Abstract: Objective To analyze the imaging characteristics and metabolic parameters of fluoro-18-deoxyglucose(¹⁸F-FDG) positron emission tomography/computed tomography(PET/CT) in patients with choroidal melanoma and choroidal metastatic carcinoma, and to explore its clinical application value in the diagnosis and differentiation of the two diseases. Methods The patients that underwent ¹⁸F-FDG PET/CT examination in the Department of Nuclear Medicine, Beijing Tongren Hospital, Capital Medical University from May 2020 to March 2022 and finally diagnosed as choroidal melanoma or choroidal metastatic carcinoma were enrolled. The CT imaging features and ¹⁸F-FDG PET metabolic parameters of the two diseases were compared with each other, the latter including maximum standardized uptake value (SUV_max), peak standardized uptake value (SUV_peak), and total lesion glycolysis (TLG). Chi-square test, Fisher exact test, two independent samples t-test and rank sum test were used to compare the differences of the above mentioned between the two group. Spearman correlation analysis was used to evaluate the correlation between metabolic parameters and lesion size. Results A total of 76 patients were enrolled, including 58 cases of choroidal melanoma and 18 cases of choroidal metastatic carcinoma. There were no significant differences in gender, age, and affected side between the two groups (all P> 0.05). There were statistically significant differences in the location(χ²=9.263, P=0.041)and shape(χ²=21.735, P<0.001)of lesions between the two groups. The thickness of the choroidal melanoma group was significantly higher than that of the choroidal metastatic carcinoma group (t=2.539, P=0.013). There was no significant difference in the largest basal diameter between the two groups (P>0.05). The SUV_max of the choroidal melanoma group was lower than that of the choroidal metastatic carcinoma group (P<0.05). There was no significant difference in SUV_peak and TLG between the two groups (all P>0.05). In the choroidal melanoma group, SUV_max, SUV_peak, and TLG were positively correlated with the largest basal diameter (r=0.528, 0.613, 0.732, all P<0.001) and thickness (r=0.521, 0.605, 0.730, all P<0.001). In the choroidal metastatic carcinoma group, SUV_peak and TLG were positively correlated with the largest basal diameter (r=0.528, 0.661, P=0.024, 0.003) and thickness (r=0.591, 0.688, P=0.010, 0.002). However, there was no significant correlation between SUV_max and the largest basal diameter and thickness (all P>0.05). Conclusion ¹⁸F-FDG PET/CT imaging findings and metabolic parameter SUV_max have certain value in the differential diagnosis of choroidal melanoma and metastatic carcinoma.

Key words: choroidal melanoma, choroidal metastatic carcinoma, positron emission tomography/computed tomography (PET/CT), metabolic parameters, the differential diagnosis