Thermal imaging to measure brown adipose tissue activity appears to be a novel, valid alternative to the current gold standard of fluorodeoxyglucose PET/CT, according to study findings presented at the Society for Endocrinology Annual Conference.
“We used an infrared thermal imaging camera to show that exposure to cold temperatures — the most potent physiological stimulator of brown adipose tissue (BAT) — caused an expected fall in skin temperature in the shoulder and chest regions but caused a rise in neck temperature in some people,” Victoria Salem, PhD, of Imperial College London, told Endocrine Today. “We directly compared these thermal images with the PET/CT images and confirmed that the hottest areas of the thermal images always directly corresponded with a depot of underlying BAT.”
Salem and colleagues collected PET/CT scans and thermal images from 10 healthy men (mean age, 26 years) during cold exposure to determine the effect of each on detecting brown adipose activity.
“Drugs are being developed to harness the heat producing/calorie burning potential of BAT, so we need to develop a more effective method to functionally image human BAT activity,” Salem said. “The current gold standard technique is fluorodeoxyglucose (FDG) PET/CT — which is expensive, exposes [people] to ionizing radiation and, importantly, only measures BAT glucose uptake, which is not always directly linked to thermogenesis.”
PET/CT scans were classified as BAT-positive (n = 7) if there was increased signal intensity, and if it was absent, as BAT-negative (n = 3). Thermal images for temperatures within the supraclavicular region were analyzed and overlaid against PET/CT scans.
In the BAT-positive group, the hottest 10% of temperature in thermal images corresponded with cold-activated BAT. Compared with the negative group, an increase in temperature was detected by thermal imaging of the supraclavicular region (P < .001) between baseline and the end of cold exposure in the positive group. Between baseline and the end of cold exposure, a comparable increase in temperature focusing on skin directly overlying BAT as seen on PET/CT was found (P < .001).
“In subjects with PET/CT-confirmed BAT deposits, thermal imaging measured a significant 0.4°C rise in neck temperature in response to cold stimulation, whereas the volunteers who had no visible BAT on PET/CT did not display a rise in neck temperature in the cold,” Salem said. “This study confirms the utility of thermal imaging as an effective and safe alternative to PET/CT for identifying and measuring human BAT thermogenesis.” – by Amber Cox
Salem V, et al. Abstract #0104. Presented at: Society for Endocrinology Annual Conference; Nov. 2-4, 2015; Edinburgh, Scotland.
Salem reported being a National Institute for Health Research clinical lecturer in diabetes and endocrinology. The study was funded in part by a grant from the Academy of Medical Sciences.