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This work presents a temporal analysis of the metabolic evolution of patients with a diagnosis of diabetic foot diseaseand a group of control individuals, this as a response of an external stimulus. For this purpose, the asymmetry and thermal response index between the infrared images in the basal state and images acquired at different evolution times post-stimulus was calculated. As a result, a difference in the temporal metabolic behavior of patients and disease-free subjects was observed

We introduce a proof of concept for multimode random laser (RL) emission with fresh whole blood (WB) as the active medium. The experimental principle is adapted from RL emission using rhodamine 6G (R6G). We achieved conditions for fresh WB to fluoresce with stochastic amplification of stimulated emission of radiation. The random conditions are placed with S i O 2 particles, suspended in isotonic solvent. The results we report are for: (1) R6G-RL, with 2 nm bandwidth centered at 567 nm, and (2) RL emission for WB at 969 nm and 437 nm, of sub-3 nm bandwidth. For validation purposes, we show that the pumping energy threshold for RL emission from blood is consistent with R6G-RL.

The purpose of the study we report is to extract radiometric information, distributed in three regions of interest (ROI’s), from the legs of patients clinically diagnosed with Diabetes Mellitus Type II (DM2) and a control group. We analyze the asymmetry of the thermal radiation emitted from the legs through two approaches: 1) comparing the higher and lower temperatures of the thermal probability distribution of each leg and 2) computing an asymmetry index based on the Spearman’s correlation coefficient; that for both groups and two views: anterior (AV) and posterior (PV). The results indicate the existence of radiometric differences between the studied groups. From the former analysis, we get that the sensitivity and specificity over the 1st, 2nd and 3rd ROI at AV are 78% and 86%, respectively. For the posterior view are 89% and 83%, respectively. Instead, by using the Spearman’s correlation coefficient, we built up an index related to the thermal asymmetry, whose (sensitivity, specificity) pair for the 1st, 2nd and 3rd ROI, (83%, 67%), (81%, 94%), and (72%, 78%), respectively.

In this work we introduce a standard framework to represent abnormal conditions related to metabolic syndrome (MetS). This framework is based on percentiles represented by reference ellipses constructed from a reference population, and it allows us to observe drifts respect references caused by MetS.

We report a methodology to analyze data extracted from infrared images. These pictures show the lower limbs of a cohort of individuals belonging to, (1) voluntary controls and (2) patients diagnosed with diabetes mellitus type II. The analysis is presented in terms of Cross Entropy and temperature distributions; both using the associated thermal histograms. The temperature analysis is placed in terms of comparing the extreme values of dS/dQ, for controls and patients. In this analysis for the frontal view, the values of specificity and sensitivity calculated were 77.77% and 91.66%, respectively. For the back view, the specificity and sensitivity obtained were 88.8% and 83.3%, respectively. Instead of that, the cross-entropy analysis is placed in the modality of self-referencing. In this part of the study we obtained the coefficient of asymmetry and thermal response (ATR). The values of specificity and sensitivity for the ATR quotient in both cases were 83.3%. The results of both studies have a significant correlation with glucose (p < 0.01) and HbA1c (p < 0.01). It means that both approaches have statistical correspondence. By means of the Mann-Whitney U test, for independent samples, we get that the characteristic parameters we analyze can be differentiated among the populations of interest with a significance of p < 0.05. This suggests that both studies show consistency with the clinical diagnosis; exhibiting clear differences between control and patient groups.

Nuevos desarrollos científicos y tecnológicos permiten generar soluciones de tratamiento y diagnóstico de bajo costo y no invasivos; para que estas solucionespuedan ser implementadas de forma exitosa es necesario que consideren el contexto de uso y los factores humanos.En este sentido, en los últimos años se ha dado más importancia al valor del diseño como agente de innovación, involucrando a esta disciplina desde la fase de investigación y desarrollo en nuevos esquemas de colaboración abierta entre universidades, empresas, centros de investigación y hospitales. En esta nueva constelación, el diseñador debe comprender los requerimientos de todos los actores involucrados: científicos, médicos, ingenieros, personal de salud, pacientes y familiares. Para que el diseñador pueda definir los requerimientos de diseño en este tipo de proyectos, se propone un enfoque a partir de la investigación a través del diseño (research through design).Este artículo presenta como caso de estudio el proyecto “Utilidad diagnóstica de termografía para pie diabético con enfermedad micro o macrovascular”, una colaboración multidisciplinaria entre el Hospital General de México, el Instituto de Ciencias Aplicadas y Tecnología y el Centro de Investigaciones de Diseño Industrial de la Universidad Nacional Autónoma de México (unam). A través del caso de estudio se expone la importancia de la investigación por medio del diseño dentro de proyectos en el área médica, así como sus principales diferencias con otros métodos de investigación y el cambio de enfoque que requiere porparte del diseñador.

