In vivo low-coherence spectroscopic measurements of local hemoglobin absorption spectra in human skin

Localized spectroscopic measurements of optical properties are invaluable for diagnostic applications that involve layered tissue structures, but conventional spectroscopic techniques lack exact control over the size and depth of the probed tissue volume. We show that low-coherence spectroscopy (LCS) overcomes these limitations by measuring local attenuation and absorption coefficient spectra in layered phantoms. In addition, we demonstrate the first in vivo LCS measurements of the human epidermis and dermis only. From the measured absorption in two distinct regions of the dermal microcirculation, we determine total hemoglobin concentration (3.0±0.5 g∕l and 7.8±1.2 g∕l) and oxygen saturation.     

Optical properties of neonatal skin measured in vivo as a function of age and skin pigmentation

Knowledge of the optical properties of neonatal skin is invaluable when developing new, or improving existing optical techniques for use at the neonatal intensive care. In this article, we present in vivo measurements of the absorption μ(a) and reduced scattering coefficient μ(s) (') of neonatal skin between 450 and 600 nm and assess the influence of age and skin pigmentation on the optical properties. The optical properties were measured using a spatially resolved, steady state diffuse reflectance spectroscopy setup, combined with a modified spatially resolved diffusion model. The method was validated on phantoms with known values for the absorption and reduced scattering coefficient. Values of μ(a) and μ(s) (') were obtained from the skin at four different body locations (forehead, sternum, hand, and foot) of 60 neonates with varying gestational age, postnatal age, and skin pigmentation. We found that μ(a) ranged from 0.02 to 1.25 mm(-1) and μ(s) (') was in the range of 1 to 2.8 mm(-1) (5th to 95th percentile of the patient population), independent of body location. In contrast to previous studies, no to very weak correlation was observed between the optical properties and gestational maturity, but a strong dependency of the absorption coefficient on postnatal age was found for dark skinned patients.     

Measurements of wavelength dependent scattering and backscattering coefficients by low-coherence spectroscopy

Quantitative measurements of scattering properties are invaluable for optical techniques in medicine. However, noninvasive, quantitative measurements of scattering properties over a large wavelength range remain challenging. We introduce low-coherence spectroscopy as a noninvasive method to locally and simultaneously measure scattering μ(s) and backscattering μ(b) coefficients from 480 to 700 nm with 8 nm spectral resolution. The method is tested on media with varying scattering properties (μ(s) = 1 to 34 mm(-1) and μ(b) = 2.10(-6) to 2.10(-3) mm(-1)), containing different sized polystyrene spheres. The results are in excellent agreement with Mie theory.     

Plaque and thrombus evaluation by optical coherence tomography

Intravascular Optical Coherence Tomography has been explored as an imaging tool for vessel wall and thrombus characterization. OCT enables a high resolution arterial wall imaging, and light properties allow tissue characterization. It has been proved one of the most valuable imaging modalities for the evaluation of vulnerable plaque and thrombus. OCT has a unique capacity in volumetric quantification of calcium, and unlike ultrasound, light can easily penetrate calcified plaques. Finally, this review paper will address aspects of the validation method of plaque characterization and potential pitfalls and put in perspective new approaches that may help the evolution of the field.     

GH replacement therapy in elderly GH-deficient patients: a systematic review

Context Recombinant human GH (rhGH) is prescribed for the treatment of adults with GH deficiency (GHD). However, conflicting data are available on the efficacy of rhGH treatment in elderly GHD patients. Objective To assess the efficacy of rhGH treatment in elderly GHD subjects. Methods We searched the available literature in PubMed, Cochrane Library, Web of Science and EMBASE. Study selection Studies on GHD patients, aged >60 years, treated with rhGH were eligible for inclusion. Data extraction was performed by two reviewers independently. Results We found 11 eligible studies with a total of 534 patients. Only two studies had prospective, randomized, placebo-controlled study designs of rhGH treatment with a duration of 6 (n=15) and 12 months (n=62), respectively. Treatment with rhGH decreased total and low density lipoprotein (LDL) cholesterol levels by 4-8 and 11-16%, respectively, but did not alter high density lipoprotein or triglyceride levels. RhGH did not affect body mass index, but decreased waist circumference (by ～3?cm) and waist/hip ratio. RhGh did not consistently affect blood pressure or bone mineral density. RhGH increased lean body mass by 2-5% and decreased total fat mass by 7-10% in four studies, but did not affect body composition in two other studies. RhGH consistently improved quality of life (QoL) parameters reflected in AGHDA-scores. There were no explicit data on elderly GHD patients aged >80 years. Conclusion RhGH replacement in elderly subjects with GHD decreases LDL cholesterol levels and improves QoL, but the effects on other parameters are not unequivocal. There were no data on the efficacy and safety of rhGH treatment in octogenarians with GHD.