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Session: Therapy: SBRT/SRS Treatment Planning [Return to Session]

Feasibility of Using RayStation^TM TPS MonteCarlo Algorithm for Evaluating Ocular Dose Delivered Via Dedicated Proton Eyeline

M Mamalui*, M Rutenberg, R Dagan, University of Florida/Radiation Oncology, Jacksonville, FL


WE-IePD-TRACK 5-4 (Wednesday, 7/28/2021) 5:30 PM - 6:00 PM [Eastern Time (GMT-4)]

Purpose: Treatment of Ocular melanoma with protons, delivered via a dedicated fixed gantry beamline (aka Eyeline) has a long history and excellent clinical outcomes. However, creating a TPS that satisfies the requirements of modern multi-professional ocular treatment team, has been largely a matter of in-house program development at a few institutions. As new commercial treatment planning systems coming on the market, some of which are offering highly accurate computational methods, such as MonteCarlo, it stands to reason to attempt adapting such an algorithm to the purpose of calculating the dose for Eyeline treatment of Ocular Melanoma.

Methods: A spectrum of PDDs and lateral profiles, corresponding to the options available in Eyeline was recreated in Raystation^TM treatment planning system, using clinically commissioned pencil beam scanning option and MonteCarlo calculation algorithm. Semi-automated inverse optimization routine was constructed in Raystation^TM optimization module to ensure target coverage. The size of the target was determined by the Range and Modulation of the option under investigation. 11 beams were inverse-optimized in this manner. In addition, a brass aperture was defined as an automatically created structure in Raystation. Block margins were kept to 2.5 mm as used clinically.

Results: Distal and lateral dose fall-off distances were compared to the counterparts from eyeline measured PDD and profiles. It is shown that, given appropriate parameters of the optimization, layer-to-layer and spot-to-spot distance and appropriate overrides (brass block, air, negligible air gap between range shifter and the external planning structure), Distal Fall-off and Lateral 80-20% penumbra can be easily recreated in the vicinity (i.e., within 0.5mm on average, maximum deviation was 0.9mm for lateral penumbra) of the true measured clinical beam values: i.e., 3mm distal fall-off and 1.1-1.7 mm penumbra, respectively.

Conclusion: It appears quite feasible to use Raystation MonteCarlo algorithm for Eyeline dose calculation and evaluation.



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