Abstract
Estimation of absorbed organ doses used in computed tomography (CT) using time-intensive Monte Carlo simulations with virtual patient anatomic models is not widely reported in the literature. Using the library of computational phantoms developed by the University of Florida and the National Cancer Institute, we performed Monte Carlo simulations to calculate organ dose values for 9 CT categories representing the most common body regions and indications for imaging (reflecting low, routine, and high radiation dose examinations), stratified by patient age (in children) and effective diameter (in adults, using diameter as a measure of patient size). Our sample of 559,202 adult and 103,423 pediatric CT examinations was prospectively assembled between 2015–2020 from 156 imaging facilities from 27 healthcare organizations in 20 U.S. states and 7 countries in the University of California San Francisco International CT Dose Registry. Organ doses varied by body region and exam type. For example, the mean brain dose associated with head CT was 20 mGy [standard deviation (SD) 14] for head low dose, 46 mGy (SD 21) for head routine dose, and 64 mGy (SD 31) for head high dose scan protocols. The mean colon doses associated with abdomen and pelvis CT were 19 mGy (SD 12), 32 mGy (SD 28), and 69 mGy (SD 42) for low, routine, and high dose examinations, respectively. Organ doses in general varied modestly by patient diameter, and for many categories the organ doses among the largest quartile of patients were no more than 10% higher than doses in the smallest quartile. For example, for abdomen and pelvis high dose, the colon dose increased from 67 to 74 mGy from the smallest to the largest patients (10% increase). With few exceptions, pediatric organ doses also varied relatively little by patient age, except for the youngest children who, on average, had higher organ doses. Thyroid dose, however, tended to increase with age in neck or cervical spine and chest CT. Overall, the highest organ doses were to the skin, thyroid, brain, and eye lens. Mean organ doses differ substantially by site. The organ dose values included in this report are derived from empirical clinical exams and offer useful, representative values. Large inter-site variations demonstrate areas for radiation dose reduction.
INTRODUCTION
The number of computed tomography (CT) examinations performed in the United States has grown significantly in the last three decades, with a corresponding increase in the population’s exposure to ionizing radiation from medical imaging (1–4). It is estimated that 93 million CT examinations were performed in 2023 alone (1). Thus, there is mounting need to quantify the radiation exposures received by patients to inform both them and referring providers regarding the magnitudes of CT radiation dose and potential, associated future harms.
A variety of metrics exist for summarizing radiation dose from CT, including computed tomography dose index volume, dose length product, and effective dose. While each metric has its merits, none is appropriate for individual patient cancer risk estimation. Instead, organ and tissue absorbed doses (in units of mGy) are required since organs and tissues differ in radiosensitivity, and potential carcinogenicity in humans depends both on the underlying organs exposed and their doses (5). Despite this importance, knowledge of actual organ and tissue radiation dose levels from CT imaging remains incomplete. Previous studies have described individual organ doses for specific types of patients or CT imaging, usually as part of methodological, theoretical, or epidemiological studies, and relatively few have produced tables of empirical organ dose values for a broad range of patients, particularly adults, from multiple clinical settings (6–15).
The objective of this study was to develop new adult and pediatric representative organ dose values using clinical exams from an international CT dose registry and an extensive library of anatomically accurate computational phantoms that together permit dose estimation across a broad range of patient, scanner, and scanning characteristics. This work adopts a novel approach of reconstructing organ doses for each individual exam (from a very large, diverse sample of exams) based on the exact CT technical parameters employed, rather than theoretically derived radiation dose values based on CT protocols, as previous works have used.
MATERIALS AND METHODS
The study population consisted of all pediatric and a random 5% sample of adult (aged 18+ years) diagnostic CT exams performed between January 1, 2015, and November 2, 2020, in the University of California San Francisco (UCSF) International CT Dose Registry (“Registry”). Exams in this sample were performed at 156 imaging facilities from 27 healthcare organizations (“sites”) in 20 geographically diverse U.S. states and 7 countries, all of whom used Radimetrics (Bayer HealthCare, Whippany, NJ) dose management software (16, 17). Most exams (84%) are from U.S. facilities.
