 mGy or less, respectively, and were largely stable across age groups, Table 4. Cardiac angiography effective doses were lower than CT: for example, 2.5 mSv for overall cardiac angiography vs 4.9 mSv for overall chest CT. Conversely, lung organ doses were higher overall than in chest CT.
Table 4.
Average effective dose and select organ doses for nuclear medicine, fluoroscopy, and angiography, by age group and examination type.
| Nuclear Medicine | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Exam type | Effective dose (mSv) | Organ dose (mGy) | Exam type | Effective dose (mSv) | Organ dose (mGy) | ||||
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | ||||||
| Overall and by age | Kidneys | Overall and by age | Small intestine | ||||||
| Renal functional imaginga | 0.7 | (0.2) | 2.1 | (0.4) | Meckel's diverticulum scintigramc | 5.5 | (1.2) | 6.4 | (1.5) |
| <1 year | 0.8 | (0.0) | 2.4 | (0.1) | <1 year | 7.0 | (0.4) | 8.3 | (0.5) |
| 1-5 years | 0.6 | (0.1) | 1.8 | (0.3) | 1-5 years | 5.3 | (0.7) | 6.0 | (0.8) |
| 6-10 years | 0.5 | (0.1) | 1.4 | (0.3) | 6-10 years | 4.8 | (1.2) | 5.5 | (1.4) |
| 11-15 years | 0.8 | (0.2) | 1.9 | (0.5) | 11-15 years | 5.2 | (1.6) | 6.2 | (1.9) |
| 16-21 years | 0.9 | (0.2) | 1.9 | (0.4) | 16-21 years | 5.4 | (1.2) | 6.4 | (1.4) |
| Bone marrow | |||||||||
| Bone scintigramb | 3.4 | (0.8) | 3.7 | (0.6) | PET-whole bodyg | 6.5 | (1.4) | ||
| <1 year | 1.9 | (0.1) | 3.9 | (0.2) | <1 year | 4.3 | (0.2) | ||
| 1-5 years | 2.3 | (0.3) | 4.0 | (0.4) | 1-5 years | 5.2 | (0.9) | ||
| 6-10 years | 3.2 | (0.8) | 3.6 | (0.8) | 6-10 years | 6.5 | (0.8) | ||
| 11-15 years | 3.9 | (0.7) | 3.7 | (0.6) | 11-15 years | 7.7 | (1.2) | ||
| 16-21 years | 3.5 | (0.4) | 3.7 | (0.4) | 16-21 years | 6.9 | (0.8) | ||
| Urinary bladder | Kidneys | ||||||||
| Radionuclide cystogramc | 2.1 | (0.6) | 2.1 | (0.4) | Renal cortical imagingh | 0.8 | (0.0) | 15.5 | (0.9) |
| <1 year | 2.8 | (0.1) | 2.6 | (0.1) | <1 year | 0.8 | (0.0) | 15.6 | (0.6) |
| 1-5 years | 2.1 | (0.3) | 2.1 | (0.2) | 1-5 years | 0.7 | (0.1) | 15.0 | (1.5) |
| 6-10 years | 1.3 | (0.2) | 1.5 | (0.1) | 6-10 years | . | . | ||
| 11-15 years | 0.9 | (0.1) | 1.1 | (0.1) | 11-15 years | . | . | ||
| 16-21 years | 0.6 | N/A | 0.7 | N/A | 16-21 years | . | . | ||
| Liver | Thyroid | ||||||||
| Liver scintigramd | 0.9 | (0.2) | 6.7 | (1.1) | Thyroid uptake scani | 2.6 | (2.9) | 47.5 | (51.1) |
| <1 year | 1.0 | (0.0) | 7.0 | (0.3) | <1 year | 8.9 | (0.0) | 158.1 | (0.6) |
| 1-5 years | 0.9 | (0.1) | 6.3 | (0.7) | 1-5 years | . | . | . | . |
| 6-10 years | 1.0 | (0.2) | 6.9 | (1.2) | 6-10 years | 3.7 | (0.4) | 70.2 | (7.4) |
| 11-15 years | 1.0 | (0.1) | 7.7 | (1.0) | 11-15 years | 1.6 | (0.1) | 29.0 | (2.5) |
