Room: Exhibit Hall
Purpose: To verify dose calculation of Multiple-Metastases-Elements treatment plan.
Methods: Multiple Metastases Elements (MME) (BrainLab, Feldkirchen, Germany) treatment planning system (TPS) was used to generate single-isocenter dynamic-arc treatment plans for brain multiple metastasis stereotactic radiosurgery (SRS) on a TrueBeam STx linear accelerator. The treatment isocenter in the plan was determined automatically by MME, which was located at the geometric center of multiple tumors and was thus blocked by multi-leaf collimator (MLC). Because the isocenter was blocked by MLC and user cannot define interest points in an MME plan, there were difficulties in verifying the MME plan dose calculation with an MU-check software, which needs calculation point (usually the isocenter) to be within treatment fields to ensure calculation accuracy. To perform MU check for MME plans, we used an Eclipse treatment planning system, which was commissioned for the same linear accelerator. MME plans were exported to Eclipse TPS and the plans were re-calculated with the same monitor units in Eclipse TPS. Heterogeneity correction was applied in both MME and Eclipse plan calculations. 71 treatment plans were studied and dose volume histograms (DVHs) of 348 planning target volumes (PTVs) were compared between MME calculation and Eclipse recalculation.
Results: The differences of PTV mean doses between MME and Eclipse calculations (Difference=Eclipse/MME-1) were 3.2Â±2.3% (range: -4.0%~8.1%) (n=348). The differences are acceptable considering that different dose calculation algorithms were used in the two planning systems (pencil beam algorithm in MME and AAA algorithm in Eclipse).
Conclusion: The study demonstrated that Eclipse TPS can be applied as a useful tool for quality assurance to verify dose calculation of MME plans. Potentially it also can be applied to check treatment plans generated with other TPS.