Data Assembly
For each CT exam performed, Digital Imaging and Communications in Medicine (DICOM) metadata, including patient data (age, sex, exam-level effective diameter), CT category (previously validated) (18), scanner manufacturer, and technical parameters (scan length, DLP, CTDI-vol, kVp, mAs, phase, collimation, 16- or 32-cm phantom) were extracted from the Registry. Effective diameter is calculated by Radimetrics on each slice and provided as a series-level mean effective diameter, averaged from all constituent slice-level acquisitions; we then take the average across all series to calculate the exam-level effective diameter (hereafter, “diameter”). CT categories reflect both the body region imaged and the radiation dose required by the underlying clinical indication; thus, some categories represent anatomy alone (e.g., neck or cervical spine), while some are sub-divided according to radiation needs (e.g., low, routine, or high dose head) (18). The sample includes 65 unique scanner models reflecting 380 individual scanners from the four largest manufacturers: General Electric, N = 27 models (General Electric Healthcare, Chicago, Illinois, U.S.); Siemens, N = 24 models (Siemens Healthcare, Erlangen, Germany); Philips, N = 12 models (Koninklijke Philips N.V., Amsterdam, The Netherlands); and Canon/Toshiba, N = 5 models (Canon Medical Systems Corporation/Toshiba, Ōtawara, Tochigi, Japan). The UCSF Committee on Human Research approved this study with a waiver of individual informed consent. Collaborating institutions obtained local Institutional Review Board approval or relied on the UCSF approval to contribute data to the Registry.
Phantom Library
The University of Florida (UF) Department of Radiology, in collaboration with the National Cancer Institute (NCI), created an expansive library of hybrid computational human phantoms, including 12 reference size computational phantoms (6 males and 6 females of differing ages) and 351 non-reference computational phantoms (19, 20). The smallest non-reference male and female phantoms are 85 cm in length and 10 kg in weight. The largest phantoms are 185 cm and 125 kg for males and 175 cm and 115 kg for females. As such, the library represents a wide distribution of patient size (19–22).
Organ Dose Estimation
Monte Carlo radiation transport simulations use random sampling of probability distributions to model the stochastic properties of radiation interactions with tissues, simulating the passage of individual photons through a computerized patient’s anatomy to calculate doses to organs (23). Using patient sex, age, effective diameter, and scan length, all exams were mapped to the closest body morphometry-matched UF/NCI hybrid computational phantom, and technical parameters from each exam were used to simulate scans and calculate organ doses for the CT categories of head (low, routine, high dose); neck or cervical spine; chest (low, routine dose); and abdomen and pelvis (low, routine, high dose). Inputs for the Monte Carlo simulations included exam-level CT scanner manufacturer, X-ray tube current (mAs), tube potential (kV), scan length, collimation, and whether the exam was performed using a fixed mA or tube current modulation. Head and neck or cervical spine exams did not use diameter for phantom matching. Monte Carlo simulations were performed using previously validated methodology to estimate organ doses (20–22), and organ doses are reported in mGy at the level of the exam, accounting for all constituent phases.
There was highly consistent use of 16-cm and 32-cm reporting phantoms (unrelated to computational phantoms) across body regions (17). Thus, dose measures were not generated separately by phantom size.
Organ Dose Representative Values
We excluded exams with any estimated organ dose ≥500 mGy (6,764 adult and 747 pediatric exams) as likely erroneous as there were inconsistencies observed across associated technical parameters. While these extreme doses might warrant individual investigation, they will not have contributed to calculating representative values. Using diameter as a measure of patient size, we then classified adult exams as small, medium, or large, if they fell into the bottom 25%, middle 50%, or top 25% of diameters, respectively, of their specific CT categories. We stratified pediatric exams by age, with age groups defined as <1 year, 1–5 years, 6–10 years, 11–15 years, 16+ years. As organ doses differ insignificantly by sex, these analyses combined females and males.
For adults, we calculated arithmetic mean (in mGy) and standard deviation organ dose values for each diameter group within each CT category. For children, we calculated the same summary measures for each age group within each CT category. For each CT category, we calculated red bone marrow, peak skin and thyroid doses, plus two additional organs specific to each CT category: for head and neck or cervical spine exams, brain and lens; for chest exams, lung and breasts; for abdomen and pelvis exams, colon and liver. For simplicity, the abdomen and pelvis category include whole spine exams, and head low dose includes sinus and face exams. In addition to the above stratifications, we also calculated organ doses (by the same cross-classifications) separately by site (N = 27). Analyses were limited to strata with at least 10 exams. Analyses used SAS version 9.3 (SAS Institute, Cary, NC) and R version 4.2.2 (2022–10-31 UCRT). Finding that organ doses varied little by patient diameter in adults or age in children (except for the youngest <1 year age group), we present summary results as the average for the CT category. Results stratified by adult diameter group and pediatric age group are provided in Supplementary Tables S1–S62 (https://doi.org/10.1667/RADE-24-00178.1.S1).
