Comparison of dosimetric impact of intra-fractional setup discrepancy between multiple- and single-isocenter approaches in linac-based stereotactic radiotherapy of multiple brain metastases.

Introduction: Treatment of multiple brain metastases by linac-based stereotactic radiotherapy (SRT) can employ either a multiple-isocenter (MI) or single-isocenter (SI) approach. The purposes of this study were to evaluate the dosimetric results of MI and SI approaches and compare the impacts of intra-fractional setup discrepancies on the robustness of respective approaches using isocenter shifts, whether the same magnitude of translational and rotational effects could lead to a significant difference between the two approaches.

Methods: Twenty-two patients with multiple brain metastases treated by linac-based SRT were recruited.