Purpose: To evaluate the normal biodistribution and kinetics of (S)-4- (3-[18F]fluoropropyl)-L-glutamic acid (18F FSPG) in healthy volunteers and to compare 18F FSPG mean and maximum standardized uptake values (SUVmean and SUVmax, respectively) with those of 18F fluorodeoxyglucose (FDG) across a variety of organs. Materials and Methods: This protocol was reviewed and approved by all appropriate regulatory authorities. An 8-mCi (610%) dose of 18F FSPG was given to five subjects (three women, two men), and seven whole-body positron emission tomography (PET) scans were performed 5, 10, 20, 30, 45, 150, and 240 minutes after injection. Regions of interest were analyzed on the resultant 18F FSPG images to evaluate the kinetics of this radiotracer. The images obtained 45 minutes after injection were used to measure SUVmean and SUVmax in additional regions of the body. These values were compared with similar values obtained with 18F FDG PET published previously. Descriptive statistics, including average and standard deviation across the five subjects, were used. 18F FSPG SUVmean and SUVmax were compared. Results: On the 18F FSPG images obtained 45 minutes after injection, there was only low-grade background activity in the majority of analyzed regions. Prominent activity was seen throughout the pancreas. Clearance of the radiotracer through the kidneys and collection in the bladder also were seen. SUV quantification shows notable differences between 18F FSPG and 18F FDG in the pancreas (18F FSPG SUVmean, 8.2; 18F FDG SUVmean, 1.3), stomach (18F FSPG SUVmax, 3.6; 18F FDG SUVmax, 1.6), and brain (18F FSPG SUVmean, 0.08; 18F FDG SUVmean, 7.8). The kinetic data showed rapid clearance of the radiotracer from the blood pool and most organs, except the pancreas. Conclusion: 18F FSPG is a PET radiopharmaceutical characterized by rapid clearance from most healthy tissues, except the pancreas and kidneys. A consistent biodistribution pattern was observed with low background uptake. The physiologic uptake of this new radiotracer throughout the body is described in more detail, which is important for improved interpretative accuracy and understanding potential clinical applications.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging