We present the anisotropic light scattering of individual red blood cells (RBCs) from a patient with sickle cell disease (SCD). To measure light scattering spectra along two independent axes of elongated-shaped sickle RBCs with arbitrary orientation, we introduce the anisotropic Fourier transform light scattering (aFTLS) technique and measured both the static and dynamic anisotropic light scattering. We observed strong anisotropy in light scattering patterns of elongated-shaped sickle RBCs along its major axes using static aFTLS. Dynamic aFTLS analysis reveals the significantly altered biophysical properties in individual sickle RBCs. These results provide evidence that effective viscosity and elasticity of sickle RBCs are significantly different from those of the healthy RBCs.

We report a fast perturbation Monte Carlo (PMC) algorithm accelerated by graphics processing units (GPU). The two-step PMC simulation [Opt. Lett. 36, 2095 (2011)] is performed by storing the seeds instead of the photon's trajectory, and thus the requirement in computer random-access memory (RAM) becomes minimal. The two-step PMC is extremely suitable for implementation onto GPU. In a standard simulation of spatially-resolved photon migration in the turbid media, the acceleration ratio between using GPU and using conventional CPU is about 1000. Furthermore, since in the two-step PMC algorithm one records the effective seeds, which is associated to the photon that reaches a region of interest in this letter, and then re-run the MC simulation based on the recorded effective seeds, radiative transfer equation (RTE) can be solved by two-step PMC not only with an arbitrary change in the absorption coefficient, but also with large change in the scattering coefficient.

A reflective, pulsed terahertz (THz) imaging system was used to acquire high-resolution (d10-90/λ ∼ 1.925) images of deep, partial thickness burns in a live rat. The rat's abdomen was burned with a brass brand heated to ∼ 220°C and pressed against the skin with contact pressure for ∼ 10 sec. The burn injury was imaged beneath a Mylar window every 15 to 30 min for up to 7 h. Initial images display an increase in local water concentration of the burned skin as evidenced by a marked increase in THz reflectivity, and this likely correlates to the post-injury inflammatory response. After ∼ 1  h the area of increased reflectivity consolidated to the region of skin that had direct contact with the brand. Additionally, a low reflecting ring of tissue could be observed surrounding the highly reflective burned tissue. We hypothesize that these regions of increased and decreased reflectivity correlate to the zones of coagulation and stasis that are the classic foundation of burn wound histopathology. While further investigations are necessary to confirm this hypothesis, if true, it likely represents the first in vivo THz images of these pathologic zones and may represent a significant step forward in clinical application of THz technology.

Subsurface fluorescence molecular tomography (FMT) has promising potential for noninvasive characterization of molecular and cellular activities in small animals by tomographic means in reflectance geometry. In this work, subsurface FMT is employed to monitor the therapeutic response of cisplatin in tumor-bearing mice in vivo. The localization and quantification accuracy of subsurface FMT are demonstrated in phantom. In the in vivo study, the red fluorescent protein activities not only on the surface but in the interior tumor are tracked three-dimensionally during the antitumor treatment.

We use a compact and flexible multiphoton microendoscope (MPME) to acquire in vivo images of unstained liver, kidney, and colon from an anesthetized rat. The device delivers femtosecond pulsed 800 nm light from the core of a raster-scanned dual-clad fiber (DCF), which is focused by a miniaturized gradient-index lens assembly into tissue. Intrinsic fluorescence and second-harmonic generation signal from the tissue is epi-collected through the core and inner clad of the same DCF. The MPME has a rigid distal tip of 3 mm in outer diameter and 4 cm in length. The image field-of-view measures 115 μm by 115 μm and was acquired at 4.1  frames/s with 75 mW illumination power at the sample. Organs were imaged after anesthetizing Sprague-Dawley rats with isofluorane gas, accessing tissues via a ventral-midline abdominal incision, and isolating the organs with tongue depressors. In vivo multiphoton images acquired from liver, kidney, and colon using this device show features similar to that of conventional histology slides, without motion artifact, in ∼ 75% of imaged frames. To the best of our knowledge, this is the first demonstration of multiphoton imaging of unstained tissue from a live subject using a compact and flexible MPME device.

