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.