Improved Delta Radiomic Fidelity with Hypersight CBCT Compared to Conventional CBCT In Pelvic Radiotherapy
Abstract
Purpose
To test whether HyperSight CBCT (HS-CBCT) improves consistency of longitudinal radiomics with planning CT versus conventional CBCT in pelvic radiotherapy.
Methods
Ten pelvic cancer patients with planning CT (pCT), HS-CBCT, and conventional CBCT were analyzed across available fractions. HS-CBCT and conventional CBCT images were rigidly registered to corresponding pCT and resampled to 1-mm isotropic resolution before radiomics extraction (PyRadiomics v3.0.1) in the CTV and femoral head. In the CTV, CT-referenced normalized deviation (δ) was modeled versus per-fraction CTV D95% using feature-wise linear mixed-effects models with patient random intercepts and a modality×D95 interaction; FDR (False Discovery Rate) correction was applied per term. In the femoral head, longitudinal stability was quantified as texture drift (Euclidean distance-to-baseline in z-scored feature space) versus normalized treatment progress.
Results
Conventional CBCT showed stronger dose-associated drift in the CTV (steeper δ-D95 trends and greater dispersion), whereas HS-CBCT showed reduced dose dependence. Across 93 CTV features, 39 showed a significant modality×D95 interaction after FDR correction (q<0.05), and HS-CBCT reduced the absolute δ-D95 slope for 38/39 (median slope 0.247→0.059 per 1 SD D95; 76% reduction). Representative slopes (CBCT→HS) included first-order interquartile range 0.989→0.278 (q=8.6×10-5), uniformity -0.247→-0.097 (q=6×10-5), and GLCM IDMN -0.100→-0.012 (q=1.1×10-6). In the femoral head, among patients with ≥2 fractions in both modalities (n=8), end-of-treatment drift was 3.61 (IQR 3.02-4.19; 55% lower) for HS-CBCT vs 7.98 (3.01-9.94) for CBCT. Integrated drift over normalized progress (AUC) was also reduced: 1.50 (1.11-1.92; HS-CBCT) vs 2.85 (2.05-6.21; conventional CBCT); one-sided paired Wilcoxon p=0.027.
Conclusion
HS-CBCT provides more CT-consistent, dose-robust radiomics than conventional CBCT in pelvic radiotherapy, supporting its use for adaptive workflows and longitudinal radiomics studies.