Rolando J. González-Peña

Monitoring of the action of drugs in melanoma cells by dynamic laser speckle.

Abstract. This work presents the development of a protocol based on the dynamic laser speckle designed to monitor the reaction of cancer cells of line MEL-RC08 to the application of the drug Colcemid in two different concentrations: 0.2 and 0.4  μg/mL. The protocol was designed using the forward scattering approach with an He-Ne laser of 632.8 nm illuminating the samples, a control, and two variations of Colcemid, being monitored along 8 h. The data were analyzed numerically in the time and in the frequency domain, and the results presented the ability of the technique to monitor the action of the drug, particularly Colcemid (0.4  μg/mL).

Infrared thermography is useful for ruling out fractures in paediatric emergencies

AbstractMusculoskeletal injuries are a leading cause of paediatric injuries and emergency department visits in Western countries. Diagnosis usually involves radiography, but this exposes children without fractures to unnecessary ionising radiation. We explored whether infrared thermography could provide a viable alternative in trauma cases. We compared radiography and thermal images of 133 children who had been diagnosed with a trauma injury in the emergency unit of a Spanish hospital. As well as the thermal variables in the literature, we introduced a new quantifier variable, the size of the lesion. Decision tree models were built to assess the technique’s accuracy in diagnosing whether a bone had been fractured or not. Infrared thermography had a sensitivity of 0.91, a specificity of 0.88 and a negative predictive value of 0.95. The new lesion size variable introduced appeared to be of main importance to the discriminatory power of the method. Conclusion: The high negative predictive value of infrared thermography suggests that it is a promising method for ruling out fractures.

Accuracy in dynamic laser speckle: optimum size of speckles for temporal and frequency analyses

Abstract. The dynamic laser-speckle phenomenon has been used as a potential tool to monitor the activity of many biological and nonbiological samples; however, a key tailoring of the experimental configuration must be taken into account to avoid wrong measurements, since the general rules addressed to speckle as information cannot be directly adopted in dynamic laser-speckle monitoring. The speckle/pixel size ratio is provided by the f-number and by the magnification of the macro lens, and attention is mainly directed toward adjusting a speckle/pixel ratio higher than 1. However, a speckle/pixel ratio much higher than one does not mean an optimum adjustment. This work tested different apertures with fixed magnification yielding to monitor a drying paint process. The outcomes were evaluated in the time and frequency domains. The highest speckle/pixel size ratio was not the best to monitor the process using the dynamic laser speckle under frequency analysis. Tailoring of the devices must take into account the optimum speckle/pixel size ratio, which could vary depending on the application, and the known Nyquist theorem cannot be considered as a sufficient condition since the setup of the optical camera with its macro and iris must also be adjusted in accordance with the frequency response.

Dynamic laser speckle analyzed considering inhomogeneities in the biological sample

Abstract. Dynamic laser speckle phenomenon allows a contactless and nondestructive way to monitor biological changes that are quantified by second-order statistics applied in the images in time using a secondary matrix known as time history of the speckle pattern (THSP). To avoid being time consuming, the traditional way to build the THSP restricts the data to a line or column. Our hypothesis is that the spatial restriction of the information could compromise the results, particularly when undesirable and unexpected optical inhomogeneities occur, such as in cell culture media. It tested a spatial random approach to collect the points to form a THSP. Cells in a culture medium and in drying paint, representing homogeneous samples in different levels, were tested, and a comparison with the traditional method was carried out. An alternative random selection based on a Gaussian distribution around a desired position was also presented. The results showed that the traditional protocol presented higher variation than the outcomes using the random method. The higher the inhomogeneity of the activity map, the higher the efficiency of the proposed method using random points. The Gaussian distribution proved to be useful when there was a well-defined area to monitor.

A Portable Dynamic Laser Speckle System for Sensing Long-Term Changes Caused by Treatments in Painting Conservation

Dynamic laser speckle (DLS) is used as a reliable sensor of activity for all types of materials. Traditional applications are based on high-rate captures (usually greater than 10 frames-per-second, fps). Even for drying processes in conservation treatments, where there is a high level of activity in the first moments after the application and slower activity after some minutes or hours, the process is based on the acquisition of images at a time rate that is the same in moments of high and low activity. In this work, we present an alternative approach to track the drying process of protective layers and other painting conservation processes that take a long time to reduce their levels of activity. We illuminate, using three different wavelength lasers, a temporary protector (cyclododecane) and a varnish, and monitor them using a low fps rate during long-term drying. The results are compared to the traditional method. This work also presents a monitoring method that uses portable equipment. The results present the feasibility of using the portable device and show the improved sensitivity of the dynamic laser speckle when sensing the long-term process for drying cyclododecane and varnish in conservation.

