Application of MRspectroscopy in differential diagnosis between basicranial tumor recurrence and radiationencephalopathy after radiotherapy for nasopharyngeal carcinoma

Abstract

：Objective To evaluatethe value of MR spectroscopy (MRS) in the differential diagnosis between recurrence andradiation encephalopathy after radiotherapy for nasopharyngeal carcinoma (NPC). MethodsMuhi-voxel proton MRS was performed on 50 patients with NPC, who were suspected ofintracalvarium tumor recurrence or radiation encephalopathy after radiotherapy byconventional MRI,including 44 males and 6 females. Among the 50 patients, 26 cases werefinally diagnosised as basicranial tumor recurrence and 24 cases as radiationencephalopathy by clinical and MRI follow-up. The following metabolites, such as Cho, NAA,Cr, lactate and lipid, were analyzed comparatively between basicranial tumor recurrenceand radiation encephalopathy(RE), and between the lesions and the relative normal braintissue. Wilcoxon's rank sum test was used to analyze the data. Results The median ofCho/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. 05). In the 14 cases whose normal brain tissue were compared with the recurrenttumor tissue in tumor recurrence group, the median of Cr, NAA, LL, Cho/Cr, Cho/NAA, LL/Crof 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 weresignificant (P <0.05). LL, Cho/Cr, Cho/NAA, LL/Cr of recurrent tumors were higher thanthose of the normal brain tissue,while NAA and Cr of recurrent tumors were lower thanthose of the normal brain tissue. In the 12 cases whose normal brain tissue were comparedwith the RE tissue in RE group, the median of Cho, Cr, NAA, LL, Cho/Cr, IX,/Cr of REtissue 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 betweenRE tissue and normal tissue were significant. Cho, Cr, NAA, Cho/Cr of RE were lower thanthose of normal tissue (P <0. 05) ,while LL and LL/Cr of RE were higher than those ofnormal tissue (P < 0. 05). Conclusion The changes of the metabolites in recurrentlesions and RE lesions were different on MRS. Parameters such as Cho/Cr, Cho/NAA andLL/Cr, which were higher in recurrent lesions than those of RE, were valuable for thedifferential diagnosis between basicranial tumor recurrence and radiation encephalopathyafter radiotherapy for NPC.