RESULTS
A total of 559,202 adult and 103,423 pediatric CT exams were assembled from the Registry (Table 1). In adults, the most common CT categories were abdomen and pelvis routine dose (34% of exams), head routine dose (24%), and chest routine dose (26%), while in children the most common CT category was head routine dose (46% of exams), abdomen and pelvis routine dose (25%), and head low dose (11%).
TABLE 1.
Computed Tomography Exams in Adults and Children by Body Region, Sex, and CT Category
| Body region and CT category | Adults |
Children |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall |
Female |
Male |
Overall |
Female |
Male |
|||||||
| N | % | N | % | N | % | N | % | N | % | N | % | |
|
| ||||||||||||
| Head | 154,231 | 27.6% | 81,237 | 52.7% | 72,994 | 47.3 | 58,853 | 56.9% | 25,155 | 42.7% | 33,698 | 57.3% |
| Head low dose | 17,196 | 3.1% | 9,281 | 54.0% | 7,915 | 46.0 | 11,070 | 10.7% | 4,703 | 42.5% | 6,367 | 57.5% |
| Head routine dose | 134,812 | 24.1% | 70,735 | 52.5% | 64,077 | 47.5 | 47,783 | 46.2% | 20,452 | 42.8% | 27,331 | 57.2% |
| Head high dose | 2,223 | 0.4% | 1,221 | 54.9% | 1,002 | 45.1 | — | — | — | — | — | — |
| Neck or cervical spine | 36,309 | 6.5% | 18,454 | 50.8% | 17,855 | 49.2 | 8,072 | 7.8% | 3,600 | 44.6% | 4,472 | 55.4% |
| Chest | 148,132 | 26.5% | 75,436 | 50.9% | 72,696 | 49.1 | 9,727 | 9.4% | 4,511 | 46.4% | 5,216 | 53.6% |
| Chest low dose | 1,571 | 0.3% | 723 | 46.0% | 848 | 54.0 | — | — | — | — | — | — |
| Chest routine dose | 146,561 | 26.2% | 74,713 | 51.0% | 71,848 | 49.0 | 9,727 | 9.4% | 4,511 | 46.4% | 5,216 | 53.6% |
| Abdomen and pelvis | 220,530 | 39.4% | 119,881 | 54.4% | 100,649 | 45.6 | 26,771 | 25.9% | 13,742 | 51.3% | 13,029 | 48.7% |
| Abdomen and pelvis low dose | 12,492 | 2.2% | 6,589 | 52.7% | 5,903 | 47.3 | 969 | 0.9% | 578 | 59.6% | 391 | 40.4% |
| Abdomen and pelvis routine dose | 191,142 | 34.2% | 106,028 | 55.5% | 85,114 | 44.5 | 25,571 | 24.7% | 13,058 | 51.1% | 12,513 | 48.9% |
| Abdomen and pelvis high dose | 16,896 | 3.0% | 7,264 | 43.0% | 9,632 | 57.0 | 231 | 0.2% | 106 | 45.9% | 125 | 54.1% |
| Total Exams | 559,202 | 100.0% | 295,008 | 52.8% | 264,194 | 47.2 | 103,423 | 100.0% | 47,008 | 45.5% | 56,415 | 54.5% |
Note. Categories not used in children are indicated by a dash.
Organ Doses
Organ doses in adults, as expected, differed by CT category based on the anatomic regions covered by the scan range, and doses consistently increased between the low and high dose categories (Table 2). For head CT, the highest doses were to the skin (79 and 156 mGy in head routine and high dose, respectively), followed by brain and lens. Brain doses increased from 20 mGy (SD 14) for head low dose, to 46 mGy (SD 21) for head routine dose, to 64 mGy (SD 31) for head high dose exams. Lens doses increased from 24 mGy (SD 19) to 58 mGy (SD 26) to 83 mGy (SD 42) across the same head low, routine, and high dose categories. While mean red bone marrow doses (range 1–5 mGy) and thyroid doses (range 3–19 mGy) were far lower for the head categories, thyroid doses in the neck or cervical spine (69 mGy) and chest routine dose (57 mGy) exams were noticeably higher. For abdomen CT, the colon was the highest exposed organ, and mean doses increased from 19 mGy (SD 12) to 32 mGy (SD 28) to 69 mGy (SD 42) for abdomen and pelvis low, routine, and high dose, respectively.