In this work, we solve the problem of modeling the generation of an acoustic pulse produced by the incidence of a pulsed laser light upon an elastic material. Our concern is about the heat transport during the absorption of electromagnetic radiation. We assume that the pulse duration is of the order of nanoseconds, and asses if under these conditions the contribution of the heat transport in the sample is an essential consideration in the description of the phenomena or if we can ignore it in the model. We begin with the energy balance analysis over the initial interaction of radiation with matter in the context of the formulation Meixner-Prigonine which is called the linear irreversible thermodynamics to describe the induced temperature field. Then we carry a momentum balance which yields the macroscopic elasticity equations with a heat source for the induced pressure field. Once established the equations for temperature and displacement fields, we solve them for the one-dimensional case, showing that the induced pressure has two components, one fast component and one slow component which is due to heat transport in the sample, which is one of the main contributions of the paper.

A study based on the general solution of the one-dimensional photoacoustic (PA) wave equation for an acoustic plane source is presented. This study relies on obtaining the impulse response of the PA system considering a heating function proportional to the Lambert–Beer law and spatially bounded by a rectangle function. The PA pressure is obtained by convoluting the impulse response with the temporal profile of the exciting pulse of light. With the obtained solution, it is possible to comprise, on a single expression, the PA pressure profile for optically thin samples (whose dimensions are smaller than the optical absorption length) and optically opaque samples (whose dimensions are larger than the optical absorption length). In the limit of weak absorption, the solution is in good agreement with the one for a uniform distribution of energy. Also, a study of the dependence of the acoustic pressure with the duration of the laser pulse is included.

A challenging issue in photoacoustic biomedical imaging is to take into account the presence of dispersive acoustic media, since these are prone to induce amplitude attenuation and scattering of the photoacoustic frequency components. These perturbations are largely the cause for which the photoacoustic tomographic image reconstruction from projections lacks a plane-wave transport formalism. Attending this problem, we further develop an analytic formalism of the transport and its numerical implementation accounting for dispersive acoustic media. We differentiate three variations of an acoustically perturbing media. Our object of interest is a numerical description of the light absorption map of a coronal human breast image. Then, we analyze conditions for which the propagation of photoacoustic perturbations can obey the generalized Heaviside telegraph equation. In addition, we provide a study of the causality consistency of the wave propagation models. We observe transport implications due to the presence of dispersive acoustic media and derive model adjustments that include attenuation and diffusion approximations within the two-dimensional forward problem. Next, we restore the inverse problem description with the deduced perturbation components. Finally, we solve the nonlinear inverse problem with a numerical strategy for a filtered backprojection reconstruction. At a stage prior to the image reconstruction, we compensate for the effect of acoustic attenuation and diffusion to calculate the inversions of the wave perturbations located within the projections. In this way, we manage to significantly reduce reconstruction artifacts. In consequence, we prevent the use of some additional image processing of noise reduction. We demonstrate a feasible strategy on how to solve the stated nonlinear inverse problem of photoacoustic tomography accounting for dispersive acoustic media. In particular, we emphasize efforts to achieve an analytical description, and thus an algorithm is placed, for imaged sound perturbations to be cleaned from acoustic scattering in a simplified manner.

