18F-FET PET differentiation of ring-enhancing brain lesions.
The aim of this study was to explore the differential diagnostic value of PET using the amino acid O-(2-(18)F-fluoroethyl)-L-tyrosine ((18)F-FET) in patients with newly diagnosed solitary intracerebral lesions showing ring enhancement on contrast-enhanced MRI.


METHODS
(18)F-FET PET analyses were performed on 14 consecutive patients with intracerebral ring-enhancing lesions. Eleven of the patients were additionally studied with (18)F-FDG PET. In all patients, the main differential diagnosis after MRI was a malignant lesion, in particular glioblastoma multiforme, versus a benign lesion, in particular brain abscess. A malignant tumor was suspected for lesions showing increased (18)F-FET uptake on PET images with a mean lesion-to-brain ratio of at least 1.6 ((18)F-FET PET positive). A nonneoplastic lesion was suspected in cases of minimal or absent (18)F-FET uptake, with a mean lesion-to-brain ratio of less than 1.6 ((18)F-FET PET negative). Histologic diagnosis was obtained by serial biopsies in 13 of the 14 patients. One patient refused the biopsy, but follow-up indicated an abscess because his lesion regressed under antibiotic therapy.


RESULTS
Histology and clinical follow-up showed high-grade malignant gliomas in 5 patients and nonneoplastic lesions in 9 patients. The findings of (18)F-FET PET were positive in all 5 glioma patients and in 3 of 9 patients with nonneoplastic lesions, including 2 patients with brain abscesses and 1 patient with a demyelinating lesion. The findings of (18)F-FDG PET were positive (mean lesion-to-gray matter ratio > or = 0.7) in 4 of 4 glioma patients and 3 of 7 patients with nonneoplastic lesions.


CONCLUSIONS
Although (18)F-FET PET has been shown to be valuable for the diagnostic evaluation of brain tumors, our data indicate that, like (18)F-FDG PET, (18)F-FET PET has limited specificity in distinguishing between neoplastic and nonneoplastic ring-enhancing intracerebral lesions. Thus, histologic investigation of biopsy specimens remains mandatory to make this important differential diagnosis.
Floeth
Frank W
FW
Department of Neurosurgery, Heinrich-Heine-University, Düsseldorf, Germany.
Pauleit
Dirk
D
Sabel
Michael
M
Reifenberger
Guido
G
Stoffels
Gabriele
G
Stummer
Walter
W
Rommel
Frank
F
Hamacher
Kurt
K
Langen
Karl-Josef
KJ
D000328:Adult; D000368:Aged; D001706:Biopsy; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology*; D005910:Glioma / Q000000981:diagnostic imaging; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000494:pharmacology; D012680:Sensitivity and Specificity
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18