TABLE 2.
Mean Organ Doses (in mGy) and Standard Deviation (SD) by CT Category in Adults and Children
| CT category | Adults |
Children |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Red bone marrow | Thyroid | Skin peak | Other | Other | Red bone marrow | Thyroid | Skin peak | Other | Other | |
|
|
|
|||||||||
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | |
|
| ||||||||||
| Head | Brain | Lens | Brain | Lens | ||||||
| Head low dose | 1 (2) | 3 (13) | 38 (33) | 20 (14) | 24 (19) | 5 (5) | 4 (14) | 41 (36) | 23 (17) | 21 (20) |
| Head routine dose | 3 (3) | 5 (17) | 79 (52) | 46 (21) | 58 (26) | 12 (11) | 18 (32) | 70 (48) | 46 (24) | 49 (26) |
| Head high dose | 5 (4) | 19 (36) | 156 (131) | 64 (31) | 83 (42) | — | — | — | — | — |
| Neck or cervical spine | 14 (14) | 69 (62) | 46 (54) | 24 (21) | 35 (30) | 10 (9) | 42 (39) | 27 (30) | 19 (17) | 24 (21) |
| Chest | Lung | Breast | Lung | Breast | ||||||
| Chest low dose | 2 (2) | 8 (7) | 3 (3) | 4 (4) | 4 (5) | — | — | — | — | — |
| Chest routine dose | 15 (14) | 57 (56) | 25 (24) | 38 (37) | 37 (37) | 12 (16) | 40 (51) | 22 (33) | 30 (39) | 26 (35) |
| Abdomen and pelvis | Colon | Liver | Colon | Liver | ||||||
| Abdomen and pelvis low dose | 9 (5) | 1 (4) | 11 (7) | 19 (12) | 17 (10) | 7 (4) | 1 (3) | 7 (4) | 15 (8) | 13 (8) |
| Abdomen and pelvis routine dose | 14 (12) | 4 (13) | 18 (18) | 32 (28) | 24 (21) | 8 (11) | 3 (11) | 11 (19) | 20 (25) | 16 (22) |
| Abdomen and pelvis high dose | 29 (18) | 6 (18) | 35 (22) | 69 (42) | 46 (36) | 23 (18) | 7 (18) | 25 (19) | 48 (39) | 39 (37) |
Note. Categories not used in children are indicated by a dash.
In children the highest doses were also in skin (70 mGy, SD 48 in head routine dose), followed by brain (46 mGy, SD 24) and lens (49 mGy, SD 26) in head routine dose, colon (48 mGy, SD 39) in abdomen and pelvis high dose, and thyroid in neck or cervical spine (42 mGy SD 39) and chest routine dose (40 mGy, SD 51) exams (Table 2). In abdomen and pelvis, all presented mean organ doses tripled (or greater) between the low dose and high dose categories (e.g., red bone marrow from 7 to 23 mGy, colon from 15 to 48 mGy, liver from 13 to 39 mGy). Not unexpectedly, bone marrow doses in head exams are far higher in children than in adults.
Dose Variation by Patient Diameter and Age
Organ doses in adults varied relatively little by patient diameter (Supplementary Tables S1–S3; https://doi.org/10.1667/RADE-24-00178.1.S1). For more than half of the 9 CT categories, including the 5 organ doses assessed within each (totaling 45 comparisons), organ doses among patients in the top quartile were no more than 15% higher than doses for patients in the smallest quartile. For example, for abdomen and pelvis high dose, the colon dose increased 10% from 67 mGy to 74 mGy from the smallest to the largest quartile of patients. One exception were thyroid doses, which were often more than twice as high for the largest quartile compared with the smallest quartile of patients in all head categories, for example doubling from 4 mGy to 9 mGy in head routine dose exams.
Pediatric brain and lens doses for head imaging increased minimally by age, except for the youngest children who consistently had the highest organ doses in almost all CT categories [Supplementary Tables S4–S6 (https://doi.org/10.1667/RADE-24-00178.1.S1) and Fig. 1A]. For example, for head routine dose, the most common CT category, brain doses were 54 mGy among children <1 year, and then increased gradually from 44 mGy in children aged 1–5 years, to 48 mGy in children aged 16+ years. A similar pattern was observed in head low-dose exams, where the mean lens dose of 36 mGy in children <1 year dropped to 19 mGy in children aged 1–5 years and then increased to 23 mGy in children aged 16+ years. For the next most common pediatric category, abdomen and pelvis imaging, there was less consistent variation in dose with patient age (Fig. 1B).
