Proton minibeam radiation therapy: Experimental dosimetry evaluation
Proton minibeam radiation therapy: Experimental dosimetry evaluation
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DOI：
10.1118/1.4935868
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发表时间：
2015-12-01
期刊：
影响因子：
3.8
通讯作者：
Prezado, Y.
中科院分区：
文献类型：
--
作者：
Peucelle, C.;Nauraye, C.;Prezado, Y.
目的：质子微束放射治疗（pMBRT）是一种新的放射治疗（RT）方法，它将质子固有的物理优势与亚毫米空间分异光束照射时观察到的正常组织保存结合起来。这项剂量学工作旨在证明pMBRT技术实施的可行性。这是在奥赛的居里质子治疗中心进行的。方法：利用黄铜多缝准直器产生宽度为400 μ m和700 μ m的质子微束。连续梁之间的中心距离分别为3200和3500 μ m。（被动散射）光束能量为100 MeV，对应7.7 cm水当量的范围。绝对剂量测定是在水箱中使用一个套管式电离室（IBA CC13）进行的。对散布在IBA RW3平板模体中的放射性致色膜进行相对剂量测定。评估了深度剂量曲线和不同深度的横向剖面。峰谷剂量比（PVDR）、波束宽度和输出因子也作为深度的函数进行了评估。结果：在6.7 cm之前，PVDR值随深度的变化呈波峰和波谷分布。从该深度开始，由于多重库仑散射，横向剂量分布变得均匀。峰谷剂量比从幻影表面的8.2 +/- 0.5扩展到布拉格峰的1.08 +/- 0.06。这是第一次在如此小的质子场中进行剂量测定。尽管存在挑战，但还是获得了指导第一批生物实验所需的一整套剂量学数据。结论：pMBRT是一种减少放射治疗副作用的新策略。这项工作为这种新放射治疗方法的概念提供了实验证明：临床质子束可能允许在位于大脑中心的脑肿瘤中沉积（高）均匀剂量（7.5 cm深度，最坏情况），而剂量的空间分割保留在光束路径中的正常组织中，可能导致组织保留。这是这项有前途的技术的第一个完整的实验实现。为了证实pMBRT的临床潜力，需要进行生物学实验。(C) 2015年美国医学物理学家协会。
Purpose: Proton minibeam radiation therapy (pMBRT) is a new radiotherapy (RT) approach that allies the inherent physical advantages of protons with the normal tissue preservation observed when irradiated with submillimetric spatially fractionated beams. This dosimetry work aims at demonstrating the feasibility of the technical implementation of pMBRT. This has been performed at the Institut Curie - Proton Therapy Center in Orsay.Methods: Proton minibeams (400 and 700 mu m-width) were generated by means of a brass multislit collimator. Center-to-center distances between consecutive beams of 3200 and 3500 mu m, respectively, were employed. The (passive scattered) beam energy was 100 MeV corresponding to a range of 7.7 cm water equivalent. Absolute dosimetry was performed with a thimble ionization chamber (IBA CC13) in a water tank. Relative dosimetry was carried out irradiating radiochromic films interspersed in a IBA RW3 slab phantom. Depth dose curves and lateral profiles at different depths were evaluated. Peak-to-valley dose ratios (PVDR), beam widths, and output factors were also assessed as a function of depth.Results: A pattern of peaks and valleys was maintained in the transverse direction with PVDR values decreasing as a function of depth until 6.7 cm. From that depth, the transverse dose profiles became homogeneous due to multiple Coulomb scattering. Peak-to-valley dose ratio values extended from 8.2 +/- 0.5 at the phantom surface to 1.08 +/- 0.06 at the Bragg peak. This was the first time that dosimetry in such small proton field sizes was performed. Despite the challenge, a complete set of dosimetric data needed to guide the first biological experiments was achieved.Conclusions: pMBRT is a novel strategy in order to reduce the side effects of RT. This works provides the experimental proof of concept of this new RT method: clinical proton beams might allow depositing a (high) uniform dose in a brain tumor located in the center of the brain (7.5 cm depth, the worst scenario), while a spatial fractionation of the dose is retained in the normal tissues in the beam path, potentially leading to a gain in tissue sparing. This is the first complete experimental implementation of this promising technique. Biological experiments are needed in order to confirm the clinical potential of pMBRT. (C) 2015 American Association of Physicists in Medicine.