Fig 1.
Imaging with each tracer was performed sequentially in baseline conditions (day -2), after acute cold exposure (day 0), after cold acclimation (day 28) and after tracer distribution in the cold (day 30). Additionally MRI/MRS was performed with another groupe at day 0 and day 28.
Fig 2.
iBAT metabolic volumes of [18F]FDG, [18F]FTHA, [123I]MIBG and [99mTc]TcMIBI, as well as iBAT and iWAT volume determined by dissection, in different temperature conditions.
Fig 3.
Transverse (A), sagittal (B) and coronal (C) slices of images from a room-temperature housed rat, centered on iBAT, depicting the anatomy, [18F]FDG distribution, [18F]FTHA distribution, [123I]MIBG distribution, [99mTc]TcMIBI and [123I]IPA distribution. Uptake in BAT is low for all tracers.
Fig 4.
Transverse (A), sagittal (B) and coronal (C) slices of images from a cold-acclimated rat, centered on iBAT, depicting the anatomy, [18F]FDG distribution, [18F]FTHA distribution, [123I]MIBG distribution, [99mTc]TcMIBI and [123I]IPA distribution. iBAT, and to some extent cBAT show a high uptake for all tracers except [123I]IPA.
Fig 5.
iBAT SUVmean values of [18F]FDG, [18F]FTHA, [123I]MIBG, [99mTc]MIBI and [123I]IPA in different temperature conditions.
Table 1.
SUV, metabolic volume and total metabolic activity of [18F]FDG, [18F]FTHA, [123I]MIBG, [99mTc]TcMIBI and [123I]IPA in iBAT in baseline conditions, after acute cold exposure, after cold acclimation and after uptake in the cold.
↑ indicates a p-value < 0,10 when compared to baseline conditions, while † indicates a p-value < 0,10 when compared to the value after acute cold exposure. NQ indicates “not quantifiable”, while NA means these data are not available.
Table 2.
Biodistribution (determined by dissection) of [18F]FDG, [18F]FTHA, [123I]MIBG, [99mTc]TcMIBI and [123I]IPA in selected organs 1h after tracer uptake in the cold.
Fig 6.
MRI Images and their corresponding spectra from different positions in the body.
BAT = Brown Adipose tissue, SAT = Subcutaneous Adipose Tissue.
Table 3.
MRS-derived temperature differences in BAT and Muscle and rectal temperature difference in control and cold-acclimated animals.
There is no statistically significant difference between cold-acclimated and control animals.