Adaptive processing for noise attenuation in laser speckle contrast imaging.

BACKGROUND AND OBJECTIVE: Blood vessel visualization is an essential task to treat and evaluate diseases such as port-wine stain. Laser Speckle Contrast Imaging (LSCI) have applications in the analysis of the microvasculature. However, it is often limited to superficial depths because the tissue among skin and microvasculature introduces noise in the image. To analyze microvasculature, traditional LSCI methods compute a Contrast Image (CI) by using a shifting window of fixed size and shape, which is inadequate in images with structures different types of morphologies in it, as happens in LSCI. This work aims to reduce the noise in the CIs to improve the visualization of blood vessels at high depths (> 300 µ m). METHODS: The proposed method processes the CIs with analysis windows that change their size and shape for each pixel to compute the contrast representation with pixels more representatives to the region. RESULTS: We performed experiments varying the depth of the blood vessels, the number of frames required to compute the representation, and the blood flow in the blood vessel. We looked for an improvement in the Contrast to Noise Ratio (CNR) in the periphery of the blood vessels using an analysis of variance. Finding that the adaptive processing of the contrast images allows a significant noise attenuation, translated into a better visualization of blood vessels. An average CNR of 2.62 ± 1 and 5.26 ± 1.7 was reached for in-vitro and in-vivo tests respectively, which is higher in comparison with traditional LSCI approaches. CONCLUSIONS: The results, backed by the measured CNR, obtained a noise reduction in the CIs, this means a better temporal and spatial resolution. The proposed awK method can obtain an image with better quality than the state-of-the-art methods using fewer frames.

Optothermal generation, trapping, and manipulation of microbubbles.

The most common approach to optically generate and manipulate bubbles in liquids involves temperature gradients induced by CW lasers. In this work, we present a method to accomplish both the generation of microbubbles and their 3D manipulation in ethanol through optothermal forces. These forces are triggered by light absorption from a nanosecond pulsed laser (λ = 532 nm) at silver nanoparticles photodeposited at the distal end of a multimode optical fiber. Light absorbed from each laser pulse quickly heats up the silver-ethanol interface beyond the ethanol critical-point (∼ 243 °C) before the heat diffuses through the liquid. Therefore, the liquid achieves a metastable state and owing to spontaneous nucleation converted to a vapor bubble attached to the optical fiber. The bubble grows with semi-spherical shape producing a counterjet in the final stage of the collapse. This jet reaches the hot nanoparticles vaporizing almost immediately and ejecting a microbubble. This microbubble-generation mechanism takes place with every laser pulse (10 kHz repetition rate) leading to the generation of a microbubbles stream. The microbubbles' velocities decrease as they move away from the optical fiber and eventually coalesce forming a larger bubble. The larger bubble is attracted to the optical fiber by the Marangoni force once it reaches a critical size while being continuously fed with each bubble of the microbubbles stream. The balance of the optothermal forces owing to the laser-pulse drives the 3D manipulation of the main bubble. A complete characterization of the trapping conditions is provided in this paper.

Theoretical and experimental study of acoustic waves generated by thermocavitation and its application in the generation of liquid jets.

Numerical simulations using the Finite-Difference Time-Domain method were used to study the propagation of an acoustic wave within a truncated ellipsoidal cavity. Based in our simulations, a fluidic device was designed and fabricated using a 3D printer in order to focus an acoustic wave more efficiently and expel a liquid jet. The device consists of an ellipsoidal shaped chamber filled with a highly absorbent solution at the operating wavelength (1064 nm) in order to create a vapor bubble using a continuous wavelength laser. The bubble rapidly expands and collapses emitting an acoustic wave that propagates inside the cavity, which was measured by using a needle hydrophone. The bubble collapse, and source of the acoustic wave, occurs in one focus of the cavity and the acoustic wave is focused on the other one, expelling a liquid jet to the exterior. The physical mechanism of the liquid jet generation is momentum transfer from the acoustic wave, which is strongly focused due to the geometry of the cavity. This mechanism is different to the methods that uses pulsed lasers for the same purpose. The maximum speed of the generated liquid microjets was approximately 20 m/s. One potential application of this fluidic device can be found for inkjet printing, coating and, maybe the most attractive, for drug delivery.

