Snapshot multispectral oximetry using image replication and birefringent spectrometry

This thesis describes the improvements to the image replicating imaging spectrometer (IRIS) and the development of novel applications in the field of oximetry. IRIS is a snapshot multispectral device with a high transmission output and no need of inversion for data recovering, hence, with high signal-to-noise ratio (SNR). IRIS shows great versatility due to the possibility of choosing multiple contiguous or non-contiguous wavelengths inside its free spectral range. IRIS uses a set of waveplates and Wollaston prisms to demultiplex the spectral information of an object and replicate the image of such object in different wavelengths. The birefringent nature of IRIS means that different wavelengths are separated by the Wollaston prisms with different angles, introducing multiple images of the same object. In addition, the spectral transmission function shows multiple spectral sidelobes that contaminate each IRIS band with light belonging to other wavelengths. These issues can lower the performance of IRIS as a multispectral imaging device. In this thesis, these problems were assessed with the introduction of a filter plate array placed in the image plane of the optical system. This filter array is a set of narrow-band filters (Full Width Half Maximum (FWHM) =10 ± 2 nm ) that removes undesired wavelengths from each IRIS band. Since the spectral transmission of IRIS is replicated along the free spectral range, the filters can be designed to match any of the present spectral lobes in IRIS. The design and fabrication of a filter array enhance the performance of IRIS as a multispectral imaging device: it allows wavelength selection and improves spectral and spatial image quality. The design and manufacture of the corresponding filter holder and camera adapter were critical in terms of offering an easy filter-camera implementation. The filter plate allowed the removal of other dispersed wavelengths by the Wollaston prisms, improving image registration between the set of spectral images created by IRIS, and so, improving the quality of the registered spectral 3-D cube. The implemented improvements on IRIS allow high quality, calibration-free oximetry using eight different wavelengths optimised for oximetry. Two main experiments were performed: 1) Using an inverted microscopy interfaced with IRIS and a linear spectral unmixing technique, we measured the deoxygenation of single horse red blood cells (RBC) in vitro in real time. The oximetry was performed with a subcellular spatial resolution of 0.5 μ m , a temporal resolution of 30 Hz, and an accuracy (standard error of the mean) of ± 1.1% in oxygen saturation. 2) Eight-wavelength calibration-free retinal oximetry performed in nine healthy subjects demonstrated an increase in the stability of the oxygen saturation measurements along retinal vessels when compared with more traditional analysis methods such as two wavelengths oximetry. The stability was measured as the standard deviation along the retinal vessels of the nine subjects and was found to be ∼ 3% in oxygen saturation for eight-wavelengths oximetry and ∼ 5% in oxygen saturation for two-wavelengths oximetry. A modified physical model was used to improve the characterization of light propagation through the eye, retina, and blood vessels by applying a set of feasible physiological assumptions. This model was optimised by an algorithm which solves for the different variables involved in the retinal vessels transmissions in order to accurately calculate the oxygen saturation. The oximetry algorithm was applied in retinal vessels, in collaboration in vivo on rat spinal cord to assess hypoxia in inflammatory diseases such as multiple sclerosis and rheumatoid arthritis and on mice legs to assess hypoxia on autoimmune diseases. A third experiment using a microscope interfaced with IRIS was performed. The experiment aimed to replicate laminar flow conditions observed in retinal vessels and to calculate oxygen diffusion between adjacent streams of blood with different oxygen saturation. For this purpose a PDMS multichannel flow cell with cross sections of 40x100 μm was designed and fabricated allowing us to replicate conditions found in retinal blood vessels. Laminar flow was replicated but the experiment failed in calculating oxygen diffusion due to flaws in the experiment. The experiment with the results and recommendations on how to improve it can be found in Apendix B for future researcher

Model and neural control of the depth of anesthesia during surgery

At present, the experimentation of anesthetic drugs on patients requires a regulation protocol, and the response of each patient to several doses of entry drug must be well known. Therefore, the development of pharmacological dose control systems is a promising field of research in anesthesiology. In this paper it has been developed a non-linear compartmental pharmacokinetic-pharmacodynamical model which describes the anesthesia depth effect on a sufficiently reliable way over a set of patients with the depth effect quantified by the Bi-Spectral Index. Afterwards, an Artificial Neural Network (ANN) predictive controller has been designed based on the depth of anesthesia model so as to keep the patient on the optimum condition while he undergoes surgical treatment. For the purpose of quantifying the efficiency of the neural predictive controller, a classical proportional-integral-derivative controller has also been developed to compare both strategies. Results show the superior performance of predictive neural controller during Bi- Spectral Index reference tracking.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Role of endogenous cannabinoids in the control of basal ganglia activity

