Comparison of 18F-FDG, 18F-FET and 18F-FLT for differentiation between tumor and inflammation in rats.
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.
Lee
Tae Sup
TS
Molecular Imaging Research Center, Korea Institutes of Radiological and Medical Sciences (KIRAMS), Seoul 139-706, Republic of Korea.
Ahn
Soon Hyuk
SH
Moon
Byung Seok
BS
Chun
Kwon Soo
KS
Kang
Joo Hyun
JH
Cheon
Gi Jeong
GJ
Choi
Chang Woon
CW
Lim
Sang Moo
SM
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
D015224:Dideoxynucleosides; C117289:O-(2-fluoroethyl)tyrosine; D019788:Fluorodeoxyglucose F18; D014443:Tyrosine; D013939:Thymidine Phosphorylase; C002854:alovudine