| 16-21 years | 0.7 | (0.1) | 5.7 | (0.4) | 16-21 years | 0.9 | (0.2) | 16.0 | (2.9) |
| Liver | Heart | ||||||||
| Hepatobiliary scintigrame | 3.5 | (0.8) | 2.9 | (0.5) | Myocardial perfusion scanj | 12.1 | (3.5) | 9.9 | (2.1) |
| <1 year | 4.6 | (0.1) | 3.1 | (0.0) | <1 year | 19.1 | N/A | 13.7 | N/A |
| 1-5 years | 2.8 | (0.1) | 2.3 | (0.1) | 1-5 years | 16.4 | (0.1) | 14.0 | (1.7) |
| 6-10 years | 2.6 | (0.7) | 2.6 | (0.7) | 6-10 years | 15.4 | (3.8) | 10.8 | (2.7) |
| 11-15 years | 3.4 | (0.6) | 3.2 | (0.5) | 11-15 years | 13.6 | (1.4) | 10.2 | (0.1) |
| 16-21 years | 3.0 | (0.4) | 2.6 | (0.3) | 16-21 years | 9.0 | (0.6) | 8.5 | (1.0) |
| Lungs | |||||||||
| Lung ventilation perfusion (VQ)f | 10.1 | (4.2) | 32.2 | (11.8) | |||||
| <1 year | 16.0 | (0.7) | 49.0 | (2.2) | |||||
| 1-5 years | 12.0 | (1.9) | 36.8 | (5.7) | |||||
| 6-10 years | 7.4 | (0.8) | 23.7 | (2.3) | |||||
| 11-15 years | 5.8 | (0.5) | 21.3 | (1.8) | |||||
| 16-21 years | 4.4 | (0.4) | 17.0 | (2.2) | |||||
| Fluoroscopy | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Exam type | Effective dose (mSv) | Organ dose (mGy) | Exam type | Effective dose (mSv) | Organ dose (mGy) | ||||
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | ||||||
| Overall and by age | Urinary bladder | Overall and by age | Small intestine | ||||||
| Voiding cystourethrogram | 0.66 | (0.19) | 1.38 | (0.53) | Upper gastrointestinal study | 0.22 | (0.09) | 0.11 | (0.05) |
| <1 year | 0.56 | (0.12) | 1.14 | (0.44) | <1 year | 0.26 | (0.04) | 0.14 | (0.02) |
| 1-5 years | 0.61 | (0.12) | 1.47 | (0.29) | 1-5 years | 0.21 | (0.06) | 0.09 | (0.03) |
| 6-10 years | 0.76 | (0.21) | 1.76 | (0.50) | 6-10 years | 0.20 | (0.06) | 0.08 | (0.02) |
| 11-15 years | 0.81 | (0.17) | 1.52 | (0.54) | 11-15 years | 0.18 | (0.10) | 0.08 | (0.04) |
| 16-21 years | 0.56 | (0.18) | 0.86 | (0.43) | 16-21 years | 0.19 | (0.16) | 0.09 | (0.08) |
| Esophagus | Colon | ||||||||
| Rehabilitation swallow | 0.05 | (0.01) | 0.14 | (0.06) | Lower gastrointestinal study | 0.08 | (0.04) | 0.16 | (0.09) |
| <1 year | 0.05 | (0.01) | 0.14 | (0.06) | <1 year | 0.13 | (0.02) | 0.24 | (0.05) |
| 1-5 years | 0.05 | (0.01) | 0.15 | (0.05) | 1-5 years | 0.08 | (0.03) | 0.17 | (0.06) |
| 6-10 years | 0.04 | (0.02) | 0.10 | (0.04) | 6-10 years | 0.07 | (0.03) | 0.16 | (0.07) |
| 11-15 years | 0.02 | (0.01) | 0.04 | (0.02) | 11-15 years | 0.07 | (0.05) | 0.12 | (0.09) |
| 16-21 years | 0.02 | (0.02) | 0.03 | (0.03) | 16-21 years | 0.05 | (0.03) | 0.08 | (0.05) |
| Stomach | |||||||||
| Gastrostomy-tube placement | 0.35 | (0.15) | 1.37 | (0.57) | |||||
| <1 year | 0.35 | (0.17) | 1.37 | (0.60) | |||||