Efficient in vitro photodynamic inactivation using repetitive light energy density on Candida albicans and Trichophyton mentagrophytes.

BACKGROUND: We compared the effectiveness of a single irradiation vs repetitive irradiation of light, for in vitro photodynamic inactivation (PDI) of Candida albicans and Trichophyton mentagrophytes, by using methylene blue (MB) and rose bengal (RB) as photosensitizers (PS). METHODS: MB from 5 to 60 µM and RB from 0.5 to 10 µM, with energy densities from 10 to 60 J/cm2, were tested in C. albicans. We further optimize the PDI by reducing the light energy density and PS concentration for the single irradiation experiments by using repetitive doses (two and three times). MB was tested in C. albicans and T. mentagrophytes, and RB was tested in C. albicans. RESULTS: MB-PDI and RB-PDI in C. albicans significantly reduced the number of colony-forming units per milliliter (CFU/mL) when compared to the control groups. Using a single irradiation, over 99% growth inhibition of C. albicans was obtained with MB at 20 µM-60 J/cm2, and with RB at 1 µM-30 J/cm2 and 5 µM-10 J/cm2. With repetitive doses, similar results were obtained by reducing several times the light energy density and the PS concentration for C. albicans and T. mentagrophytes. CONCLUSIONS: The results showed that RB was more effective than MB for C. albicans inactivation. In addition, it is possible to significantly reduce the amount of PS and light energy density requirements by using repetitive irradiations in both genera tested. It makes the technique less invasive and could reduce the side effects in people extremely sensitive to the PS or the light.

Controllable direction of liquid jets generated by thermocavitation within a droplet.

A high-velocity fluid stream ejected from an orifice or nozzle is a common mechanism to produce liquid jets in inkjet printers or to produce sprays among other applications. In the present research, we show the generation of liquid jets of controllable direction produced within a sessile water droplet by thermocavitation. The jets are driven by an acoustic shock wave emitted by the collapse of a hemispherical vapor bubble at the liquid-solid/substrate interface. The generated shock wave is reflected at the liquid-air interface due to acoustic impedance mismatch generating multiple reflections inside the droplet. During each reflection, a force is exerted on the interface driving the jets. Depending on the position of the generation of the bubble within the droplet, the mechanical energy of the shock wave is focused on different regions at the liquid-air interface, ejecting cylindrical liquid jets at different angles. The ejected jet angle dependence is explained by a simple ray tracing model of the propagation of the acoustic shock wave inside the droplet.

Improving the Outcomes of Organs Obtained From Controlled Donation After Circulatory Death Donors Using Abdominal Normothermic Regional Perfusion.

The use of donation after circulatory death (DCD) has increased significantly during the past decade. However, warm ischemia results in a greater risk for transplantation. Indeed, controlled DCD (cDCD) was associated with inferior outcomes compared with donation after brain death. The use of abdominal normothermic regional perfusion (nRP) to restore blood flow before organ recovery in cDCD has been proposed as better than rapid recovery to reverse the effect of ischemia and improve recipients' outcome. Here, the first Spanish series using abdominal nRP as an in situ conditioning method is reported. A specific methodology to avoid restoring circulation to the brain after death determination is described. Twenty-seven cDCD donors underwent abdominal nRP during at least 60 min. Thirty-seven kidneys, 11 livers, six bilateral lungs, and one pancreas were transplanted. The 1-year death-censored kidney survival was 91%, and delayed graft function rate was 27%. The 1-year liver survival rate was 90.1% with no cases of ischemic cholangiopathy. Transplanted lungs and pancreas exhibited primary function. The use of nRP may represent an advance to increase the number and quality of grafts in cDCD. Poor results in cDCD livers could be reversed with nRP. Concerns about restoring brain circulation after death are easily solved.

