title: Statistical parametric maps of ¹⁸F-FDG PET and 3-D autoradiography in the rat brain: a cross-validation study.
abstract: OBJECTIVE
  Although specific positron emission tomography (PET) scanners have been developed for small animals, spatial resolution remains one of the most critical technical limitations, particularly in the evaluation of the rodent brain. The purpose of the present study was to examine the reliability of voxel-based statistical analysis (Statistical Parametric Mapping, SPM) applied to (18)F-fluorodeoxyglucose (FDG) PET images of the rat brain, acquired on a small animal PET not specifically designed for rodents. The gold standard for the validation of the PET results was the autoradiography of the same animals acquired under the same physiological conditions, reconstructed as a 3-D volume and analysed using SPM.
  
  
  METHODS
  Eleven rats were studied under two different conditions: conscious or under inhalatory anaesthesia during (18)F-FDG uptake. All animals were studied in vivo under both conditions in a dedicated small animal Philips MOSAIC PET scanner and magnetic resonance images were obtained for subsequent spatial processing. Then, rats were randomly assigned to a conscious or anaesthetized group for postmortem autoradiography, and slices from each animal were aligned and stacked to create a 3-D autoradiographic volume. Finally, differences in (18)F-FDG uptake between conscious and anaesthetized states were assessed from PET and autoradiography data by SPM analysis and results were compared.
  
  
  RESULTS
  SPM results of PET and 3-D autoradiography are in good agreement and led to the detection of consistent cortical differences between the conscious and anaesthetized groups, particularly in the bilateral somatosensory cortices. However, SPM analysis of 3-D autoradiography also highlighted differences in the thalamus that were not detected with PET.
  
  
  CONCLUSIONS
  This study demonstrates that any difference detected with SPM analysis of MOSAIC PET images of rat brain is detected also by the gold standard autoradiographic technique, confirming that this methodology provides reliable results, although partial volume effects might make it difficult to detect slight differences in small regions.
authors.affiliation: Nuclear Medicine Department, Clínica Universidad de Navarra, Av. Pío XII 36, 31008 Pamplona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Prieto
authors.forename: María
authors.initials: M
authors.lastname: Collantes
authors.forename: Mercedes
authors.initials: M
authors.lastname: Delgado
authors.forename: Carlos
authors.initials: C
authors.lastname: Juri
authors.forename: Luis
authors.initials: L
authors.lastname: García-García
authors.forename: Francisco
authors.initials: F
authors.lastname: Molinet
authors.forename: María E
authors.initials: ME
authors.lastname: Fernández-Valle
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Pozo
authors.forename: Belén
authors.initials: B
authors.lastname: Gago
authors.forename: Josep M
authors.initials: JM
authors.lastname: Martí-Climent
authors.forename: José A
authors.initials: JA
authors.lastname: Obeso
authors.forename: Iván
authors.initials: I
authors.lastname: Peñuelas
mesh_terms: D000818:Animals; D001345:Autoradiography / Q000379:methods*; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D001931:Brain Mapping / Q000379:methods*; D003627:Data Interpretation, Statistical; D019788:Fluorodeoxyglucose F18; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*; D011859:Radiography; D019275:Radiopharmaceuticals; D051381:Rats; D017207:Rats, Sprague-Dawley; D013223:Statistics as Topic; D013382:Subtraction Technique; D014018:Tissue Distribution
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18