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Background Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods A multilayer 3D computational model was created in HFSS™ with 1.5 mm skin, 3–10 mm subcutaneous fat, 200 mm muscle and a BAT region (2–6 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSS™ were combined with simulated thermal distributions computed in COMSOL® to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results The optimized frequency band was 1.5–2.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 2–9 mdBm (noradrenergic stimulus) and 4–15 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions Results demonstrated the ability to detect thermal radiation from small volumes (2–6 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5 °C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism.

High strain rate compression of soft tissues has recently gained attention due to its application in computational simulation of traumatic injuries. To understand high rate tissue behavior, a comparative study is needed to examine the biomechanical responses of multiple soft tissues. We hypothesized that the underlying mechanisms of soft tissue high rate compression is dependent upon water, microstructural organization, and extracellular matrix (ECM). Porcine brain, liver, and tendon, which have similar material density (brain: 1.05[Formula: see text]g/cm3, liver: 1.06[Formula: see text]g/cm3, and tendon: 1.12[Formula: see text]g/cm3) and water content (brain: [Formula: see text][Formula: see text]78%, liver: [Formula: see text][Formula: see text]71–75%, and tendon: [Formula: see text][Formula: see text]70%) but different cellularity and ECM properties, were subjected to polymeric split Hopkinson pressure bar (PSHPB) testing. Hydrated brain tissue, due to its high microstructural cavities (cavity area [Formula: see text]) and low ECM content, had a high initial stress spike of [Formula: see text][Formula: see text]MPa. Hydrated liver, with moderate microstructural cavities (cavity area [Formula: see text]) and moderate ECM content, had a moderate stress spike of [Formula: see text][Formula: see text]MPa. Hydrated tendon had low microstructural cavities (cavity area [Formula: see text]) and high ECM content and had a minimal initial stress spike of [Formula: see text][Formula: see text]MPa. Electron microscopy of the tissues’ microstructural cavities revealed a first-order estimation of water content that was not bound to ECM (e.g., intracellular water). Linear regression analysis showed that the initial spike was highly correlated ([Formula: see text]) with intracellular water. To understand the role of water in each tissue’s response to high deformation, each soft tissue was completely dehydrated and subjected to the same PSHPB compression test. After removal of all the water, neither the brain, liver, nor tendon revealed an initial stress spike, implicating the essential nature of water in the initial responses of high-rate compression. These results suggest that cellular water and ECM content play a critical role in the biomechanical responses to high strain rate compression.

We propose an alternative microwave ablation therapy, Ultra-wideband Microwave Ablation Therapy (UMAT), that can potentially be used for the treatment of various cancers including liver, kidney, breast, lung, and bone. The technology relies on extremely small size ultra-wideband antennas that can deliver power to the tissue with more than 90% power transmission efficiency from beginning to the end of the ablation procedure. The resulting ablation technology is far superior to the existing microwave ablation therapies in terms of power usage, ablation time and zones. In order to validate the system, we provide ex vivo animal experiments.

Brown adipose tissue (BAT) plays an important role in whole body metabolism and with appropriate stimulus could potentially mediate weight gain and insulin sensitivity. Although imaging techniques are available to detect subsurface BAT, there are currently no viable methods for continuous acquisition of BAT energy expenditure. Microwave (MW) radiometry is an emerging technology that allows the quantification of tissue temperature variations at depths of several centimeters. Such temperature differentials may be correlated with variations in metabolic rate, thus providing a quantitative approach to monitor BAT metabolism. In order to optimize MW radiometry, numerical and experimental phantoms with accurate dielectric properties are required to develop and calibrate radiometric sensors. Thus, we present for the first time, the characterization of relative permittivity and electrical conductivity of brown (BAT) and white (WAT) adipose tissues in rats across the MW range 0.5-10GHz. Measurements were carried out in situ and post mortem in six female rats of approximately 200g. A Cole-Cole model was used to fit the experimental data into a parametric model that describes the variation of dielectric properties as a function of frequency. Measurements confirm that the dielectric properties of BAT (ε r = 14.0-19.4, σ = 0.3-3.3S/m) are significantly higher than those of WAT (ε r = 9.1-11.9, σ = 0.1-1.9S/m), in accordance with the higher water content of BAT.