Diabetic foot disease (DFD) is one of the major complications of the Diabetes Mellitus; within which the Diabetic Neurophaty (DN) and the peripheral vascular disease (PVD) (arteriosclerosis mainly) are among the most important causal factors in the pathogenesis of diabetic foot ulcers. Once ulcers are present, the risk of limb amputation is extremely high. A side effect from the DN and PVD is the change of the rate release of metabolic heat at quite specific areas. Here we present early advancements on the pattern recognition on infrared imagenology (thermography) picturing the altered distribution of the metabolic heat release driven by the DFD with arteriosclerosis. The thermograms are compared against corresponding simple-radiology images. As part of the analysis, we apply a computational algorithm to obtain the emission temperature averages, and we qualify the pattern distribution via a quantitative marker. Since the pathology of the limbs does not develop in a symmetric manner, then it is expected th...

We describe new experiments in which the signals induced inside a solid conductor by external excitation using nanosecond long pulsed laser radiation are detected using a pyro-electric material. From the data obtained, it is shown that there is a previously unreported ‘early’ or ‘fast’ signal which propagates inside the solid at a speed greater than that reported for sound in the same media. This signal is observed in addition to the usually observed thermal and acoustic waves that travel at the speed of sound in the same media. We demonstrate that this signal cannot be adequately accounted for by existing theories of thermo-elastic wave propagation in solids.

We model theoretically the voltage response to an acoustic pulse of a multilayer system forming a low noise capacitive sensor including a Polyvinylidene Fluoride piezoelectric film. First we model a generic piezoelectric detector consisting of a piezoelectric film between two metallic electrodes that are the responsible to convert the acoustic signal into a voltage signal. Then we calculate the pressure-to-voltage transfer function for a N-layer piezo-electric capacitor detector, allowing to study the effects of the electrode and protective layers thickness in typical layered piezoelectric sensors. The derived transfer function, when multiplied by the Fourier transform of the incident acoustic pulse, gives the voltage electric response in the frequency domain. An important concern regarding the transfer function is that it may have zeros at specific frequencies, and thus inverting the voltage Fourier transform of the pulse to recover the pressure signal in the time domain is not always, in principle, possible. Our formulas can be used to predict the existence and locations of such zeroes. We illustrate the use of the transfer function by predicting the electric signal generated at a multilayer piezoelectric sensor to an ultrasonic pulse generated photoacoustically by a laser pulse at a three media system with impedance mismatch. This theoretical calculations are compared with our own experimental measurements.

We investigate the spectral response of capacitive sensors with 28 μm thick Polyvinylidene Fluoride (PVDF) films operating in the piezoelectric mode. We present spectra of signals obtained from laser-induced photoacoustic emissions in several materials. We examine the sensor response to direct laser pulses and to ultrasonic signals generated by laser pulses interacting with polyvinyl alcohol (PVA) phantoms, neoprene slabs and a composite of PVA phantom with a hidden slab of neoprene. We exhibit the sensor's sensitivity to the phantom thickness, affecting the amplitude and bandwidth of the ultrasonic output signal. The sensors fabricated and tested under water achieved an operational frequency bandwidth ranging from 1 to 50 MHz.

Stimulated emission in pulsed dye lasers was characterized in several experimental conditions by analyzing the changes in the acoustic signals generated in a dye solution, with the dye laser cavity either active or inhibited (i.e., by blocking the optical path or misaligning of the optical components). Pump energy threshold, optimum dye concentration, tuning range and maximum-emission wavelength of a rhodamine 6G dye laser were measured by this method. An approximate model for the photoacoustic signal generation consistent with the experiments is presented.

This study examines one of the open problems yet to solve in photoacoustic tomography: How to prepare photoacoustic signals to ensure interpretation as projection data? The main part of this difficulty is related to the setting of the linear photoacoustic transport model. Notably errors are due to the discrepancy between the mathematical reconstruction and the physical realization: Tomographic image reconstruction from projections require a linear acquisition system. However in practice, the physical reality presents different non-linear phenomena. In account of this incompatibility, it was our purpose to provide some advancement in signal processing for dealing the projection issue while considering different perspectives in the interpretation of the transport model to be applied in a broader manner. Numerical examples are analyzed in detail and unveil the foundations for photoacoustic signal processing methodologies focused on the task of tomographic image reconstruction from projections.

