点扫描和被动散射质子治疗：培养细胞中的相对生物效应和氧增比。

Spot Scanning and Passive Scattering Proton Therapy: Relative Biological Effectiveness and Oxygen Enhancement Ratio in Cultured Cells.

机构信息

Department of Radiation Oncology, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya, Japan; Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.

Department of Radiation Oncology, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya, Japan.

出版信息

Int J Radiat Oncol Biol Phys. 2016 May 1;95(1):95-102. doi: 10.1016/j.ijrobp.2016.01.017. Epub 2016 Jan 19.

DOI:10.1016/j.ijrobp.2016.01.017

PMID:27084632

Abstract

PURPOSE

To determine the relative biological effectiveness (RBE), oxygen enhancement ratio (OER), and contribution of the indirect effect of spot scanning proton beams, passive scattering proton beams, or both in cultured cells in comparison with clinically used photons.

METHODS AND MATERIALS

The RBE of passive scattering proton beams at the center of the spread-out Bragg peak (SOBP) was determined from dose-survival curves in 4 cell lines using 6-MV X rays as controls. Survival of 2 cell lines after spot scanning and passive scattering proton irradiation was then compared. Biological effects at the distal end region of the SOBP were also investigated. The OER of passive scattering proton beams and 6 MX X rays were investigated in 2 cell lines. The RBE and OER values were estimated at a 10% cell survival level. The maximum degree of protection of radiation effects by dimethyl sulfoxide was determined to estimate the contribution of the indirect effect against DNA damage. All experiments comparing protons and X rays were made under the same biological conditions.

RESULTS

The RBE values of passive scattering proton beams in the 4 cell lines examined were 1.01 to 1.22 (average, 1.14) and were almost identical to those of spot scanning beams. Biological effects increased at the distal end of the SOBP. In the 2 cell lines examined, the OER was 2.74 (95% confidence interval, 2.56-2.80) and 3.08 (2.84-3.11), respectively, for X rays, and 2.39 (2.38-2.43) and 2.72 (2.69-2.75), respectively, for protons (P<.05 for both cells between X rays and protons). The maximum degree of protection was significantly higher for X rays than for proton beams (P<.05).

CONCLUSIONS

The RBE values of spot scanning and passive scattering proton beams were almost identical. The OER was lower for protons than for X rays. The lower contribution of the indirect effect may partly account for the lower OER of protons.

摘要

目的

确定在与临床应用的光子相比时，扫描点状质子束、散射质子束或两者结合在培养细胞中的相对生物效应（RBE）、氧增强比（OER）以及间接效应的贡献。

方法和材料

使用 6MV X 射线作为对照，通过 4 种细胞系中布喇格峰（SOBP）中心的剂量存活曲线确定散射质子束的 RBE。然后比较 2 种细胞系的点状扫描和散射质子照射后的存活情况。还研究了 SOBP 末端区域的生物学效应。在 2 种细胞系中研究了散射质子束和 6MV X 射线的 OER。在 10%细胞存活水平估计 RBE 和 OER 值。通过二甲亚砜确定最大程度的辐射效应保护来估计对 DNA 损伤的间接效应的贡献。比较质子和 X 射线的所有实验都是在相同的生物学条件下进行的。

结果

在所检查的 4 种细胞系中，散射质子束的 RBE 值为 1.01 至 1.22（平均值为 1.14），与点状扫描束几乎相同。SOBP 末端的生物学效应增加。在所检查的 2 种细胞系中，X 射线的 OER 分别为 2.74（95%置信区间，2.56-2.80）和 3.08（2.84-3.11），质子的 OER 分别为 2.39（2.38-2.43）和 2.72（2.69-2.75）（X 射线和质子之间的两个细胞均 P<.05）。最大程度的保护对于 X 射线明显高于质子束（P<.05）。