鼻咽癌放疗后放射性脑病的磁共振氢波谱研究

目的 探讨鼻咽癌放疗后放射性脑病的磁共振氢波谱(1H-MRS)表现,了解N-乙酰天门冬氨酸(NAA)、肌酸(Cr)和胆碱(Cho)3种物质的代谢规律,为放射性脑病的早期诊断提供方法.方法 选取10例健康志愿者作为对照组,21例病理诊断为鼻咽癌并进行根治性放疗后经症状及影像学诊断为放射性脑病的病人作为病例组,用化学位移成像法(CSI)行1H-MRS检查.观察各像素中NAA、Cr和Cho的含量、代谢图及它们之间的比例.结果 磁共振成像(MRI)可见放射性脑病病灶中的液化坏死区3种物质含量基本为零,代谢图中无信号;病灶中非液化坏死区NAA轻度升高,Cr和Cho明显降低或为零,NAA代谢图呈高信号,Cr和Cho低信号.病灶周边存在一个区域NAA降低,Cf和Cho升高,NAA/Cr和NAA/Cho＜1,代谢图中信号区分不明显.远离可见病灶的区域NAA、Cr和Cho含量及比例正常.结论 1H-MRS可显示放射性脑病的物质代谢变化规律,发生变化的区域面积大于MRI中可见病变区,从而为该病的早期诊断提供了可能.

Proton magnetic resonance spectroscopy for radiation encephalopathy induced by radiotherapy for nasopharyngeal carcinoma

Objective To understand the metabolic patterns of NAA, Cr and Cho in radiation encephalopathy (RE) induced by radiotherapy for nasopharyngeal carcinoma detected by proton magnetic resonance spectroscopy (1H-MRS), and provide useful evidence for early diagnosis of this disease. Methods Chemical shift imaging 1H-MRS was performed for 10 healthy volunteers (control group) and 21 patients with pathologically confirmed nasopharyngeal carcinomas, who developed RE after radical radiotherapy as diagnosed on the basis of clinical symptoms and imaging findings. The contents of NAA, Cr and Cho in the pixels were observed, the metabolic maps generated, and NAA/Cr and NAA/Cho ratios calculated for all the subjects. Results The concentrations of NAA, Cr and Cho were rarely observed in the necrosis and liquefaction foci in the patients, nor were any signals displayed on their metabolic maps. In the visible lesions, with the exception of the necrosis and liquefaction foci, the content of NAA increased slightly, whereas that of Cr or Cho decreased obviously or even became absent. An area around the lesion was identified where NAA content decreased but Cr or Cho increased. The signal in the metabolic maps appeared indistinguishable. The NAA/Cr and NAA/Cho ratios were less than 1. Farther away from the visible lesions, the NAA, Cr and Cho contents remained normal with NAA/Cr and NAA/Cho ratios of less than 1. Conclusion 1H-MRS is capable of displaying the patterns of metabolite changes in RE induced by radiotherapy, and identifying larger area of abnormal metabolism in RE than the visible lesion in MRI, which suggests the possibility of earlier detection of RE with 1H-MRS.