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

Abstract

Objective<br />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 (18FDG-PET), the current gold standard for non-invasive BAT quantification.<br />Materials/Methods<br />Eleven rats were studied using both 18FDG-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 18FDG-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.<br />Results<br />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 18FDG-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.<br />Conclusions<br />This study demonstrates the potential for MRI to reliably detect and quantify BAT in vivo. MRI can provide information beyond that provided by 18FDG-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.