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 μs and backscattering μb coefficients from 480 to 700 nm with 8 nm spectral resolution. The method is tested on media with varying scattering properties (μs = 1 to 34 mm−1 and μb = 2.10−6 to 2.10−3 mm−1), containing different sized polystyrene spheres. The results are in excellent agreement with Mie theor

Quantitative measurements of absorption spectra in scattering media by low-coherence spectroscopy

Low-coherence spectroscopy (LCS) is a spectroscopic method that allows for quantitative and localized assessment of absorption spectra by combining reflection spectroscopy with low-coherence interferometry. We describe absorption coefficient (µa) measurements by LCS in tissue simulating phantoms with varying scattering and absorbing properties. We used LCS in the 455–680 nm wavelength range with a spectral resolution of 8 nmto obtain µa spectra with ±0.5 mm−1 accuracy. We conclude that LCS is a promising technique for the in vivo determination of tissue chromophore concentrations

Quantitative comparison of analysis methods for spectroscopic optical coherence tomography

Spectroscopic optical coherence tomography (sOCT) enables the mapping of chromophore concentrations and image contrast enhancement in tissue. Acquisition of depth resolved spectra by sOCT requires analysis methods with optimal spectral/spatial resolution and spectral recovery. In this article, we quantitatively compare the available methods, i.e. the short time Fourier transform (STFT), wavelet transforms, the Wigner-Ville distribution and the dual window method through simulations in tissue-like media. We conclude that all methods suffer from the trade-off in spectral/spatial resolution, and that the STFT is the optimal method for the specific application of the localized quantification of hemoglobin concentration and oxygen saturation

Photoacoustic Imaging of Valves in Superficial Veins

Background and Objectives: In intravenous access to veins there is a risk of puncturing venous valves or blocking of the catheter by the valves. Therefore, we have investigated whether and how photoacoustic imaging (PAI), which visualizes the lumen of blood vessels, can be used to detect these valves. - Study Design/Materials and Methods: Venous valves in superficial veins on the dorsal side of the hand of human volunteers were located by palpation and visual inspection. Next, this location was imaged using PAI. - Results: In 16 of 21 human volunteers venous valves that were found by palpation could be observed by PAI as local discontinuities in the imaged vessel. From these images, four characteristic features by which venous valves can be recognized in photoacoustic images were identified. - Conclusions: PAI has the potential to be applied in the detection of venous valves. Lasers Surg. Med. 38:740-744, 2006

Preoperative biliary drainage in severely jaundiced patients with pancreatic head cancer: A retrospective cohort study

Background: Guidelines recommend against preoperative biliary drainage (PBD) in patients with pancreatic head cancer if bilirubin levels are <250 μmol/l. However, patients with higher bilirubin levels undergo PBD, despite the lack of supporting evidence. This study aims to evaluate outcomes in patients with a bilirubin level ≥250 and < 250. Methods: Patients were identified from databases of 3 centers. Outcomes were compared in patients with a bilirubin level ≥250 versus <250 both at the time of diagnosis and directly prior to surgery. Results: 244 patients were included. PBD was performed in 64% (123/191) with bilirubin <250 at diagnosis and 91% (48/53) with bilirubin ≥250. PBD technical success (83% vs. 81%, p = 0.80) and PBD related complications (33% vs. 29%, p = 0.60) did not differ between these groups. Analyzing bilirubin levels ≥250 versus <250 directly prior to surgery, no differences in severe postoperative complications and mortality were found. Conclusions: In patients with a pancreatic head cancer, PBD technical success and complications, and severe postoperative complications did not differ between patients with a bilirubin level ≥250 and < 250. Our study does not support a different approach regarding PBD in patients with severe jaundice

Variation in the plasma membrane monoamine transporter (PMAT) (encoded by SLC29A4) and organic cation transporter 1 (OCT1) (encoded by SLC22A1) and gastrointestinal intolerance to metformin in type 2 diabetes:An IMI direct study

OBJECTIVE Gastrointestinal adverse effects occur in 20–30% of patients with metformin-treated type 2 diabetes, leading to premature discontinuation in 5–10% of the cases. Gastrointestinal intolerance may reflect localized high concentrations of metformin in the gut. We hypothesized that reduced transport of metformin via the plasma membrane monoamine transporter (PMAT) and organic cation transporter 1 (OCT1) could increase the risk of severe gastrointestinal adverse effects. RESEARCH DESIGN AND METHODS The study included 286 severe metformin-intolerant and 1,128 metformin-tolerant individuals from the IMI DIRECT (Innovative Medicines Initiative: DIabetes REsearCh on patient straTification) consortium. We assessed the association of patient characteristics, concomitant medication, and the burden of mutations in the SLC29A4 and SLC22A1 genes on odds of intolerance. RESULTS Women (P < 0.001) and older people (P < 0.001) were more likely to develop metformin intolerance. Concomitant use of transporter-inhibiting drugs increased the odds of intolerance (odds ratio [OR] 1.72, P < 0.001). In an adjusted logistic regression model, the G allele at rs3889348 (SLC29A4) was associated with gastrointestinal intolerance (OR 1.34, P = 0.005). rs3889348 is the top cis-expression quantitative trait locus for SLC29A4 in gut tissue where carriers of the G allele had reduced expression. Homozygous carriers of the G allele treated with transporter-inhibiting drugs had more than three times higher odds of intolerance compared with carriers of no G allele and not treated with inhibiting drugs (OR 3.23, P < 0.001). Use of a genetic risk score derived from rs3889348 and SLC22A1 variants found that the odds of intolerance were more than twice as high in individuals who carry three or more risk alleles compared with those carrying none (OR 2.15, P = 0.01). CONCLUSIONS These results suggest that intestinal metformin transporters and concomitant medications play an important role in the gastrointestinal adverse effects of metformin

Vaginal bacterium Prevotella timonensis turns protective Langerhans cells into HIV-1 reservoirs for virus dissemination

Dysbiosis of vaginal microbiota is associated with increased HIV-1 acquisition, but the underlying cellular mechanisms remain unclear. Vaginal Langerhans cells (LCs) protect against mucosal HIV-1 infection via autophagy-mediated degradation of HIV-1. As LCs are in continuous contact with bacterial members of the vaginal microbiome, we investigated the impact of commensal and dysbiosis-associated vaginal (an)aerobic bacterial species on the antiviral function of LCs. Most of the tested bacteria did not affect the HIV-1 restrictive function of LCs. However, Prevotella timonensis induced a vast uptake of HIV-1 by vaginal LCs. Internalized virus remained infectious for days and uptake was unaffected by antiretroviral drugs. P. timonensis-exposed LCs efficiently transmitted HIV-1 to target cells both in vitro and ex vivo. Additionally, P. timonensis exposure enhanced uptake and transmission of the HIV-1 variants that establish infection after sexual transmission, the so-called Transmitted Founder variants. Our findings, therefore, suggest that P. timonensis might set the stage for enhanced HIV-1 susceptibility during vaginal dysbiosis and advocate targeted treatment of P. timonensis during bacterial vaginosis to limit HIV-1 infection