We present experimental results related to the manufacturing of phantoms based on polyvinyl-alcohol (PVA) mixedwith SiO2, graphite and Ag nanoparticles. These phantoms are dummy representations of the human tissue of thebreast gland. We focus our attention on the representation of the optical and the mechanical properties of the actualbiological healthy tissue and of that representing a hidden cancer tumor (lesion). The quality of the samples is testedby ultrasonic imaging and laser induced photothermal (PT) detection technique. From the former test, the mechanicalcontrast that one can achieve is apparent. Instead, the laser detection technique makes it possible to determine thatthe optical contrast is achievable. For the laser induced PT method we register the so-called photothermal amplitudes,rather known as photoacoustic (PA) signals. These are the ultimate expression of laser-induced bursts ofphotothermal processes, whose engine is the fraction of the optically absorbed energy that decays through nonradiativechannels. In our case we look for the conditions at which the PT phenomena are produced by a hiddendummy-tumor alone; meaning that the output signals are nearly free from substantial contributions from the bulk of thephantom. This is so as to mimic the actual mechanical and optical absorption performance of breast tissue with aninner cancer tumor. From the ultrasound images one can see how apparent the resemblance with the actual humantissue is.

Basados en el efecto fotoacústico pulsado, se desarrolló un dispositivo experimental para generar imágenesbidimensionales de muestras ópticamente opacas ocultas en un medio turbio. El medio turbio se hizo de agar ynanopartículas monodispersas, con estos materiales indujimos una absorción y esparcimiento óptico semejante al delos tejidos humanos. La señal PA se genera por la absorción óptica del la muestra; una vez producida viaja a travésdel medio esparsor. Las propiedades de ópticas de la muestra así como la forma de éste definen la amplitud y formade la señal PA. En el sistema fotoacústico se utilizaron pulsos láser de Nd: YAG de 10 ns, con frecuencia derepetición de 10Hz, y longitud de onda de 1064 nm. Las señales generadas fueron registradas por un transductorultrasónico con frecuencia de corte de 10 MHz. Tanto la muestra como el medio esparsor se rotaron para obtener 36proyecciones, las cuales fueron utilizadas para alimentar un algoritmo de reconstrucción de imágenes basado en latransformada de Radon. Como resultado se obtuvieron imágenes tomográficas 2D de tres muestras distintas.

International audience; The absorption of modulated or pulsed light leads to non-radiative processes that generate a photo-acoustic (PA) wave. The standard model assumes that the amplitude of the PA wave is proportional to the optical absorption. In previous reports we have demonstrated experimentally and theoretically that from this proportionality: 1) one can obtain quantitative measurements of optical properties of dielectric thin films, and 2) that there may exist a relationship between the amplitude of the PA wave and the thermal conductivity of a given sample. Here we present analytic results that clearly show that the optical absorption and the thermal conductivity are coupled to the amplitude of the photoacoustic wave in the modulated regime and that this correlation holds for any type of macroscopic optical and thermal transparency. In particular, the present analysis shows that the product of the optical absorption and the thermal conductivity is related to the PA-amplitude via a partition function.

We propose the use of a structured planar mirror as the way to obtain the physical conditions for which the combination of an evanescent field and a surface plasmon potential would result in an atom-trap well located at similar to 0.6 mu m above the mirror's surface. We present calculations from which we obtain a well depth slightly bigger than 7 mu K. The configuration and calculations we present are for a single trap, however, there would appear to be no restrictions to extend this idea to a two-dimensional matrixlike array of traps, hinting on the possibility for tailored design of latticelike trap structures.

In photoacoustic imaging, the signal attenuation is a well-known source of artifacts over the image reconstruction. It is recognized that this is caused by optical absorption effects and by the ultrasound broadband scattering. However, the sound dispersion is generally neglected, although it appears notably in thick or heterogeneous tissues. In the present Letter, we give an experimental example in which both attenuation and sound dispersion are dealt with as relevant features to be taken into consideration. An analytic perspective of these perturbations leads us to a waveform transport-model extension that provides a linear description of the induced acoustic effects. We find a near match between the theoretical predictions and the experimental results in the frequency domain. These outcomes approximate projection data that represent forward solutions in photoacoustic image reconstruction.

