Encrypted login | home

Program Information

Feasibility Study of Esophagus Adaptive Planning Using Elekta MR-Linac Beam Model

Z Wen

Z Wen*, J Pollard , G Ibbott , S Lin , UT MD Anderson Cancer Center, Houston, TX


SU-I-GPD-J-101 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To test the plan quality using the Elekta MR-Linac beam model and predict the potential dosimetric benefit of adaptive treatment on an esophagus patient (50.4Gy in 28 fractions) whose GTV underwent significant changes after two weeks into treatment.

Methods: The original clinical plan using a Varian Linac beam model was exported from a Pinnacle treatment planning system (TPS) and imported into a Monaco TPS. The dose was recalculated in Monaco as the reference plan. The initial Monaco plan was optimized using the MR-Linac beam model with corrections for the 1.5 T magnetic field. Based on the change in the GTV shown in MRI after two weeks of treatment, the PTV was modified by the physician and the adapted plan was re-optimized using the MR-Linac beam model. Coverage of new PTV was maintained the same, and doses to critical structures were evaluated among the original reference plan, the initial MR-Linac plan, and the adapted MR-Linac plan.

Results: The differences among the original Pinnacle plan, the reference Monaco plan, and the initial Monaco plan were insignificant. For the adapted Monaco plan, the plan has the same coverage for the new PTV, and the dose to critical structures was similar to the reference plan, except for the heart. The mean heart dose was reduced to 17.9 Gy from 19.9 Gy (reference plan) and 19.2 Gy(initial MRL plan) due to shrinkage of the GTV near the heart.

Conclusion: Plan optimization with Monaco using the MR-Linac beam model can produce a plan of similar quality compared to the original clinical plan. The presence of the 1.5 T magnetic field and differences in beam energy, MLC configuration, and beam penumbra did not affect plan quality. Adaptive planning can reduce dose to critical structures due to tumor shrinkage.

Funding Support, Disclosures, and Conflict of Interest: The authors acknowledge research support from Elekta AB.

Contact Email: