Clinical APBI‐VMAT plans
LEAKAGE
Highly conformal and homogeneous clinical APBI VMAT plans were generated in Eclipse TPS using three partial unilateral coplanar arcs on an SBRT‐dedicated TrueBeam Linac (Varian Medical Systems, Palo Alto, California, USA) equipped with a standard Millennium 120 MLC and a 6MV (600 MU/min) beam per our departmental SBRT protocol. The isocenter position was set to the geometric center of the PTV. These partial coplanar arcs had an arc length of approximately 230°, and different collimator angles were manually optimized to reduce MLC tongue‐and‐groove leakage dose throughout the arc rotation. On TrueBeam, the jaw‐tracking option was used during plan optimization to further minimize out‐of‐field dose.