Diffuse optical spectroscopic method for tissue and body composition assessment.

SIGNIFICANCE: Growing levels of obesity and metabolic syndrome have driven demand for more advanced forms of body composition assessment. While various techniques exist to measure body composition, devices are typically expensive and not portable, involve radiation [in the case of dual-energy x-ray absorptiometry (DXA)], and are limited to analysis of adiposity while metabolic information from blood supply and oxygenation are not considered. AIM: We evaluate whether diffuse optical spectroscopic imaging (DOSI) can be used to predict site-specific adiposity and percent fat (whole body) while simultaneously providing information about local tissue hemoglobin levels and oxygenation. APPROACH: DOSI measures of tissue composition in gastrocnemius, quadriceps, abdomen, and biceps, DXA whole-body composition, and ultrasound-derived skin and adipose tissue thickness (SATT) in the quadriceps were obtained from 99 individuals aged 7 to 34 years old. RESULTS: Various DOSI-derived parameters were correlated with SATT and an optical method is proposed for estimating SATT using a newly defined parameter, the optical fat fraction (OFF), which considers all parameters that correlate with SATT. Broadband absorption and scattering spectra from study participants with the thinnest (SATT ≈ 0.25 ± 0.02 cm) and thickest SATT (SATT ≈ 1.55 ± 0.14 cm), representing best estimates for pure in vivo lean and fatty tissue, respectively, are reported. Finally, a trained prediction model is developed which allows DOSI assessment of OFF to predict DXA body-fat percentage, demonstrating that DOSI can be used to quantify body composition. CONCLUSIONS: This study shows that DOSI can be used to assess the adiposity of specific tissues or the entire human body, and the OFF parameter is defined for corroboration and further evaluation in future research.

Laboratory assessment of rice husk ash (RHA) in the solidification/stabilization of heavy metal contaminated slurry.

This article presents a laboratory study investigating the effects of RHA on the immobilisation of lead and copper in a slurry treated with a binder content ranging from 100 to 300 kg/m3. Increased binder content was significant in the immobilisation of Pb, but less effective for Cu. A minimum binder content of 200 kg/m3 was required to stabilise Cu in the slurry. The incorporation of RHA significantly reduced the coefficient of diffusion of Pb and Cu spiked samples in comparison to samples treated with only cement. Sorption and precipitation reaction were important mechanisms that controlled the leaching of Cu and Pb. The increase of RHA content led to increase in sorption and precipitation reaction in the solidified/stabilised matrix. The results from mercury intrusion porosimetry (MIP) revealed that specimen spiked with Cu exhibited more macropores than those spiked with Pb. It is postulated that the cement hydration may be retarded due to the presence of Cu. The performance of the RHA stabilised samples is influenced significantly by the pH. The amount of binder content was crucial for Cu and Pb leachability. The presence of RHA offered little resistance under acidic conditions but minimised the leachability under neutral and alkaline conditions.

Exercise and Repeated Testing Improves Accuracy of Laser Doppler Assessment of Microvascular Function Following Shortened (1-minute) Blood Flow Occlusion.

OBJECTIVES: To determine whether stability/accuracy of post-occlusive LDF following shortened, one-minute blood flow occlusion, increases in the post-exercise state or by averaging multiple measurements. METHODS: Six healthy adults (3F) underwent LDF eight times at rest and following exercise, assessing post-occlusive (one-minute occlusion) reactive hyperemia in the cutaneous microcirculation of the forefinger. Measured variables included: pre- and post-occlusion steady-state perfusion (Plat1, Plat2), maximum post-occlusive perfusion (Max), PkT, and the ratio Max/Plat1. RESULTS: Stability/accuracy of all variables improved performing measurements after exercise (p < 0.05 Plat 1, Plat 2, Max and Max/Plat1). PkT and Max/Plat 1 displayed the greatest accuracy at rest (26.6 ± 5.1% and 26.6 ± 4.4% average difference, %Diff, of single measurements from individual "true" means, respectively); for these variables, %Diff improved to 19.5 ± 5.3 and 17.6 ± 2.1, respectively, following exercise. Overall, averaging multiple measurements performed at rest also improved stability/accuracy in all variables. This improvement was comparable to that obtained with a single measurement following exercise. CONCLUSIONS: A standardized exercise stimulus prior to testing significantly improves stability/accuracy of LDF following shortened, one-minute blood flow occlusion. Our results suggest the possibilities of broader applications of exercise to optimize measurements from a variety of skin perfusion methodologies.