Document Type

Conference Proceeding

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Publication Title

Medical Physics


Linear energy transfer (LET)-guided optimization in intensity-modulated proton therapy (IMPT) via alternating direction method of multipliers (ADMM) has the potential to improve its biological effectiveness (IMPTLET- ADMM), in which the LET distribution in target can be escalated, while the LET distribution in the organs at risk can be mitigated. This study aims to quantitatively investigate the effectiveness of LET optimization in IMPT via ADMM with different solvers in its iteration loop. Methods: The clinical dose-volume-histogram (DVH) constraint noted dose sub-problem and clinical LET -volume-histogram (LVH) constraint noted LET sub-problem are combined to generate a composite objective function, which is available to LET incorporated IMPT optimization. Such optimization problem can be solved through ADMM. In the iteration loop of ADMM, the dose sub-problem is a linear least-square problem, which can be effectively solved by conjugate gradient method. At the same time, the LET sub-problem is a nonlinear least-square problem, which can be solved using gradient descent methods. In this study, the BB, LMF, and L-BFGS methods are adopted to solve the LET sub-problem, respectively. Three representative cases (brain, prostate and liver cancer) were used for testing purposes. The dose and LET distribution were assessed. Results: With a similar physical dose distribution compared to the clinical IMPT plan, LVH comparison indicated IMPTLET- ADMM with L-BFGS solver (LETOpt[L-BFGS]) has the best LET distribution. More specifically, for the brain case, the mean LET of CTV was improved by 0%, 3%, 10% by LETOpt[BB], LETOpt[LMF], LETOpt[L-BFGS]; the max LET of the brainstem was reduced by 21%, 39%, 48% compared to the clinical IMPT. The other two cases show similar results. Conclusion: IMPTLET- ADMM is able to modulate the LET distribution while maintaining dose distribution. L-BGFS solver is more effective in LET distribution modulation than BB and LMF solver





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American Association of Physicists in Medicine 65th Annual Meeting & Exhibition, July 23-27, 2023, Houston, TX