Influence of sildenafil on blood oxygen saturation of the obstructed bladder

Background: Blood oxygen saturation (BOS) is decreased in a low-compliant, overactive obstructed bladder. The objective of this study is to determine the effect of Sildenafil (SC) on bladder function and BOS) in an in vivo animal model of bladder outlet obstruction. Methods. Thirty-two guinea pigs; sham operated (n = 8), sham operated + SC (n = 8), urethrally obstructed (n = 8) and urethrally obstructed + SC (n = 8) were studied during an 8 week period. BOS of the bladder wall was measured by differential path-length spectroscopy (DPS) before obstruction, at day 0, and at week 8. The bladder function was evaluated by urodynamic studies every week. Results: Before surgery and after sham operation all study parameters were comparable. After sham operation, bladder function and BOS did not change. In the obstructed group the urodynamic parameters were deteriorated and BOS was decreased. In the group obstruction + SC, bladder compliance remained normal and overactivity occurred only sporadic. BOS remained unchanged compared to the sham group and was significantly higher compared to the obstruction group. Conclusions: In an obstructed bladder the loss of bladder function is accompanied by a significant decrease in BOS. Treatment of obstructed bladders with SC yields a situation of high saturation, high bladder compliance and almost no overactivity. Maintaining the microcirculation of the bladder wall might result in better bladder performance without significant loss of bladder function. Measurement of BOS and interventions focussing on tissue microcirculation may have a place in the evaluation / treatment of various bladder dysfunctions

Optical detection of field cancerization in the buccal mucosa of patients with esophageal cancer

Introduction: Esophageal cancer is an increasingly common type of neoplasm with a very poor prognosis. This prognosis could improve with more early tumor detection. We have previously shown that we can use an optical spectroscopy to detect field cancerization in the buccal mucosa of patients with laryngeal cancer. The aim of this prospective study was to investigate whether we could detect field cancerization of buccal mucosa of patients with esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC). Methods: Optical measurements were performed in vivo using a novel optical technique: multidiameter single-fiber reflectance (MDSFR) spectroscopy. MDSFR spectra were acquired by a handheld probe incorporating three fiber diameters. Multiple absorption and scattering parameters that are related to the physiological and ultrastructural properties of the buccal mucosa were derived from these spectra. A linear discriminant analysis of the parameters was performed to create a combined biomarker σ to discriminate oncologic from non-oncologic patients. Results: Twelve ESCC, 12 EAC, and 24 control patients were included in the study. The median value of our biomarker σ was significantly higher in patients with ESCC (2.07 [1.93-2.10]) than control patients (1.86 [1.73-1.95], p = 0.022). After cross-validation σ was able to identify ESCC patients with a sensitivity of 66.7% and a specificity of 70.8%. There were no significant differences between the EAC group and the control group. Conclusion: Field cancerization in the buccal mucosa can be detected using optical spectroscopy in ESCC patients. This may be the first step towards non-invasive ESCC cancer screening

In vivo quantification of photosensitizer concentration using fluorescence differential path-length spectroscopy:influence of photosensitizer formulation and tissue location

In vivo measurement of photosensitizer concentrations may optimize clinical photodynamic therapy (PDT). Fluorescence differential path-length spectroscopy (FDPS) is a non-invasive optical technique that has been shown to accurately quantify the concentration of Foscan (R) in rat liver. As a next step towards clinical translation, the effect of two liposomal formulations of mTHPC, Fospeg (R) and Foslip (R), on FDPS response was investigated. Furthermore, FDPS was evaluated in target organs for head-and-neck PDT. Fifty-four healthy rats were intravenously injected with one of the three formulations of mTHPC at 0.15 mgkg(-1). FDPS was performed on liver, tongue, and lip. The mTHPC concentrations estimated using FDPS were correlated with the results of the subsequent harvested and chemically extracted organs. An excellent goodness of fit (R-2) between FDPS and extraction was found for all formulations in the liver (R-2 = 0.79). A much lower R-2 between FDPS and extraction was found in lip (R-2 = 0.46) and tongue (R-2 = 0.10). The lower performance in lip and in particular tongue was mainly attributed to the more layered anatomical structure, which influences scattering properties and photosensitizer distribution. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JBO. 17.6.067001

In vivo quantification of photosensitizer fluorescence in the skin-fold observation chamber using dual-wavelength excitation and NIR imaging

A major challenge in biomedical optics is the accurate quantification of in vivo fluorescence images. Fluorescence imaging is often used to determine the pharmacokinetics of photosensitizers used for photodynamic therapy. Often, however, this type of imaging does not take into account differences in and changes to tissue volume and optical properties of the tissue under interrogation. To address this problem, a ratiometric quantification method was developed and applied to monitor photosensitizer meso-tetra (hydroxyphenyl) chlorin (mTHPC) pharmacokinetics in the rat skin-fold observation chamber. The method employs a combination of dual-wavelength excitation and dualwavelength detection. Excitation and detection wavelengths were selected in the NIR region. One excitation wavelength was chosen to be at the Q band of mTHPC, whereas the second excitation wavelength was close to its absorption minimum. Two fluorescence emission bands were used; one at the secondary fluorescence maximum of mTHPC centered on 720 nm, and one in a region of tissue autofluorescence. The first excitation wavelength was used to excite the mTHPC and autofluorescence and the second to excite only autofluorescence, so that this could be subtracted. Subsequently, the autofluorescence-corrected mTHPC image was divided by the autofluorescence signal to correct for variations in tissue optical properties. This correction algorithm in principle results in a linear relation between the corrected fluorescence and photosensitizer concentration. The limitations of the presented method and comparison with previously published and validated techniques are discussed