| 1-5 years | 0.41 | (0.08) | 1.67 | (0.26) | |||||
| 6-10 years | 0.31 | (0.11) | 1.40 | (0.54) | |||||
| 11-15 years | 0.15 | (0.05) | 0.57 | (0.18) | |||||
| 16-21 years | 0.29 | (0.00) | 0.93 | (0.02) | |||||
|
Angiography |
|||||||||
| Exam type | Effective dose (mSv) | Organ dose (mGy) | |||||||
| Mean (SD) | Mean (SD) | ||||||||
| Lungs | |||||||||
| Cardiac | 2.5 | (1.5) | 12.8 | (7.1) | |||||
| <1 year | 3.5 | (1.4) | 16.5 | (5.9) | |||||
| 1-5 years | 2.5 | (0.2) | 13.9 | (1.1) | |||||
| 6-10 years | 1.2 | (0.2) | 7.1 | (1.0) | |||||
| 11-15 years | 0.3 | (0.0) | 1.4 | (0.1) | |||||
| 16-21 years | 4.0 | (0.7) | 21.2 | (3.8) | |||||
Footnotes:
Cells containing a period ( . ) identify strata with 0 exams.
N/A indicates N=1 exam; insufficient sample size to calculate standard deviation.
Tc99m MAG3
Tc99m Medronate
Tc99m Pertechnetate
Tc99m Sulfur Colloid
Tc99m Mebrofenin
Tc99m MAA and Tc99m DTPA Aerosol
F18 FDG
Tc99m DMSA
Iodine 123
Tc99m Sestamibi
Nuclear Medicine Doses
Nuclear medicine varied considerably in overall effective dose, ranging from 0.7 mSv for renal functional imaging to 10.1 mSv for chest ventilation perfusion studies, Table 4. Myocardial perfusion (stress) examinations had relatively high effective dose (12.1 mSv), but low frequency in children. No nuclear medicine examinations showed a strong trend in dose by age except for chest ventilation perfusion, which had higher lung doses in the youngest children: 49.0 mGy in infants <1 year decreasing to 17.0 in 16-21–year-olds. These were higher than lung doses from chest CT and cardiac angiography.
Contributions to Population Cumulative Radiation Exposure
CT, which comprised 3.6% (30 413/835 643) of all examinations and had a mean effective dose of 3.6 mSv, contributed 79.1% of the total effective dose received by the study cohort from medical imaging (Figure eTable1). By age, CT contributed 67.4% of total dose in infants <1 rising to 85.5% in children 16-21 years, but this was not a monotonic increase. Nuclear medicine, with a mean effective dose of 2.7 mSv, was the second highest contributor, delivering 6.7% of total effective dose while comprising 0.4% (3353/835 643) of examinations. The contribution to total dose from nuclear medicine and fluoroscopy (mean effective dose = 0.5 mSv) both trended downward by age: ranging from around 10% in children <1 to around 4.5% in those 16-21 years. Despite having a mean effective dose of only 0.01 mSv, radiography contributed 5.6% of the total exposure due to its high utilization.
Figure 1.
Percentage contribution to total radiation exposure from medical imaging, measured in effective dose, by modality and age group. RIC Study, January 1, 2012, and January 31, 2017.
