A new sparse optimization scheme for simultaneous beam angle and fluence map optimization in radiotherapy planning

Abstract

-minimization-based sparse optimization was employed to solve the beam angle optimization (BAO) in intensity-modulated radiation therapy (IMRT) planning. The technique approximates the exact BAO formulation with efficiently computable convex surrogates, leading to plans that are inferior to those attainable with recently proposed gradient-based greedy schemes. In this paper, we alleviate/reduce the nontrivial inconsistencies between the -based formulations and the exact BAO model by proposing a new sparse optimization framework based on the most recent developments in group variable selection.We propose the incorporation of the group-folded concave penalty (gFCP) as a substitution to the -minimization framework. The new formulation is then solved by a variation of an existing gradient method. The performance of the proposed scheme is evaluated by both plan quality and the computational efficiency using three IMRT cases: a coplanar prostate case, a coplanar head-and-neck case, and a noncoplanar liver case. Involved in the evaluation are two alternative schemes: the -minimization approach and the gradient norm method (GNM).The gFCP-based scheme outperforms both counterpart approaches. In particular, gFCP generates better plans than those obtained using the -minimization for all three cases with a comparable computation time. As compared to the GNM, the gFCP improves both the plan quality and computational efficiency.The proposed gFCP-based scheme provides a promising framework for BAO and promises to improve both planning time and plan quality.