Determination of strain and stress distribution on shearwalls by using the speckle photography technique

Abstract Speckle photography (SP) is a powerful tool that is adequate to determine small displacements in micrometer range. This information shows other characteristics of structure deformation under loads and can be determined as stress and strain distribution. In this paper we present the results of the application of the SP technique used to study the behaviour of discontinuities in a shearwall model. These structural elements are very important to the stability of buildings. The displacement whole field around the discontinuities and loading points was determined using the pointwise method. This allows us to determine stress distribution at the point of interest by means of the suitable equations. We also present the stress distribution obtained through the finite element method in order to compare the results obtained by means of these two techniques. Good correspondence was found between the displacements determined by both techniques (r=0.982) and also between the stress values we obtained.

Dynamic Laser Speckle Technique Sensing Long-Term Changes Caused by Painting Treatments in Restauration of Paintings

Dynamic laser speckle is applied as a reliable sensor of activity in all sort of material. 1 Traditional applications are based on a time rate that is usually higher than 10 frames-per-second 2 (FPS). Even in drying processes, where there is a high activity in the first moments after the painting 3 and a slow activity after some minutes or hours, the process is based on the acquisition of images in 4 a time rate that is the same in both moments of high and low activity. In this work, we present an 5 alternative approach to follow the drying of paint and the other processes related to restauration of 6 paintings that takes long-term to reduce the activity. We illuminated, using three different 7 wavelength lasers, an accelerator (Cyclododecane) and a varnish used in restauration of paintings 8 and monitor them at long-term drying using an alternative fps, comparing the results to the 9 traditional method. The work also presents a way to do the monitoring using a portable equipment. 10 The results present the feasibility to use the portable device and show the improvement in the 11 sensitivity of the dynamic laser speckle to sense long-term process regarding the drying of 12 Cyclododecane and Varnish used in restauration. 13

Infrared Thermography Versus Conventional Image Techniques in Pediatrics: Cases Study

The use of infrared thermography has been shown to be useful in several areas. Its applicability in medicine is based on the fact that the skin emits spontaneously and continuously infrared radiation, whose body distribution is symmetrical in a healthy individual. Infrared thermography can offer an alternative to X-rays for a large number of diseases related to peripheral vascularization. In these cases, infrared thermography can avoid the use of biologically ionizing radiation. This is of special interest in pediatric patients who, because of their age, are more radiosensitive.

Infrared Thermography Protocol for the Diagnosis and Monitoring of the Diabetic Foot: Preliminary Results

The diabetic foot, according to the International Consensus on the Diabetic Foot, is an infection, ulceration or destruction of the deep tissues related to neurological alterations and peripheral vascular disease in the lower limbs [1]. This pathology represents an important problem of public health because the affected patients can suffer amputations and even the death [2].

ζ-potential determination using a ZetaMeter-Dynamic Speckle assembly

Electrophoretic mobility and ζ-potential are important physical parameters for the characterization of micro- and nanosystems. In this communication we describe a new method for determining the ζ-potential through the assembly of two well known techniques: free electrophoresis and Dynamic Speckle. When coherent light passes through a fluid having scattering centres, the far field interference originates a speckled image. If the scattering centres are contained within the cylindrical electrophoresis cell of a ZetaMeter and are forced to move in an orderly way under the action of an external electric field, the time variation of the light intensity in the far field speckle images follows a temporal autocorrelation function g(τ). The corresponding correlation time can then be obtained and related with the velocity, from which the electrophoretic mobility and the ζ-potential of the scattering centres can be determined. We have applied this method to microparticles, like natural air-floated silica and two classes of bioceramics, hydroxyapatite and biphasic calcium phosphate. For comparison, we analysed the same samples in parallel using a commercial Zetasizer Nano from Malvern Instruments. The values of ζ-potential determined using the two techniques were the same within ~3% error. These results validate our new method as a useful and efficient alternative for ζ-potential determination of particles, at least within the micrometer scale.