一种新型的标准二次规划方法实现固定射野调强放疗的角度优化

A new standard quadratic optimization approach to beam angle optimization for fixed-field intensity modulated radiation therapy

射束角度优化极大程度上决定了固定野调强放疗的效果,但其一般被认为是一个非凸的NP难问题.本文将该问题转化为一个标准的二次规划问题进行高效求解.每个射野的最大出光强度被选作稀疏化指标,通过重赋权的L1最小化方法结合线性约束条件,实现射束角度稀疏化.该方案的有效性在一个数字模体和两个临床案例上进行了验证.最终得出结论:新的凸优化方法可以实现高效准确的放疗射束角度稀疏化,在治疗中更好地保护了危及器官.

Beam angle optimization(BAO)largely determines the performance of the fixed-field intensity modulated radiation therapy(IMRT),and it is usually considered as non-convex optimization and a non-deterministic polynomial(NP)hard problem.In this work,BAO is reformulated into a highly efficient framework of standard quadratic optimization.The maximum of beamlet intensities for each incident field as the surrogate variable indicates whether one radiation field has been selected.By converting the function of maximum value in the objective into a set of linear constraints,the problem is solved as standard quadratic optimization via reweighting l_(1)-norm scheme.The performance of the proposed BAO has been verified on a digital phantom and two patients.And the conclusion is drawn:the proposed convex optimization framework is able to find an optimal set of beam angles,leading to improved dose sparing on organs-at-risk(OARs)in the fixed-field IMRT.