Measurement of brown adipose tissue mass using a novel dual-echo magnetic resonance imaging approach: A validation study

Abstract Objective The aim of this study was to evaluate and validate magnetic resonance imaging (MRI) for the visualization and quantification of brown adipose tissue (BAT) in vivo in a rat model. We hypothesized that, based on differences in tissue water and lipid content, MRI could reliably differentiate between BAT and white adipose tissue (WAT) and could therefore be a possible alternative for 18  F-Fluorodeoxyglucose Positron Emission Tomography ( 18 FDG-PET), the current gold standard for non-invasive BAT quantification. Materials/Methods Eleven rats were studied using both 18 FDG-PET/CT and MRI (1.5 T). A dual echo (in-and-out-of-phase) sequence was used, both with and without spectral presaturation inversion recovery (SPIR) fat suppression (DUAL-SPIR) to visualize BAT, after which all BAT was surgically excised. The BAT volume measurements obtained via 18 FDG-PET/CT and DUAL-SPIR MR were quantitatively compared with the histological findings. All study protocols were reviewed and approved by the local ethics committee. Results The BAT mass measurements that were obtained using DUAL-SPIR MR subtraction images correlated better with the histological findings (P = 0.017, R = 0.89) than did the measurements obtained using 18 FDG-PET/CT (P = 0.78, R = 0.15), regardless of the BAT metabolic activation state. Additionally, the basic feasibility of the DUAL-SPIR method was demonstrated in three human pilot subjects. Conclusions This study demonstrates the potential for MRI to reliably detect and quantify BAT in vivo. MRI can provide information beyond that provided by 18 FDG-PET imaging, and its ability to detect BAT is independent of its metabolic activation state. Additionally, MRI is a low-cost alternative that does not require radiation.