Trapping and manipulation of microparticles using laser-induced convection currents and photophoresis.

In this work we demonstrate optical trapping and manipulation of microparticles suspended in water due to laser-induced convection currents. Convection currents are generated due to laser light absorption in an hydrogenated amorphous silicon (a:Si-H) thin film. The particles are dragged towards the beam's center by the convection currents (Stokes drag force) allowing trapping with powers as low as 0.8 mW. However, for powers >3 mW trapped particles form a ring around the beam due to two competing forces: Stokes drag and thermo-photophoretic forces. Additionally, we show that dynamic beam shaping can be used to trap and manipulate multiple particles by photophotophoresis without the need of lithographically created resistive heaters.

Simple correction factor for laser speckle imaging of flow dynamics.

One of the major constraints facing laser speckle imaging for blood-flow measurement is reliable measurement of the correlation time (τ(C)) of the back-scattered light and, hence, the blood's speed in blood vessels. In this Letter, we present a new model expression for integrated speckle contrast, which accounts not only for temporal integration but spatial integration, too, due to the finite size of the pixel of the CCD camera; as a result, we find that a correction factor should be introduced to the measured speckle contrast to properly determine τ(C); otherwise, the measured blood's speed is overestimated. Experimental results support our theoretical model.

Effects of speckle/pixel size ratio on temporal and spatial speckle-contrast analysis of dynamic scattering systems: Implications for measurements of blood-flow dynamics.

Laser Speckle Contrast Imaging (LSCI) is an optical technique used to generate blood flow maps with high spatial and temporal resolution. It is well known that in LSCI, the speckle size must exceed the Nyquist criterion to maximize the speckle's pattern contrast. In this work, we study experimentally the effect of speckle-pixel size ratio not only in dynamic speckle contrast, but also on the calculation of the relative flow speed for temporal and spatial analysis. Our data suggest that the temporal LSCI algorithm is more accurate at assessing the relative changes in flow speed than the spatial algorithm.

Fast optical source for quantum key distribution based on semiconductor optical amplifiers.

A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as 1.14×10⁻² while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.

Medidas de resucitación precoz durante la pandemia de gripe A (H1N1). ¿Se beneficiaron los pacientes? / Resuscitation measures early in the pandemic of influenza A (H1N1). HE benefited the patients?

