Application—Infrared Thermal Imaging Projection Cold-Induced Glucose Uptake Rate in Brown Tissue

Infrared Thermal Imaging Projection Cold-Induced Glucose Uptake Rate in Brown Tissue

   Human adipose tissue can be divided into white and brown adipose tissue (BAT), largely consisting of white and brown adipocytes, respectively. The main purpose of white adipose tissue is energy storage, while the main function of BAT is thermoregulation by non-shivering thermogenesis as a response to cold. Its ability to expend energy could potentially be used to prevent or treat overweight, obesity, and metabolic dysfunctions such as type 2 diabetes. In adult humans, brown adipocytes are mixed with white adipocytes and are located in multiple depots. For simplicity these depots may be called BAT depots, even though they contain a mixture of brown and white adipocytes.

   One well-established method for estimating BAT metabolic activity is using 18F-fuorodeoxyglucose (18F-FDG) positron emission tomography (PET)/ computed tomography (CT). To measure the BAT metabolic activity the subjects are preferably exposed to cold since most persons do not have thermogenically active BAT under thermoneutral conditions. 18F-FDG PET/CT scans expose the subjects to potentially harmful levels of ionizing radiation and are expensive. The amount of ionizing radiation can be partially reduced by using a PET/magnetic resonance (MR) scanner instead of a PET/CT scanner. However, to enable large-scale or longitudinal prospective studies of BAT activity safe, reliable, and preferably cheap, methods are needed.

Figure 1. IRT image of a subject with hands and feet in cold water.

   The temperature of the supraclavicular fossae (SCF) during cooling, or its temperature during cooling relative to other skin temperature measurements, has been found to be positively associated to measurements of cold-induced BAT metabolic activity performed using 18F-FDG PET. The temperature may be measured either using attachable temperature probes or by infrared thermography (IRT). The correlations were likely due to the proximity between the SCF and the supraclavicular BAT depot. The metabolic activity of the BAT increases its temperature, which in turn increases the temperature of the nearby SCF, or at least prevents it from declining as much it otherwise would during cold exposure.

   The purpose of the present study was to evaluate and further develop techniques using IRT and MRI for estimating cold-induced BAT metabolic activity by examining healthy adult subjects. It is possible to estimate BAT metabolic activity during individualized cooling. The adjusted R2 values indicate that the IRT protocol used in this study is as good as, or possibly even superior to, the MRI protocol for the estimation of cold-induced BAT metabolic activity.

Reference

Jonathan Andersson, Elin Lundström1, Mathias Engström, et al. estimating the cold-induced brown adipose tissue glucose uptake rate measured by 18f-fDG pet using infrared thermography and waterfat separated MRi. Scientific Reports. 9:12358, 2019.