Size-specific dose estimation in pediatric computed tomography: From dose characterization to individualized optimization

Table 1 Evolution of the size-specific dose estimate methodology and its application in pediatric computed tomography

Methodology	Core parameters	Suitable scenarios for pediatric	Main contributions	Limitations
TG-204	AP, LAT, Deff, CTDIvol × body conversion factors	Pediatric body CT, especially used for basal dose correction of chest, abdomen, and pelvic CT	Easy to implement and traceable, the foundation of clinical popularization	Geometric dimensions cannot reflect tissue attenuation, and there may be deviations in chest and body composition scenarios
TG-220	Dw, cross-sectional area + CT value information	Scenarios with significant differences in chest, abdominal, and body composition among children	Closer to the attenuated body shape than Deff and represents a refined direction in SSDE development	Manual delineation time-consuming and poor repeatability, automatic delineation requires excellent algorithms
TG-293	Specialized conversion factor for head CT, head circumference/Dw-related stratification	Pediatric cranial CT examinations, non-enhanced cranial CT scans, and optimized cranial imaging protocols	Avoids inappropriate application of body CT conversion factors to head CT	Still cannot represent the dose received by organs such as the lens or thyroid gland
Automatic dimension calculation	Automatic boundary segmentation, batch calculation of Deff, Dw, SSDE	Dose database, DRL, continuous quality control, and abnormal dose alert system	Minimizing human error is crucial for clinical translation	Requires validation across scanners, protocols, vendors, and age groups

TG-204: Task Group 204; TG-220: Task Group 220; TG-293: Task Group 293; AP: Anteroposterior; LAT: Lateral; D_eff: Effective diameter; CTDI_vol: Conventional volume computed tomography dose index; D_w: Water-equivalent diameter; CT: Computed tomography; SSDE: Size-specific dose estimate; DRL: Diagnostic reference level.

Table 2 Comparison of computed tomography size-specific dose estimate body type parameters in pediatric

Body size parameters	Data sources	Advantage	Limitations	Localization in pediatric CT
Age	Clinical data	Most readily available and convenient for initial protocol screening	Significant differences in body size among the same age pediatrics	Rough stratification variable
Weight	Clinical data	Available before scanning, related to body size	Does not reflect cross-sectional attenuation or organ distribution	Practical variable for protocol stratification
AP/LAT	CT topogram or cross-sectional image	Simple to measure and suitable for use with the TG-204	Influenced by slice and direction, it does not reflect organizational composition.	Basic geometric dimension specifications
Deff	AP and LAT geometric mean	Highly standardized, easy to promote	Differences in chest and body composition may result in potential biases	Common Metrics for Traditional SSDE
Dw	CT image area + CT value	Simultaneously reflecting size and attenuation	Requires reliable segmentation and validation across scanners, protocols, and body regions	Recommended indicators for the future
Automatic size segmentation	Image algorithms	High throughput, reproducible, suitable for quality control	Need to verify cross device generalization	Development direction of dose management system

TG-204: Task Group 204; CT: Computed tomography; AP: Anteroposterior; LAT: Lateral; D_eff: Effective diameter; SSDE: Size-specific dose estimate; D_w: Water-equivalent diameter.

Table 3 Summary of the translational roles of size-specific dose estimate in pediatric computed tomography dose management

Application domain	Representative studies	Evidence summary	Practical implication
Pediatric DRL	Kanal et al[61], Hwang et al[64], Bos et al[63], Kamdem et al[48], and Ploussi et al[65]	DRL should be stratified by age, body weight, body diameter, examination site, and clinical indication	SSDE can complement CTDIvol and DLP for establishing pediatric DRLs that better reflect body-size differences
Automated dose monitoring	Bos et al[63], Abdulkadir et al[36], Anam et al[27]	Automated extraction of dose reports and automated calculation of Dw and SSDE can support high-throughput quality control	Become a core function of pediatric CT dose-management platforms
Patient-level cumulative dose assessment	Tabari et al[66]	Simple summation of CTDIvol or SSDE cannot characterize local peak dose along the Z-axis	Scan start and end positions, scan length, tube-current modulation, and dose line integral should be recorded
Image-quality constraints	Raslau et al[51], Kim and Newman[41], Sayed et al[68]	Dose reduction may alter image noise and low-contrast resolution; optimization should be based on the diagnostic task	SSDE should be jointly modeled with image-quality metrics to avoid diagnostically insufficient low-dose imaging

DRL: Diagnostic reference level; SSDE: Size-specific dose estimate; CTDI_vol: Conventional volume computed tomography dose index; D_w: Water-equivalent diameter; CT: Computed tomography; DLP: Dose-length product.