Objetivo. Evaluar el impacto del uso de un protocolo de medidas de detección y resucitación precoz durante la pandemia de gripe A (H1N1) sobre el ingreso de pacientes en el Servicio de Terapia Intensiva (STI). Diseño. Estudio de observación y retrospectivo de pacientes críticos. Ámbito. Un STI médico-quirúrgico. Pacientes. Adultos que ingresaron en el STI desde el Servicio de Urgencia entre el 28 de abril de 2009 y el 4 de septiembre de 2009. Variables de interés principal. Sexo, edad, comorbilidades, APACHE II, SOFA al ingreso en el STI, sintomatología clínica, imágenes radiográficas, necesidad de asistencia respiratoria mecánica (ARM), ácido láctico (AL), creatinfosfoquinasa (CPK), lactato deshidrogenasa (LDH), leucocitosis, saturación de O2 (SatO2) y PaO2/FiO2 al ingresar en el STI, presión al final de la espiración (PEEP), días de ARM, tratamiento con oseltamivir (dosis/tiempo), aislamiento bacteriológico y virológico en secreción bronquial, tratamiento con corticoides, estadía en el STI y mortalidad. Resultados. Se incluyeron 13 pacientes que ingresaron en el STI durante el período estudiado; media de la edad 45 ± 3; mujeres: 8 (61,5%), comorbilidades (n = 7, 53,8%): enfermedad pulmonar obstructiva crónica (n = 3), diabetes (n = 2), insuficiencia cardíaca (n = 1), cirrosis (n = 1), APACHE II: 18, SOFA: 9 ± 2. La sintomatología clínica predominante fue la siguiente: fiebre (n = 13, 100%), tos (n = 11, 84,6%), disnea (n = 9, 69,2%), infiltrados intersticiales (5/13, 38,4%), opacidades alveolares (6/13, 46,1%), opacidades mixtas (2/13, 15,3%), cuatro cuadrantes (9/13, 69,2%) y dos cuadrantes (4/13, 30,7%); se hallaron los siguientes valores medios: AL 25 mg/dl, CPK 480 U/l (p <0,05), LDH 2100 U/l (p <0,001), leucocitosis 12.500 mm3 , PEEP 18 cm H2O, SatO2 <91% (n = 11, 84,6%), PaO2/FiO2 <150 (n = 11, 84,6%), necesidad de ARM (n = 11, 84,6%), días de ARM 9,5 ± 3 días. Oseltamivir: dosis 150 mg/12 h; aislamiento bacteriológico: neumococo (n = 7, 53,8%); aislamiento virológico: H1N1 (n = 5, 38,4%); duración: 9,5 ± 3 días, corticoides (n = 8, 61,5%). Tiempo en el STI: 11 ± 4. No hubo muertes.    Conclusión. La aplicación de un protocolo inicial en el que además se evalúo la gravedad benefició la correcta evaluación y resucitación inicial en el grupo estudiado. Los valores de CPK y de LDH se acompañaron de hipoxemia severa y mayor compromiso pulmonar en la radiología de tórax(AU)

Objective. To evaluate the impact of a protocol for screening and resuscitation measures during the pandemic H1N1 on patients´ admission to the Intensive Care Unit (ICU). Design. Retrospective observational study of critically ill patients. Place. A medical-surgical Intensive Care Unit (ICU). Patients. Adults admitted to the ICU from the Emergency Department from April 28th 2009 to September 4th 2009. Variables of primary interest. Sex, age, comorbidities, APACHE II, SOFA at admission to the ICU, clinical symptoms, radiographic images, need for mechanical ventilation (MV), lactic acid (AL), creatine kinase (CPK), lactate dehydrogenase (LDH), leukocytosis, O2 saturation (O2Sat) and PaO2/FiO2 at admission to the ICU, end-expiratory pressure (PEEP), days of MV (DMV), oseltamivir (dose/time), bacteriological and virological isolations in bronchial secretions, corticosteroid treatment, stay in the ICU and mortality. Results. We included 13 patients admitted to ICU during the study period; mean age: 45 ± 3; females: 8 (61.5%); comorbidities (n = 7, 53.8%): COPD (n = 3), diabetes (n = 2), heart failure (n = 1), cirrhosis (n = 1), APACHE II: 18, SOFA: 9 ±-2. Clinical symptoms were: fever (n = 13, 100%), cough (n = 11, 84.6%), dyspnea (n = 9, 69.2%), interstitial infiltrates (5/13, 38.4%), alveolar opacities (6/13, 46.1%), mixed opacities (2/13, 15.3%), four quadrants (9/13, 69.2%) and two quadrants (4/13, 30.7%), average measures: AL 25 mg/dL, CPK 480 U/L (p <0.05), LDH 2,100 U/L (p <0.001), leukocytosis 12,500 mm3 , PEEP 18 cm H2O, O2Sat <91% (n = 11, 84.6%), PaO2/FiO2 <150 (n = 11, 84.6%), MV (n = 11, 84.6%), DMV: 9.5 ± 3; oseltamivir: 150 mg/12 hours; bacteriological isolation (Pneumococcus: n = 7, 53.8%), virological isolation (H1N1: n = 5, 38.4%); length: 9.5 ± 3 days, corticosteroids (n = 8, 61.5%); ICU stay 11 ± 4; no deaths were reported. Conclusion. The application of a protocol in which severity was also evaluated benefited in the correct assessment and initial resuscitation. The values of CPK and LDH were associated with severe hypoxemia and lung involvement in the thorax xrays. (AU)

Integration of image exposure time into a modified laser speckle imaging method.