In vivo Cerenkov luminescence imaging is a rapidly growing molecular imaging research field based on the detection of Cerenkov radiation induced by beta particles when traveling though biological tissues. We investigated theoretically the possibility of enhancing the number of the detected Cerenkov photons in the near infrared (NIR) region of the spectrum. The analysis is based on applying a photon propagation diffusion model to Cerenkov photons in the tissue. Results show that despite the smaller number of Cerenkov photons in the NIR region, the fraction exiting the tissues is greater than in the visible range, and thus, a charge-coupled device detector optimized for the NIR range will allow to obtain a higher signal. The comparison was performed considering Cerenkov point sources located at different depths inside the animal. We concluded that the improvement can be up to 35% and is more significant when the Cerenkov source to be imaged is located deeper inside the animal.

tutorial article is presented for the use of linear and nonlinear Raman microspectroscopies in biomedical diagnostics. Coherent anti-Stokes Raman scattering (CARS) is the most frequently applied nonlinear variant of Raman spectroscopy. The basic concepts of Raman and CARS are introduced first, and subsequent biomedical applications of Raman and CARS are described. Raman microspectroscopy is applied to both in-vivo and in-vitro tissue diagnostics, and the characterization and identification of individual mammalian cells. These applications benefit from the fact that Raman spectra provide specific information on the chemical composition and molecular structure in a label-free and nondestructive manner. Combining the chemical specificity of Raman spectroscopy with the spatial resolution of an optical microscope allows recording hyperspectral images with molecular contrast. We also elaborate on interfacing Raman spectroscopic tools with other technologies such as optical tweezing, microfluidics and fiber optic probes. Thereby, we aim at presenting a guide into one exciting branch of modern biophotonics research.

Acousto-optic (AO) is an emerging hybrid technique for measuring optical contrast in turbid media using coherent light and ultrasound (US). A turbid object is illuminated with a coherent light source leading to speckle formation in the remitted light. With the use of US, a small volume is selected,which is commonly referred to as the "tagging" volume. This volume acts as a source of modulated light, where modulation might involve phase and intensity change. The tagging volume is created by focusing ultrasound for good lateral resolution; the axial resolution is accomplished by making either the US frequency, amplitude, or phase time-dependent. Typical resolutions are in the order of 1 mm. We will concentrate on the progress in the field since 2003. Different schemes will be discussed to detect the modulated photons based on speckle detection, heterodyne detection, photorefractive crystal (PRC) assisted detection, and spectral hole burning (SHB) as well as Fabry-Perot interferometers. The SHB and Fabry-Perot interferometer techniques are insensitive to speckle decorrelation and therefore suitable for in vivo imaging. However, heterodyne and PRC methods also have potential for in vivo measurements. Besides measuring optical properties such as scattering and absorption, AO can be applied in fluorescence and elastography applications.

This study investigates a photoacoustic/ultrasound dual-modality contrast agent, including extending its applications from image-contrast enhancement to combined diagnosis and therapy with site-specific targeting. The contrast agent comprises albumin-shelled microbubbles with encapsulated gold nanorods (AuMBs). The gas-filled microbubbles, whose diameters range from submicrometer to several micrometers, are not only echogenic but also can serve as drug-delivery vehicles. The gold nanorods are used to enhance the generation of both photoacoustic and photothermal signals. The optical absorption peak of the gold nanorods is tuned to 760 nm and is invariant after microbubble encapsulation. Dual-modality contrast enhancement is first described here, and the applications to cellular targeting and laser-induced thermotherapy in a phantom are demonstrated. Photoacoustic imaging can be used to monitor temperature increases during the treatment. The targeting capability of AuMBs was verified, and the temperature increased by 26°C for a laser power of 980 mW, demonstrating the potential of combined diagnosis and therapy with the dual-modality agent. Targeted photo- or acoustic-mediated delivery is also possible.

The development of a highly prallel simulation of the acousto-optic effect is detailed. The simulation supports optically heterogeneous simulation domains under insonification by arbitrary monochromatic ultrasound fields. An adjoint method for acousto-optics is proposed to permit point-source/point-detector simulations. The flexibility and efficiency of this simulation code is demonstrated in the development of spatial absorption sensitivity maps which are in broad agreement with current experimental investigations. The simulation code has the potential to provide guidance in the feasibility and optimization of future studies of the acousto-optic technique, and its speed may permit its use as part of an iterative inversion model.