Discussion
This work provides a summary of organ and effective doses for common radiation-based medical imaging tests in children. Doses were derived from clinical examinations reflecting recent practice across large diverse US health care systems, using optimal organ dosimetry approaches. This information can help clinicians understand the comparative magnitude of radiation doses from different imaging tests and guide informed consent about harms from radiation exposure from medical imaging exams.
CT uses, on average, considerably more radiation than other medical imaging modalities. CT accounted for almost 80% of the radiation exposure received from imaging, despite making up a fraction (4%) of all examinations, due to relatively higher doses per examination. For example, chest CT had 360 times the effective dose of chest radiography. This is consistent with a 2019 estimate from the National Council on Radiation Protection and Measurements, which had CT delivering 84% of total dose to children in the US.43
Radiation-Induced Harms
While risk of cancer associated with CT is low, the radiation doses currently used are statistically significantly associated with increased risk of cancer in children. The recent multinational EPI-CT and RIC studies observed elevated cancer incidence in children who had undergone CT, with excess cancer risk proportionate to radiation exposure. In EPI-CT, cumulative bone marrow doses of 8 mGy were associated with 1.4 hematologic cancers per 10 000 CT examinations within 12 years.4 In RIC, a bone marrow dose of 5-<10 mGy was associated with a 40% increased risk of hematologic cancer compared to those with no exposure (relative risk = 1.41, 95% CI = 1.00-1.93).44 Thus the average bone marrow dose from head CT in this paper (9.8 mGy) falls in the same range as those shown to increase hematologic cancer risk.
Likewise, average brain doses in the EPI-CT study, shown to be significantly associated with brain cancer, were similar to observed doses in this analysis (around 38 mGy). At these doses, the risk associated with radiation exposure was 1 brain cancer per 10 000 head examinations within 5-15 years.3 Overall, children in EPI-CT undergoing 2-3 head CT examinations had double the risk for developing brain cancer compared to children who had never undergone a head CT. Thus, CT examinations in recent practice are routinely delivering doses that have been shown to be associated with increased cancer risk.
It is important to note that EPI-CT and RIC observed cancers occurring in childhood or young adulthood, though the incidence of radiation-induced cancer likely rises with longer follow-up. Empirical research on Japanese atomic bomb survivors—from which most radiation-related cancer risk models derive—found excess risk for some cancers persisting more than five decades following exposure.6,45,46 A recent paper modeling lifetime risk of cancer from current CT use projects the most frequent cancers stemming from CT in children are thyroid and lung (two highly radiosensitive organs), followed by breast cancer in girls.47 The authors estimate 3 cancers will occur over the lifetime from every 1000 CT examinations performed in children under 18 years of age.
While the risk for an individual child from a given exam depends on age at exposure, time since exposure, and attained age, the widely accepted linear no-threshold model of radiation carcinogenesis holds that there is no dose below which radiation is harmless and that cancer risk is generally directly proportional to dose.1 To that effect, it is important to highlight that radiography doses are orders of magnitude smaller than CT: for example, the effective dose of chest radiography vs chest CT is 13.6 microSv (=.0136 mSv) vs 4.9 mSv, respectively. Thus the risk of cancer from radiography is orders of magnitude lower than CT.
It is commonly thought that cancer risk is highest in the youngest children. Indeed, in addition to bone marrow doses, thyroid doses in head CT were highest in the youngest children (<1 year), likely due to greater inclusion of the neck in infant head examinations. However, organ doses for several CT types increased with age. For abdomen (the second most common CT type) and chest imaging, the average organ dose was 30%-160% higher in 16-21 year olds than in other ages. Brain doses from head CT also increased by age. Furthermore, radiation doses from other modalities were lower than in CT but not negligible, particularly for nuclear medicine and for radiosensitive organs such as the lungs and thyroid.
