S2063
Physics - Image acquisition and processing
ESTRO 2026
processing pipeline, and images were reconstructed using the filtered backprojection algorithm in the Reconstruction Tool Kit (RTK) software. Quantitative image quality metrics, including CT number error and CT artifact amplitude relative to the reference planning CT, adipose–soft-tissue contrast, contrast-to-noise ratio (CNR), peak Signal-to-Noise Ratio (pSNR), and structural similarity index, were calculated. Differences between the two CBCT configurations were evaluated using the Wilcoxon signed-rank test. Results: Compared with scatter-corrected clinical CBCT, the 2D- ASG substantially reduced median [min–max] soft tissue CT number errors from 169 [150–185] HU to 56 [43–92] HU (p < 0.002), indicating a reduction in scatter-induced image artifacts. Median soft-tissue contrast increased from 62 [42–74] HU to 115 [90–133] HU (p < 0.002), and the CNR improved from 0.99 [0.37– 1.38] to 1.55 [1.27–1.76] (p < 0.002). The Structural Similarity Index relative to the planning CT rose from 0.53 [0.38–0.67] to 0.85 [0.82–0.93] (p < 0.002). Similar trends were observed for the pSNR and artifact amplitude metrics.
patient-level. References:
1. Villegas F et al. Challenges and opportunities in the development and clinical implementation of artificial intelligence based synthetic computed tomography for magnetic resonance only radiotherapy. Radiother Oncol. 2024;198:110387. doi:10.1016/j.radonc.2024.110387 2. Bao J et al. BMAD: Benchmarks for Medical Anomaly Detection. In: 2024 IEEE/CVF Conference on Computer Vision and Pattern Recognition Workshops (CVPRW). 2024:4042- 4053. doi:10.1109/CVPRW63382.2024.00408 Keywords: MR-only RT, synthetic CT, quality assurance Proffered Paper 1635 Improvement of soft tissue contrast and CT number accuracy in proton therapy CBCT with a 2D antiscatter grid: results from a prospective trial Uttam Pyakurel 1 , Yawei Zhang 2 , Ryan Sabounchi 1 , Farhang Bayat 1 , Junxiao Hu 3 , Sébastien Brousmiche 4 , Curtis Bryant 2 , Nancy Mendenhall 2 , Perry Johnson 2 , Cem Altunbas 1 1 Radiation Oncology, University of Colorado School of Medicine, Aurora, USA. 2 Radiation Oncology, University of Florida Health Proton Therapy Institute, Jacksonville, USA. 3 Pediatrics, University of Colorado School of Medicine, Aurora, USA. 4 R&D, Ion Beam Applications, Louvain-la-Neuve, Belgium Purpose/Objective: Adaptive proton therapy using cone beam CT (CBCT) requires accurate CT numbers for direct dose calculation and sufficient soft-tissue visibility to enable reliable target and normal structure delineation. However, high levels of scattered radiation in conventional CBCT lead to substantial CT number inaccuracies and poor soft-tissue contrast, posing a major limitation to its use in adaptive treatment workflows. To overcome these challenges, a novel two- dimensional anti-scatter grid (2D-ASG) prototype and raw-data correction algorithms were developed for a CBCT system integrated with a proton therapy gantry. This study prospectively evaluated their effect on CBCT image quality in human subjects. Material/Methods: Ten patients receiving proton therapy for prostate cancer were enrolled in an Institutional Review Board approved imaging study. Each participant underwent two CBCT scans on a Proteus Plus system (IBA, Louvain-la-Neuve, Belgium): (1) the standard clinical pelvis CBCT incorporating software-based scatter correction, and (2) a scan with the 2D-ASG prototype installed. Acquisition parameters and imaging dose were identical across both scans. For the 2D-ASG scan, residual scatter was further corrected using an offline
Conclusion: This first prospective evaluation of a prototype 2D- ASG-equipped CBCT system for proton therapy
Made with FlippingBook - Share PDF online