Serduc Raphaël, van de Looij Yohan, Francony Gilles, Verdonck Olivier, van der Sanden Boudewijn, Laissue Jean, Farion Régine, Bräuer-Krisch Elke, Siegbahn Erik Albert, Bravin Alberto, Prezado Yolanda, Segebarth Christoph, Rémy Chantal, Lahrech Hana
INSERM, U836, F-38043 Grenoble, France.
Phys Med Biol. 2008 Mar 7;53(5):1153-66. doi: 10.1088/0031-9155/53/5/001. Epub 2008 Feb 8.
Cerebral edema is one of the main acute complications arising after irradiation of brain tumors. Microbeam radiation therapy (MRT), an innovative experimental radiotherapy technique using spatially fractionated synchrotron x-rays, has been shown to spare radiosensitive tissues such as mammal brains. The aim of this study was to determine if cerebral edema occurs after MRT using diffusion-weighted MRI and microgravimetry. Prone Swiss nude mice's heads were positioned horizontally in the synchrotron x-ray beam and the upper part of the left hemisphere was irradiated in the antero-posterior direction by an array of 18 planar microbeams (25 mm wide, on-center spacing 211 mm, height 4 mm, entrance dose 312 Gy or 1000 Gy). An apparent diffusion coefficient (ADC) was measured at 7 T 1, 7, 14, 21 and 28 days after irradiation. Eventually, the cerebral water content (CWC) was determined by microgravimetry. The ADC and CWC in the irradiated (312 Gy or 1000 Gy) and in the contralateral non-irradiated hemispheres were not significantly different at all measurement times, with two exceptions: (1) a 9% ADC decrease (p < 0.05) was observed in the irradiated cortex 1 day after exposure to 312 Gy, (2) a 0.7% increase (p < 0.05) in the CWC was measured in the irradiated hemispheres 1 day after exposure to 1000 Gy. The results demonstrate the presence of a minor and transient cellular edema (ADC decrease) at 1 day after a 312 Gy exposure, without a significant CWC increase. One day after a 1000 Gy exposure, the CWC increased, while the ADC remained unchanged and may reflect the simultaneous presence of cellular and vasogenic edema. Both types of edema disappear within a week after microbeam exposure which may confirm the normal tissue sparing effect of MRT.
脑水肿是脑肿瘤放疗后出现的主要急性并发症之一。微束放射治疗（MRT）是一种使用空间分割同步加速器X射线的创新性实验性放射治疗技术，已被证明可使诸如哺乳动物大脑等放射敏感组织免受辐射。本研究的目的是使用扩散加权磁共振成像和微量重力测定法来确定MRT后是否会发生脑水肿。将俯卧的瑞士裸鼠头部水平放置在同步加速器X射线束中，通过18个平面微束阵列（宽25毫米，中心间距211毫米，高4毫米，入射剂量312 Gy或1000 Gy）在前后方向上照射左半球上部。在照射后1、7、14、21和28天在7 T下测量表观扩散系数（ADC）。最终，通过微量重力测定法确定脑含水量（CWC）。在所有测量时间，照射（312 Gy或1000 Gy）侧和对侧未照射半球的ADC和CWC均无显著差异，但有两个例外：（1）在暴露于312 Gy后1天，照射的皮质中观察到ADC下降9%（p<0.05），（2）在暴露于1000 Gy后1天，照射半球的CWC测量值增加0.7%（p<0.05）。结果表明，在暴露于312 Gy后1天存在轻微且短暂的细胞性水肿（ADC下降），而CWC无显著增加。在暴露于1000 Gy后1天，CWC增加，而ADC保持不变，这可能反映了细胞性水肿和血管源性水肿同时存在。两种类型的水肿在微束照射后一周内消失，这可能证实了MRT对正常组织的保护作用。
