Optimizing the acquisition protocol of 18F-Choline PET/CT in prostate cancer patients

Objectives To optimize the acquisition protocol of 18F-Choline PET/CT in prostate cancer pts.

Methods A total of 269 pts were referred to our centre to perform a 18F-Choline PET/CT to investigate a biochemical relapse (increased PSA) of prostate cancer with inconclusive conventional imaging. Various acquisition protocols were tested. A last generation hybrid PET/16-slices CT scanner was used. A 5-steps protocol was adopted in the first studied 30 pts: a)a 10-min dynamic acquisition in list-mode of the pelvic region, commencing acquisition during 3.0 MBq/Kg/b.w. 18F-Choline e.v. injection was obtained; b)an early 4-min static image of the pelvic region was acquired; c)a delayed 4-min static image of the pelvic region 1 hour P.I. was acquired; d) a WB scan in 3D mode from the vertex to the thighs, 3 min/bed, 1 hour P.I. was acquired; e) a further WB scan 2-hrs P.I. was acquired. Images were blinded interpreted by 3 skilful nuclear physicians, diagnosis was reached by consensus.

Results In our experience the most informative imaging modality was the 1-hr WB scan: in 4 pts a local relapse was diagnosed, in 6 to lymph nodes, in 4 to skeleton, in 3 multiple metastases. The early pelvic static acquisition was particularly important in identifying the physiologic activity related to uretral tracer excretion, therefore to make a differential diagnosis with a local relapse. On the other hand, the dynamic acquisition and the delayed static acquisition of the pelvic region did not provide additional diagnostic information. The 2-hr WB scan was helpful in some cases to better delineate the metastatic deposits as a consequance of an increase of the T/B ratio.

Conclusions On the basis of the above data, we adopted a routinary acquisition protocol for 18F-Choline PET/CT based on a) early static pelvic acquisition obtained 10 min after tracer injection and b) 1-hr WB scan. In selected cases an additional 2-hrs WB scan is also obtained, while the early dynamic acquisition and the delayed pelvic static acquisition were abandoned