ObjectiveTo assess the use of 18-Fluorine-labelled 2-deoxy-2-fluoro-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the diagnosis of uveal melanoma. MethodsTwenty-three patients with uveal melanoma confirmed by histopathologic examination or imaging examination were enrolled. There were 16 male, 7 female, and the mean age was (49.8±12.3) years. All the lesions were unilateral, with 11 cases in OD, 12 cases in OS. Diagnosis was confirmed by histopathological examination of enucleated eyeballs in 15 cases, by ophthalmoscope, fundus fluorescein angiography, ocular B-mode ultrasound and magnetic resonance imaging and other imaging technology in 8 cases. 15 patients diagnosed by histopathologic examination of enucleated eyeballs were divided into three types including mixed (7 patients), spindle cell (6 patients) and epithelioid cell (2 patients) types. The mixed cell type and epithelioid cell type are considered as high-risk; spindle cell type is low-risk. All the patients were evaluated by whole body PET/CT. The location, size, shape, boundary of the lesions, and the relationship with adjacent structures were observed in CT images. 18F-FDG uptake was quantitative expression by standardized uptake value (SUV) in PET image; positive diagnosis should be made when the maximum standardized uptake value (SUVmax) was not less than 2.5. The correlation between SUVmax and maximum diameter of tumor base, tumor height was analyzed by Spearman rank correlation test. The detection rate of high-risk and low-risk patients between 18F-FDG PET and CT methods was comparative analyzed. ResultsAll the CT images showed abnormal high density ocular lesions. The shape of the lesions included 8 patients of semi sphere-like, 7 patients of flat-like, 4 patients of mushroom-like, 3 patients of round-like and 1 patient of diffuse lesions. The tumors were located in the posterior pole (9 patients), temporal equator (5 patients), nasal equator (4 patients), superior equator (1 patient), temporal ciliary body (1 patient), inferior ciliary body (1 patient), temporal iris (1 patient), and nasal iris and ciliary body (1 patient). SUVmax≥2.5 were found in 9 patients (39.13%), the largest basal diameter and height were (17.53±3.48), (11.37±3.85) mm respectively. SUVmax < 2.5 were found in 14 patients (60.87%), the largest basal diameter and height were (10.66±3.25), (5.33±2.23) mm respectively. The former's largest basal diameter and height were greater than the latter's and the difference was statistically significant (t=4.815, 4.786; P < 0.01). SUVmax was positively correlated with the largest basal diameter and height respectively (r=0.881, 0.809; P < 0.01). 15 patients (39.13%) were diagnosed by histopathological diagnosis after enucleation, of which SUVmax≥2.5 were found in 8 patients which included 6 patients of mixed type, 1 patient of epithelioid cell type, and 1 patient of spindle cell type. The detection rate of high-risk type (77.78%, 7/9) was higher than that of low-risk type (16.67%, 1/6), the difference was statistically significant (χ2=5.402, P < 0.05). Conclusions18F-FDG PET-CT examination can show large uveal melanoma tumor from cell metabolism, and may help to evaluate the prognosis of the preoperative patients. But, for small tumor, it has little value. We don't recommend 18F-FDG PET-CT is used as a routine examination for uveal melanoma.