Browsing by Issue Date, starting with "2019-04-18"
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- Automatic versus semi-automatic method for the striatum specific uptake ratio quantification based on [I-123]FP-CIT SPECT imagesPublication . Elias, Maria; Jorge, Pedro; Figueiredo, Sérgio; Oliveira, Luís; Pereira, Edgar L.The aim of this work was to implement an automatic application (AA) for the quantification of the striatum transaxial slices based on [I-123]FP-CIT SPECT (Single Photon Emission Tomography) images. A sample of 68 subjects with and without pathology was collected from the nuclear medicine department of the Hospital Particular de Almada. In order to compare the striatum specific uptake ratios (SUR), a semi-automatic application (SAA) was also developed allowing manual adjustments by a specialist operator. The obtained results were compared with the DaTSCAN (R) V4 application, from General Electric Healthcare. The experimental results based on SUR demonstrate that the AA can successfully discriminate the healthy patients from the pathological subjects. Additionally, a strong correlation was verified between the AA and the semi-automatic methods (DaTSCAN (R) V4 and the SAA). These methods also evidence intra and inter-operator variability, suppressed by the AA. The proposed methodology for segmentation and quantification of the striatum transaxial images obtained by [I-123]FP-CIT SPECT demonstrated that the developed application can accurately complement the visual analysis, requiring future optimization.
- Spectral biomarkers of genotoxicity from methanol extracts of bloodPublication . Teixeira, Hélder Paz; Ramalhete, Luís; Ladeira, Carina; Calado, CecíliaIt is relevant to develop new monitoring techniques of carcinogenic risk associated to environmental exposition to genotoxic chemicals. The conventional biomonitoring techniques are based on laborious, expensive methods as the ones requiring isolation of lymphocytes from peripheral blood, in vitro cell culture, followed by e.g. cytokinesis-block assay and microscope observation of chromosomal abnormalities. The present work evaluated an infrared spectroscopy method, based on a simple, more economic and high-throughput procedure of analysis of whole blood processed with methanol. It was possible to identify ratios of spectral bands that are statistically different between hospital professionals occupationally exposed to antineoplastic drugs, such as 5-fluorouracil and non-hospital professionals without this exposure. It was also identified ratios of spectral bands which are statistically different between participants presenting lymphocytes with chromosomal abnormalities (as micronucleus, nuclear buds and nucleoplasmatic bridges) and participants not presenting these abnormalities. The infrared spectroscopy-based method presents therefore appealing characteristics to be applied in more intensive and/or large-scale studies of monitoring genotoxic risks.
- Automatic versus semi-automatic method for the striatum specific uptake ratio quantification based on [I-123]FP-CIT SPECT imagesPublication . Elias, Maria; Jorge, Pedro; Figueiredo, Sérgio; Oliveira, Luís; Pereira, Edgar L.The aim of this work was to implement an automatic application (AA) for the quantification of the striatum transaxial slices based on [I-123]FP-CIT SPECT (Single Photon Emission Tomography) images. A sample of 68 subjects with and without pathology was collected from the nuclear medicine department of the Hospital Particular de Almada. In order to compare the striatum specific uptake ratios (SUR), a semi-automatic application (SAA) was also developed allowing manual adjustments by a specialist operator. The obtained results were compared with the DaTSCAN (R) V4 application, from General Electric Healthcare. The experimental results based on SUR demonstrate that the AA can successfully discriminate the healthy patients from the pathological subjects. Additionally, a strong correlation was verified between the AA and the semi-automatic methods (DaTSCAN (R) V4 and the SAA). These methods also evidence intra and inter-operator variability, suppressed by the AA. The proposed methodology for segmentation and quantification of the striatum transaxial images obtained by [I-123]FP-CIT SPECT demonstrated that the developed application can accurately complement the visual analysis, requiring future optimization.
