~1H-MRS study on radiation-induced injury of the brain in early acute reaction stage after nasopharyngeal carcinoma radiotherapy / 中华放射学杂志

ABSTRACT

Objective To evaluate the diagnostic value of in vivo 1H-MRS in the hyper acute reaction stage of radiation-induced brain injury after nasopharyngeal carcinoma radiotherapy. Methods Eighteen patients with nasopharyngeal carcinoma accepted radiotherapy for the first time. Bilateral temporal lobes in all cases were examined by conventional MRI and 1H-MRS before and after radiotherapy with radiation dose of 20 Gy, 40 Gy, and 60 Gy, respectively. MR image was performed with T_1-weighted gradient- and spin-echo, T_2-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. Results There were no changes of signal in the temporal lobes with conventional MRI, but the peak height of NAA and Cho decreased obviously in the anterior half of the temporal lobes with 1H-MRS after radiotherapy. The post-radiotherapy changes of different metabolic peak in the anterior temporal lobes presented as two types one type was that Cho and NAA peak were of the same height simultaneously. There were 20 locations (56%) of the 36 reaching the peak when accepting 20 Gy, 22 (61%) when accepting 40 Gy, and 13 (36%) when accepting 60 Gy, respectively. The other type was that Cho peak became the highest, whereas NAA peak was obviously lower and decreased to be the second highest. There were 4 locations(11%) of the 36 reaching the peak when accepting 20 Gy, 10 (28%) when accepting 40 Gy, and 23 (64%) when accepting 60 Gy, respectively. The ratio of Cho/Cr, NAA/Cr, and NAA/Cho decreased 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 be used to diagnose the radiation-induced injury of the brain in early acute reaction stage after nasopharyngeal carcinoma radiotherapy through reflecting histiocytic metabolism, and provide objective basis for pathology development and cellular metabolism study, also it can provide feasible projects for the clinic.