Magnetic Resonance of Brown Adipose Tissue: A Review of Current Techniques

This article reviews recent efforts in magnetic resonance imaging (MRI) and spectroscopy (MRS) of brown adipose tissues (BAT). The article does not differentiate classical BAT from more recently introduced beige/ brite adipocytes, as the unequivocal detection of these hybrid adipocytes with MRI and MRS remains an unmet need and unsolved challenge. BAT studies in both animals and humans have progressed rapidly during the past decade, spanning a broad spectrum of researchers from basic science laboratories to clinical investigators in primary care hospitals. While positron emission and computed tomography (PET/CT) is likely to remain as a reference modality in BAT imaging in the near future, approaches using MRI and MRS have emerged as viable alternatives. The specific signal contrasts that allow an MR system to assess BAT morphology and function are emphasized. Methods that measure tissue fat content, blood flow and perfusion, water diffusion, temperature, and substrate metabolism are explained and pertinent literature reports that utilize these approaches are highlighted. Finally, this article provides an outlook on research opportunities and future directions.