- Ankle Foot Orthosis (AFO) stiffness design for mitigation of ankle inversion injuryPublication . Teixeira, D.; Milho, João; Carvalho, M. S.; Loja, AméliaModelling and simulation of human movement has the potential to improve the design of medical devices and rehabilitation process by enabling the identification of cause-effect relationships in individuals suffering from neurological and musculoskeletal issues. The main goal of this work was to provide a simulation-based stiffness design for an Ankle Foot Orthosis (AFO) that can help to mitigate the risk of a sprain by ankle inversion during the landing in freefall which is known to occur for subtalar angles higher than 25 degrees. Computational simulations were performed using human movement models with and without a passive AFO, to access the AFO sensitivity for the translational stiffness that prevents the cuff from translating with respect to the footplate. The Design of Experiments (DoE) methodology was used to access sensitivities between the three principal directions of the AFO stiffness. Results revealed that the ankle inversion angle was less than 25 degrees when increasingly larger values of translational stiffness were used, although a nonlinear behaviour was observed between the three principal directions of the AFO stiffness, for which injury safe design configurations were obtained.
- Impact of the solvent extraction method on the plasma metabolome profilePublication . Pires, Filipa A. R.; Ramalhete, Luís M.; Ribeiro, Edna; Calado, CecíliaMetabolomics of biofluids as plasma implies the sample pre-processment to eliminate diverse macromolecules as proteins. The optimization of this procedure is conducted according to the main method to analyses the metabolome and the type of metabolites to be studied. In the present work, it was evaluated the effect of diverse processes to eliminate macromolecules from plasma samples on the metabolome profile achieved by mid-infrared spectroscopy. It was evaluated the effect on the metabolome of proteins extraction by methanol, acetone and acetonitrile. The highest efficiency of protein extraction was observed with acetone, been achieved 2.4- and 4.7-fold lower quantities of proteins in relation to methanol and acetonitrile, respectively. This resulted in acetone as the highest reproducible extraction process, i.e. with replicate samples with a more homogenous molecular signature between them, in relation to the other two extraction processes. Despite that, acetone resulted in the spectra with the lowest signal to noise (S/N) ratio that could hamper the biological information output. The extraction with acetonitrile presented a spectrum with a S/N ratio like the obtained with methanol, and 2.7-fold higher than the obtained with acetone. However, it resulted in the lowest reproductible process probably due to the presence of 2.2 more proteins in the final sample in relation to the acetone process. All these observations point that different extraction process will complement each other in the view of a more complete metabolome of a system.
- Rheology of living cellsPublication . Portela, R.; Franco, Jose M.; Almeida, Pedro L.; Patricio, Pedro; Sobral, Rita; R. Leal, CatarinaThe mechanical behavior of living cells, during planktonic growth, has been thoroughly explored combining common biological techniques with rheology and rheo-imaging measurements. Under a shear flow, bacterial cultures of Staphylococcus aureus revealed a complex and rich rheological behavior not usually accessed in biological studies. In particular, in stationary shear flow, the viscosity increased during the exponential phase and returned close to its initial value at the late phase of growth, accompanied by the stabilization of the bacterial population. In oscillatory flow, the elastic and viscous moduli exhibited power-law behaviors whose exponents are dependent on the bacteria growth stage, and can be associated to a Soft Glassy Material behavior. These behaviors were framed in a microscopic model that suggests the formation of a dynamic web-like structure, where specific aggregation phenomena may occur, depending on growth stage and cell density. Furthermore, systematic measurements combining optical density and dry weight techniques presented new evidences, which confirmed that the observed cell aggregation patterns developed during growth, under shear, can not only be cell density dependent.
- Development of a tool for selection and acquisition of medical devices based on the analytic hierarchy processPublication . Oliveira, V.; Sobral, José; Ribeiro, M. MargaridaThe existence of a tool to select and acquire Medical Devices is fundamental to manage the Life Cycle (LC) of Medical Devices (MD). The objective of this work is to create a structured, organized and optimized application to use on the selection and acquisition stage of a tender process, in order to help those responsible for the decision make. In addition it will turn the process exempt and transparent. The methodology is based on a defined hierarchical multi criteria decision making approach, the Analytic Hierarchy Process (AHP) optimizing and validating all the requirements stated in a tender process and ensuring, free from human manipulation, that the best option will be chosen. The demonstrative study is applied to Computed Tomography (CT), with the aim of applying the methodology in the selection and acquisition of the best choice between four alternatives. The developed tool includes some weights that are assigned to the established criteria and sub-criteria according to the present and future needs of each healthcare provider. It has been proven that the price is not the only criteria, and perhaps not the most important. All technical and operational requirements as maintenance costs, availability, image quality, safety, and client satisfaction must also be included in the decision making process.
