MR波谱在鼻咽癌放疗后颅底复发与放射性脑病鉴别诊断中的应用

目的 应用MR波谱(MRS)对鼻咽癌颅底复发与放射性脑病进行对比研究,探讨MRS对两者的鉴别诊断价值.方法 选择鼻咽癌根治性放射治疗后经常规MRI怀疑鼻咽癌颅底复发或放射性脑病患者50例行MRS,其中男44例,女6例,经临床及MRI复查综合诊断,26例为鼻咽癌颅底复发,24例为颞叶放射性脑病.对比分析放疗后复发与放射性脑病之间及其与相对"正常"脑组织之间胆碱(Cho)、N-乙酰天冬氨酸(NAA)、肌酸(Cr)、乳酸-脂质(LL)等主要代谢物含量的异同.采用秩和检验对所得数据进行统计分析.结果 复发组的Cho/Cr、Cho/NAA、LL/Cr中位数分别为2.22、2.13、1.77,放射性脑病组分别为1.40、1.31、0.57,两者间差异有统计学意义(P值均<0.01),复发组高于放射性脑病组.肿瘤复发组Cho、Cr、NAA的中位数分别为3366.00、1023.00、1930.00,放射性脑病组分别为2469.50、1864.50、1734.00,3个代谢产物的含量在肿瘤复发与放射性脑病之间差异均无统计学意义(P值均>0.05).在取得了"正常"脑组织对比的14个肿瘤复发病例中,复发灶的Cr、NAA、LL、Cho/Cr、Cho/NAA、LL/Cr的中位数分别为1023.00、1930.00、2090.00、3.76、2.13、3.39,"正常"区域分别为2370.00、3012.00、1680.00、1.64、1.17、0.75,两组各参数间差异均有统计学意义(P值均<0.05),复发灶的LL、Cho/Cr、Cho/NAA、LL/Cr高于"正常"区域,而NAA、Cr低于"正常"区域;在取得了"正常"脑组织对照的12个放射性脑病病例中,放射性脑病的Cho、Cr、NAA、LL、Cho/Cr、LL/Cr的中位数分别为390.00、217.50、427.50、39.00、1.30、0.40,而"正常"脑组织分别为680.00、360.00、610.00、30.00、1.54、0.09,上述参数在放射性脑病与其"正常"区域之间差异有统计学意义,放射性脑病的Cho(P<0.01)、Cr(P<0.01)、NAA(P<0.01)、Cho/Cr(P<0.05)低于"正常"区域,而放射性脑病的LL(P<0.05)、LL/Cr(P<0.01)高于"正常"组织.结论 鼻咽癌放疗后复发与放射件脑病在MRS上主要代谢物的变化各有特点,尤其是Cho/Cr、Cho/NAA、LL/Cr等指标复发灶明显高于放射性脑病,对于两者的鉴别诊断具有很高的价值.

Application of MR spectroscopy in differential diagnosis between basicranial tumor recurrence and radiation encephalopathy after radiotherapy for nasopharyngeal carcinoma

Objective To evaluate the value of MR spectroscopy (MRS) in the differential diagnosis between recurrence and radiation encephalopathy after radiotherapy for nasopharyngeal carcinoma (NPC). Methods Muhi-voxel proton MRS was performed on 50 patients with NPC, who were suspected of intracalvarium tumor recurrence or radiation encephalopathy after radiotherapy by conventional MRI,including 44 males and 6 females. Among the 50 patients, 26 cases were finally diagnosised as basicranial tumor recurrence and 24 cases as radiation encephalopathy by clinical and MRI follow-up. The following metabolites, such as Cho, NAA, Cr, lactate and lipid, were analyzed comparatively between basicranial tumor recurrence and radiation encephalopathy(RE), and between the lesions and the relative normal brain tissue. Wilcoxon's rank sum test was used to analyze the data. Results The median of Cho/Cr, Cho/NAA,LI/Cr in tumor recurrence group were 2. 22, 2. 13, and 1.77, respectively, and 1.40, 1.31, and 0. 57,respectively, in RE group. The difference of Cho/Cr, Cho/NAA, and LL/Cr between the two groups were statistically significant (P < 0. 01). Those in tumor recurrence group were higher than in RE group. The median of Cho, Cr, NAA in tumor recurrence group and in RE group were 3366. 00, 1023.00, 1930. 00 and 2469.50, 1864.50, 1734.00. There were no significant difference of Cho, Cr, and NAA between the two groups (P > 0. 05). In the 14 cases whose normal brain tissue were compared with the recurrent tumor tissue in tumor recurrence group, the median of Cr, NAA, LL, Cho/Cr, Cho/NAA, LL/Cr of recurrent tumor tissue and normal brain tissue were 1023.00, 1930.00, 2090.00, 3.76, 2. 13, 3.39 and 2370.00, 3012.00, 1680.00, 1.64, 1.17, 0.75,The difference of Cr, NAA, LL, Cho/Cr, Cho/NAA, LL/Cr between the normal tissue and recurrent tumor tissue were significant (P <0.05). LL, Cho/Cr, Cho/NAA, LL/Cr of recurrent tumors were higher than those of the normal brain tissue,while NAA and Cr of recurrent tumors were lower than those of the normal brain tissue. In the 12 cases whose normal brain tissue were compared with the RE tissue in RE group, the median of Cho, Cr, NAA, LL, Cho/Cr, IX,/Cr of RE tissue and normal brain tissue were 390.00, 217.50, 427.50, 39.00, 1.30, 0.40 and 680.00, 360.00, 610.00, 30.00, 1.54, 0. 09. The difference of above-mentioned parameters between RE tissue and normal tissue were significant. Cho, Cr, NAA, Cho/Cr of RE were lower than those of normal tissue (P <0. 05) ,while LL and LL/Cr of RE were higher than those of normal tissue (P < 0. 05). Conclusion The changes of the metabolites in recurrent lesions and RE lesions were different on MRS. Parameters such as Cho/Cr, Cho/NAA and LL/Cr, which were higher in recurrent lesions than those of RE, were valuable for the differential diagnosis between basicranial tumor recurrence and radiation encephalopathy after radiotherapy for NPC.