Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Int J Radiat Oncol Biol Phys. 2012 Jul 1;83(3):e431-6. doi: 10.1016/j.ijrobp.2011.12.087. Epub 2012 Apr 5.
Radiation necrosis is a major complication of radiation therapy. We explore the features of radiation-induced brain necrosis in the rat, using multiple MRI approaches, including T(1), T(2), apparent diffusion constant (ADC), cerebral blood flow (CBF), magnetization transfer ratio (MTR), and amide proton transfer (APT) of endogenous mobile proteins and peptides.
Adult rats (Fischer 344; n = 15) were irradiated with a single, well-collimated X-ray beam (40 Gy; 10 × 10 mm(2)) in the left brain hemisphere. MRI was acquired on a 4.7-T animal scanner at ~25 weeks' postradiation. The MRI signals of necrotic cores and perinecrotic regions were assessed with a one-way analysis of variance. Histological evaluation was accomplished with hematoxylin and eosin staining.
ADC and CBF MRI could separate perinecrotic and contralateral normal brain tissue (p < 0.01 and < 0.05, respectively), whereas T(1), T(2), MTR, and APT could not. MRI signal intensities were significantly lower in the necrotic core than in normal brain for CBF (p < 0.001) and APT (p < 0.01) and insignificantly higher or lower for T(1), T(2), MTR, and ADC. Histological results demonstrated coagulative necrosis within the necrotic core and reactive astrogliosis and vascular damage within the perinecrotic region.
ADC and CBF are promising imaging biomarkers for identifying perinecrotic regions, whereas CBF and APT are promising for identifying necrotic cores.
放射性坏死是放射治疗的主要并发症。我们通过多种 MRI 方法，包括 T1、T2、表观扩散系数（ADC）、脑血流（CBF）、磁化转移率（MTR）和内源性移动蛋白和肽的酰胺质子转移（APT），探索大鼠放射性脑坏死的特征。
成年大鼠（Fischer 344；n=15）在左脑半球接受单次准直 X 射线照射（40 Gy；10×10mm2）。在 4.7-T 动物扫描仪上进行 MRI 采集，约在放射后 25 周进行。使用单因素方差分析评估坏死核心和坏死周围区域的 MRI 信号。采用苏木精和伊红染色进行组织学评估。
ADC 和 CBF MRI 可分离坏死周围和对侧正常脑组织（分别为 p<0.01 和 p<0.05），而 T1、T2、MTR 和 APT 则不能。与正常脑相比，坏死核心的 CBF（p<0.001）和 APT（p<0.01）的 MRI 信号强度显著降低，而 T1、T2、MTR 和 ADC 的 MRI 信号强度则显著升高或降低。组织学结果显示，坏死核心内有凝固性坏死，坏死周围区域有反应性星形胶质增生和血管损伤。
ADC 和 CBF 是识别坏死周围区域的有前途的成像生物标志物，而 CBF 和 APT 是识别坏死核心的有前途的成像生物标志物。