For many research areas in biomedical optics, information about scattering of polarized light in turbid media is of increasing importance. Scattering simulations within this field are mainly performed on the basis of radiative transfer theory. In this study a polarization sensitive Monte Carlo solution of radiative transfer theory is compared to exact Maxwell solutions for all elements of the scattering Müller matrix. Different scatterer volume concentrations are modeled as a multitude of monodisperse nonabsorbing spheres randomly positioned in a cubic simulation volume which is irradiated with monochromatic incident light. For all Müller matrix elements effects due to dependent scattering and multiple scattering are analysed. The results are in overall good agreement between the two methods with deviations related to dependent scattering being prominent for high volume concentrations and high scattering angles.

We present a quantitative study of depolarization in biological tissues and correlate it with measured optical properties (reduced scattering and absorption coefficients). Polarized light imaging was used to examine optically thick samples of both isotropic (liver, kidney cortex, and brain) and anisotropic (cardiac muscle, loin muscle, and tendon) pig tissues in transmission and reflection geometries. Depolarization (total, linear, and circular), as derived from polar decomposition of the measured tissue Mueller matrix, was shown to be related to the measured optical properties. We observed that depolarization increases with the transport albedo for isotropic and anisotropic tissues, independent of measurement geometry. For anisotropic tissues, depolarization was higher compared to isotropic tissues of similar transport albedo, indicating birefringence-caused depolarization effects. For tissues with large transport albedos (greater than ∼ 0.97), backscattering geometry was preferred over transmission due to its greater retention of light polarization; this was not the case for tissues with lower transport albedo. Preferential preservation of linearly polarized light over circularly polarized light was seen in all tissue types and all measurement geometries, implying the dominance of Rayleigh-like scattering. The tabulated polarization properties of different tissue types and their links to bulk optical properties should prove useful in future polarimetric tissue characterization and imaging studies.

The spatial distribution of second harmonic generation (SHG) signal from collagen fibers for incident elliptical polarized light has been modeled. The beam was assumed to focus on a horizontal fiber through a microscope objective. For elliptical polarized states located along a vertical meridian of the Poincare sphere, the SHG intensity has been optimized in terms of the incident wavelength and the numerical aperture (NA) of the objective. Our results show that polarization modulates the SHG signal. Elliptical polarization can generate high signals (even greater than those corresponding to linear polarization) when combined with appropriate values of both incident wavelength and NA. On the other hand, the SHG intensity might also be identically zero for particular elliptical polarization states, a condition that depends exclusively on the ratio of hyperpolarizabilities of the collagen fibers. The highest forward-to-backward SHG signal distribution occurs along the propagating direction, depends on the incident wavelength, and reduces when NA increases. Furthermore, the direction of maximum SHG emission was found to be more sensitive to changes in the NA rather than variations in the incident wavelength. These findings could help to optimize the experimental conditions of multiphoton microscopes and to increase SHG signals from biological tissues containing collagen.

Mitochondrial DNA (mtDNA) in tumor cells was found to play an important role in maintaining the malignant phenotype. Using laser scanning confocal fluorescence microscopy (LSCFM) in a recent work, we reported a variable fluorescence intensity of ethidium bromide (EB) in mitochondria nucleoids of living carcinoma cells. Since when EB is bound to nucleic acids its fluorescence is intensified; a higher EB fluorescence intensity could reflect a higher DNA accessibility to EB, suggesting a higher mtDNA replication activity. To prove this hypothesis, in the present work we studied, by LSCFM, the EB fluorescence in mitochondria nucleoids of living neuroblastoma cells, a model system in which differentiation affects the level of mtDNA replication. A drastic decrease of fluorescence was observed after differentiation. To correlate EB fluorescence intensity to the mtDNA replication state, we evaluated the mtDNA nascent strands content by ligation-mediated real-time PCR, and we found a halved amount of replicating mtDNA molecules in differentiating cells. A similar result was obtained by BrdU incorporation. These results indicate that the low EB fluorescence of nucleoids in differentiated cells is correlated to a low content of replicating mtDNA, suggesting that EB may be used as a marker of mtDNA replication in living cells.

