In Vivo Assessment of Cold Stimulation Effects on the Fat Fraction of Brown Adipose Tissue Using DIXON MRI

Purpose: To evaluate the volume and changes of human brown adipose tissue (BAT) in vivo following exposure to cold using magnetic resonance imaging (MRI). Materials and Methods: The clavicular region of 10 healthy volunteers was examined with a 3T MRI system. One volunteer participated twice. A cooling vest that was circulated with temperature-controlled water was used to expose each volunteer to a cold environment. Three different water temperature phases were employed: baseline (23 degrees C, 20 min), cooling (12 degrees C, 90 min), and a final warming phase (37 degrees C, 30 min). Temperatures of the water in the circuit, of the body, and at the back skin of the volunteers were monitored with fiberoptic temperature probes. Applying the 2-point DIXON pulse sequence every 5 minutes, fat fraction (FF) maps were determined and evaluated over time to distinguish between brown and white adipose tissue. Results: Temperature measurements showed a decrease of 3.8 +/- 1.0 degrees C of the back skin temperature, while the body temperature stayed constant at 37.2 +/- 0.9 degrees C. Focusing on the two interscapular BAT depots, a mean FF decrease of -2.9 +/- 2.0%/ h (P < 0.001) was detected during cold stimulation in a mean absolute volume of 1.31 +/- 1.43 ml. Also, a correlation of FF decrease to back skin temperature decrease was observed in all volunteers (correlation coefficients: vertical bar r vertical bar=[0.51; 0.99]). Conclusion: We found that FF decreases in BAT begin immediately with mild cooling of the body and continue during long-time cooling.