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Updated: Aug 17, 2026
Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies
Published on: February 6, 2019
A Novel Lattice Technique via Adaptive Spot Assignment and LET Optimization-Based Proton Arc Therapy
Yujia Qian1, Yajun Jia2, Qingkun Fan3
1School of Physics and Technology, Wuhan University, Wuhan, China; Cancer Center, Hubei Key Laboratory of Precision Radiation Oncology, Institute of Radiation Oncology, Hubei International Scientific and Technological Cooperation Base of Precision Radiation Oncology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, China; Key Laboratory of Biological Targeted Therapy (Huazhong University of Science and Technology), Ministry of Education, Wuhan, Hubei 430022, China.
Purpose:
Lattice radiation therapy is an innovative 3-dimensional implementation of spatially fractionated radiation therapy. This study aimed to develop a novel lattice-based proton arc therapy (PAT) technique to deliver a highly modulated peak-valley spatial dose distribution and a modulated linear energy transfer (LET) distribution.
Methods And Materials:
We introduced a PAT lattice algorithm that optimizes 3 key components, including energy-layer selection, spot assignment, and LET optimization (PATLESL). A simulated annealing algorithm was used to select the optimal energy layers. Meanwhile, an adaptive spot assignment strategy was implemented using a spot sparsity optimization algorithm based on the primal-dual active set with continuation to achieve an improved peak-to-valley dose ratio. Subsequently, LET optimization was achieved using the alternating direction method of multipliers with a minimum monitor unit constraint. Eighteen patients were selected to evaluate plan quality and delivery efficiency compared with the lattice technique based on the previously reported spot-scanning PAT energy sequence optimization algorithm. Feasibility and dosimetric accuracy were further validated using clinical phantom measurements.
Results:
Compared with PAT energy sequence optimization algorithm, the PATLESL plan exhibited improved dose and LET distributions with higher delivery efficiency. More specifically, PATLESL achieved steeper dose gradients, improving the peak-to-valley dose ratio from 16.90 ± 18.04 to 41.85 ± 29.69 (P < .01), shortening the beam delivery time by 37.43%, and increasing the target spot coverage by 44.12% while reducing the spot number by 93.78%. It also increased the mean LET in the lattice tumor volume from 2.84 ± 0.38 to 3.59 ± 0.26 keV/μm (P < .01), on average. Meanwhile, the phantom measurement confirmed high agreement between the planned and delivered results.
Conclusions:
A novel PAT lattice technique using adaptive spot assignment and LET optimization could deliver an enhanced peak-valley spatial dose distribution. Experimental validation on a clinical proton system confirmed deliverability and dosimetric accuracy, which may facilitate future clinical translation of proton lattice radiation therapy.