The aim of this study was to develop and characterize multifunctional biodegradable and biocompatible poly lactic-co-glycolic acid (PLGA) nanoparticles loaded with indocyanine green (ICG) as an optical-imaging contrast agent for cancer imaging and as a photothermal therapy agent for cancer treatment. PLGA-ICG nanoparticles (PIN) were synthesized with a particle diameter of 246±11  nm, a polydispersity index of 0.10±0.03, and ICG loading efficiency of 48.75±5.48%. PIN were optically characterized with peak excitation and emission at 765 and 810± 5  nm, a fluorescence lifetime of 0.30±0.01  ns, and peak absorbance at 780 nm. The cytocompatibility study of PIN showed 85% cell viability till 1-mg/ml concentration of PIN. Successful cellular uptake of ligand conjugated PIN by prostate cancer cells (PC3) was also obtained. Both phantom-based and in vitro cell culture results demonstrated that PIN (1) have the great potential to induce local hyperthermia (i.e., temperature increase of 8 to 10°C) in tissue within 5 mm both in radius and in depth; (2) result in improved optical stability, excellent biocompatibility with healthy cells, and a great targeting capability; (3) have the ability to serve as an image contrast agent for deep-tissue imaging in diffuse optical tomography.

Ratiometric fluorescence-imaging technique is commonly used to measure extracellular pH in tumors and surrounding tissue within a dorsal skin-fold window chamber. Using a pH-sensitive fluorophore such as carboxy SNARF-1 one can measure pH distributions with high precision. However, it is often observed that the measured pH is lower than expected, with a bias that varies from one image to another. A comprehensive analysis of possible error sources is presented. These error sources include photon noise, estimator bias, instrument errors, temperature, and calibration errors from biological factors.

Biological tissue is non-homogeneous in nature. It is difficult to measure its optical properties due to non-uniformity throughout the tissue being tested. To obtain the spatial distribution of optical parameters, conventional approaches use an array of light sources and detectors to reconstruct the image, thus, there is very limited spatial resolution. In contrast, solutions that provide high resolution have a high computational complexity. In this paper, we propose a fast, simple scheme to resolve the effective attenuation profile from the spatial diffuse reflectance. Rather than giving one single value for the absorption and reduced scattering coefficients, a novel algorithm is proposed for the reconstruction of an effective attenuation profile in 2-dimension from a diffuse reflectance curve. This technique is applied to the reconstruction of a 2-D effective attenuation profile. By obtaining the diffuse reflectance image from a camera and using the algorithm developed here, fast imaging of the effective attenuation profile with relatively high spatial resolution can be achieved.

A noninvasive approach to vasectomy may eliminate male fear of complications related to surgery and increase its acceptance. Noninvasive laser thermal occlusion of the canine vas deferens has recently been reported. Optical coherence tomography (OCT) and high-frequency ultrasound (HFUS) are compared for monitoring laser thermal coagulation of the vas in an acute canine model. Bilateral noninvasive laser coagulation of the vas was performed in six dogs (n = 12 vasa) using a Ytterbium fiber laser wavelength of 1075 nm, incident power of 9.0 W, pulse duration of 500 ms, pulse rate of 1 Hz, and 3-mm-diameter spot. Cryogen spray cooling was used to prevent skin burns during the procedure. An OCT system with endoscopic probe and a HFUS system with 20-MHz transducer were used to image the vas immediately before and after the procedure. Vasa were then excised and processed for gross and histologic analysis for comparison with OCT and HFUS images. OCT provided high-resolution, superficial imaging of the compressed vas within the vas ring clamp, while HFUS provided deeper imaging of the vas held manually in the scrotal fold. Both OCT and high HFUS are promising imaging modalities for real-time confirmation of vas occlusion during noninvasive laser vasectomy.

Visualization of individual cutaneous nerve endings has previously relied on laborious procedures of tissue excision, fixation, sectioning and staining for light or electron microscopy. We present a method for non-invasive, longitudinal two-photon microscopy of single nerve endings within the skin of anesthetized transgenic mice. Besides excellent signal-to-background ratio and nanometer-scale spatial resolution, this method offers time-lapse "movies" of pathophysiological changes in nerve fine structure over minutes, hours, days or weeks. Structure of keratinocytes and dermal matrix is visualized simultaneously with nerve endings, providing clear landmarks for longitudinal analysis. We further demonstrate feasibility of dissecting individual nerve fibers with infra-red laser and monitoring their degradation and regeneration. In summary, our excision-free optical biopsy technique is ideal for longitudinal microscopic analysis of animal skin and skin innervations in vivo and can be applied widely in preclinical models of chronic pain, allergies, skin cancers and a variety of dermatological disorders.

