Navegação por Autores IPEN "PRETTO, LUCAS R. de"

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  • IPEN-DOC 26419

    PRETTO, LUCAS R. de ; MOULT, ERIC M.; ALIBHAI, A.Y.; CARRASCO-ZEVALLOS, OSCAR M.; CHEN, SIYU; LEE, BYUNGKUN; WITKIN, ANDRE J.; BAUMAL, CAROLINE R.; REICHEL, ELIAS; FREITAS, ANDERSON Z. de ; DUKER, JAY S.; WAHEED, NADIA K.; FUJIMOTO, JAMES G.. Controlling for artifacts in widefield optical coherence tomography angiography measurements of non-perfusion area. Scientific Reports, v. 9, p. 1-15, 2019. DOI: 10.1038/s41598-019-43958-1

    Abstract: The recent clinical adoption of optical coherence tomography (OCT) angiography (OCTA) has enabled non-invasive, volumetric visualization of ocular vasculature at micron-scale resolutions. Initially limited to 3 mm × 3 mm and 6 mm × 6 mm fields-of-view (FOV), commercial OCTA systems now offer 12 mm × 12 mm, or larger, imaging fields. While larger FOVs promise a more complete visualization of retinal disease, they also introduce new challenges to the accurate and reliable interpretation of OCTA data. In particular, because of vignetting, wide-field imaging increases occurrence of low-OCT-signal artifacts, which leads to thresholding and/or segmentation artifacts, complicating OCTA analysis. This study presents theoretical and case-based descriptions of the causes and effects of low-OCTsignal artifacts. Through these descriptions, we demonstrate that OCTA data interpretation can be ambiguous if performed without consulting corresponding OCT data. Furthermore, using wide-field non-perfusion analysis in diabetic retinopathy as a model widefield OCTA usage-case, we show how qualitative and quantitative analysis can be confounded by low-OCT-signal artifacts. Based on these results, we suggest methods and best-practices for preventing and managing low-OCT-signal artifacts, thereby reducing errors in OCTA quantitative analysis of non-perfusion and improving reproducibility. These methods promise to be especially important for longitudinal studies detecting progression and response to therapy.

    Palavras-Chave: ophthalmology; retina; biomedical radiography; tomography; vascular diseases; optical equipment; coherent radiation; images; blood vessels; beam scanners

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  • IPEN-DOC 27274

    PRETTO, LUCAS R. de . Desenvolvimento de técnicas diagnósticas quantitativas baseadas em decorrelação de speckle presente nos sinais de Tomografia de Coerência Óptica / Development of quantitative diagnostic techniques based on decorrelation of speckle present in Optical Coherence Tomography signals . 2019. Tese (Doutorado em Tecnologia Nuclear) - Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, São Paulo. 107 p. Orientador: Anderson Zanardi de Freitas. DOI: 10.11606/T.85.2019.tde-17092020-142834

    Abstract: Segundo dados da Organização Mundial da Saúde (OMS), doenças crônicas não transmissíveis (DCNT), são uma das principais causas de morte no mundo, principalmente diabetes mellitus (DM). De particular importância para a DM, a manutenção de elevados níveis glicêmicos contribui de forma direta para o prejuízo das funções vasculares. Ainda, a DM impacta diretamente na qualidade de vida através de outros fatores associados à doença. Destaca-se a Retinopatia Diabética (RD), uma das principais causas de cegueira no mundo. A Tomografia por Coerência Óptica (OCT, do inglês, Optical Coherence Tomography) é uma modalidade de diagnóstico por imagem baseada em interferometria óptica que não utiliza radiação ionizante. Análise das flutuações de intensidade do sinal de OCT, devido ao padrão de ruído denominado speckle, possibilita análises angiográficas e de fluxo. Este estudo apresenta, então, o uso de OCT como ferramenta diagnóstica tanto para medir níveis glicêmicos no sangue de forma sem-contato, como para analisar in vivo a microvasculatura retinal. Desta maneira, novas técnicas diagnósticas para controle do nível glicêmico e para acompanhamento e estudo da retinopatia diabética são propostas. Os resultados de diferenciação da concentração de glicose no sangue obtidos, com métodos de análise espacial e temporal, são animadores e mostram boa sensibilidade do OCT para aplicações ex vivo, indicando uma potencial técnica de monitoramento glicêmico não-invasiva. Adicionalmente, as novas formas de análise microvascular da retina possibilitam um diagnóstico precoce da severidade da RD, o que possibilita melhor indicação do tratamento adequado a cada caso. Ainda, esta análise revela informações novas sobre a angiogênese da RD. É necessário, entretanto, um conhecimento adequado sobre as imagens adquiridas e métricas utilizadas, e um relatório sobre estes fatores foi desenvolvido. Com isto, esta tese demonstra a importância do desenvolvimento de técnicas de OCT para aplicações clínicas e para saúde dos pacientes com DM.

