Penumbra evaluation of the varian millennium and BrainLAB M3 multileaf collimators

摘要: Purpose: This study compares the width of penumbra obtained from two small-leaf multileaf collimators (MLCs) recommended for use in small field shaping such techniques as stereotactic radiosurgery. Methods and Materials: High-resolution film dosimetry measurements were taken to characterize MLCs with 3-mm 5-mm leaf at isocenter. The differences observed between tip edge measured 80% 20% maximum explained using a simple model calculating transmission through geometry. Results: Substantial found MLCs. MLC designed size 9.8 cm × showed values 2.4 ± 0.1 mm both directions perpendicular parallel motion. sizes up 40 comparable direction motion 3.2 modeling illustrated that this difference is largely due curvature tip. It was accommodate larger must have greater curvature, resulting penumbra. Conclusions: results show precision radiation therapy. may be attributed design determined by MLC. currently not modeled all treatment planning systems should into account part any procurement assessment system therapy same way isocenter would considered.