Study on SPECT/CT Imaging Features and Related Pathology of Cystic Generation of the Talus

Objective: To explore the imaging features of three-phase bone and SPECT/CT images of cystic lesions on the talus. Methods: A total of 189 patients with suspected chronic pain in the ankle joint of the talus cystic degeneration were enrolled in this retrospective study, who underwent 99mTc-MDP three-phase bone imaging and delayed SPECT/CT scans in our hospital. The location, range of involvement, classification, CT value, and radioactivity uptake of the sclerosis of cystic lesions on the talus, and the continuity of articular surface were observed. Comparisons were analyzed with the pathological results. Results: Totally, 83% (157/189) of the talar cysts were located to the medial fornix, most of which involved the anterior middle part (43.27%), and the larger cysts involved the posterior part (9.6%). 63% (119/189) of the patients were type I, and 37% (70/189) of the patients were type II. The articular surface of the medial dome of the talus of all of the patients was intact, and the subchondral bony articular surface of 88% (166/189) patients was rough. The coincidence rate of the location, type, range of involvement of cystic lesions with pathological results was 87.83% (166/189). The CT value of cystic lesions was 45 15Hu (30-60Hu). The percentage of pathological chondrogenesis in the high CT value ≥ 50Hu (19/70) group and the low CT value < 50Hu (51/70) group were 89.47% (17/19) and 29.14% (15/51) (c2=20.12, P＜0.001), respectively. The T/B ratio of the radioactivity uptake area of the talus vault was 2.0±0.5(1.5-2.5). The percentage of pathological new trabecular bones in T/B ratio≥2.0 (157/189) group and T/B ratio＜2.0 (32/189) group (c2=45.08，P＜0.001) were 82.80% (130/157) and 25.00% (8/32), respectively. Conclusions: Three-phase bone imaging could identify the damage of the talus caused by cystic degeneration, and delayed SPECT/CT images have certain advantages in display the location, range of involvement, classification, and repair of cystic lesions of the talus.