The cannabinoid system is a novel intercellular signaling system that plays a prominent role, among others, in the control of basal ganglia function. This finding can be concluded from the data obtained in different series of anatomical, biochemical, electrophysiological and pharmacological studies. These data demonstrated: (i) that the basal ganglia contain high levels of endocannabinoids and their receptors, mainly including the cannabinoid CB1 receptor subtype but also a related receptor type, the vanilloid TRPV1 receptor; (ii) that the activation or the blockade of this system produces important changes in motor behavior, changes that are originated as a consequence of interactions of the cannabinoid system with various classic neurotransmitters such as GABA, dopamine or glutamate; and (iii) the occurrence of marked changes in specific elements of the cannabinoid signaling system in various basal ganglia disorders, with emphasis in the induction/upregulation of the cannabinoid CB2 receptor subtype. This large evidence relating endocannabinoids and their receptors to the function of the basal ganglia, both in the healthy and the pathological brain, has provided support for the idea that cannabinoid-based medicines, with selectivity for different targets of the cannabinoid signaling system (synthetic enzymes, receptors, inactivation system), might have therapeutic potential to alleviate symptoms and/or provide neuroprotection in basal ganglia disorders, in particular Parkinson´s disease and Huntington´s chorea. The present chapter will review the knowledge on this issue trying to establish the future lines for the research on the therapeutic potential of the cannabinoid signaling system in basal ganglia disorders.peer-reviewe

Assessment of acute mild hypoxia on retinal oxygen saturation using snapshot retinal oximetry

Purpose.: To study the effect of acute mild hypoxia on retinal oxygen saturation. Methods.: Spectral retinal images were acquired under normoxic and hypoxic conditions for 10 healthy human volunteers (six male, four female, aged 25 ± 5 years [mean ± SD]) using a modified fundus camera fitted with an image-replicating imaging spectrometer (IRIS). Acute, mild hypoxia was induced by changing the oxygen saturation of inhaled air from 21% to 15% using a hypoxia generator with subjects breathing the hypoxic gas mixture for 10 minutes. Peripheral arterial oxygen saturation of the subjects was monitored using fingertip-pulse oximetry. Images were processed to calculate oxygen saturation, arteriovenous difference in oxygen saturation, and vessel diameter. Data are presented as mean ± SD and were analyzed using paired sample t-test with significance accepted at P < 0.05. Results.: The retinal arterial and venous oxygen saturation was 98.5% ± 1.6% and 70.7% ± 2.7% during normoxia. A reduction in the fraction of inspired oxygen resulted in a decline (P < 0.001) in both retinal-arterial and venous oxygen saturation to 90.3% ± 2.0% and 62.4% ± 2.2%, respectively. The arteriovenous oxygen saturation difference in normoxia (27.8% ± 2.9%) and hypoxia (27.9% ± 2.1%) did not change. Retinal arteriolar and venular diameters increased (P < 0.001) by 4% and 3%, respectively, under hypoxia. Conclusions.: The acute inhalation of a hypoxic gas mixture resulted in a decline in both retinal-arterial and venous saturation, while arteriovenous oxygen difference was maintained with an accompanying significant increase in retinal vessel diameter. This may suggest an autoregulatory response to acute mild hypoxia

A multispectral microscope for in vivo oximetry of rat dorsal spinal cord vasculature

Quantification of blood oxygen saturation (SO2) in vivo is essential for understanding the pathogenesis of diseases in which hypoxia is thought to play a role, including inflammatory disorders such as multiple sclerosis (MS) and rheumatoid arthritis (RA). We describe a low-cost multispectral microscope and oximetry technique for calibration-free absolute oximetry of surgically exposed blood vessels in vivo. We imaged the vasculature of the dorsal spinal cord in healthy rats, and varied inspired oxygen (FiO2) in order to evaluate the sensitivity of the imaging system to changes in SO2. The venous SO2 was calculated as 67.8  ±  10.4% (average  ±  standard deviation), increasing to 83.1  ±  11.6% under hyperoxic conditions (100% FiO2) and returning to 67.4  ±  10.9% for a second normoxic period; the venous SO2 was 50.9  ±  15.5% and 29.2  ±  24.6% during subsequent hypoxic states (18% and 15% FiO2 respectively). We discuss the design and performance of our multispectral imaging system, and the future scope for extending this oximetry technique to quantification of hypoxia in inflamed tissue

