title: Comparison of 18F-FDG, 18F-FET and 18F-FLT for differentiation between tumor and inflammation in rats.
abstract: BACKGROUND
  The goal of this study was to compare the glucose analog, 2-[18F]fluoro-2-deoxy-d-glucose ([18F]-FDG), the amino acid analog, o-(2-[18F]fluoroethyl)-l-tyrosine ([18F]-FET) and nucleoside analog, 3'-[18F]fluoro-3'-deoxythymidine ([18F]-FLT) with regard to their feasibility for differentiating tumors from inflammation.
  
  
  METHODS
  In Fisher rat models bearing both 9L tumor and inflammation, the biodistributions and positron emission tomography (PET) images of [18F]-FDG, [18F]-FET and [18F]-FLT at 60 min post injection were compared. Pretreatment with thymidine phosphorylase before injection of [18F]-FLT was performed.
  
  
  RESULTS
  The tumor-to-blood (T/B) and tumor-to-muscle (T/M) ratios of [18F]-FDG were significantly higher than those of [18F]-FET and [18F]-FLT (P<.01); however, the accumulation of [18F]-FDG [1.23+/-0.52 percent injected dose per gram of tissue (%ID/g)] in inflammation was also elevated. T/B and T/M ratios of [18F]-FET (2.3+/-0.5 and 2.2+/-0.5) were higher than those of [18F]-FLT (1.6+/-0.6 and 1.6+/-0.5), and inflammation uptake of those tracers was very low (0.63+/-0.19 and 0.27+/-0.16 %ID/g, respectively). [18F]-FET and [18F]-FLT showed higher selectivity indices (tumor-to-inflammation ratio corrected background) than [18F]-FDG. In PET images, [18F]-FDG was found to be accumulated in both tumor and inflammation, but [18F]-FET and [18F]-FLT selectively localized in tumor.
  
  
  CONCLUSIONS
  Our data confirm the result of previous studies that [18F]-FET and [18F]-FLT are superior to [18F]-FDG in differentiating tumor from inflammation.
authors: Molecular Imaging Research Center, Korea Institutes of Radiological and Medical Sciences (KIRAMS), Seoul 139-706, Republic of Korea.
authors: Tae Sup
authors: TS
authors: Lee
authors: Soon Hyuk
authors: SH
authors: Ahn
authors: Byung Seok
authors: BS
authors: Moon
authors: Kwon Soo
authors: KS
authors: Chun
authors: Joo Hyun
authors: JH
authors: Kang
authors: Gi Jeong
authors: GJ
authors: Cheon
authors: Chang Woon
authors: CW
authors: Choi
authors: Sang Moo
authors: SM
authors: Lim
mesh_terms: D000818:Animals; D003937:Diagnosis, Differential; D015224:Dideoxynucleosides / Q000493:pharmacokinetics*; D005240:Feasibility Studies; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D007249:Inflammation / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D009369:Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D049268:Positron-Emission Tomography; D051381:Rats; D013939:Thymidine Phosphorylase / Q000494:pharmacology; D014018:Tissue Distribution / Q000187:drug effects; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
chemical_list: D015224:Dideoxynucleosides; C117289:O-(2-fluoroethyl)tyrosine; D019788:Fluorodeoxyglucose F18; D014443:Tyrosine; D013939:Thymidine Phosphorylase; C002854:alovudine