Different hydration protocols for the quantification of healthy tissue uptake of half-dose ¹⁸F-FDG total-body positron emission tomography-computed tomography: a prospective study

Background: This study aimed to investigate the effects of the volume and time of hydration on the quantification of healthy tissue uptake for 2-deoxy-2-[F-18]-fluoro-D-glucose (F-18-FDG) total-body positron emission tomography (PET)-computed tomography (CT) with half-dose activity. Methods: This study prospectively enrolled 180 patients who underwent a total-body PET- CT scan 10 min after injection of a half-dose (1.85 MBq/kg) of 18F-FDG. These patients were placed in hydration groups ( 30 patients in each group) according to different hydration volumes and times: oral hydration with 500 mL of water 20 min before (G1), 5 min after (G2), and 30 min after (G3) the F-18-FDG injection; and oral hydration with 200 mL of water 20 min before (G4), 5 min after (G5), and 30 min after (G6) the F-18-FDG injection. Another 30 patients underwent dynamic imaging without hydration and were used a nonhydration group. The analysis of quantification of healthy tissue uptake included the maximum standardized uptake value (SUVmax) and the mean SUV (SUVmean) of the blood pool and muscle, as well as the SUVmax, SUVmean, and signal-to-noise ratio (SNR) of the liver. Results: The SUVmax of the blood pool (2.33 +/- 0.36), liver (3.03 +/- 0.42), and muscle ( 0.81 +/- 0.15) was significantly higher in the nonhydration group than in any of the 6 hydrated groups (P<0.05 for all hydration groups vs. nonhydration group). Muscle SUVmax and SUVmean were significantly (P<0.05) lower in G1 and G2 than in G3 and were lower in G4 and G5 than in G6. The SUVmax and SUVmean of the blood pool were significantly (P<0.05) lower in G1 than in G3 and G4 and lower in G3 than in G6. Conclusions: When total-body PET-CT with a half dose of F-18-FDG activity is performed, hydration can significantly affect the quantification of healthy tissue uptake. Oral administration of 500 mL of water 20 min before injection could reduce background radioactivity.