Infrared Thermography

Abstract

Historically, brown adipose tissue has been elusive and not easy to detect, hence its relative obscurity in human physiology until its rediscovery in 2009. At that point, it was proven that the symmetrical artefacts frequently detected on positron emission tomography-computed tomography (PET-CT), which resolved if the environment was kept warm, were brown adipose tissue deposits. PET-CT has remained the stalwart of human brown adipose tissue research and is still considered the gold standard. However, PET-CT exposes the participant to ionising radiation, limiting studies to large, but retrospective, review of clinical imaging or a small-scale, but prospective, design. Within this context, alternative imaging modalities have been sought. Due to the heat-generating properties of brown adipose tissue, infrared thermography is a natural candidate for measuring its activity and the supraclavicular depot is relatively superficial, allowing detection of the heat signature. Infrared thermography is a non-invasive, non-contact technique for measuring temperature remotely. Recent developments in image analysis techniques have facilitated the use of infrared thermography to study brown adipose tissue activation in populations, and in ways, not previously feasible.

Caffeine exposure induces browning features in adipose tissue in vitro and in vivo

“…It has been suggested that thermal imaging may not give an optimal measure of BAT 36,37 , however, such studies have not considered the changes in temperature of the supraclavicular region with an appropriate reference point that correlate well with BAT function as assessed by PET-CT 24 . In addition, single point measures of supraclavicular temperature can be misleading as they cannot reliably detect the hottest region of brown fat as identified with thermal imaging approach used here 38 . Although caffeine has been reported to cause changes in blood flow 39–41 , this was not expected to cause substantial changes in skin temperature, as this typically does not occur until at least 2 h after caffeine consumption 34 .…”

Brown Adipose Tissue Response to Cold Stimulation Is Reduced in Girls With Autoimmune Hypothyroidism

“…Data were analyzed within the MATLAB programming environment, as previously described [18]. In brief, the image was displayed on a graphical user interface allowing the user to identify five points representing the apices of the supraclavicular ROIs [18, 50]. The outline of the ROI was then calculated as (i) straight lines from the neck and shoulder apices to the central apex and (ii) the shoulder contour between the shoulder and neck apices.…”

Semi-automated analysis of supraclavicular thermal images increases speed of brown adipose tissue analysis without increasing variation in results

“…Thermal imaging is increasingly used in a wide range of medical and physiological applications, both in humans ( Law et al, 2018b ) and animals, for instance to monitor stress and welfare remotely in a non-invasive manner ( McManus et al, 2016 ). There remains the potential to adapt the method presented here to enable it to be applied in alternative-use scenarios.…”