RT Journal Article
SR Electronic
T1 Absolute Quantification of Regional Cerebral Glucose Utilization in Mice by <sup>18</sup>F-FDG Small Animal PET Scanning and 2-<sup>14</sup>C-DG Autoradiography
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1398
OP 1405
VO 45
IS 8
A1 Hiroshi Toyama
A1 Masanori Ichise
A1 Jeih-San Liow
A1 Kendra J. Modell
A1 Douglass C. Vines
A1 Takanori Esaki
A1 Michelle Cook
A1 Jurgen Seidel
A1 Louis Sokoloff
A1 Michael V. Green
A1 Robert B. Innis
YR 2004
UL http://jnm.snmjournals.org/content/45/8/1398.abstract
AB The purpose of this study was to evaluate the feasibility of absolute quantification of regional cerebral glucose utilization (rCMRglc) in mice by use of 18F-FDG and a small animal PET scanner. rCMRglc determined with 18F-FDG PET was compared with values determined simultaneously by the autoradiographic 2-14C-DG method. In addition, we compared the rCMRglc values under isoflurane, ketamine and xylazine anesthesia, and awake states. Methods: Immediately after injection of 18F-FDG and 2-14C-DG into mice, timed arterial samples were drawn over 45 min to determine the time courses of 18F-FDG and 2-14C-DG. Animals were euthanized at 45 min and their brain was imaged with the PET scanner. The brains were then processed for 2-14C-DG autoradiography. Regions of interest were manually placed over cortical regions on corresponding coronal 18F-FDG PET and 2-14C-DG autoradiographic images. rCMRglc values were calculated for both tracers by the autoradiographic 2-14C-DG method with modifications for the different rate and lumped constants for the 2 tracers. Results: Average rCMRglc values in cerebral cortex with 18F-FDG PET under normoglycemic conditions (isoflurane and awake) were generally lower (by 8.3%) but strongly correlated with those of 2-14C-DG (r2 = 0.95). On the other hand, under hyperglycemic conditions (ketamine/xylazine) average cortical rCMRglc values with 18F-FDG PET were higher (by 17.3%) than those with 2-14C-DG. Values for rCMRglc and uptake (percentage injected dose per gram [%ID/g]) with 18F-FDG PET were significantly lower under both isoflurane and ketamine/xylazine anesthesia than in the awake mice. However, the reductions of rCMRglc were markedly greater under isoflurane (by 57%) than under ketamine and xylazine (by 19%), whereas more marked reductions of %ID/g were observed with ketamine/xylazine (by 54%) than with isoflurane (by 37%). These reverse differences between isoflurane and ketamine/xylazine may be due to competitive effect of 18F-FDG and glucose uptake to the brain under hyperglycemia. Conclusion: We were able to obtain accurate absolute quantification of rCMRglc with mouse 18F-FDG PET imaging as confirmed by concurrent use of the autoradiographic 2-14C-DG method. Underestimation of rCMRglc by 18F-FDG in normoglycemic conditions may be due to partial-volume effects. Computation of rCMRglc from 18F-FDG data in hyperglycemic animals may require, however, alternative rate and lumped constants for 18F-FDG.