(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Using Multi-Criteria Optimization (MCO) tool to improve critical Organ at Risk (OAR) dosimetric parameters of Prostate and Head-Neck plans.
Methods: Sixteen Prostate and eleven Head-Neck previously treated clinical cases were retrospectively chosen and re-optimized using Varian Eclipse V15.5 MCO. The goal of the optimization was to explore the trade-offs of further reducing critical OAR doses while maintaining same target coverage, as well as keeping other OAR doses minimal changed. Critical OARs were chosen as rectum and bladder for Prostate and spinal cord and parotids were used for Head-Neck. The re-optimized plans were normalized to have the same 95% PTV doses (D95) as the clinical ones. Head-Neck cases have multi-dose prescription; plans were normalized to the highest dose level.
Results: For Prostate MCO plans, average Rectum dose volume percentage V75, V65 and V40 have reduced from 6.72%, 12.03% and 27.91% to 6.44%, 11.25% and 24.89%; with improvements of 4.2%, 6.5% and 10.8% respectively. Average Bladder dose volume percentage V80, V65 and V40 have reduced from 3.52%, 8.56% and 21.92% to 3.08%, 7.61% and 18.86%; with improvements of 12.5%, 11.1% and 14.0% respectively. The D95 of PTVs are unchanged and the maximal point doses increase less than 1%.For Head-Neck MCO plans, average Spinal Cord maximal doses have reduced from 40.16 Gy to 36.92 Gy, an improvement of 8.1%. Mean Left and Right Parotid doses have reduced from 23.80 Gy and 22.24 Gy to 21.63 Gy and 20.12 Gy, with improvements of 9.1% and 9.6%. The high dose level PTV D95 and the maximal point doses are unchanged; the intermediate and low dose level PTV D95 reduce less than 1%.
Conclusion: MCO is an effective tool to improve Rapid-Arc plan quality by exploring trade-offs between OAR dosimetric parameters and target coverage.
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