FIG. 1.
Panels A and B. Organ dose distributions in children by age group, for select CT categories and organs.
Inter-Site Variability in Organ Doses
Inter-site comparisons reveal substantial variation in mean adult organ doses (Fig. 2). For example, in abdomen and pelvis routine dose exams in medium diameter adults (i.e., the 50% of adults between the 25th and 75th percentiles), the highest observed site-level mean colon dose (68.5 mGy) is 4.7 times higher than the lowest observed dose (14.7 mGy). In head routine dose exams in medium-diameter adults, the highest observed site-level thyroid dose (113.1 mGy) is 12.7 times higher than the lowest (8.9 mGy). Similar inter-site variation was found in children: for the most common category of head routine dose, the 6–10-year age group had the greatest variability, with the highest observed site-level brain dose (59.1 mGy) being 2.0 times the lowest (29.6 mGy) (Fig. 3). Variation in other CT categories is generally much higher than in head exams. For example, in routine abdomen and pelvis exams for 6–10-year-olds, the highest observed site-level mean colon dose (116.6 mGy) is 21 times the lowest (5.6 mGy).
FIG. 2.
Site-level mean organ doses (in mGy) in adults by small, medium, and large patient effective diameter groups, for select CT categories and organs.
FIG. 3.
Site-level mean organs doses (in mGy) in children by age group, for select CT categories and organs.
DISCUSSION
The organ doses included in this paper are the best available estimates of the radiation doses patients receive when they undergo CT, as they were calculated with patient-dependent dosimetry for over 662,000 CT examinations mapped to the most extensive known library of computational phantoms. As such, they are likely to reflect recent CT practice with great fidelity.
While effective dose has proven a highly useful measure for cumulative dose tracking and cross-modality comparisons, and while it may be calculated for individual exams in the service of estimating population cancer risk, it was not designed for individual patient cancer risk estimation. For that purpose, we must know which organs were irradiated and with what absorbed dose. The current study offers a broad foundational view of organ-based cancer risk across an international CT radiation dose registry for a recent five-year period.
We observed relatively modest variation in organ doses across patient diameter or age groups, except in the youngest (<1 year old) patients and in a few select CT categories. In general, this likely reflects that while radiation doses commonly increase with increasing patient size, the higher dose is distributed over a larger sized patient, resulting in unchanged organ doses relative to a smaller dose in a smaller patient. An exception to this pattern was thyroid doses in adults, where larger patients had far higher thyroid doses than smaller patients, for example in neck or cervical spine CT. This may reflect relatively less change in neck size across the patient diameter groups, so that the higher dose used in larger patients is absorbed in a similarly sized neck, resulting in higher thyroid doses in these patients. Thyroid doses in head imaging in children <1 year were particularly elevated compared to older children, as well as to thyroid doses in neck or cervical spine examinations; this reflects complete capture of the thyroid in the irradiated area in head CT in infants, as well as a higher radiation dose (CTDIvol) used for head compared with neck imaging.
Inter-site variation in organ dose was considerable with some sites using orders of magnitude more radiation dose than another site in the same size patient, and the order of dose values by patient diameter or age group was not consistent or predictable. For example, some sites had highest doses in large diameter patients, while others had highest doses in small diameter patients. This may be a result of sites adjusting (or not adjusting) their acquisition parameters by patient size: i.e., where sites use approximately equal radiation dose (machine output) in small as in large patients, the smaller patients will have higher organ dose. Conversely, where sites adjust parameters to patient size, larger patients receive more radiation dose and may display higher resulting organ doses.
The doses observed in this study are in the range known to be harmful to a small proportion of patients. For example, the observed average bone marrow doses for most CT exam types in children are in the same range as those in the recent European cohort study, which identified an incidence of 1–2 hematological cancers per 10,000 children exposed to a single CT examination within 12 years (24). The observed mean brain dose for head routine dose CT in children (46 mGy) has been shown to double the risk of brain cancer (i.e., increase incidence of brain cancer by 1 case per 10,000 examinations) within the same time frame (25). And in adults, a large and broad literature has shown elevated cancer risks in the range of the organ doses reflecting a single CT examination (3, 4, 13, 26–28).