Remote sensing of blood oxygenation using red-eye pupil reflection

To access publisher's full text version of this article click on the hyperlink belowObjective: To develop a technique for remote sensing of systemic blood oxygenation using red-eye pupil reflection. Approach: The ratio of the intensities of light from the bright pupil reflections at oxygen sensitive and isosbestic wavelengths is shown to be sensitive to the oxygenation of blood in the eye. A conventional retinal camera, fitted with an image-replicating imaging spectrometer, was used at standoff range to record snapshot spectral images of the face and eyes at eight different wavelengths. In our pilot study we measured optical-density ratios (ODRs) of pupil reflections at wavelengths of 780 nm and 800 nm, simultaneous with pulse oximetry, for ten healthy human subjects under conditions of normoxia and mild hypoxia (15% oxygen). The low absorption at these infrared wavelengths localises the sensing to the choroid. We propose that this can be used for as a proxy for systemic oximetry. Main results: A significant reduction (P < 0.001) in ODR of the pupil images was observed during hypoxia and returned to baseline on resumption of normoxia. We demonstrate that measurement of the choroidal ODR can be used to detect changes in blood oxygenation that correlate positively with pulse oximetry and with a noise-equivalent oximetry precision of 0.5%. Significance: We describe a new method to remotely and non-invasively sense the oxygen saturation of choroidal blood. The methodology provides a proxy for remote sensing of cerebral and systemic blood oxygenation. We demonstrate the technique at short range but it has potential for systemic oximetry at large standoff ranges

Reforma Educativa en Misiones: organización curricular y prácticas de enseñanza en el campo de las Ciencias Económicas en el Trayecto Profesional de E. 16H375

Este proyecto de investigación se cuestiona sobre la estructura organizativa de la Educación Técnica Profesional en escuelas de la ciudad de Misiones y las características didácticas y pedagógicas que asumen los procesos de enseñanza y aprendizaje en esta modalidad educativa, para el campo de las Ciencias Económicas. La reestructuración del Sistema Educativo supone el establecimiento de acuerdos y redefiniciones al interior de las escuelas, en relación con la norma que propicia la vinculación de la educación, el trabajo y la producción, y la realización de prácticas educativas que permitan a los estudiantes el manejo de tecnologías o brinden la experiencia adecuada a su formación y orientación vocacional. Por ello realizaremos una revisión crítica de las documentaciones, marcos legales y orientaciones curriculares, así como de su impacto en las prácticas educativas desde la perspectiva de los actores, teniendo presente las peculiaridades de esta modalidad formativa

New VVV Survey Globular Cluster Candidates in the Milky Way Bulge

© 2017 The American Astronomical Society. All rights reserved.It is likely that a number of Galactic globular clusters remain to be discovered, especially toward the Galactic bulge. High stellar density combined with high and differential interstellar reddening are the two major problems for finding globular clusters located toward the bulge. We use the deep near-IR photometry of the VISTA Variables in the Vía Láctea (VVV) Survey to search for globular clusters projected toward the Galactic bulge, and hereby report the discovery of 22 new candidate globular clusters. These objects, detected as high density regions in our maps of bulge red giants, are confirmed as globular cluster candidates by their color-magnitude diagrams. We provide their coordinates as well as their near-IR color-magnitude diagrams, from which some basic parameters are derived, such as reddenings and heliocentric distances. The color-magnitude diagrams reveal well defined red giant branches in all cases, often including a prominent red clump. The new globular cluster candidates exhibit a variety of extinctions (0.06 < A Ks < 2.77) and distances (5.3 < D < 9.5 kpc). We also classify the globular cluster candidates into 10 metal-poor and 12 metal-rich clusters, based on the comparison of their color-magnitude diagrams with those of known globular clusters also observed by the VVV Survey. Finally, we argue that the census for Galactic globular clusters still remains incomplete, and that many more candidate globular clusters (particularly the low luminosity ones) await to be found and studied in detail in the central regions of the Milky Way.Peer reviewedFinal Accepted Versio