title: Assessment of rodent brain activity using combined [(15)O]H2O-PET and BOLD-fMRI.
abstract: The study of brain activation in small animals is of high interest for neurological research. In this study, we proposed a protocol to monitor brain activation in rats following whisker stimulation using the short half-life PET tracer [(15)O]H2O as a marker for cerebral blood flow. This technique enables the study of baseline and activation conditions in fast succession within the same scanning session. Furthermore, we compared the results obtained from PET imaging with additional BOLD-fMRI data acquired in the same animals within the same anesthetic session in immediate succession. Although the maximum relative signal changes during brain activity observed with PET were substantially higher compared to the BOLD-fMRI results, statistical analyses showed that the number of activated voxels in PET was lower compared to the fMRI measurements. Furthermore, there was a difference in the activation centers in both the shape and location between PET and fMRI. The discrepancy in the number of activated voxels could be attributed to a lower overall contrast-to-noise ratio of the PET images compared to BOLD-fMRI, whereas the difference in the spatial location indicates a more fundamental process, involving the different physiological origins of the PET and BOLD-fMRI response. This study clearly demonstrates that [(15)O]H2O-PET activation studies may be performed in small laboratory animals, and shows the complementary nature of studying brain activation using [(15)O]H2O-PET and fMRI.
authors: Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Germany.
authors: Hans F
authors: HF
authors: Wehrl
authors: Department of Radiology, Section on Experimental Radiology, Eberhard Karls University Tuebingen, Tuebingen, Germany.
authors: Petros
authors: P
authors: Martirosian
authors: Department of Radiology, Section on Experimental Radiology, Eberhard Karls University Tuebingen, Tuebingen, Germany.
authors: Fritz
authors: F
authors: Schick
authors: Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Germany.
authors: Gerald
authors: G
authors: Reischl
authors: Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Germany. Electronic address: bernd.pichler@med.uni-tuebingen.de.
authors: Bernd J
authors: BJ
authors: Pichler
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging; D001931:Brain Mapping; D008279:Magnetic Resonance Imaging; D008297:Male; D064847:Multimodal Imaging; D010104:Oxygen Radioisotopes; D049268:Positron-Emission Tomography; D051381:Rats; D020318:Rats, Long-Evans
chemical_list: D010104:Oxygen Radioisotopes
keywords: BOLD; Brain activation; PET; Small animal; fMRI