Comparison with existing organ dose values is not straightforward because of methodological differences (6–15). Earlier studies modeled average organ doses using technical parameters from surveys, clinical protocols, regulatory databases, literature, or from a small sample of clinical exams (but decoupled from individualized patient data, such as the patient’s size).
In their study of 1,200 adult oncology patients, Gao et al. produced tables of organ dose values (for males and females combined) (9). Their brain (49.3 mGy) and lens (59.9 mGy) values are very similar to the head routine dose exams reported in this study (brain 46 mGy, lens 58 mGy). However, their lung (9.1 mGy) and breast (7.3 mGy) organ doses are only 25% of the lung and breast doses reported herein for chest routine dose CT (38 mGy and 37 mGy, respectively), while their colon (16.0 mGy) and liver (17.5 mGy) organ dose values are around 50% of the abdomen and pelvis routine dose exam values from this study (32 and 24 mGy respectively). Gao et al. also report that a “factor of two difference in dose estimates was observed between patients of various body habitus,” whereas we observed more stability of organ doses across patient diameter groups for most CT categories.
The European Epidemiological Study on Pediatric Computed Tomography (EPI-CT) study produced select organ dose values for children and adults in European countries, from 1977–2014 based on some sampling of patient records combined with extrapolation from published protocols (14). Focusing on the most recent period, (2010) we compared their newborn group to our <1-year olds, their 5 years of age group to our 6–10 year age group, and their 15 year age group to our 16+ years age group. Notably, we compare our values against their examination-level values (not scanlevel), as the examination level may include multiple-phase exams, as ours do. Brain doses for the youngest age group were higher in our study [54 mGy in our study (head routine) vs. approximately 35 mGy in EPI-CT] and comparable for the other age groups (around 40–50 mGy in both studies). Thyroid doses from head routine dose exams were considerably higher in our study in the youngest children (67 vs. about 20 mGy) and similar for older age groups (≤ 10 mGy), but our study found higher thyroid doses in chest exams across all age groups. Bone marrow doses from head routine dose exams in the youngest children were higher in our study (23 vs. approximately 13 mGy), while other age groups were comparable. EPI-CT also gives bone marrow doses for adults, and these were equal to ours for head CT (approximately 3 mGy), and lower than ours in neck, chest, and abdomen exams.
Limitations
We used effective diameter, not water equivalent diameter (because it is mostly missing in the Registry), patient height, weight, or body mass index, to match patients to computational phantoms of varying body size. Among patients of similar diameter, body fat distribution and precise organ shapes and positions may vary. In addition, the simulation methods make assumptions about exactly what anatomy was imaged/radiated. Moreover, over-scanning or under-scanning that occurred in clinical practice can result in selection of suboptimal phantoms and thus miscalculation of radiation dose to tissues in adjacent anatomy. These unavoidable inaccuracies should minimally impact the results. Another limitation concerns the use of a single representative organ dose value, when the standard deviation in many strata is as large or larger than the organ dose value itself. This reflects tremendous variation in practice, as illustrated by the inter-site comparisons in Fig. 2, with some sites using very high radiation doses independent of patient diameter or age. Summary doses in the supplemental tables illustrate slightly more variation by age or diameter, yet large standard deviations persist. Lastly, all sites contributing to the Registry used Radimetrics dose monitoring software and therefore might not fully represent all imaging facilities, for example, in demonstrating a higher awareness of radiation dose.
CONCLUSIONS
These new organ dose values, created from a large, international registry using one of the most extensive libraries of computational phantoms, offer a picture of representative organ doses from diverse clinical settings. Organ doses vary minimally by patient diameter (in adults) and age (in children), except for in the very youngest children and in a small number of CT categories. Some organs doses, from a single exam, fall within the ranges previously reported to be associated with increased cancer risk. Finally, as with most areas of CT radiation dose comparisons, inter-site differences in organ dose levels show considerable variation that suggest ample room for radiation dose optimization and reduction.
Supplementary Material
Supplemental Table S1. Mean organ doses with standard deviation by patient effective diameter group and by CT category, for head and neck or cervical spine imaging in adults.
Supplemental Table S2. Mean organ doses with standard deviation by patient effective diameter group and by CT category, for chest imaging in adults.