Speckle-based methods have been developed to characterize tissue blood flow and perfusion. One such method, called modified laser speckle imaging (mLSI), enables computation of blood flow maps with relatively high spatial resolution. Although it is known that the sensitivity and noise in LSI measurements depend on image exposure time, a fundamental disadvantage of mLSI is that it does not take into account this parameter. In this work, we integrate the exposure time into the mLSI method and provide experimental support of our approach with measurements from an in vitro flow phantom.

Time-resolved analysis of cavitation induced by CW lasers in absorbing liquids.

We present novel results on thermocavitation using a CW medium-power near infrared laser (lambda=975 nm) focused into a saturated copper nitrate saline solution. Due to the large absorption coefficient at the laser wavelength, the solution can be heated to its superheat limit (T(sh) approximately 270-300 degrees C). Superheated water undergoes explosive phase transition around T(sh) producing approximately half-hemispheric bubbles (gamma approximately 0.5) in close contact with the substrate. We report the temporal dynamic of the cavitation bubble, which is much shorter than previously reported under similar conditions. It was found that the bubble radius and pressure wave amplitude emitted on bubble collapse decreases exponentially with the power laser. Thermocavitation can be a useful tool for the generation of ultrasonic waves and controlled ablation for use in high-resolution lithography.

Polarization-controlled contrasted images using dye-doped nematic liquid crystals.

We explore the polarization dependence of the nonlinear response of a planar nematic liquid crystal cell doped with 1% wt of methyl red dye. The results obtained show that the refractive index change can be switched from a positive value to a negative one as the polarization of the beam changes from parallel to perpendicular with respect to the rubbing direction. This property is exploited in a phase contrast system, where a dynamic phase filter is photoinduced in a liquid crystal cell placed in the system's Fourier plane. Real-time contrast inversion in the resulting images is demonstrated.

Estudio de concordancia diagnóstica en Dermatología entre Atención Primaria y Especializada en el área de salud de un hospital de referencia / Diagnostic agreement between primary care physicians and dermatologists in the health area of a referral hospital

Introducción. Las enfermedades dermatológicas representan un porcentaje importante de los motivos de consulta en Atención Primaria. En nuestro ámbito la creciente demanda de consulta y la consecuente aparición de listas de espera hace necesario establecer algún tipo de criterio para una adecuada derivación. Pretendemos en este estudio describir las características de la derivación desde los centros de Atención Primaria a las consultas de Dermatología, así como la correlación existente entre el motivo de consulta y el diagnóstico dermatológico final. Material y métodos. Se recogen los datos de 3.164 pacientes atendidos por primera vez en nuestras consultas de Dermatología, durante 1998, clasificándose según el centro de Atención Primaria de procedencia y el motivo de consulta. Se realiza un estudio de concordancia entre el motivo de consulta y el diagnóstico dermatológico final, averiguando para cada caso el valor predictivo positivo, la sensibilidad diagnóstica y el índice de concordancia kappa. Resultados. La concordancia diagnóstica global ha sido del 65,52 %. Se detecta por parte del médico de Atención Primaria un sobrediagnóstico de las enfermedades por papilomavirus y una sensibilidad diagnóstica muy baja en patologías como el carcinoma basocelular y las queratosis seborreicas. Conclusiones. Se hace necesario insistir en la formación de los médicos de Atención Primaria, en una adecuada derivación desde los centros de Atención Primaria y en potenciar un buen modelo de interconsulta con el especialista (AU)