High-content cell imaging based on fluorescent protein reporters has recently been used to track the transcriptional activities of multiple genes under different external stimuli for extended periods. This technology enhances our ability to discover treatment-induced regulatory mechanisms, temporally order their onsets and recognize their relationships. To fully realize these possibilities and explore their potential in biological and pharmaceutical applications, we introduce a new data processing procedure to extract information about the dynamics of cell processes based on this technology. The proposed procedure contains two parts: (1) image processing, where the fluorescent images are processed to identify individual cells and allow their transcriptional activity levels to be quantified; and (2) data representation, where the extracted time course data are summarized and represented in a way that facilitates efficient evaluation. Experiments show that the proposed procedure achieves fast and robust image segmentation with sufficient accuracy. The extracted cellular dynamics are highly reproducible and sensitive enough to detect subtle activity differences and identify mechanisms responding to selected perturbations. This method should be able to help biologists identify the alterations of cellular mechanisms that allow drug candidates to change cell behavior and thereby improve the efficiency of drug discovery and treatment design.

Speckles have been considered ubiquitous in all scattering-based coherent imaging technologies. However, as an optical-absorption-based coherent imaging technology, photoacoustic (PA) tomography (PAT) suppresses speckles by building up prominent boundary signals. We theoretically study the dependence of PAT speckles on the boundary roughness, which is quantified by the root-mean-squared value and the correlation length of the boundary height. Both the speckle visibility and the correlation coefficient between the reconstructed and actual boundaries are quantified. If the root-mean-squared height fluctuation is much greater than, and the height correlation length is much smaller than the imaging resolution, the reconstructed boundaries become fully developed speckles. In other words, speckle formation requires large uncorrelated height fluctuations within the resolution cell. The first- and second-order statistics of PAT speckles are also studied experimentally. While the amplitude of the speckles follows a Gaussian distribution, the autocorrelation of the speckle patterns tracks that of the system point spread function.

Ventilation with enhanced fractions of O₂ (hyperoxia) is a common and necessary treatment for hypoxemia in patients with lung failure, but prolonged exposure to hyperoxia causes lung injury. Ischemia-reperfusion (IR) injury of lung tissue is common in lung transplant or crush injury to the chest. These conditions are associated with apoptosis and decreased survival of lung tissue. The objective of this work is to use cryoimaging to evaluate the effect of exposure to hyperoxia and IR injury on lung tissue mitochondrial redox state in rats. The autofluorescent mitochondrial metabolic coenzymes nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are electron carriers in ATP generation. These intrinsic fluorophores were imaged for rat lungs using low-temperature fluorescence imaging (cryoimaging). Perfused lungs from four groups of rats were studied: normoxia (control), control perfused with an mitochondrial complex IV inhibitor (potassium cyanide, KCN), rats exposed to hyperoxia (85% O₂) for seven days, and from rats subjected to lung IR in vivo 24 hours prior to study. Each lung was sectioned sequentially in the transverse direction, and the images were used to reconstruct a three-dimensional (3-D) rendering. In KCN perfused lungs the respiratory chain was more reduced, whereas hyperoxic and IR lung tissue have a more oxidized respiratory chain than control lung tissue, consistent with previously measured mitochondrial dysfunction in both hyperoxic and IR lungs.

Segmentation of optical coherence tomography (OCT) cross-sectional structural images is important for assisting ophthalmologists in clinical decision making in terms of both diagnosis and treatment. We present an automatic approach for segmenting intramacular layers in Fourier domain optical coherence tomography (FD-OCT) images using a searching strategy based on locally weighted gradient extrema, coupled with an error-removing technique based on statistical error estimation. A two-step denoising preprocess in different directions is also employed to suppress random speckle noise while preserving the layer boundary as intact as possible. The algorithms are tested on the FD-OCT volume images obtained from four normal subjects, which successfully identify the boundaries of seven physiological layers, consistent with the results based on manual determination of macular OCT images.

