Abstract
An editable rounded leaf offset (RLO) table is provided in the Pinnacle3 treatment planning software. Default tables are provided for major linear accelerator manufacturers, but it is not clear how the default table values should be adjusted by the user to optimize agreement between the calculated leaf tip value and the actual measured value. Since we wish for the calculated MLC‐defined field edge to closely match the actual delivered field edge, optimal RLO table values are crucial. This is especially true for IMRT fields containing a large number of segments, since any errors would add together. A method based on the calculated MLC‐defined field edge was developed for optimizing and modifying the default RLO table values. Modified RLO tables were developed and evaluated for both dosimetric and light field‐based MLC leaf calibrations. It was shown, using a Picket Fence type test, that the optimized RLO table better modeled the calculated leaf tip than the Pinnacle3 default table. This was demonstrated for both an Elekta Synergy 80‐leaf and a Varian 120‐leaf MLC.PACS numbers: 87.55.D‐, 87.55.de, 87.55.Qr
Highlights
129 Rice: Optimization of rounded leaf offset table based on calculation by the Pinnacle3 treatment planning software and is dependent upon the Pinnacle machine’s specific modeling parameters
From version 7.4, the Pinnacle treatment planning software has supported the modeling of rounded Multileaf collimation (MLC) leaf ends.[9]. The graph of the default table in the Pinnacle software for the Elekta 80-leaf MLC is shown in the blue curve of Fig. 1
A method based on calculated dose profiles was developed to obtain machine-specific rounded leaf offsets in the Pinnacle3 treatment planning software
Summary
129 Rice: Optimization of rounded leaf offset table based on calculation by the Pinnacle treatment planning software and is dependent upon the Pinnacle machine’s specific modeling parameters. If the user defines the MLC leaf position according the light field at isocenter (light field-based MLC calibration), the method is still applicable using conversion data between the dosimetric and light field calibration values. Such data will be provided for an 80-leaf Elekta MLC (Elekta Corportation, Stokholm, Sweden). As can be seen in the default table (Fig. 1), all rounded leaf offsets for the Elekta 80-leaf MLC are less than or equal to 0, which means the leaves are always moved away from the opposing leaf bank before the dose is calculated
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