Pediatric Chest Photon-counting CT: Dose and Noise Behavior of Clinical Sn100 kVp and 90 kVp Protocols across Image Quality Levels - a Phantom Study.

PURPOSE: Photon-counting CT (PCCT) and spectral shaping enable new approaches in pediatric imaging, but the effects of clinically implemented tin-filtered pediatric chest protocols on radiation dose and image noise across image quality levels (IQLs) remain insufficiently characterized. This study compared a clinical Sn100 kVp ultra-high resolution (UHR) protocol with a non-tin-filtered 90 kVp standard-resolution protocol using anthropomorphic pediatric phantoms. MATERIALS AND METHODS: Three pediatric phantoms (1, 5, and 10 years) were scanned on a commercial PCCT system across IQLs 1-300 using the clinical Sn100 kVp UHR and non-tin-filtered 90 kVp standard-resolution protocols. Radiation dose and ROI-based image noise in lung parenchyma and bone were recorded. RESULTS: The Sn100 kVp UHR protocol showed lower lung-parenchymal noise across all phantom sizes and IQLs and generally lower bone noise. In the ultra-low-dose range (IQL 1-10), lung-parenchymal noise reductions ranged from 31% to 52% and bone-noise reductions reached 58%. Across most IQLs, the Sn100 kVp UHR protocol was associated with higher radiation dose. At high IQLs, dose plateaus occurred at approximately IQL 150 and 100 in the 5- and 10-year-old phantoms, followed by dose crossovers at approximately IQL 220 and 150, respectively. At very low IQLs, the Sn100 kVp UHR protocol showed a dose advantage up to IQL 5, 4, and 3 in the 1-, 5-, and 10-year-old phantoms, respectively. CONCLUSIONS: The Sn100 kVp UHR protocol was associated with lower image noise but was not universally dose-saving compared with the non-tin-filtered 90 kVp standard-resolution protocol. In addition, the observed dose behavior was influenced not only by spectral shaping but also by detector readout mode and protocol-specific technical constraints. These findings may support future pediatric chest PCCT protocol optimization. KEY POINTS: · The clinical Sn100 kVp UHR protocol was associated with lower lung-parenchymal noise and generally lower bone noise compared with the non-tin-filtered 90 kVp standard-resolution protocol.. · The dose advantage of the Sn100 kVp UHR protocol was limited to very low IQLs, while most IQLs showed higher radiation dose compared with the 90 kVp standard-resolution protocol.. · At high image quality levels, the Sn100 kVp UHR protocol exhibited dose plateaus, limiting further dose increase despite higher target image quality.. CITATION FORMAT: · Klüner LV, Zensen S, Peuster H et al. Pediatric Chest Photon-counting CT: Dose and Noise Behavior of Clinical Sn100 kVp and 90 kVp Protocols across Image Quality Levels - a Phantom Study. Rofo 2026; DOI 10.1055/a-2935-4084.