PT  - JOURNAL ARTICLE
AU  - Hiroshi Toyama
AU  - Masanori Ichise
AU  - Jeih-San Liow
AU  - Kendra J. Modell
AU  - Douglass C. Vines
AU  - Takanori Esaki
AU  - Michelle Cook
AU  - Jurgen Seidel
AU  - Louis Sokoloff
AU  - Michael V. Green
AU  - Robert B. Innis
TI  - 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
DP  - 2004 Aug 01
TA  - Journal of Nuclear Medicine
PG  - 1398--1405
VI  - 45
IP  - 8
4099  - http://jnm.snmjournals.org/content/45/8/1398.short
4100  - http://jnm.snmjournals.org/content/45/8/1398.full
SO  - J Nucl Med2004 Aug 01; 45
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.