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.