Supplemental Table S3. Mean organ doses with standard deviation by patient effective diameter group and by CT category, for abdomen and pelvis imaging in adults.
Supplemental Table S4. Mean organ doses with standard deviation by age group and by CT category, for head and neck or cervical spine imaging in children. Cells with a dash reflect strata with insufficient sample size for analysis (<10 exams).
Supplemental Table S5. Mean organ doses with standard deviation by age group and by CT category, for chest imaging in children. Cells with a dash reflect strata with insufficient sample size for analysis (<10 exams).
Supplemental Table S6. Mean organ doses with standard deviation by age group and by CT category, for abdomen and pelvis imaging in children. Cells with a dash reflect strata with insufficient sample size for analysis (<10 exams).
ACKNOWLEDGMENTS
Funded by the U.S. National Institutes of Health (R01-CA181191) and the Patient-Centered Outcomes Research Institute (CD-1304-7043 and DI-2018C1-11375). Funders had no role in study design, collection, analysis, interpretation, and reporting of data, or decision to publish. The views in this article are solely the responsibility of the authors and do not necessarily represent the views of the Patient-Centered Outcomes Research Institute, its Board of Governors, or Methodology Committee, or other funders.
Footnotes
Editor’s note. The online version of this article (DOI: https://doi.org/10.1667/RADE-24-00178.1) contains supplementary information that is available to all authorized users.
REFERENCES
- 1.Division IMI. 2023 CT Market Outlook Report. 2024. [Google Scholar]
- 2.NCRP Report No. 184 Medical Radiation Exposure of Patients in the United States. Bethesda, Maryland; 2019. [Google Scholar]
- 3.Board of Radiation Effects Research Division on Earth and Life Sciences National Research Council of the National Academies. Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2, Washington, D.C.: The National Academies Press; 2006. [Google Scholar]
- 4.Hauptmann M, Daniels RD, Cardis E, Cullings HM, Kendall G, Laurier D, et al. Epidemiological Studies of Low-Dose Ionizing Radiation and Cancer: Summary Bias Assessment and Meta-Analysis. J Natl Cancer Inst Monogr. 2020;2020(56):188–200. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Damilakis J CT Dosimetry: What Has Been Achieved and What Remains to Be Done. Invest Radiol. 2021; 56(1):62–8. [DOI] [PubMed] [Google Scholar]
- 6.Lee C, Kim KP, Bolch WE, Moroz BE, Folio L. NCICT: a computational solution to estimate organ doses for pediatric and adult patients undergoing CT scans. J Radiol Prot. 2015; 35(4):891–909. [DOI] [PubMed] [Google Scholar]
- 7.Jansen JT, Shrimpton PC. Development of Monte Carlo simulations to provide scanner-specific organ dose coefficients for contemporary CT. Phys Med Biol. 2016; 61(14):5356–77. [DOI] [PubMed] [Google Scholar]
- 8.Gao Y, Quinn B, Mahmood U, Long D, Erdi Y, St Germain J, et al. A comparison of pediatric and adult CT organ dose estimation methods. BMC Med Imaging. 2017; 17(1):28. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Gao Y, Mahmood U, Liu T, Quinn B, Gollub MJ, Xu XG, et al. Patient-Specific Organ and Effective Dose Estimates in Adult Oncologic CT. AJR American journal of roentgenology. 2020; 214(4):738–46. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Lee C, Journy N, Moroz BE, Little M, Harbron R, McHugh K, et al. Organ Dose Estimation Accounting for Uncertainty for Pediatric and Young Adult CT Scans in the United Kingdom. Radiat Prot Dosimetry. 2019; 184(1):44–53. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Brady Z, Forsythe A, McBain-Miller J, Scurrah KJ, Smoll N, Lin Y, et al. CT Dosimetry for The Australian Cohort Data Linkage Study. Radiat Prot Dosimetry. 2020. [DOI] [PubMed] [Google Scholar]
- 12.Kim KP, Berrington de Gonzalez A, Pearce MS, Salotti JA, Parker L, McHugh K, et al. Development of a database of organ doses for paediatric and young adult CT scans in the United Kingdom. Radiat Prot Dosimetry. 2012; 150(4):415–26. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Pearce MS, Salotti JA, Little MP, McHugh K, Lee C, Kim KP, et al. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. Lancet. 2012; 380(9840):499–505. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Thierry-Chef I, Ferro G, Le Cornet L, Dabin J, Istad TS, Jahnen A, et al. Dose Estimation for the European Epidemiological Study on Pediatric Computed Tomography (EPI-CT). Radiation research. 2021; 196(1):74–99. [DOI] [PubMed] [Google Scholar]
