Evaluation of a Novel CBCT-Based Dose Calculation for Lung Treatment Plans Using End-to-End Phantom
Abstract
Purpose
The purpose of this study is to evaluate the accuracy of dose calculation using TrueBeam HyperSight CBCT (HS-CBCT) for measured values in lung treatment planning using the End-to-End (E2E) phantom.
Methods
A CT–ED phantom (062M, CIRS, USA) and an E2E phantom (036S, CIRS, USA) were imaged using HS-CBCT and a planning CT (pCT) system (Aquilion ONE, Canon Medical Systems, Japan). HS-CBCT acquisitions were performed of 125 and 140 kV with four tube currents (530, 1060, 1680, and 2210 mAs). The reconstruction algorithms were performed using Feldkamp-Davis-Kress (FDK), iterative CBCT (iCBCT), and iCBCT with metal artifact reduction (iCBCT MAR). CT–ED tables were generated for each imaging parameter set and imported into the Eclipse (AcurosXB v18.0.1, Siemens Healthineers, USA) for dose calculation. The calculated doses of 3D-CRT and IMRT for a simulated lung tumor in the E2E phantom were compared with the doses measured using an ionization chamber (PTW, Freiburg, Germany).
Results
For the 3D-CRT and IMRT plans, the dose difference to the pCT were 0.07% and 0.48%. HS-CBCT showed the highest agreement at 140 kV and 1680 mAs with iCBCT (−0.23%) for 3D-CRT, at 125 kV and 1060 mAs with iCBCT (0.52%) for IMRT. In 3D-CRT, average dose differences and standard deviation (SD) by reconstruction algorithms were 0.57% ± 0.21% for FDK, −0.61% ± 0.30% for iCBCT, and −0.61% ± 0.32% for iCBCT MAR. In IMRT, average dose differences and SD were 1.25% ± 0.12% for FDK, 0.73% ± 0.16% for iCBCT, and 0.82% ± 0.17% for iCBCT MAR.
Conclusion
The dose calculation accuracy of HS-CBCT using the E2E phantom was within ± 2.0%, and the iCBCT conditions demonstrated dose calculation accuracy within ± 1.0%.