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An Improved Sequencing Algorithm for Dynamic Multileaf Collimator in Intensity Modulated Radiotherapy

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j jia

j jia*, J Chow, Princess Margaret Hospital, Toronto, ON

SU-E-T-396 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: In intensity modulated radiotherapy delivery, a multileaf collimator (MLC) is indispensable with its leaf sequencing algorithm being the link between the external beam treatment plan and the linear accelerator hardware control. In this study, a dynamic MLC leaf sequencing algorithm was developed based on the bixel width of intensity map, which can verify the speed of MLC leaf easier. This results in a better hardware variable-speed performance lessening the workload of the MLC system.

Methods: In dynamic MLC sequencing, we assume each pair of leaves forms a window and moves from left to right with the dose rate of photon beam kept constant. The intensity map was normalized and divided into bixels based on the equal-space clustering method. For each bixel, the actual travelling distance of leaf was determined by the MLC mount position. So in each single bixel the MLC leaf travels, one leaf pair can keep in constant speed and the accumulated dose from all bixels can form the intensity map.

Results:From experimental results of validation using various intensity maps in treatment plans of phantoms and patients, it is found that accurate dose distribution or dose-volume histogram can be obtained. Our new leaf sequencing algorithm was therefore verified.

Conclusion:It is concluded that the performance of the proposed dynamic MLC sequencing algorithm is better than previous works, as the algorithm decreases the need for mechanical constraint in MLC.

Funding Support, Disclosures, and Conflict of Interest: Natural Science Foundation of Anhui Province (11040606M132),Fundamental Research Funds for the Central Universities (Nos. 2012HGXJ0057,2012HGXJ0062,2012HGXJ0071,2012HGBZ0190)and Seed Foundation of Hefei University of Technology(2012HGZY0007),P.R.China

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