18F-FDG-labeled red blood cell PET for blood-pool imaging: preclinical evaluation in rats

BACKGROUND Red blood cells (RBCs) labeled with single-photon emitters have been clinically used for blood-pool imaging. Although some PET tracers have been introduced for blood-pool imaging, they have not yet been widely used. The present study investigated the feasibility of labeling RBCs with 18F-2-deoxy-2-fluoro-D-glucose (18F-FDG) for blood-pool imaging with PET. RBCs isolated from venous blood of rats were washed with glucose-free phosphate-buffered saline and labeled with 18F-FDG. To optimize labeling efficiency, the effects of glucose deprivation time and incubation (labeling) time with 18F-FDG were investigated. Post-labeling stability was assessed by calculating the release fraction of radioactivity and identifying the chemical forms of 18F in the released and intracellular components of 18F-FDG-labeled RBCs incubated in plasma. Just after intravenous injection of the optimized autologous 18F-FDG-labeled RBCs, dynamic PET scans were performed to evaluate in vivo imaging in normal rats and intraabdominal bleeding models (temporary and persistent bleeding). RESULTS The optimal durations of glucose deprivation and incubation (labeling) with 18F-FDG were 60 and 30 min, respectively. As low as 10% of 18F was released as the form of 18F-FDG from 18F-FDG-labeled RBCs after a 60-min incubation. Dynamic PET images of normal rats showed strong persistence in the cardiovascular system for at least 120 min. In the intraabdominal bleeding models, 18F-FDG-labeled RBC PET visualized the extravascular blood clearly and revealed the dynamic changes of the extravascular radioactivity in the temporary and persistent bleeding. CONCLUSIONS RBCs can be effectively labeled with 18F-FDG and used for blood-pool imaging with PET in rats.