title: The comparison of 13N-ammonia and 18F-FDG in the evaluation of untreated gliomas.
abstract: OBJECTIVE
  Noninvasive evaluation of glioma is of great help for clinical practice. In this study, we investigated the utility of 13N-ammonia in the evaluation of untreated gliomas and compared the results with that of 18F-FDG.
  
  
  METHODS
  Forty-five consecutive patients with final diagnosis of glioma were included in this study. PET/CT imaging was performed for all of them with both 18F-FDG and 13N-ammonia as tracers. Imaging results were analyzed by tumor-to-gray matter (T/G) ratios. Receiver operating characteristic curve analysis was conducted to determine the optimal T/G cutoff values of each tracer between low-grade and high-grade gliomas.
  
  
  RESULTS
  Forty-eight separate lesions were identified in all (grade II, n = 16; grade III, n = 12; and grade IV, n = 20). Twenty-nine out of 32 high-grade lesions (91%) showed higher uptakes than normal gray matter with N-ammonia in comparison with the result of 21 lesions (66%) with 18F-FDG. The optimal T/G cutoff values for 18F-FDG and 13N-ammonia were 0.64 and 0.86 separately with the area under each curve 0.910 and 0.943. The sensitivity and specificity of predicting high-grade gliomas with optimal cutoff values were 83% and 93% for 18F-FDG and 94% and 94% for 13N-ammonia, respectively.
  
  
  CONCLUSIONS
  13N-Ammonia is superior to 18F-FDG not only in separating low-grade gliomas from high-grade ones but also in the detection of high-grade gliomas for better tumor to normal gray matter contrast.
authors.affiliation: Department of Nuclear Medicine, the First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China.
authors.forename: Xinchong
authors.initials: X
authors.lastname: Shi
authors.forename: Yubo
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiangsong
authors.initials: X
authors.lastname: Zhang
authors.forename: Chang
authors.initials: C
authors.lastname: Yi
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wang
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Chen
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000641:Ammonia; D001254:Astrocytoma / Q000000981:diagnostic imaging; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18; D005909:Glioblastoma / Q000000981:diagnostic imaging; D005910:Glioma / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009590:Nitrogen Radioisotopes; D049268:Positron-Emission Tomography; D055815:Young Adult
chemical_list: D009590:Nitrogen Radioisotopes; D019788:Fluorodeoxyglucose F18; D000641:Ammonia