The future of medical diagnostics: Review paper

While histopathology of excised tissue remains the gold standard for diagnosis, several new, non-invasive diagnostic techniques are being developed. They rely on physical and biochemical changes that precede and mirror malignant change within tissue. The basic principle involves simple optical techniques of tissue interrogation. Their accuracy, expressed as sensitivity and specificity, are reported in a number of studies suggests that they have a potential for cost effective, real-time, in situ diagnosis. We review the Third Scientific Meeting of the Head and Neck Optical Diagnostics Society held in Congress Innsbruck, Innsbruck, Austria on the 11th May 2011. For the first time the HNODS Annual Scientific Meeting was held in association with the International Photodynamic Association (IPA) and the European Platform for Photodynamic Medicine (EPPM). The aim was to enhance the interdisciplinary aspects of optical diagnostics and other photodynamic applications. The meeting included 2 sections: oral communication sessions running in parallel to the IPA programme and poster presentation sessions combined with the IPA and EPPM posters sessions. © 2011 Jerjes et al; licensee BioMed Central Ltd

Effect of hemoglobin extinction spectra on optical spectroscopic measurements of blood oxygen saturation

Fiber-optic reflectance measurements were performed on scattering phantoms containing red blood cells. The oxygen pressure in the phantom was decreased by nitrogen gas bubbling, while carefully controlling and monitoring the temperature (37°C) and pH (7.4). The blood oxygen saturation (SO 2) was extracted from the optical spectroscopic measurements by fitting the spectra over the wavelength range of 350-850 nm to a model that includes the effects of pigment packaging. The effect of using different oxy- and deoxyhemoglobin extinction spectra on the quality and accuracy of the fits is analyzed. The optically extracted SO2 is compared with the standard oxygen dissociation curve (ODC). Depending on the choice of hemoglobin extinction spectra the absolute deviation between the ODC and the optically extracted SO2 is less than 2.5% over the measured range of saturations (4%-99%)

Extraction of intrinsic fluorescence from single fiber fluorescence measurements on a turbid medium

This study utilizes Monte Carlo simulations of single fiber fluorescence to develop an empirical model that corrects for the influence of scattering and absorption on fluorescence intensity (FSF). The model expresses FSF in terms of the reduced scattering coefficient (?0 s) and absorption coefficient (μs), each determined independently at excitation and emission wavelengths (λx and λm), and the fiber diameter (μa). This model returns accurate descriptions (mean residual <6%) of FSF across a biologically relevant range of μs and μs values and is insensitive to the form of the scattering phase function

Use of a coherent fiber bundle for multi-diameter single fiber reflectance spectroscopy

Multi-diameter single fiber reflectance (MDSFR) spectroscopy enables quantitative measurement of tissue optical properties, including the reduced scattering coefficient and the phase function parameter γHowever, the accuracy and speed of the procedure are currently limited by the need for co-localized measurements using multiple fiber optic probes with different fiber diameters. This study demonstrates the use of a coherent fiber bundle acting as a single fiber with a variable diameter for the purposes of MDSFR spectroscopy. Using Intralipid optical phantoms with reduced scattering coefficients between 0.24 and 3 mm1, we find that the spectral reflectance and effective path lengths measured by the fiber bundle (NA = 0.40) are equivalent to those measured by single solid-core fibers (NA = 0.22) for fiber diameters between 0.4 and 1.0 mm (r ≥ 0.997). This one-to-one correlation may hold for a 0.2 mm fiber diameter as well (r = 0.816); however, the experimental system used in this study suffers from a low signal-to-noise for small dimensionless reduced scattering coefficients due to spurious back reflections within the experimental system. Based on these results, the coherent fiber bundle is suitable for use as a variable-diameter fiber in clinical MDSFR quantification of tissue optical properties

Method to quantitatively estimate wavelength-dependent scattering properties from multidiameter single fiber reflectance spectra measured in a turbid medium

This study utilizes experimentally validated Monte Carlo simulations to identify a mathematical formulation of the reflectance intensity collected by a single fiber probe expressed in terms of the reduced scattering coefficient (μprime;s), fiber diameter dfiber, and a property of the first two moments of the scattering phase function (γ). This model is then utilized to accurately obtain wavelength-dependent estimates of μ prime;s(λ) and γ (λ) from multiple single fiber spectral measurements of a turbid medium obtained with different diameters. This method returns accurate descriptions (mean residual <3%) of both μ prime;s and γ across the biologically relevant range

Quantification of the reduced scattering coefficient and phase-function-dependent parameter γ of turbid media using multidiameter single fiber reflectance spectroscopy: Experimental validation

Multidiameter single fiber reflectance (MDSFR) spectroscopy is a method that allows the quantification of μ's and the phase-function- dependent parameter γ of a turbid medium by utilizing multiple fibers with different diameters. We have previously introduced the theory behind MDSFR and its limitations, and here we present an experimental validation of this method based on phantoms containing a fractal distribution of polystyrene spheres both in the absence and presence of the absorber Evans Blue