- Classification of recombinant Saccharomyces cerevisiae cells using PLS-DA modelling based on MIR spectroscopyPublication . Sampaio, Pedro; Calado, CecíliaTowards the optimization and control of bioprocesses, as the culture step of recombinant microorganisms, it is crucial to develop high-throughput monitoring techniques enabling the acquisition of a large data sets of information, as the ones based on mid infrared (MIR) spectroscopy. To maximize the knowledge associated to this this new large-scale data, it is also relevant to apply machine learning techniques, as Partial Least-Squares Discriminant Analysis (PLS-DA). In the present work, Principal Component Analysis followed by PLS-DA were applied to discriminate different growth phases of recombinant Saccharomyces cerevisiae along the production of an heterologous protein, conducted in bioreactor and monitored by high-throughput MIR spectroscopy. It was possible to derive PLS-DA models enabling to discriminate, from the MIR spectra, the yeast cells according to its metabolic status associated to the culture growth phase with an accuracy, sensitivity, and specificity between 83% and 100%. The optimised PLS-DA presented very low calibration errors, of 97% and 100% based on a cross-validation and an independent data-set, respectively. In conclusion, it was possible to build a PLS-DA model discriminating the cells metabolic status that will promote the knowledge of the bioprocess and future better control and optimization procedures.
- Detection and adsorption of Triclosan on sensors based on PAH/PVS thin-filmsPublication . Pereira-da-Silva, J.; Zagalo, P. M..; Magro, Cátia; Pinto, Iola; Ribeiro, P. A.; Raposo, MariaGiven the vital role of water in life it is paramount to thrive and succeed in areas that look to clean and prevent further contamination in water bodies. Triclosan (TCS) is present in most of our day-to-day products and if left unchecked it can lead to long-term significant problems due to its many inauspicious effects in both human and animal health. Thus arose the need to develop sensors to detect and possibly remove TCS for aqueous solutions. This work was rooted on this premise and sensors based on LbL polyectrolyte thin-films were developed, such as poly(allylamine hydrochloride) (PAH) and poly(vinylsulfonic acid, sodium salt) (PVS), namely (PAH/PVS)(10) and (PAH/PVS)/PAH(10). The goal of this work was to analyze the amount of TCS adsorbed onto reused (PAH/PVS)(10) and (PAH/PVS)/PAH(10) LbL thin-films when immersed in TCS aqueous solutions with decreasing pH. It was demonstrated that sensors with an outer layer of PAH led to a significantly better TCS molecules adsorption (removal). Additionally, sensors composed of (PAH/PVS)(10) presented higher sensibility in discriminating TCS solutions with concentrations between 10(-5) M and 10(-8) M, using impedance spectroscopy.
- Towards an automated statistical workflow for biomarker screening in Fourier-transform infrared spectroscopyPublication . Ribeiro Da Cunha, Bernardo; Aleixo, Sandra; Fonseca, Luís P.; Calado, CecíliaThe increasing availability and sensitivity of analytical technologies has resulted in much higher complexity of molecular and cellular data, which biomarkers facilitate the bridge with a given biological state under scrutiny. Importantly, biomarkers are critical in spectroscopic technologies, as is the case of Fourier-transform infrared spectroscopy, for which different approaches to identify biomarkers have been established, for instance univariate statistical hypothesis tests. A workflow for the automatic application of said statistical tests is proposed with the objective of enabling a high throughput screening-approach that ensures statistical robustness, and works in a user-independent manner, thereby reducing analysis bias. The proposed workflow is the first step towards an automated method for biomarker screening, thus it is limited to distinguishing two populations. Firstly, the method used in previous work was improved to ensure the most powerful and accurate statistical tests are applied. Then, the statistical workflow was generalized to a more comprehensive range of data sets of two populations, for instance when sample size is not deemed high (less than thirty observations). Lastly, future work is outlined regarding the extension of the workflow to cases with more than two populations, but also of methods that can increase the pool of putative biomarkers that will then be screened for statistical significance.
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