Program Information
Proton Pencil Beam Planning Optimization On Monitor Unit Threshold Setting and Target Coverage in Conformality and Uniformity
D Freund*, J Syh , X Ding , J Syh , B Patel , x song , J Zhang , H Wu , l rosen , Willis-Knighton Medical Center, Shreveport, LA
Presentations
PO-BPC-Exhibit Hall-15 (Saturday, March 7, 2015) Room: Exhibit Hall
Purpose:To emphasize differences between standard proton pencil beam scanning (PBS) treatment plan versus hybrid plan. The threshold setting of monitor unit (MU) optimizes the plan with efficient spot monitor unit and improve efficacy with less number of energy layer to benefit plan quality.
Methods:A proton treatment plan needs to meet the proton machine characterization. Various threshold of monitor unit was initiated without sacrificing plan quality. It was also determined that the number of energy layer can be decreased to decline low count spots i.e. increases of spot MU efficiency in hybrid plan. Specifically, certain energy layers were re-optimized. The little weighting of MU was removed because of scarce spreading of beam spots with low MU’s.
Results:There are three main outcomes of plan quality to be probed. Firstly, the minimal required MU/fraction threshold was inserted. Secondly, spot spacing and spots layer by layer were all countable for the contribution of plan quality. Thirdly, total number of energy layer and the relative weighting of energy layer of each delivered beam need to be explored and evaluated. DVHs of PTV_Evaluation in our cases were compared for each separate plan.
Conclusion:Spot size is equivalent to the relative dose in the beam delivery system. The energy layer is associated with the depth of beam penetrates. More of beam layer count and fine tiny inefficient spots are not necessary to generate a high quality PBS treatment plan. In the opposite, it might degrade the plan quality and might increase the chance of beam pauses during MU delivery. Our work is to maintain the best possible quality plan by beam spot threshold optimization. To keep integrity and harmony among all elements such as spot size, spot number, layer number and the relative weighting of each layer in all beams is important in this study.
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