Application of MR spectroscopy in differential diagnosis between basicranial tumor recurrence and radiation encephalopathy after radiotherapy for nasopharyngeal carcinoma / 中华放射学杂志

ABSTRACT

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.