Diagnostic value of18F-FDG coincidence imaging in thymic epithelial tumors / 中华核医学杂志

ABSTRACT

Objective Thymic epithelial tumors(TET) consist of thymoma and thymic carcinoma. The purpose of this study was to investigate the diagnostic value of 18 F-fluorodeoxyglucose (FDG) coinci-dence SPECT imaging in TET. Methods 18 F-FDG coincidence SPECT images of 37 TET patients ( male 16, female 21, age range 24-82 years; mean age 55 years) were retrospectively analyzed according to the simplified WHO histological classification: high survival thymoma (types A, AB and B1 ), median survival thymoma (types B2 and B3 ), and low survival thymoma (thymic carcinoma). Qualitative visual interpreta-tion was based on foci of18F-FDG uptake'higher than that of normal mediastinum. Turnour/lung radioactivity ratio (TLR) was calculated from the counts of region of interest (ROI) drawn around the mass and over a comparable area of normal lung tissue in TET patients. The distribution of18F-FDG uptake was compared with the enhanced CT findings. TLR was also correlated with the Ki67-1abeling index. Statistical comparison for TLR in different groups were performed with variance analysis. Results Thirty-four TET were positive and 3 negative ( A, A, AB) by 18 F-FDG coincidence SPECT images. The differences among the 3 sub-groups were statistically significant (F=9.99,P<0.05). The TLR of these 3 subgroups was variable: 1.42±0.27, 2.13±0.74, 3.00±1.19, respectively. A close correlation (r=0.613, P=0.002) of the TLR with the Ki67 labeling index (n= 22) was found. In addition, 18 F-FDG coincidence SPECT detected two metastases ( anterior chest wall and right supraclavicular fossa lymph node) that were not identified on enhanced CT. Conclusions 18 F-FDG coincidence SPECT is useful in differentiating subgroups of thymic epithelial tumors and in identifying more invasive thymic lesions.18 F-FDG may be a novel tracer that ena-bles in vivo evaluation of cellular proliferation in human TET.