Evaluation of Brown Adipose Tissue Using Near-Infrared Time-Resolved Spectroscopy

Human brown adipose tissue (BAT) activity (SUVmax) has been typically evaluated by 18F-fluorodeoxy glucose (FDG)-positron emission tomography (PET) combined with computed tomography (CT). In this study, the objective was to detect human BAT by near-infrared time-resolved spectroscopy (NIRTRS), a noninvasive and simple method for measuring total hemoglobin concentration [total-Hb] and reduced scattering coefficient (μs') in the tissue. The [total-Hb] in the supraclavicular region of the BAT (+) (SUVmax≥2.0) group was 95.0±28.2 μM (mean+/-SD), which was significantly higher than that of the BAT (-) (SUVmax<2.0) group (52.0±14.8 μM), but not in other regions apart from the BAT deposits. The μs' in the supraclavicular region of the BAT (+) group was 8.4±1.7 cm(-1), which was significantly higher than that of BAT (-) group (4.3±1.0 cm(-1)), but not in other regions. The area under the receiver operating characteristic curve closest to (0, 1) for [total-Hb] and μs' to discriminate BAT (+) from BAT (-) was 72.5 μM and 6.3 cm(-1), respectively. The sensitivity, specificity, and accuracy for both parameters were 87.5, 100, and 93.3%, respectively. Our novel NIRTRS method is noninvasive, simple, and inexpensive compared with FDG-PET/CT, and is reliable for detecting human BAT.