Dosimetric Evaluation of TrueBeam HyperSight Imaging for Adaptive Radiotherapy Planning in Breast Cancer
Authors: Rofikun Nahar Rosmi
Institution: Gono University
Introduction
Accurate dose calculation is essential for effective radiotherapy treatment planning. Conventional cone-beam computed tomography (CBCT) has limitations in dosimetric accuracy due to scatter-related artifacts and inaccuracies in Hounsfield unit (HU) estimation. TrueBeam HyperSight CBCT (HS-CBCT), incorporating advanced iterative reconstruction algorithms, including iterative CBCT (iCBCT) and iterative CBCT with metal artifact reduction (iCBCT-MAR), may improve image quality and dose calculation accuracy. This study aims to evaluate the feasibility of using HyperSight imaging for adaptive radiotherapy treatment planning in breast cancer patients.
Methods
Ten breast cancer patients enrolled in a prospective clinical trial were included in the study. HyperSight CBCT images were acquired using two imaging protocols (HS-A and HS-B) at 125 kV, with 1.2 mAs and 0.3 mAs, respectively. The images were reconstructed using standard filtered back projection (FDK), iCBCT, and iCBCT-MAR algorithms. Treatment plans and anatomical structures from the original CT simulation (CT-sim) were transferred to the CBCT and HS-CBCT datasets following image registration. Dose distributions were recalculated, and dose-volume histogram (DVH) parameters were extracted. The evaluation focused on planning target volume (PTV) D95 and mean doses to the heart and lungs. Dosimetric differences between CT-sim and CBCT-based calculations were assessed using two-tailed paired t-tests.
Results
HyperSight CBCT demonstrated promising dosimetric performance compared with the original CT-sim. The mean difference in PTV D95 was 2.06 ± 4.75% for HS-A and 2.82 ± 6.01% for HS-B, with no statistically significant differences (p = 0.11 and p = 0.10, respectively). Mean heart dose differences were −0.12 ± 4.76 cGy for HS-A and 1.37 ± 5.89 cGy for HS-B, also without statistically significant differences (p = 0.68 and p = 0.74, respectively). Both HyperSight protocols demonstrated improved mean heart and lung dose representation compared with standard CBCT, although statistically significant differences in mean lung dose remained (p = 0.03 and p = 0.04 for HS-A and HS-B, respectively). The iCBCT-MAR reconstruction algorithm showed potential for improving HU accuracy and reducing image artifacts, particularly in cases involving metal implants.
Conclusion
TrueBeam HyperSight CBCT demonstrated promising feasibility for dose calculation in breast radiotherapy, with acceptable agreement in target coverage and mean heart dose compared with CT simulation. Advanced reconstruction algorithms may further improve the reliability of CBCT-based dose calculations. These findings support the potential integration of HyperSight imaging into adaptive radiotherapy workflows for breast cancer patients. Further validation using a larger patient cohort is recommended before routine clinical implementation.