Systematic Review and Meta-Analysis of Radiation Dose Reduction Studies in Pediatric Head CT

Conventional imaging protocols used in pediatric head CT scanning without specific adaptations to lower radiation dose or "standard dose" pediatric head CTs increase unnecessary radiation exposure. Modifying CT parameters, utilizing iterative reconstruction, and adopting specialized protocols are ongoing strategies to lower radiation dose in pediatric head CTs. This article will review studies reducing radiation exposure in pediatric patients undergoing head CT and provide metaanalysis of percent radiation dose reduction of the studies. Following PRISMA guidelines, we utilized Embase.com, Ovid Medline, Scopus, the Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Database of Systematic Reviews (CDSR), and Clinicaltrials.gov to identify all relevant articles pertaining to radiation dose reduction in pediatric head CT. All human studies (excluding animal, phantom, and cadaveric) published after 2012, aiming to lower radiation dose of a "Routine" or "Standard" dose CT protocol in use, were selected for review and metanalyses. We extracted study characteristics such as location, sample size, scanner, clinical indication, CT protocol parameter modifications, iterative reconstruction method if applicable, dose reduction, image quality metrics, and overall findings. CT protocol parameter modifications and dose reduction were summarized using descriptive statistics. Metanalyses on percent dose reduction were performed. Metanalyses were subgrouped by clinical indication, use of iterative reconstruction, and age group to isolate sources of heterogeneity between studies. This review identified 20 studies modifying their routine or standard dose pediatric head CT protocols on human patients. These studies modified CT parameters with or without the use of iterative reconstruction and/or used specialized protocols. Most common CT parameters modifications consisted of decreasing tube current time product (mAs) (N=13) and/or tube voltage (kV) (N=9). The most successful dose reduction studies had the clinical indication of craniosynostosis and utilized iterative reconstruction. Ernst et al. (2016) utilized Model Based Iterative Reconstruction (MBIR) for craniosynostosis and reduced effective dose by 97% and Lyoo et al. (2023) utilized Advanced Modeled Iterative Reconstruction (ADMIRE) with ClariCT for craniosynostosis and reduced CTDIvol by 95.9%. Metanalyses revealed significant differences in percent dose reduction based on clinical indication. Heterogeneity of study protocols, incomplete protocol/outcome reporting, and variability of institution, scanner, patient demographics, and clinical indication limit the generalizability of our findings. This systematic review and metanalysis identifies tube current time product as the most commonly modified CT parameter and also highlights CT clinical indication as an important factor to isolate when comparing dose reduction studies. Further research should further investigate iterative reconstruction techniques as well as photon-counting CT to maximize radiation dose reduction of pediatric head CT. ADMIRE = advanced modeled iterative reconstruction, ASIR = adaptive statistical iterative reconstruction, CTDIvol = CT dose index volume, DLIR = deep learning iterative reconstruction, DLP = dose length product, FBP = filtered back-projection, IMR = iterative model reconstruction, MBIR = model-based iterative reconstruction.