juan pichardo

Many photoacoustic imaging systems use back projection-based image reconstruction algorithms to estimate photoacoustic source locations from the time-of-flight pressure information collected by either a scanned single transducer or an array of stationary transducer elements. Accurate image reconstruction requires that the transducer(s) locations relative to the imaged volume and the transducer(s) sensitivity distribution within the imaged volume be accurately known. The objective of this work was to develop a method for estimation of the sensitivity distribution of a transducer array. Our approach was to capture for each transducer element the response to a photoacoustic point source that was robotically scanned throughout the imaging volume. The temporally resolved photoacoustic signal was then processed to obtain the relative transducer sensitivity at the source location. We performed a scan over a transducer array fabricated in our laboratory that consisted of twelve 3 mm element...

ABSTRACT Optical Coherence Tomography (OCT) is an imaging technique to get cross-sectional images with resolutions of a few microns and deep penetration in tissue of some millimeters. For many years OCT has been applied to analyze different human tissues like eyes, skin, teeth, urinary bladders, gastrointestinal, respiratory or genitourinary tracts and recently breast cancer tissues have been studied. Many of these tissues are composed specially of lipids and collagen, proteins which cause multiple light scattering (MLS) reducing significantly the optical depth and the contrast of OCT imaging. So, one of the big challenges of this technique is to acquire images with good contrast. Gold nanoparticles (NPs) exhibit interesting optical properties due to its plasmon resonance frequency. Optical absorbance is strong when gold NPs have dimension under 50 nm, but over this size optical scattering becomes dominant. In this work we show the preliminary results of the use of gold NPs as a contrast medium to enhance the OCT images quality. Our experimental results show which type of particles (morphology and size) present the best enhancement in the region of 1325 nm which corresponds to the central wavelength source excitation. All our experiments were carried out with a commercial OCT (thorlabs) system and our NPs were tested in water and gel phantoms.

ABSTRACT We propose the use of branched gold nanoparticles (B-GNPs) as a contrast agent for optical coherence tomography (OCT) imaging. Our results show that even when the central source of our OCT (1325 nm) is too far from the maximum peak of the plasmon resonance, branched nanoparticles scatter light very efficiently at this wavelength. B-GNPs were tested as a contrast agent in water and agarose-TiO2 tissue phantoms; the estimated increments in contrast were 9.19 dB and 15.07 dB for branched nanoparticles in water with concentrations of 2.2 × 109 NPs/mL and 6.6 × 109 NPs/mL, respectively, while for agarose-TiO2 tissue phantoms the estimated value was 3.17 dB. These results show the promising application of B-GNPs as a contrast agent for tissue imaging using OCT, not only for sources at 1325nm but also at other central wavelengths located between 800 and 1000 nm.

In this work, fast and reliable spectroscopic methods in combination with chemometric tools were developed for simultaneous determination of Acetylsalicylic Acid, Acetaminophen and Caffeine in commercial formulations. For the first-order multivariate calibration method (PLS-1), calibration and validation sets were constructed with 23 and 10 samples respectively according to a central composite design. The Micro-Raman, FTIR-HATR and UV absorption spectra in

ABSTRACT A brief review of the state of the art in quantitative photoacoustic spectroscopy for thermally thick samples is presented. We demonstrate that it is possible to find an analytical expression that allows studying the optical absorption coefficient by combining the amplitude and phase of the photoacoustic signal, obtained from the heat diffusion model, for thermally thick samples.

In this work the two-photon activity of nanoparticles obtained from a fluorene monomer (M1) and its cross-conjugated polymer (P1) is reported. Aqueous suspensions of M1 and P1 nanoparticles prepared through the reprecipitation method exhibited maximum two-photon absorption (TPA) cross-sections of 84 and 9860 GM (1 GM = 10(-50) cm(4) s) at 740 nm, respectively, and a fluorescence quantum yield of ~1. Such a two-photon activity was practically equal with respect to that for molecular solutions of M1 and P1. These materials were then successfully encapsulated into silica nanoparticles to provide bio-compatibly. A lung cancer cell line (A549) and a human cervical cancer cell line (HeLa cells) were incubated with our fluorescent silica nanoparticles to carry out two-photon imaging. By means of these studies we demonstrate that optimized nonlinear optical polymers loaded in silica nanoparticles can be used as efficient probes with low cytotoxicity and good photostability for two-photon fluorescence microscopy. To the best of our knowledge, studies concerning polymer-doped silica nanoparticles exhibiting large two-photon activity have not been reported in the literature.

More than 60 million people in the United States and 23 million people in Mexico probably are infected with the Toxoplasma parasite, but very few have symptoms because the immune system usually keeps the parasite from causing illness. However, for people whose immune system is compromised, the consequences can be fatal. Toxoplasmosis is detected indirectly by different serological tests, where the sample requires a previous preparation. We analyze the feasibility to use Raman spectroscopy and principal component analysis (PCA) as an alternative method to detect the presence or absence of antibodies IgG (immunoglobulin G), IgM (immunoglobulin M), and IgA (immunoglobulin A), against Toxoplasma gondii, in a simple and fast way, in samples of human colostrum from a group of volunteers who were in contact with the parasite and others who were not in contact with the parasite.