Hypersight-Archer Head and Neck Clinical Trial: Image Quality and Dose Calculation Accuracy In the Presence of Metal Artifacts
Abstract
Purpose
This work evaluates Varian’s HyperSight CBCT system installed on the Ethos radiotherapy platform using head-and-neck (H&N) patient cases to characterize the image quality and dose-calculation accuracy in the presence of metal-induced artifacts for CBCT-based adaptive radiotherapy.
Methods
Images from 30 H&N cancer patients (24 with dental implants) were acquired using a planning FBCT (GE Healthcare), HyperSight CBCT on Ethos, and conventional CBCT on TrueBeam (Varian Medical Systems). HyperSight images were reconstructed using iCBCT Acuros and iCBCT Metal Artifact Reduction (MAR). Image quality was assessed using structure-based and whole-image metrics relative to FBCT. For dose calculation evaluation, CBCT images were rigidly registered to FBCT, and clinically approved plans were forward calculated. Gamma analyses were performed relative to FBCT in artifact-free and artifact-affected slices, with the latter also analyzed as a function of artifact index (AI). DVH metrics were evaluated for the PTV and selected OARs.
Results
HyperSight iCBCT MAR significantly reduced artifact severity and improved HU accuracy around metal (p<0.0004). However, iCBCT Acuros achieved significantly superior image quality metrics compared to conventional TrueBeam CBCT and HyperSight iCBCT MAR in regions with bone and air (p<0.04). Dosimetrically, HyperSight Acuros produced the highest gamma pass rates in artifact-free slices (p<0.03), while HyperSight MAR demonstrated the least sensitivity to increasing AI in artifact-affected slices (p<0.001). The largest median DVH deviations were observed for the Dmax metric, reaching 1.6% ± 1.0% for HyperSight iCBCT Acuros, 1.5% ± 1.5% for HyperSight iCBCT MAR, and 2.0% ± 2.2% for TrueBeam across all OARs, and 3.0% ± 2.4%, 3.5% ± 2.4%, and 4.6% ± 1.9%, respectively, for the PTV.
Conclusion
HyperSight provides imaging suitable for direct dose calculation in H&N adaptive radiotherapy with iCBCT MAR improving accuracy near metal artifacts, while iCBCT Acuros is preferred when artifact reduction is less critical.