Abstract
Rodent models and genetically altered mice have recently become available to study many human diseases. A sensitive and accurate PET scanner for small animals would be useful to evaluate treatment of these diseases in rodent models. To examine the feasibility of performing quantitative PET studies, we performed dynamic scans with arterial blood sampling in anesthetized rats with the ATLAS (Advanced Technology Laboratory Animal Scanner) small animal PET scanner developed at the National Institutes of Health and 18F-FDG and compared activities determined by PET scanning with those obtained by direct tissue sampling. Methods: Dynamic PET scans after a bolus of ∼48 MBq (1.3 mCi) 18F-FDG were performed in rats anesthetized with isoflurane. Arterial blood sampling was performed throughout the scanning period. At 60 min the rat was killed, and the brain was rapidly removed and dissected into 5 structures (thalamus [TH], cortex [CX], brain stem [BS], cerebellum [CB], and half brain). Activity in the tissue samples was compared with the mean activity of the last 5 min of calibrated PET data. Results: Plasma activity peaked at ∼0.2 min and then cleared rapidly. Brain activity initially rose rapidly; the rate of increase then progressively slowed until activity was approximately constant between 30 and 60 min. Recovery coefficients (MBq/mL in PET images)/(MBq/mL in tissue samples) were 0.99 ± 0.04, 0.90 ± 0.19, 1.01 ± 0.24, 0.84 ± 0.05, and 1.01 ± 0.17, respectively, in TH, CX, BS, CB, and half brain (mean ± SD, n = 6–9). Cerebral glucose utilization determined by Patlak analyses of PET data measured 30–60 min after injection of 18F-FDG was 31.7 ± 5.2, 23.9 ± 4.8, 29.9 ± 5.0, 39.3 ± 7.3, and 28.1 ± 4.6 μmol/100 g/min (mean ± SD, n = 9) in TH, CX, BS, CB, and whole brain, respectively. These results are consistent with a previous 14C-deoxyglucose study of the isoflurane-anesthetized rat. Conclusion: Expected values for glucose metabolic rates and recovery coefficients near unity suggest that quantitatively accurate dynamic 18F-FDG brain imaging can be performed in the rat with arterial blood sampling and the ATLAS small animal PET scanner.
Footnotes
Received Sep. 10, 2003; revision accepted Dec. 8, 2003.
For correspondence contact: William C. Eckelman, PhD, Positron Emission Tomography Department, Building 10, Room 1C495, 10 Center Dr., MSC 1180, Bethesda, MD 20892.
E-mail: Eckelman{at}nih.gov