Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA.
Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA; Maryland Proton Treatment Center, Baltimore, MD, USA.
Phys Med. 2024 Nov;127:104829. doi: 10.1016/j.ejmp.2024.104829. Epub 2024 Oct 4.
To explore the feasibility of a novel intensity-modulated proton arc technique that uses a single-energy beam from the cyclotron. The beam energy is externally modulated at each gantry angle by a tertiary energy modulator (EM). We hypothesize that irradiating in an arc without requiring an energy change from the cyclotron will achieve a faster delivery (main advantage of our technique) while keeping clinically desirable dosimetric results.
In a retrospective cohort of four patients with female pelvis, prostate, lung, and brain cancers, we investigated our volumetric-modulated proton arc therapy (VPAT) technique. Arcs were simulated by sectors of 1°-spaced static beams. Keeping the energy requested from the cyclotron the same for each entire arc was supported by a predesigned EM placed in front of the nozzle. As a feasibility measure, EM thicknesses were calculated. Delivery times and doses to targets and organs at risk (OARs) were compared to those of the clinical plans.
VPAT plans were comparable to their clinical counterparts in achieving target dose conformity, being robust to uncertainties, and meeting clinical dose-volume constraints. Cyclotron energies for the four cases were within 159-220 MeV, and energy modulation range was 69-100 MeV, equivalent to 13-19 cm of water-equivalent thickness (WET). Plan delivery times were reduced from > 5 min in our clinical practice to < 3.5 min in VPAT.
For the evaluated plans, the novel VPAT approach achieved shorter delivery times without sacrificing robustness, OAR sparing or target coverage. VPAT's EMs had WETs implementable in a clinical setup.
探索一种新的强度调制质子弧技术的可行性，该技术使用来自回旋加速器的单一能量束。通过三级能量调制器（EM）在每个旋转架角度对外调制束能。我们假设，在不要求回旋加速器改变能量的情况下以弧形照射将实现更快的输送（我们技术的主要优势），同时保持临床所需的剂量学结果。
在四名患有女性骨盆、前列腺、肺癌和脑癌的患者的回顾性队列中，我们研究了我们的容积调制质子弧治疗（VPAT）技术。通过间隔 1°的静态束扇形来模拟弧形。通过在喷嘴前放置预先设计的 EM 来支持为每个完整弧形请求的回旋加速器相同的能量。作为可行性措施，计算了 EM 的厚度。将目标和危及器官（OAR）的输送时间和剂量与临床计划进行了比较。
VPAT 计划在实现目标剂量一致性、对不确定性具有鲁棒性和满足临床剂量体积限制方面与临床对照方案相当。四个病例的回旋加速器能量在 159-220 MeV 之间，能量调制范围为 69-100 MeV，相当于 13-19 cm 的水等效厚度（WET）。计划输送时间从我们临床实践中的>5 分钟减少到 VPAT 中的<3.5 分钟。
对于评估的计划，新的 VPAT 方法在不牺牲稳健性、OAR 保护或目标覆盖的情况下实现了更短的输送时间。VPAT 的 EM 具有可在临床设置中实施的 WET。
