Evaluation of Feasibility of Truebeam Hypersight Imaging for Adaptive Treatment Planning for Breast Patients
Abstract
Purpose
HyperSight imaging (HS-CBCT) is commercially available for TrueBeam linear accelerators enabling an advanced iterative reconstruction algorithm with metal artifact reduction (iCBCT-MAR). iCBCT-MAR reduces scatter and improves image quality in the presence of metal implants, creating CBCTs which may be viable for dose calculation. HS-CBCT also offers a higher panel grid ratio, faster gantry rotation speed, larger maximum area, and an extended radial field-of-view (eFOV). This study evaluates the dose calculation accuracy of HS-CBCT by comparing the dosimetric difference with the standard CT-simulation images for breast cancer patients.
Methods
Ten breast cancer patients as part of a larger prospective clinical trial (NCT06681233) were evaluated. Four patients were treated using breath-hold techniques, four were treated in the prone position, and two had metal implants. HS-CBCT images were acquired using eFOV and two different 125kV protocols with 1.2mAs (HS-A) and 0.3mAs (HS-B) per projection. Images were reconstructed using standard and advanced reconstruction algorithms. CT-sim and HS-CBCT images were registered in Eclipse. Structure sets and treatment plans from CT-sim were duplicated to HS-CBCT for dose calculation. Dose–volume histogram (DVH) metrics were evaluated for PTVs and OARs, including the heart and lungs.
Results
When comparing the results of the clinical plan with the dose calculated on the respective CBCTs, the difference between the standard reconstruction, HS-A, and HS-B protocols had mean lung doses differences of -30.7±46.5, -9.2±28.0, and -14.0±18.5cGy and difference in mean heart dose was 3.6±9.0, 3.9±9.5, and 1.2±6.0cGy, respectively. PTV D95 values were -0.6±1.2%, 4.6±11.1%, and 2.7±6.1% respectively.
Conclusion
Lower DVH metric deviations for OARs while maintaining PTV coverage observed between CT-sim and HS-CBCT supports the feasibility of using HyperSight for treatment planning in breast cases and may support opportunities for adaptive radiotherapy workflows in other disease sites. HS-CBCT with iCBCT-MAR improves image quality by reducing scatter and metal artifacts.