Vai Alessandro, Mirandola Alfredo, Pavanello Vittoria, Magro Giuseppe, Bagnalasta Matteo, Trombetta Luca, Camarda Anna Maria, Ingargiola Rossana, Ronchi Sara, Cavallo Anna, Franceschini Marzia, Filippi Andrea Riccardo, Iacovelli Nicola Alessandro, Ciocca Mario, Orlandi Ester
Medical Physics Unit, CNAO National Center for Oncological Hadrontherapy, 27100 Pavia, Italy.
IUSS University School for Advanced Studies of Pavia, University of Pavia 27100 Pavia, Italy.
Phys Imaging Radiat Oncol. 2025 May 10;34:100777. doi: 10.1016/j.phro.2025.100777. eCollection 2025 Apr.
Optimizing head and neck cancer (HNC) plans with single-energy proton beams that fully traverse the patient (transmission beams) can improve robustness and delivery efficiency, complementing conventional approaches.
Experimental measurements, validated with Monte Carlo (MC) simulations, were carried out on a uniform water-equivalent plastic phantom (RW3) containing a metal component (2-Euro coins) irradiated with a single high energy proton field (228.6 MeV) to verify the transmission beam concept. 28 nasopharyngeal cancer (NPC) intensity modulated proton therapy (IMPT) were then optimized with nine coplanar single-energy fields (228.6 MeV), positioning the Bragg peaks well beyond the patient body, so called transmission beam mode. These plans (IMPT-TB) were compared to conventional IMPT and volumetric modulated arc therapy (VMAT) photon plans in terms of dose distributions quality, expected organ at risk (OAR) toxicity, robustness and delivery time.
Transmission beams minimized dose perturbation by metal objects (∼7% max relative variation at 18 cm depth). IMPT-TB plans achieved comparable dose distribution and expected toxicities to IMPT, increasing the dose bath (+96 % vs. IMPT) but remaining significantly lower than VMAT (-31.4 %). For 94 % of patients (N = 26), IMPT-TB met at least one additional dose constraint that the corresponding IMPT plan failed to satisfy. Moreover, in the analyzed subgroup (N = 5), IMPT-TB plans delivered with our synchrotron exhibit a 67 % reduction in beam time compared to IMPT plans.
IMPT-TB plans demonstrated enhanced robustness and significantly faster delivery compared to IMPT. Transmission beams could be clinically implemented, also in conjunction with standard IMPT, for proton radiation treatment of NPC.
利用完全穿透患者的单能质子束（透射束）优化头颈癌（HNC）计划，可提高稳健性和治疗效率，作为传统方法的补充。
在一个含有金属部件（2欧元硬币）的均匀水等效塑料模体（RW3）上进行实验测量，并通过蒙特卡罗（MC）模拟验证，该模体用单个高能质子束（228.6 MeV）照射，以验证透射束概念。然后用九个共面单能场（228.6 MeV）对28例鼻咽癌（NPC）强度调制质子治疗（IMPT）进行优化，将布拉格峰定位在患者身体之外，即所谓的透射束模式。将这些计划（IMPT-TB）与传统IMPT和容积调强弧形治疗（VMAT）光子计划在剂量分布质量、预期危及器官（OAR）毒性、稳健性和治疗时间方面进行比较。
透射束使金属物体引起的剂量扰动最小化（在18 cm深度处最大相对变化约为7%）。IMPT-TB计划在剂量分布和预期毒性方面与IMPT相当，增加了剂量包络（与IMPT相比增加96%），但仍显著低于VMAT（低31.4%）。对于94%的患者（N = 26），IMPT-TB至少满足了一项相应IMPT计划未能满足的额外剂量约束。此外，在分析的亚组（N = 5）中，与IMPT计划相比，我们的同步加速器实施的IMPT-TB计划的束流时间减少了67%。
与IMPT相比，IMPT-TB计划显示出更高的稳健性和显著更快的治疗速度。透射束也可与标准IMPT联合临床应用于NPC的质子放射治疗。
