(18)F-FDG PET for the evaluation of thymic epithelial tumors: Correlation with the World Health Organization classification in addition to dual-time-point imaging.
OBJECTIVE
Our aim was to determine dual-phase (18)F-FDG PET imaging features for various subtypes of thymic epithelial tumors based on the World Health Organization classification.


METHODS
Forty-six patients with histologically verified thymic epithelial tumors [23 with low-risk tumors (4 with type A, 16 with AB, and 3 with B1) and 23 with high-risk tumors (7 with B2, 5 with B3, and 11 with thymic carcinoma] were enrolled in this study. All patients were injected with (18)F-FDG.; after 1 h, they underwent scanning; after 3 h, 23 patients underwent an additional scanning. The maximum standard uptake value (SUV(max)) and the retention index (RI%) of the lesions were determined.


RESULTS
The early and delayed SUV(max) values in the patients with high-risk tumors [early SUV(max) (mean: 6.0) and delayed SUV(max) (mean: 7.4)] were both significantly larger than those in patients with low-risk tumors [early SUV(max) (mean: 3.2) and delayed SUV(max) (mean: 3.4)] (P < 0.05). Early SUV(max) values of greater than 7.1 differentiated thymic carcinomas from other types of tumors. For the histological differentiation between high-risk tumors and low-risk tumors, an early SUV(max) value of 4.5 was used as the cutoff. The sensitivity, specificity, and accuracy were 78.3, 91.3, and 84.8%, respectively.


CONCLUSIONS
High SUV values (early SUV > 4.5) suggest the presence of high-risk tumors. A very high SUV value (early SUV > 7.1) is useful for the differentiation of thymic carcinomas from other types of tumors. The delayed SUV values were higher than the early SUV values in all types of tumors.
Inoue
Atsuo
A
Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan. ainoue@radiol.med.osaka-u.ac.jp
Tomiyama
Noriyuki
N
Tatsumi
Mitsuaki
M
Ikeda
Naoki
N
Okumura
Meinoshin
M
Shiono
Hiroyuki
H
Inoue
Masayoshi
M
Higuchi
Ichiro
I
Aozasa
Katsuyuki
K
Johkoh
Takeshi
T
Nakamura
Hironobu
H
Hatazawa
Jun
J
D000328:Adult; D000368:Aged; D002277:Carcinoma / Q000145:classification* / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D013953:Thymus Neoplasms / Q000145:classification* / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D014944:World Health Organization
D019788:Fluorodeoxyglucose F18