To investigate the diagnostic value of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/CT delayed imaging in the diagnosis of primary liver cancer.

Clinical data of 80 patients with primary liver cancer who were admitted to the Third Affiliated Hospital of Sun Yat-sen University between October 2014 and December 2016 were retrospectively analyzed. Among them, 62 cases were males and 18 were females, aged (58±12) years old on average. According to the tumor diameter, the patients were divided into the small liver cancer group (n=30), nodular liver cancer group (n=23) and large liver cancer group (n=27). The informed consents of all patients were obtained and the local ethical committee approval was received. PET/CT early imaging was performed on the patients at 40-60 min after they were intravenously injected with contrast agent ¹⁸F-FDG, and PET/CT delayed imaging was performed at 2 h later. The maximal standardized uptake values (SUV_max) of the lesions in two imagings were detected. The early imaging, delayed imaging and the imaging changes at different stages were observed and compared among three groups. The SUV_max values were compared among three groups using one-way analysis of variance and LSD-t test, and were compared between two groups using t test. The rates were compared using Chi-square test.

The SUV_max values of the early imaging and delayed imaging were respectively 5.1±1.9 and 5.5±2.3 in the nodular liver cancer group, significantly higher than 3.9±1.4 and 4.3±2.0 in the small liver cancer group (LSD-t=2.60, 2.03; P<0.05), whereas significantly lower than 6.9±2.6 and 8.5±2.9 in the large liver cancer group (LSD-t=-2.82, -4.08; P<0.05). The SUV_max value of the delayed imaging in the large liver cancer group was significantly higher than that of the early imaging (t=2.05, P<0.05). The percentage of patients with SUV_max values of the delayed imaging higher than that of the early imaging was 93%(25/27) in the large liver cancer group, significantly higher than 53%(16/30) in the small liver cancer group and 61%(14/23) in the nodular liver cancer group (χ²=10.85, 7.28; P<0.05).

The ¹⁸F-FDG uptake of the delayed imaging increases significantly along with the tumor diameter increases. Application of ¹⁸F-FDG PET/CT delayed imaging can elevate the detection rate of liver cancer, especially large liver cancer.