Room: Exhibit Hall | Forum 1
Purpose: Efficient and promising solution from auto-planning(AP) can standardize the plan quality and minimize the variations between planners in the management of multiple brain metastases. This study aims to evaluate the dosimetric performance of AP implementation between TPS platforms.
Methods: For 6 clinical patients with 2-3 brain metastases, AP was performed with the Multiple Brain Mets(AP-MBM) ELEMETNS v.1.0(Brainlab AB, Munich, Germany) based on a set of pre-defined clinical and beam setup protocols. The interference of MLC-trajectory between targets is minimized during the arc-geometry optimization. For comparison, two other AP implementations were investigated using the RayStation v.8A(Raysearch AB, Stockholm, Sweden). The ELEMENTS plans and doses were loaded into the RayStation. With the same beam geometries and prescriptions, the first AP(AP1) mimicked the ELEMENTS plan doses through a script varying the target-to-organ ratio from 10 to 100% in 10% steps. An optimal plan with minimal volume of normal brain receiving 10 and 12Gy(V10Gy and V12Gy) and the optimal Paddick conformity index(CI) was chosen. The second AP(AP2) with a script that created a simple optimization structure(whole brain minus the PTVs) and automatically assigned a dose-fall off constraint(from 26Gy to 14Gy within 5mm). CI, gradient index(GI), and the normal brai(NB-V12Gy) were compared among 3 AP.
Results: Medians of CI are 1.30(AP-MBM), 1.99 (AP1), and 1.88(AP2). For one plan with three lesions, AP1 produced unacceptably large CI of 41.09 and 8.85 for two lesions. Medians of GI are 3.02(AP-MBM), 3.58(AP1), and 3.31(AP2), and for NB-V12Gy 17.96(AP-MBM), 27.79(AP1), and 23.49(AP2). AP-MBM is statistically better than AP1 and AP2(p<0.001) in terms of CI, GI, and NB-V12Gy.
Conclusion: For SRS planning for multiple brain metastases using a single isocenter, AP-MBM that integrates 4-pi optimization to optimize the MLC trajectory in the presence of target overlapping provides high-quality plan in an efficient manner.
Not Applicable / None Entered.