We investigate theoretically and experimentally the performance of low-noise capacitive sensors based on polyvinylidene fluoride (PVDF) piezoelectric films to sense water-borne ultrasound signals for their use in photoacoustic tomography. We derive a mechanical-to-electrical transfer function of a piezoelectric capacitor sensor of infinite lateral dimensions and arbitrary thickness assuming that an ultrasound wave is normally incident. Then, we analyse the response for obliquely incident ultrasound waves on sensors of large but finite area and derive an expression for the angle dependence of the sensor's response. We also present experimental different measurements with home-made sensors and compare with our theoretical model. We present measurements of the sensors' response to harmonic signals of variable frequency in the range from 0.5 to 50 MHz and of the angular-dependence factor at 6 MHz. Additionally, because of the scope of interest in these kinds of sensors, we also tested the sensors' response for photoacoustic perturbations. These are generated by laser pulses from directly impinging on the sensor and from ultrasound perturbations produced on neoprene by the same kind of laser pulses and then travelling through water to the sensor.

Augusto GarcIa-Valenzuela, J. M. Saniger, and C. GarcIa-SegundoCentro de Instrumentos, UniversidadNacional Autonoma de Mexico, Cd. Universitaria A.P. 70-186,Mexico D.F. 04510, Mexico.ABSTRACTWe investigate theoretically the limit to the resolution imposed by the fundamental optical noises in film-based chemicalsensors interrogated by optical reflectometry. We suggest a dynamic reflectometry approach as a possible technique toachieve the ultimate resolution. We fmd that a theoretical resolution around 1010

We present an experimental analysis of the angular distribution of the emission of a random laser (RL) operating in the diffusive regime (∼1% volume fraction of scatterers). The RL ensemble was made of silica particles suspended in a 1:1 methanol:water matrix with Rhodamine 6G dye as the active medium. We found that, for specific pumping-energy-dependent scattering strength, the RL spectrum reached stable features that were angularly preserved. From the analysis, we propose that this defines a novel parametric condition that may well be the equivalent of the RL critical volume, as proposed by Letokhov.

We investigate the spectral response to ultrasound waves in water of low-noise capacitive sensors based on PVDF polymer piezoelectric films. First, we analyze theoretically the mechanical-to-electrical transduction as a function of the frequency of ultrasonic signals and derive an analytic expression of the sensor's transfer function. Then we present experimental results of the frequency response of a home-made PDVF in water to test signals from 1 to 20 MHz induced by a commercial hydrophone powered by a signal generator and compare with our theoretical model.

We present an experimental and theoretical method to simultaneously obtain the optical dispersion curves and the thermal properties of thin film samples. From the experimental and analytical perspectives, we establish the physical conditions to validate this novel approach. Similarly, the method is tested on thin films of aluminium nitride (AlN) deposited on quartz and crystalline silicon substrates. The experimental set-up is that used for the open photoacoustic cell pseudo-transmittance spectroscopy (OPC-PATS). The sample is illuminated with modulated light as a pre-condition to induce and detect photothermal waves. The amplitude of these waves is proportional to the optical absorption and to the thermal properties of the sample. This is displayed in the so-called pseudo-transmittance spectra that we report here. Theoretically, we extend a previously reported self-consistent method to provide, in addition to the refractive index and the extinction coefficient spectral curves, the ratio of the thermal to the optical transparency and the thermal conductivity. Although the current analysis is applied to the optical range, the conditions of the method are such that it can readily be extended to other wavelengths.

Random lasers varying concentration and size of SiO2 scatterers were analyzed. We report on the dependence of the spectral features (wavelength and full width at half maximum) on the size and concentration of the scatterers.

We present experimental results of a random laser in a cylindrical cell. With this configuration we manage to exhibit that the laser's lasing modes, the lasing threshold and the peak wavelength exhibit angular dependence.

We investigate, theoretically and experimentally, a simple technique for sensing very small changes on the index of refraction. The technique consists on measuring the derivative of the reflectivity near the critical angle by modulating the angle of incidence and measuring the AC amplitude of the reflectivity variations. Analytical results on the reflection of a Gaussian beam near the critical angle are used to derive simple formulas for the sensitivity, dynamic range, and the optical-limit to the resolution. Experimental results validating the theory are presented. We found an experimental resolution of about 1×10 −6 , while the ultimate theoretical resolution calculated for our experimental setup was 5.7×10 −8 . This technique may be a useful alternative in designing a refractive index probe for some applications.