We develop a label-free optical technique to image and discriminate undifferentiated human embryonic stem cells (hESCs) from their differentiating progenies in vitro. Using intrinsic cellular fluorophores, we perform fluorescence lifetime microscopy (FLIM) and phasor analysis to obtain hESC metabolic signatures. We identify two optical biomarkers to define the differentiation status of hESCs: Nicotinamide adenine dinucleotide (NADH) and lipid droplet-associated granules (LDAGs). These granules have a unique lifetime signature and could be formed by the interaction of reactive oxygen species and unsaturated metabolic precursor that are known to be abundant in hESC. Changes in the relative concentrations of these two intrinsic biomarkers allow for the discrimination of undifferentiated hESCs from differentiating hESCs. During early hESC differentiation we show that NADH concentrations increase, while the concentration of LDAGs decrease. These results are in agreement with a decrease in oxidative phosphorylation rate. Single-cell phasor FLIM signatures reveal an increased heterogeneity in the metabolic states of differentiating H9 and H1 hESC colonies. This technique is a promising noninvasive tool to monitor hESC metabolism during differentiation, which can have applications in high throughput analysis, drug screening, functional metabolomics and induced pluripotent stem cell generation.

The aged human eye is commonly affected by presbyopia, and therefore, it gradually loses its capability to form images of objects placed at different distances. Extended depth of focus (EDOF) imaging elements can overcome this inability, despite the introduction of a certain amount of aberration. This paper evaluates the EDOF imaging performance of the so-called peacock eye phase diffractive element, which focuses an incident plane wave into a segment of the optical axis and explores the element's potential use for ophthalmic presbyopia compensation optics. Two designs of the element are analyzed: the single peacock eye, which produces one focal segment along the axis, and the double peacock eye, which is a spatially multiplexed element that produces two focal segments with partial overlapping along the axis. The performances of the peacock eye elements are compared with those of multifocal lenses through numerical simulations as well as optical experiments in the image space. The results demonstrate that the peacock eye elements form sharper images along the focal segment than the multifocal lenses and, therefore, are more suitable for presbyopia compensation. The extreme points of the depth of field in the object space, which represent the remote and the near object points, have been experimentally obtained for both the single and the double peacock eye optical elements. The double peacock eye element has better imaging quality for relatively short and intermediate distances than the single peacock eye, whereas the latter seems better for far distance vision.

In near-infrared spectroscopy (NIRS) for monitoring brain activity and cerebral functional connectivity, the effect of superficial tissue on NIRS signals needs to be considered. Although some methods for determining the effect of scalp and brain have been proposed, direct validation of the methods has been difficult because the actual absorption changes cannot be known. In response to this problem, we developed a dynamic phantom that mimics hemoglobin changes in superficial and deep tissues, thus allowing us to experimentally validate the methods. Two absorber layers are independently driven with two one-axis automatic stages. We can use the phantom to design any type of waveform (e.g., brain activity or systemic fluctuation) of absorption change, which can then be reproducibly measured. To determine the effectiveness of the phantom, we used it for a multiple source-detector distance measurement. We also investigated the performance of a subtraction method with a short-distance regressor. The most accurate lower-layer change was obtained when a shortest-distance channel was used. Furthermore, when an independent component analysis was applied to the same data, the extracted components were in good agreement with the actual signals. These results demonstrate that the proposed phantom can be used for evaluating methods of discriminating the effects of superficial tissue.

Optical spectroscopy has been proposed as an accurate and low-cost alternative for detection of cervical intraepithelial neoplasia. We previously published an algorithm using optical spectroscopy as an adjunct to colposcopy and found good accuracy (sensitivity = 1.00 [95% confidence interval (CI) = 0.92 to 1.00], specificity = 0.71 [95% CI = 0.62 to 0.79]). Those results used measurements taken by expert colposcopists as well as the colposcopy diagnosis. In this study, we trained and tested an algorithm for the detection of cervical intraepithelial neoplasia (i.e., identifying those patients who had histology reading CIN 2 or worse) that did not include the colposcopic diagnosis. Furthermore, we explored the interaction between spectroscopy and colposcopy, examining the importance of probe placement expertise. The colposcopic diagnosis-independent spectroscopy algorithm had a sensitivity of 0.98 (95% CI = 0.89 to 1.00) and a specificity of 0.62 (95% CI = 0.52 to 0.71). The difference in the partial area under the ROC curves between spectroscopy with and without the colposcopic diagnosis was statistically significant at the patient level (p = 0.05) but not the site level (p = 0.13). The results suggest that the device has high accuracy over a wide range of provider accuracy and hence could plausibly be implemented by providers with limited training.

