Author: Yi-Fang Wang, Yading Yuan 👨🔬
Affiliation: Columbia University Irving Medical Center, Department of Radiation Oncology, Columbia University Irving Medical Center 🌍
Purpose: HyperSight, the latest CBCT technology from Varian Medical Systems, integrates rapid 6-second data acquisition with advanced iterative reconstruction and upgraded hardware. Previous studies have shown that HyperSight made improvements in signal-to-noise ratio, artifact reduction, scattering correction, and Hounsfield Unit (HU) accuracy, achieving comparable imaging quality as simulation fan-beam CT. This study evaluates HyperSight CBCT's potential to enhance dual-energy CBCT (DE-CBCT) imaging compared to non-HyperSight CBCT. DE-CBCT holds promise for functional imaging in CBCT-based online adaptive radiotherapy (OART).
Methods: We used a CIRS electron density phantom and a multi-energy QA phantom to compare DE-CBCT performance for iodine enhancement and soft tissue differentiation between HyperSight and TrueBeam (TB) non-HyperSight CBCT. Both phantoms were imaged using 80 kV and 140 kV CBCT protocols at 515 mAs on both systems. Non-linear moidal blending algorithms were developed and optimized to achieve optimal results.
Results: For iodine enhancement, HyperSight DE-CBCT increased contrast-to-noise ratios (CNR) for iodine in blood (0.5, 2, 5, 10, and 15 mg/cc) by 23%, 15%, 18%, 12%, and 68%, respectively, compared to HyperSight 140 kV. TB 80 kV and 140 kV failed to differentiate iodine concentrations of 0.5 and 2 mg/cc, with no improvement observed using blended DE-CBCT. For 5, 10, and 15 mg/cc, TB DE-CBCT showed a 43% decrease and 31% and 58% increases in CNR, respectively compared to HyperSight, but with noise levels 10 times higher. For soft tissue differentiation, HyperSight DE-CBCT increased liver CNR by 290% compared to HyperSight 140 kV. CNR differences for breast and adipose, breast and muscle, and adipose and muscle improved by 4%, 219%, and 163%, respectively. HyperSight DECT also outperformed TB DE-CBCT, with 8 and 12 times higher CNR differences for breast-muscle and adipose-muscle differentiation.
Conclusion: HyperSight enhances DE-CBCT with potential for functional imaging in tumor visualization, treatment response, and material differentiation in OART.