The clinical analysis of double PET studies using 11C and 18F-FDG

Objectives Positron pharmaceuticals have short half-lives, and it is theoretically possible to perform studies using plural pharmaceuticals based according to the timing of injection.The purpose of this study is to establish clinical protocol using 18-F (18-F-FDG)and 11-C nucleus (11-C-methionine, 11-C-choline) on one day.

Methods We studied the injection delay timing between 11-C nucleus and 18-F.We conducted research using two NEMA Body phantoms. One is filled with 18-F (as hot spot) and with 11-C (as background). Their density ratio is 1:1.The other is filled with 18-F plus 11-C, 18-F and 11-C, their density ratio is 1:1:1.Based on those data, we performed 35 clinical studies.One hour after the injection of 18-F, we obtained early images and delayed images and delineating ROI in the patients’ liver to cariculate the contamination rate.

Results Our study using the phantoms showed delayed acquisition time of over 100 minutes bettered contrast of the hot spot.In clinical investigation, delayed acquisition time of over 50 minutes lessened the contamination rate to 10 %.

Conclusions We set delayed injection time as 60 minutes. It is suggested that PET can be performed utilizing multi kinds of pharmaceuticals. And it is anticipated that reducing the burden of the patients and broadening the range of the study.