S2059
Physics - Image acquisition and processing
ESTRO 2026
the model’s performance, DEplanar scans with fast kV switching (60/120 kVp) were acquired at multiple mAs settings(0.435, 0.580, 0.760, 0.900, 1.050, 1.140, 1.400) using an in-house phantom consisting ofpork ribs mounted on a cylinder with a holder for an artificial tumor. WLS was applied tosuppress bones and enhance tumor contrast, with weighting factors (WF) ranging from 0.50to 0.70 in increments of 0.01. The contrast-to-noise ratio (CNR) was calculated to evaluateimage quality by comparing tumor segmentation with the background. Imaging dose foreach protocol was measured using a kV-calibrated detector and compared to the defaultlung radiography protocol (120 kVp, 0.24 mAs) provided by the manufacturer. CNR/doseefficiency was calculated to identify the protocol that provided the optimal balance betweenimage quality and radiation dose. Results: The optimal WF for effective bone removal ranged from 0.53 to 0.57. The cubic modelachieved the highest CNR, improving tumor visibility by 196.3% and 139.5% compared toLE and HE images, followed by the linear model (145% and 98.5%) and WLS (37.5% and11.2%). The best balance between dose and image quality occurred at 0.580–0.760 mAs,with a 20–35% dose increase from the standard protocol (14.146 μ Gy). Beyond 0.760 mAs,CNR/dose ratio declined, indicating that higher doses did not further improve image quality.
Conclusion: This study demonstrates the effectiveness of the tested models in enhancing lung tumorvisibility, achieving a balance between radiation dose and image quality which is robust tovariable mAs settings Keywords: Dual energy imaging, Material decomposition, Lung Mini-Oral 1373 Reducing cone-beam artifacts in Gamma Knife CBCT images through non-circular scan trajectories Alexandra Alain-Beaudoin 1,2 , Håkan Nordström 3 , Luc Beaulieu 1,2 , Joakim da Silva 3 1 Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Canada. 2 Service de physique médicale et radio-protection, et Axe Oncologie du CRCHU de Québec, CHU de Québec Université Laval, Québec, Canada. 3 Physics and Advanced Applications, Business Line Neuro, Elekta Instrument AB, Stockholm, Sweden
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