- 15.Ngaile JE, Msaki PK. Estimation of patient organ doses from CT examinations in Tanzania. J Appl Clin Med Phys. 2006; 7(3):80–94. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Smith-Bindman R, Wang Y, Chu P, Chung R, Einstein AJ, Balcombe J, et al. International variation in radiation dose for computed tomography examinations: prospective cohort study. BMJ (Clinical research ed). 2019; 364:k4931. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Chu PW, Yu S, Wang Y, Seibert JA, Cervantes LF, Kasraie N, et al. Reference phantom selection in pediatric computed tomography using data from a large, multicenter registry. Pediatric Radiology. 2022; 52(3):445–52. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Smith-Bindman R, Yu S, Wang Y, Kohli MD, Chu P, Chung R, et al. An Image Quality-informed Framework for CT Characterization. Radiology. 2022; 302(2):380–9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Lee C, Lodwick D, Hurtado J, Pafundi D, Williams JL, Bolch WE. The UF family of reference hybrid phantoms for computational radiation dosimetry. Phys Med Biol. 2010; 55(2):339–63. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Geyer AM, O’Reilly S, Lee C, Long DJ, Bolch WE. The UF/NCI family of hybrid computational phantoms representing the current US population of male and female children, adolescents, and adults–application to CT dosimetry. Phys Med Biol. 2014; 59(18):5225–42. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Stepusin EJ, Long DJ, Ficarrotta KR, Hintenlang DE, Bolch WE. Physical validation of a Monte Carlo-based, phantom-derived approach to computed tomography organ dosimetry under tube current modulation. Med Phys. 2017; 44(10):5423–32. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Long DJ, Lee C, Tien C, Fisher R, Hoerner MR, Hintenlang D, et al. Monte Carlo simulations of adult and pediatric computed tomography exams: validation studies of organ doses with physical phantoms. Med Phys. 2013; 40(1):013901. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.AAPM. The Report of AAPM Task Group 246: Estimating Patient Organ Dose with Computed Tomography: A Review of Present Methodology and Required DICOM Information. 2019. [Google Scholar]
- 24.Bosch de Basea Gomez M, Thierry-Chef I, Harbron R, Hauptmann M, Byrnes G, Bernier MO, et al. Risk of hematological malignancies from CT radiation exposure in children, adolescents and young adults. Nat Med. 2023; 29(12):3111–9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Hauptmann M, Byrnes G, Cardis E, Bernier MO, Blettner M, Dabin J, et al. Brain cancer after radiation exposure from CT examinations of children and young adults: results from the EPI-CT cohort study. Lancet Oncol. 2023; 24(1):45–53. [DOI] [PubMed] [Google Scholar]
- 26.Berrington de Gonzalez A, Mahesh M, Kim KP, Bhargavan M, Lewis R, Mettler F, et al. Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med. 2009; 169(22):2071–7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Mathews JD, Forsythe AV, Brady Z, Butler MW, Goergen SK, Byrnes GB, et al. Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians. BMJ (Clinical research ed). 2013; 346:f2360. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Miglioretti DL, Johnson E, Williams A, Greenlee RT, Weinmann S, Solberg LI, et al. The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risk. JAMA pediatrics. 2013; 167(8):700–7. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplemental Table S1. Mean organ doses with standard deviation by patient effective diameter group and by CT category, for head and neck or cervical spine imaging in adults.
Supplemental Table S2. Mean organ doses with standard deviation by patient effective diameter group and by CT category, for chest imaging in adults.
Supplemental Table S3. Mean organ doses with standard deviation by patient effective diameter group and by CT category, for abdomen and pelvis imaging in adults.
Supplemental Table S4. Mean organ doses with standard deviation by age group and by CT category, for head and neck or cervical spine imaging in children. Cells with a dash reflect strata with insufficient sample size for analysis (<10 exams).
Supplemental Table S5. Mean organ doses with standard deviation by age group and by CT category, for chest imaging in children. Cells with a dash reflect strata with insufficient sample size for analysis (<10 exams).
Supplemental Table S6. Mean organ doses with standard deviation by age group and by CT category, for abdomen and pelvis imaging in children. Cells with a dash reflect strata with insufficient sample size for analysis (<10 exams).