(Sunday, 7/29/2018) 3:00 PM - 3:30 PM
Room: Exhibit Hall | Forum 5
Purpose: To reduce radiation dose of functional lung (FL) in lung cancer patients by Intensity-Modulated Proton Therapy (IMPT) technique and automated beam orientation optimization (BOO) algorithm.
Methods: Retrospective IMPT planning was performed on two patient cases to spare the dose in functional lung. In the first case, the functional lung volume was acquired from functional MR Imaging using hyperpolarized Xe-129 gas, and a pseudo CT image was derived for planning by overriding patient MR image with three tissue types: air, lung and soft tissue. In the second case, the functional lung information was estimated by biomechanically modeling elasticity from 4DCT datasets. IMPT plans considering FL sparing were created with 1) manually selected beams, 2) coplanar beams selected by IMPT-BOO algorithm, and 3) non-coplanar beams selected by IMPT-BOO algorithm. And these proton plans were compared against VMAT plans.
Results: Three beams were selected and optimized in each proton plan for every patient. IMPT plans achieved superior PTV coverage and functional lung sparing compared with VMAT plans. The average reduction in the mean dose of functional lung from the VMAT plan was 4.78Gy, 5.34Gy and 5.27Gy, for manual plan, coplanar BOO plan and non-coplanar BOO plan, respectively. The average reduction in the FL volume receiving dose larger than [10%, 20%, 40%] of prescription dose is [61.65%, 80.95%, 82.65%] for manual beam proton plan, [70.69%, 84.70%, 85.39%] for coplanar BOO plan, and [67.45%, 90.70%, 90.9%] for non-coplanar BOO plan.
Conclusion: IMPT planning is promising to improve the dose sparing in functional lung and advanced beam orientation optimization algorithm can further enhance the ability to preserve functional lung.
Funding Support, Disclosures, and Conflict of Interest: NIH U19AI067769 DE-SC0017687 NIH R21CA228160 DE-SC0017057 NIH R44CA183390 NIH R43CA183390 NIH R01CA188300
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