Browsing by Issue Date, starting with "2011-05"
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- Synthetic volume from real optical coherence tomography dataPublication . Serranho, Pedro; Bernardes, Rui; Maduro, Cristina; Santos, Torcato; Cunha-Vaz, JoséPurpose: To build a mathematical model to mimic a real OCT b-scan/volume without noise, in order to establish a ground truth for image processing performance metrics. Methods: Current image processing techniques (eg. despeckling filtering methods) with application to optical coherence tomography (OCT) rely on the respective qualitative evaluation of its results. Quantitative approaches are reduced to using synthetic images which consists of an homogeneous background and a set of abstract objects, eg. cubes and spheres. In this work, we suggest a mathematical model to address this issue by creating a synthetic b-scan/volume based on any real OCT data scan, that can be used as ground truth for processing methods testing. Eye scans of healthy volunteers and eyes of patients with age-related macular degeneration and diabetic retinopathy were used following Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA) scans using both the 200x200x1024 and the 512x128x1024 Macular Cube Protocols. Each of these eye scans was processed in order to extract required parameters. For healthy subjects, only the segmentation of the inner limiting membrane (ILM) and the retinal pigment epithelium (RPE) are needed, though for pathologic eyes, the segmentation of other structures to be preserved might also be needed. In each segmented region, OCT data is surface fitted using appropriate basis functions. Results: A total of 45 scans were processed resulting in the synthetic data representing the major characteristics of the respective real OCT scans. These results have been used for testing the performance of an improved complex diffusion despeckling method proposed by some of the authors. Conclusions: This process allows to automatically compute a synthetic OCT scan mimicking a real one. In this way, this process makes it possible to quantify the result of any processing (eg. filtering) by providing adequate synthetic data as ground truth.
- Volumetric properties and spectroscopic studies of pyridine or nicotine solutions in liquid polyethylene glycolsPublication . Visak, Zoran P.; Ilharco, Laura; Garcia, Ana Rosa; Najdanovic-Visak, Vesna; Fareleira, João M. N. A.; Caetano, Fernando J. P.; Kijevcanin, Mirjana; Serbanovic, SlobodanDensities and molar excess volumes of the solutions of pyridine or nicotine in liquid polyethylene glycol, PEG200 and PEG400, have been determined at several temperatures. The experimental molar excess volumes are negative, thus indicating strong attractive interactions between the components, as could be expected considering their highly polar nature and good hydrogen bond abilities. For the pyridine systems, this negativity is slightly increased as the temperature rises, while the opposite tendency is observed for the nicotine mixtures. When pyridine and nicotine solutions are compared, the former—particularly those with PEG400—exhibit substantially more negative molar excess volumes than the latter. The effect of the polymer chain length on the results for the nicotine solutions is almost negligible. However, this is not the case when pyridine is one of the components: a longer chain induced considerably higher compression on mixing. The Fourier-transform infrared analysis allowed interpretation of the negative experimental molar excess volumes in terms of specific inter- and intramolecular interactions.
- A arte da paz : a ONU e Portugal no combate ao terrorismo : estudo de direito e de política InternacionalPublication . Fontes, JoséProjeto científico
- Adaptive complex diffusion noise despeckling for 3D OCT DataPublication . Bernardes, Rui; Maduro, Cristina; Serranho, Pedro; Dinis, João; Cunha-Vaz, JoséPurpose: To demonstrate the performance of a recently proposed despeckling filter when extended to 3D in OCT data. Methods: A new formulation for a complex diffusion filter was recently proposed [1] being adaptive in time and adjusting parameters to data, facilitating diffusion in the vitreous and reducing it in the retina to preserve tissue information. This new formulation outperformed, both quantitatively and qualitatively, currently existing filters, while at the same time was computationally more efficient attaining the same despeckling level in 34% of the computing time. We have now extended it to perform 3D OCT despeckling achieving a significant improvement in noise removal. We have resorted to a mathematical based synthetic OCT scan in order to assess quantitative results in 3D. In addition, we have applied this 3D filter to a set of 72 eye scans, from healthy volunteers (20), diabetic retinopathy (20), cystoid macular edema (2), age-related macular degeneration (20) and choroidal neo-vascularization (10), who underwent high-definition Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA) using macular cube protocols (200x200x1024 and/or 512x128x1024). Results: The extension from 2D to 3D of this adaptive complex diffusion filter proved to be beneficial by achieving an increased level of noise reduction while simultaneously better preserving fundamental information. These facts are supported from well known metrics (e.g. MSE-mean squared error, ENL-effective number of looks and CNR-contrast-to-noise ratio) for the synthetic OCT scan and from the assessment made by 3 retina specialist who graded qualitatively the output of the 2D and 3D filters. Conclusions: These findings demonstrate this new formulation and its extension to 3D is beneficial for human analysis of OCT data and suggest it might be an important tool for automated data processing as in segmentation of retinal structures. [1] Bernardes R, Maduro C, Serranho P, Araújo A, Barbeiro S, Cunha-Vaz J. Improved adaptive complex diffusion despeckling filter. OPTICS EXPRESS 18(23):24048-24059, 2010.
- Redes sociais virtuais e tecnologias da informação e da comunicação no sector da saúde: linhas de força e desafiosPublication . Carrilho, Tiago; Porfírio, José; Jacquinet, MarcO sistema de saúde, por razões políticas e pela própria evolução do sector, correspondendo aos interesses e às necessidades dos prestadores de serviços e dos utentes, tem vindo a introduzir sistematicamente e de maneira crescente as tecnologias da informação e da comunicação (TIC) no âmbito do funcionamento e da gestão do sistema nacional de saúde e das entidades que nele actuam. O presente trabalho basear-se-á numa cuidada revisão da literatura sobre saúde e em particular sobre saúde electrónica assim como o estudo de vários relatórios de avaliação de políticas ou execução de medidas e de sites em que recolhemos os primeiros dados sobre o impacto das TIC e das redes virtuais no sector. A globalização e a reestruturação dos processos de trabalho relacionam-se com esta mudança assim como os utentes e os profissionais do sector. Neste trabalho propomos uma definição da saúde electrónica e das traves mestras das transformações actuais, como a emergência de um modelo de gestão: a saúde electrónica ou e-health. Central a esta nova realidade emergente são as redes sociais virtuais ou online e que constituem a pedra angular da saúde electrónica. Na parte final, procedemos a uma breve caracterização da evolução internacional no sector, analisando as práticas mais recentes.