The Study Of 1H-MRS On Cerebral Hyper Acute Injury Induced By Radiation After Nasopharyngeal Carcinoma Radiotherapy

Objective:1. To evaluate the diagnostic value of in vivo 1H - MRS in the cerebral hyper acute injury induced by radiation after the radiotherapy of nasopharyngeal carcinoma. 2. To identify the spectroscopic characteristics of 1H– MRS in the hyper acute reaction stage of radiation-induced brain injury.Methods:18 patients with nasopharyngeal carcinoma were accepted radiotherapy for the first time. Bilateral temporal lobes of all patients underwent conventional MRI and 1H - MRS before and after radiotherapy with radiant dose of 20Gy,40Gy and 60Gy respectively. MR image was performed with T1-weighted gradient- and spin-echo, T2-weighted spin-echo, fluid-attenuated inversion-recovery, and point resolution spectroscopy. The change of the spectroscopic morphology and the ratios of the metabolites were observed. Cho/Cr,NAA/Cr and NAA/Cho ratios at different stages were analyzed with ANOVA by SPSS11.5 statistical software, and P<0.001 was considered to be statistical significance.Results:There weren't change of signal in the temporal lobes with conventional MRI, but the peak height of NAA and Cho descended obviously in the anterior half of the temporal lobes with 1H - MRS after radiotherapy. Before the radiotherapy, and when the radiant dose of 20Gy,40Gy and 60Gy after radiotherapy, the ratio of Cho/Cr was 1.649±0.17,1.459±0.16,1.258±0.16 and 1.120±0.14 respectively; the ratio of NAA/Cr was 2.173±0.17,1.385±0.13,1.218±0.09 and 1.133±0.10 respectively; The ratio of NAA/Cho was 1.359±0.08,1.139±0.28,0.977±0.29 and 0.815±0.18 respectively. The ratios of Cho/Cr,NAA/Cr and NAA/Cho descended with the increasing of accepting radiant dose. The ratios of different stages is of statistical significance(P<0.001).The more dosage the more great decrease in ratio of NAA/Cr compared to the ratio of Cho/Cr. The post-radiotherapy changes of different metabolic peak in the anterior temporal lobes had two types: One type is that Cho and NAA peak were of the same height simultaneously. There are 20 locations (56%) of the 36 reaching the peak when accepting 20Gy, 22(61%) when accepting 40Gy, 13(36%) when accepting 60Gy. The other type is that Cho peak became the highest, whereas NAA peak was obviously lower and descended to be the second highest. There are 4 locations (11%) of the 36 reaching the peak when accepting 20Gy, 10(28%) when accepting 40Gy, 23 (64%) when accepting 60Gy. The ratio of Cho/Cr,NAA/Cr and NAA/Cho descended in the same position too. In addition,There was positive correlation between the ratios of the metabolites and the dose of radiotherapy.Conclusion:1H-MRS can detect and evaluate in vivo the metabolic effects in the cerebral hyper acute injury induced by radiation after the radiotherapy of nasopharyngeal carcinoma. During the period, NAA and Cho descended obviously in the inferior half of the temporal lobes. Cho/Cr, NAA/Cr and NAA/Cho descended in the same position too. 1H-MRS provide objective basis for pathology development and cellular metabolism study, also can provide feasible projects for the clinic.