Dose Course 2018_Flipping book

Example 4: Modelling the MLC in Eclipse by Varian Eclipse Algorithms Reference Guide v13+

Fluence delivery modelling algorithms: programs to convert optimal fluence patterns to deliverable fluence patterns, where the influence of the MLC is taken into account (Leaf Motion Calculator, LMC)

Leaf Ends

Transmission and Tongue & Groove effect

Leaf-end shape is modelled flat .

•

• MLC Transmission parameter accounts for both inter- and intra- leaf transmission.

• The dosimetric leaf gap (DLG) parameter is a configuration parameter used in the fluence delivery models. It is used to shift the MLC leaf tip position by half its value to account for the transmission through the rounded leaf.

• Initial estimates of the DLG & MLC Trans parameters are measured by the user using a set of dynamic MLC fields (sliding window delivery patterns) defined by the vendor • There is no ray-tracing through leaf ends or between leaves

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Lo Sasso, Med. Phys., 25(10), 1998m 1919-1927