Introduction. Skin diseases account for a high proportion of presenting complaints in primary health care. In Spain, the growing demand for consultations and the resulting longer waiting lists make it necessary to establish criteria for appropriate referrals to a specialist. This study aimed to investigate the characteristics of referrals from primary care centers to dermatology specialists as well as the correlation between the presenting complaint and the final dermatologic diagnosis. Patients and methods. We collected data from 3164 patients seen for the first time by dermatologists in our specialist service during 1998. Patients were stratified according to the referring primary health care center and the reason for referral. The agreement between the presenting complaint and the final dermatologic diagnosis was studied. For each dermatologic condition, the positive predictive value, diagnostic sensitivity, and k statistic were calculated. Results. The overall diagnostic agreement was 65.52 %. Primary care physicians were found to overdiagnose diseases caused by papillomavirus and the diagnostic sensitivity was very low for diseases such as basal cell carcinoma and seborrheic keratosis. Conclusions. It is necessary to insist on training primary care physicians, ensuring appropriate referral from primary health care clinics, and promoting an effective dialogue with the specialist (AU)

Estudio de las derivaciones preferentes al Servicio de Dermatología de un hospital de referencia / Study of urgent referrals to the dermatology department of a referral hospital

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[Diagnostic agreement between primary care physicians and dermatologists in the health area of a referral hospital]. / Estudio de concordancia diagnóstica en Dermatología entre Atención Primaria y Especializada en el área de salud de un hospital de referencia.

INTRODUCTION: Skin diseases account for a high proportion of presenting complaints in primary health care. In Spain, the growing demand for consultations and the resulting longer waiting lists make it necessary to establish criteria for appropriate referrals to a specialist. This study aimed to investigate the characteristics of referrals from primary care centers to dermatology specialists as well as the correlation between the presenting complaint and the final dermatologic diagnosis. PATIENTS AND METHODS: We collected data from 3164 patients seen for the first time by dermatologists in our specialist service during 1998. Patients were stratified according to the referring primary health care center and the reason for referral. The agreement between the presenting complaint and the final dermatologic diagnosis was studied. For each dermatologic condition, the positive predictive value, diagnostic sensitivity, and k statistic were calculated. RESULTS: The overall diagnostic agreement was 65.52 %. Primary care physicians were found to over diagnose diseases caused by papillomavirus and the diagnostic sensitivity was very low for diseases such as basal cell carcinoma and seborrheic keratosis. CONCLUSIONS: It is necessary to insist on training primary care physicians, ensuring appropriate referral from primary health care clinics, and promoting an effective dialogue with the specialist.

[Analysis of the demand for dermatological care in the immigrant population served by hospital Miguel Servet in Saragossa, Spain]. / Análisis de la demanda asistencial de Dermatología en la población inmigrante del área de salud del Hospital Miguel Servet de Zaragoza.

INTRODUCTION: In recent years there has been an increase in the size of the immigrant population consulting dermatology services in Spain. The aim of this study was to describe the epidemiological characteristics of this sector of the population in the health care area served by Miguel Servet Hospital in Saragossa, Spain. MATERIAL AND METHODS: Data were collected on immigrant patients seen in the dermatology department of our hospital during 2004. Dermatological diagnoses were classified according to the International Classification of Diseases, Ninth Revision, Clinical Modification. Statistical analysis was undertaken using the SPSS statistical package, Access database management software, and Excel spreadsheets. RESULTS: A total of 706 patients were seen, corresponding to approximately 4 % of all first appointments, and more women were seen than men, a difference that was statistically significant. The mean age of the patients was 31 years and there were no statistically significant differences in age between the sexes. In order of frequency, the most common countries of origin of the patients were Ecuador, Colombia, Romania, Morocco, Gambia, Guinea, and Senegal. The most common skin diseases in this population group were infectious diseases, in particular mycoses, followed by viral diseases and pyodermatitis, as well as sexually transmitted diseases. In all cases, the incidence of the disease was higher than in the Spanish population. CONCLUSIONS: An appropriate knowledge of dermatological diseases in this population group is necessary both to obtain correct diagnosis and to develop preventative measures for imported diseases.