Energy layer optimization via energy matrix regularization for proton spot‐scanning arc therapy

Abstract

Purpose Spot‐scanning arc therapy (SPArc) is an emerging proton modality that can potentially offer a combination of advantages in plan quality and delivery efficiency, compared with traditional IMPT of a few beam angles. Unlike IMPT, frequent low‐to‐high energy layer switching (so called switch‐up (SU)) can degrade delivery efficiency for SPArc. However, it is a tradeoff between the minimization of SU times and the optimization of plan quality. This work will consider the energy layer optimization (ELO) problem for SPArc and develop a new ELO method via energy matrix (EM) regularization to improve plan quality and delivery efficiency. Methods The major innovation of EM method for ELO is to design an EM that encourages desirable energy‐layer map with minimal SU during SPArc, and then incorporate this EM into the SPArc treatment planning to simultaneously minimize the number of SU and optimize plan quality. The EM method is solved by the fast iterative shrinkage‐thresholding algorithm and validated in comparison with a state‐of‐the‐art method, so‐called energy sequencing (ES). Results EM is validated and compared with ES using representative clinical cases. In terms of delivery efficiency, EM had fewer SU than ES with an average of 35% reduction of SU. In terms of plan quality, compared with ES, EM had smaller optimization objective values and better target dose conformality, and generally lower dose to organs‐at‐risk and lower integral dose to body. In terms of computational efficiency, EM was substantially more efficient than ES by at least 10‐fold. Conclusion We have developed a new ELO method for SPArc using EM regularization and shown that this new method EM can improve both delivery efficiency and plan quality, with substantially reduced computational time, compared with ES.

Beam angle optimization for proton therapy via group‐sparsity based angle generation method

“…Spot-scanning arc therapy is an emerging proton modality 56 and rapidly developing [57][58][59][60] as a viable alternative to fixed-beam IMPT that can potentially offer a combination of advantages in plan quality and delivery efficiency, compared to fixed beam IMPT. But currently fixed-beam IMPT remains to be the mainstream for proton treatments, for which BAO is still relevant.…”

“…To test the sensitivity of AG to the initial guess (B = 72), for 2-angle brain, we ran AG with 16 randomlychosen initial angular set S0, that is, (1,2), (18,55), (55,56), (9,42), (4,7), (2,15), (25,56), (16,30), (44,55), (38,39), (70,71), (9,44), (5,18), (33,71), (14,28), and (6,66), and these all converged to (13,58), that is, (60 • ,285 • ), which is the same as the result with B = 24; for 3-angle lung, we ran AG with 16 randomly-chosen S0, that is, (1,25,49), (2,31,41), (3,21,51), (7,17,66), (7,19,29) (7,32,72), (9,…”

FLASH instead of proton arc therapy is a more promising advancement for the next generation proton radiotherapy

“…The proton system manufacturers such as IBA are taking the key steps to such development, while the Treatment Planning System (TPS) providers such as RaySearch and Elekta are also providing the proton arc module in support of future clinical implementations 68,69 . Additionally, many ideas have been formed to optimize particle arc therapy in a more efficient way 70–75 . In recent years, we saw exponentially increased publications on the topic of particle arc therapy.…”

“…68,69 Additionally, many ideas have been formed to optimize particle arc therapy in a more efficient way. [70][71][72][73][74][75] In recent years, we saw exponentially increased publications on the topic of particle arc therapy.These encouraging trends and global efforts might suggest that the proton RT is at an important turning point, similar to the invention of VMAT in the 2000s in the photon world. 30 Besides the potential clinical benefits, one driving factor that pushes particle arc therapy to dominate the future market is simplifying the clinical workflow and shortening the treatment delivery time.…”

Bi-criteria Pareto optimization to balance irradiation time and dosimetric objectives in proton arc therapy

“…Among the few published PAT optimizers currently available, the oncology group from UCLA was the first one presenting a simultaneous approach for energy delivery sequence and plan quality optimization (Gu et al 2020). Based on this paper, Zhang et al (2022) have speed up the optimization and improved both delivery efficiency and plan quality using energy matrix regularization. The other previous published paper, however, do not directly optimize the energy sequence simultaneously with the spot intensities yet.…”