Contribution of perfusion to the11C-acetate signal in brown adipose tissue assessed by DCE-MRI and68Ga-DOTA PET in a rat model

Purpose Determine if dynamic contrast enhanced (DCE) -MRI and/or 68 gallium 1,4,7,10-tetraazacyclododecane N, N ', N '', N'-tretraacetic acid (Ga-68-DOTA) positron emission tomography (PET) can assess perfusion in rat brown adipose tissue (BAT). Evaluate changes in perfusion between cold-stimulated and heat-inhibited BAT. Determine if the(11)C-acetate pharmacokinetic model can be constrained with perfusion information to improve assessment of BAT oxidative metabolism. Methods Rats were split into three groups. In group 1 (N = 6), DCE-MRI with gadobutrol was compared directly to(68)Ga-DOTA PET following exposure to 10 degrees C for 48 h.C-11-Acetate PET was also performed to assess oxidation. In group 2 (N = 4), only(68)Ga-DOTA PET was acquired following exposure to 10 degrees C for 48 h. Finally, in group 3 (N = 10), perfusion was assessed with DCE-MRI in rats exposed to 10 degrees C or 30 degrees C for 48 h, and oxidation was measured with(11)C-acetate. Perfusion was quantified with a two-compartment pharmacokinetic model, while oxidation was assessed by a four-compartment model. Results DCE-MRI and(68)Ga-DOTA PET provided similar perfusion measures, but a decrease in the perfusion signal was noted with longer imaging sessions. Exposure to 10 degrees C or 30 degrees C did not affect the perfusion measures, but the(11)C-acetate signal increased in BAT at 10 degrees C. Without prior information about blood volume, the(11)C-acetate compartment model overestimated blood volume and underestimated oxidation in 10 degrees C BAT. Conclusion Precise assessment of oxidation via(11)C-acetate PET requires prior information about blood volume which can be obtained by DCE-MRI or(68)Ga-DOTA PET. Since perfusion can change rapidly, simultaneous PET-MRI would be preferred.

Automated summary

The study aimed to evaluate the perfusion in rat brown adipose tissue (BAT) using MRI and PET techniques, showing that DCE-MRI and (68)Ga-DOTA PET provided similar results. These techniques can improve the assessment of BAT oxidative metabolism, but a decrease in perfusion signal was noted with longer imaging sessions.