The goal of this research is to use the information contained in the mechanisms occurring during the laser tattoo removal process. We simultaneously employed a laser-beam deflection probe (LBDP) to measure the shock wave and a camera to detect the plasma radiation, both originating from a high-intensity laser-pulse interaction with a tattoo. The experiments were performed in vitro (skin phantoms), ex vivo (marking tattoos on pig skin), and in vivo (professional and amateur decorative tattoos). The LBDP signal includes the information about the energy released during the interaction and indicates textural changes in the skin, which are specific for different skin and tattoo conditions. Using both sensors, we evaluated a measurement of threshold for skin damage and studied the effect of multiple pulses. In vivo results show that a prepulse reduces the interaction strength and that a single strong pulse produces better removal results.

Model based data analysis of diffuse reflectance spectroscopy data enables the estimation of optical and structural tissue parameters. The aim of this study was to present an inverse Monte Carlo method based on spectra from two source-detector distances (0.4 and 1.2 mm), using a multilayered tissue model. The tissue model variables include geometrical properties, light scattering properties, tissue chromophores such as melanin and hemoglobin, oxygen saturation and average vessel diameter. The method utilizes a small set of presimulated Monte Carlo data for combinations of different levels of epidermal thickness and tissue scattering. The path length distributions in the different layers are stored and the effect of the other parameters is added in the post-processing. The accuracy of the method was evaluated using Monte Carlo simulations of tissue-like models containing discrete blood vessels, evaluating blood tissue fraction and oxygenation. It was also compared to a homogeneous model. The multilayer model performed better than the homogeneous model and all tissue parameters significantly improved spectral fitting. Recorded in vivo spectra were fitted well at both distances, which we previously found was not possible with a homogeneous model. No absolute intensity calibration is needed and the algorithm is fast enough for real-time processing.

Polarization-gated spectroscopy is an established method to depth-selectively interrogate the structural properties of biological tissue. We employ this method in vivo in the azoxymethane (AOM)-treated rat model to monitor the morphological changes that occur in the field of a tumor during early carcinogenesis. The results demonstrate a statistically significant change in the shape of the refractive-index correlation function for AOM-treated rats versus saline-treated controls. Since refractive index is linearly proportional to mass density, these refractive-index changes can be directly linked to alterations in the spatial distribution patterns of macromolecular density. Furthermore, we found that alterations in the shape of the refractive-index correlation function shape were an indicator of both present and future risk of tumor development. These results suggest that noninvasive measurement of the shape of the refractive-index correlation function could be a promising marker of early cancer development.

Femtosecond lasers have been widely used in laser surgery as an instrument for contact-free tissue removal of hard dental, restorative materials, and osseous tissues, complementing conventional drilling or cutting tools. In order to obtain a laser system that provides an ablation efficiency comparable to mechanical instruments, the laser pulse rate must be maximal without causing thermal damage. The aim of this study was to compare the different morphological characteristics of the hard tissue after exposure to lasers operating in the femtosecond pulse regime. Two different kinds of samples were irradiated: dentin from human extracted teeth and bovine femur samples. Different procedures were applied, while paying special care to preserving the structures. The incubation factor S was calculated to be 0.788±0.004 for the bovine femur bone. These results indicate that the incubation effect is still substantial during the femtosecond laser ablation of hard tissues. The plasma-induced ablation has reduced side effects, i.e., we observe less thermal and mechanical damage when using a superficial femtosecond laser irradiation close to the threshold conditions. In the femtosecond regime, the morphology characteristics of the cavity were strongly influenced by the change of the effective number of pulses.

The introduction of new techniques for endodontic procedures requires the analysis of the biomechanical behavior of dental structures. Digital speckle shearing pattern interferometry (DSSPI) is a nondestructive optical measuring technique that allows one to directly quantify deformations in teeth that are subjected to stress. DSSPI technique was applied to measure small deformations caused by flexion in different types of teeth. The test was carried out both before and after endodontic treatment with the ProTaper method in order to evaluate the variation of dental elasticity, taking into the account the type of tooth and the endodontic treatment. The results obtained show that dental elasticity, established by means of the apparent Young's modulus, before and after the endodontic treatment, differs between incisors and premolars. The endodontic process does not affect dental elasticity (p>0.7). Specifically, 57.1% of central incisors and 56.3% of second premolars slightly increase their elasticity after the endodontic process. In turn, 42.9% of central incisors and 43.7% of second premolars slightly decrease elasticity. The endodontic treatment especially affects the "neutral fibre"; therefore, there is little influence on elasticity by flexion. However, after finishing the process, the channel was restored with material, which can slightly increase tooth elasticity in some cases.

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