Abstract
Positron emission tomography (PET) scans of the mouse brain are usually performed with anesthesia to immobilize the animal. However, it is desirable to avoid the confounding factor of anesthesia in mouse-brain response. Methods: We develop and validate brain PET imaging of awake, freely moving mice. Head-motion tracking is performed using radioactive point source markers and we use the tracking information for PET-image motion correction. Regional 18F-Fluorodeoxyglucose (18F-FDG) brain uptake in a test, retest, and memantine challenge study was performed in awake (n = 8) and anesthetized (n = 8) C57BL/6 mice. An awake uptake period was considered for the anesthesia scans. Results: Awake (motion corrected) PET images showed an 18F-FDG uptake pattern comparable to the pattern of anesthetized mice. The test-retest variability (represented by the intraclass correlation coefficient (ICC)) of the regional standardized uptake value (SUV) quantification in the awake images (0.424-0.555) was marginally lower compared to anesthesia images (ICC, 0.491-0.629) over the different regions. The increased memantine-induced 18F-FDG uptake was more pronounced in awake (+63.6%) than in anesthesia (+24.2%) animals. Additional behavioral information, acquired during awake scans, showed increased motor activity on a memantine challenge (total distance travelled, 18.2 ± 5.28 m) compared to test-retest (6.49 ± 2.21 m). Conclusion: The present method enables brain PET imaging on awake mice, thereby avoiding the confounding effects of anesthesia on the PET reading. It allows the simultaneous measurement of behavioral information during PET acquisitions. The method does not require any additional hardware, and it can be deployed in typical high-throughput scan protocols.
- Copyright © 2018 by the Society of Nuclear Medicine and Molecular Imaging, Inc.