Quantitative Phantom and Clinical Assessment of Tin-Filtered CT for Dose Reduction and Metal Artifact Suppression In PET/CT
Abstract
Purpose
Tin (Sn) spectral filtration improves CT dose efficiency and mitigates beam hardening and photon starvation, two major contributors to metal artifacts that also affect PET attenuation correction. This work presents a comprehensive evaluation of Sn-filtered CT in PET/CT, combining quantitative assessment of metal artifact behavior with a large-scale clinical analysis of dose reduction across patient populations.
Methods
A uniform phantom containing a metallic insert was scanned on a long axial field-of-view PET/CT system using conventional low-dose CT and Sn-filtered low-dose CT at 100 and 140 kV. Artifact Index (AI) and contrast-to-noise ratio (CNR) were measured in ROIs adjacent to metal and in artifact-free background regions. Radial Artifact Spread Function (RASF) analysis was performed by sampling concentric paths around the metal to characterize spatial decay of streak artifacts. In parallel, 1,000 adult PET/CT studies acquired on the same PET/CT system were retrospectively analyzed, comparing Sn-filtered and non-Sn CT protocols for single-bed and whole-body continuous-bed-motion acquisitions, covering a wide range of patient body mass indexes (BMI).
Results
Phantom experiments showed that Sn filtration reduced metal-ROI noise by 51% (100 kV) and 41% (140 kV), decreased AI by 14% and 38%, and increased CNR by 22% and 5%, respectively. While 100 kV provided superior noise performance, 140 kV achieved stronger artifact suppression and faster radial decay in RASF profiles. Clinically, Sn filtration achieved consistent CT dose reductions of approximately 25–45% across BMI ranges, with the greatest benefit in patients with BMI ≥40, while preserving linear dose–BMI scaling.
Conclusion
Sn-filtered CT in PET/CT simultaneously reduces radiation dose and mitigates metal artifacts, with pronounced benefits in high-BMI patients and regions prone to severe streaking. Results demonstrate that Sn filtration preserves diagnostic image quality while supporting accurate PET attenuation correction, providing a practical strategy for optimizing non-contrast CT protocols in PET/CT.