Lastly, eye lens doses were the highest of all observed organ doses in the RIC study (around 47 mGy in children >11 years), and clinicians should bear in mind the deterministic risk of cataracts following doses of 500 mGy to the eye lens.48 Deterministic risk means these outcomes will predictably occur at this dose, and contrasts with the stochastic risk of cancer which is a probabilistic risk, meaning it might occur. The eye lens dose from a single head CT in the RIC study approaches the annual occupational eye lens exposure limit to avoid cataracts recommended by the National Council on Radiation Protection and Measurements (50 mGy).48 While ophthalmologic screening is not currently recommended, more research is warranted to assess the benefit of screening in children who undergo multiple head examinations.
Comparisons with Previous Publications
CT bone marrow and brain doses in the RIC study were similar to or slightly higher than in EPI-CT and other large studies in children, yet generally lower than those observed in a large CT dose registry (eTable 2).49, 50, 51, 52 This delta may be due to our novel dosimetry approach relying on examination-level CT technical parameters and patients' exact weight and height, while earlier studies modeled organ doses using technical parameters from national surveys, clinical protocols, regulatory databases, literature, or a small sample of real examinations. Compared with the seminal 2008 catalog of effective doses for radiologic procedures in adults by Mettler et al, our CT effective doses in young adults (aged 16-21 years) largely align, while for nuclear medicine, fluoroscopy, and angiography, Mettler's doses are higher than ours (eTable 3).53 These variances may reflect both underlying temporal or practice differences (such as the reduction of young adult doses compared with adults) as well as differences in the approaches used to estimate dose (reconstructed from examination-level data vs averaged from reported literature). For the most common nuclear medicine studies in our cohort, effective doses in the RIC study were consistent with prior reports in children (eTable 3).54, 55, 56, 57, 58 For fluoroscopy, LaBella et al observed lower doses in virtually all examination types (eTable 3). However, LaBella's examinations were performed in a pediatric hospital, which tends to use more optimized radiation doses in children than general hospitals.59,60
Clinical Considerations
Cancer risk from CT can be minimized by avoiding low-value examinations and by optimizing the radiation doses used. To the first point, when resource availability permits, referring clinicians should follow evidence-based guidelines that recommend nonradiation-based imaging (such as MRI and ultrasound) or recommend against the use of imaging (such as head imaging in the evaluation of mild head injury).61, 62, 63
Referring clinicians can help reduce the radiation doses used in CT in several ways. First, they should clearly communicate the clinical indication upon ordering the examination, as ambiguity in why a test is ordered (eg, “rule out pathology”) can lead those performing the CT to overscan beyond the indicated body region or through multiple irradiating phases. Second, in the absence of a system for tracking patients’ cumulative radiation dose, clinicians should pay attention to and avoid unnecessary repeat imaging in their patients to minimize cumulative exposure. Lastly, CT radiation doses are not standardized and are known to differ by hospital type; for example, pediatric hospitals use less radiation for CT than general hospitals that care for adults and children.59,64 Therefore, clinicians can learn about dosing practices at their institutions and advocate for radiation dose reduction. Leadership support and various quality improvement initiatives have been associated with driving lower CT doses.65,66
Lastly, while the potential benefits of CT may be easily grasped (rapid noninvasive diagnosis), clinicians need guidelines for how to discuss potential harms with patient families when considering CT. Indeed, most patients report limited understanding of imaging and wish to be informed of the risks.17,18,20,22,23,25, 26, 27, 28 These may include exposure to ionizing radiation (a risk factor for cancer), as well as the identification of false positives or incidental findings that may lead to additional, potentially unnecessary, testing and treatment. To help patients and families understand the magnitude of radiation, clinicians may explain that a CT examination is equal to around 350-400 radiographs (“x-rays”), as this study demonstrated. Overall, for every 10 000 children receiving CT, 1-2 cancers are expected to occur in the next 5-15 years, and approximately 3 cancers per 1000 examinations over the lifetime.3,4,47 Clinicians should explain their rationale for ordering CT and whether they perceive the benefits to outweigh potential harms, for example, if the child had a high pretest probability of the condition based on clinical guidelines. They should also describe the appropriateness of nonradiation alternatives (ultrasound, MRI, observation). Simple educational sheets haven been shown to be effective for cases of mild head trauma in improving parental knowledge, reducing decisional conflict, and increasing engagement in decision making about imaging.67
