Evaluation of primary brain tumors with FLT-PET: usefulness and limitations.
OBJECTIVE
The purpose of this report was to investigate the potential of positron emission tomography using F-18 fluorodeoxythymidine (FLT-PET) in evaluating primary brain tumors.


METHODS
FLT-PET was performed in 25 patients with primary brain tumors. FLT uptake in the lesion was semiquantitatively evaluated by measuring the maximal standardized uptake value (SUVmax) and the tumor-to-normal tissue ratio (TNR). SUVmax and TNR were compared with the histologic grade and the expression of the proliferation marker (Ki-67).


RESULTS
FLT uptake in normal brain parenchyma was very low, resulting in the visualization of brain tumors with high contrast. Both SUVmax and TNR significantly correlated with the malignant grade of brain gliomas, in which high SUVmax/TNR was obtained for high-grade gliomas. Patients with primary lymphoma also showed SUVmax/TNR equivalent to glioblastoma. There was a positive correlation between SUVmax/TNR and the Ki-67 index. In contrast, spuriously high SUVmax and TNR were obtained in 3 of 6 patients with suspected recurrent tumors (2 patients with recurrent grade 2 glioma and one patient with postoperative granuloma), all of which showed lesion enhancement on MRI after Gd administration.


CONCLUSIONS
FLT-PET can be used to evaluate the malignant grade and proliferation activity of primary brain tumors, especially malignant brain tumors. However, the presence of benign lesions showing blood-brain barrier disruption cannot be distinguished from malignant tumors and needs to be carefully evaluated.
Saga
Tsuneo
T
Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Kawashima
Hidekazu
H
Araki
Norio
N
Takahashi
Jun A
JA
Nakashima
Yasuaki
Y
Higashi
Tatsuya
T
Oya
Natsuo
N
Mukai
Takahiro
T
Hojo
Masato
M
Hashimoto
Nobuo
N
Manabe
Toshiaki
T
Hiraoka
Masahiro
M
Togashi
Kaori
K
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D002648:Child; D015224:Dideoxynucleosides; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D015224:Dideoxynucleosides; D019275:Radiopharmaceuticals; C002854:alovudine