Limitations
Some modalities are underrepresented in this work, particularly angiography and positron emission tomography (PET). Examinations in children with cancer, who undergo frequent imaging (including PET and CT), are excluded, which may have affected the utilization percentages. About half of all examinations came from KP Northern California, and we have not examined dose variation by site. The population is skewed towards younger children due to the study's enrollment criteria that children be born into the health care system and followed continuously until censoring.30 Dose estimation methods did not take into account differences in body composition, such as fat distribution, or organ shape or size (which may differ between same-sized individuals), or differences in organ location (such as in heterotaxy), and it is not known how these variations impact organ dose estimations. CT doses were imputed using a model that was developed using all 25 301 abstracted examinations between 1996 and 2017, of which only 24% occurred between 2012 and 2017. Given the downward trend in doses between 1996 and 2017, this likely resulted in smaller predicted CT doses for the 2012 and 2017 time period (ie, those presented in this work); thus true doses could be slightly higher than reported. The dose imputation model was extensively validated against chart review. Finally, these doses come from 2012 to 2017, and it is possible that with improvements in CT technique, doses may be lower today; however, a large study of CT organ doses from 2015 to 2020 does not support this.52
Conclusion
In this first large-scale report of pediatric organ doses from medical imaging in the US, CT bone marrow and brain radiation doses fell within ranges previously associated with increased cancer risk, introducing potential harms that may sometimes outweigh the benefits of imaging. These findings underscore the obligation to minimize radiation exposure from medical imaging in every child and should motivate careful consideration to ensure CT and other radiation-based imaging is limited to children who are likely to benefit, given the small inherent risk of cancer.
CRediT authorship contribution statement
Carly Stewart: Writing – review & editing, Writing – original draft, Visualization, Validation, Project administration. Susan Alber: Writing – review & editing, Validation, Methodology, Formal analysis, Data curation. Malini Mahendra: Writing – review & editing, Conceptualization. Cameron Kofler: Writing – review & editing, Resources, Data curation. Trung Tran: Writing – review & editing, Resources, Data curation. Sean Domal: Writing – review & editing, Resources, Data curation. Erin J.A. Bowles: Writing – review & editing, Supervision, Investigation. Sheila Weinmann: Writing – review & editing, Supervision, Investigation. Robert T. Greenlee: Writing – review & editing, Supervision, Investigation. Natasha K. Stout: Writing – review & editing, Supervision, Investigation. Priscila Pequeno: Writing – review & editing. Lisa M. Moy: Writing – review & editing, Project administration, Investigation. James R. Duncan: Writing – review & editing. Jason D. Pole: Writing – review & editing, Supervision, Methodology. Wesley E. Bolch: Writing – review & editing, Supervision, Resources, Data curation. Marilyn L. Kwan: Writing – review & editing, Supervision, Project administration, Methodology, Investigation. Diana L. Miglioretti: Writing – review & editing, Validation, Supervision, Project administration, Methodology, Funding acquisition, Data curation, Conceptualization. Rebecca Smith-Bindman: Writing – review & editing, Validation, Supervision, Project administration, Methodology, Funding acquisition, Data curation, Conceptualization.
Declaration of Competing Interest
This study was supported by the National Cancer Institute at the National Institutes of Health (R01CA185687 and R50CA211115). The analyses, conclusions, opinions, and statements expressed herein are solely those of the authors and do not reflect those of the National Institutes of Health. R.S.-B. is a cofounder of Alara Imaging Inc, a company focused on improving the clinical and operational aspects of health systems, including collecting and reporting radiation dose and image quality associated with computed tomography as part of payer-led quality programs. Alara Imaging played no role in any aspect of the article, and this work does not overlap with Alara’s commercial activities.
Supplementary data
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