    Palavras-Chave: diagnostic techniques; optical microscopy; scanning light microscopy; image processing; computerized tomography; interference; wave propagation; on-line measurement systems; dimensionless numbers; signal-to-noise ratio; glucose; control; blood chemistry; performance testing; angiography; endocrine diseases; metabolic diseases; diabetes mellitus; eyes; retina

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  • IPEN-DOC 20771

    PRETTO, LUCAS R. de . Desenvolvimento de um algoritimo otimizado para caracterização de fluxos microfluídicos utilizando padrões de speckle presentes no sinal de tomografia por coerência óptica / Development of an optimized algorithm for the characterization of microflow using speckle patterns present in optical coherence tomography signal . 2015. Dissertação (Mestrado em Tecnologia Nuclear) - Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP, São Paulo. 124 p. Orientador: Anderson Zanardi de Freitas. DOI: 10.11606/D.85.2015.tde-21052015-131941

    Abstract: O presente trabalho abordou o sistema de Tomografia por Coerência Óptica (OCT) e sua aplicação à área de microfluídica. Para tanto, foram realizados testes de caracterização física de circuitos microfluídicos, utilizando modelos 3D (tridimensionais) construídos a partir de imagens de OCT destes circuitos. A técnica foi, assim, avaliada como potencial ferramenta de auxílio na aferição de microcanais. Indo além, este trabalho estuda e desenvolve técnicas de análise para fluxos microfluídicos, em especial técnicas baseadas no padrão de speckle. Em primeiro momento, métodos já existentes foram estudados e aprimorados, como o Speckle Variance OCT, em que foi obtido um ganho de 31% em tempo de processamento. Outros métodos, como o LASCA (Laser speckle Contrast Analysis), baseados na autocorrelação de speckle, são adaptados às imagens de OCT. Derivado do LASCA, o método de análise desenvolvido baseado na autocorrelação de intensidade motivou o desenvolvimento de um arranjo de OCT próprio e software de aquisição customizado, com taxa de amostragem da ordem de 8 kHz. O método proposto foi, então, capaz de distinguir fluxos volumétricos variados, e seus limites de detecção foram testados, comprovando sua viabilidade de aplicação para análise de movimento browniano e fluxos volumétricos abaixo de 10 μl/min.

    Palavras-Chave: tomography; optical properties; algorithms; flow rate; velocity; three-dimensional calculations; brownian movement; volumetric analysis

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  • IPEN-DOC 23822

    RAELE, MARCUS P. ; PRETTO, LUCAS R. de ; SAMAD, RICARDO E. ; FREITAS, ANDERSON Z. de ; ROSSI, WAGNER de ; VIEIRA JUNIOR, NILSON D. ; WETTER, NIKLAUS U. . Development of a dynamic interferometric focusing system for femtosecond laser machining. In: HEISTERKAMP, ALEXANDER (Ed.); HERMAN, PETER R. (Ed.); MEUNIER, MICHEL (Ed.); OSELLAME, ROBERTO (Ed.) FRONTIERS IN ULTRAFAST OPTICS: BIOMEDICAL, SCIENTIFIC, AND INDUSTRIAL APPLICATIONS, 18th, January 28, 2017, San Francisco, California, United States. Proceedings... Bellingham, Washington USA: Society of Photo-optical Instrumentation Engineers, 2017. p. 100940N-1 - 100940N-13. (SPIE Proceedings Series, 10094).

    Abstract: Taking advantage of the inherent characteristics of femtosecond laser used for machining, we developed an interferometric system able to evaluate and correct the focal position with an accuracy of a few microns, implementing a technique based on low coherence interferometry. This approach measures at the exact spot that the laser is machining, in real time, and is sensitive to any sample that acts as a scatterer to the wavelength in use. The experimental evaluation was divided in two steps: in the first a system based on a superluminescent LED was mounted to check the viability and develop the controlling software; in the second part a setup was mounted employing a femtosecond laser, and several kinds of samples using the active focus control, among which the results obtained with glass sample and a bovine tooth are meticulously described in this paper. The system was able to improve the performance in both samples, keeping them in the confocal region for an extended positioning range, resulting in better engraving by the laser.

    Palavras-Chave: laser beam machining; lasers; interferometry; laser radiation; ablation; michelson interferometer; cattle; teeth; bone tissues

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  • IPEN-DOC 20913

    RAELE, MARCUS P. ; PRETTO, LUCAS R. de ; FREITAS, ANDERSON Z. de . Enhance resolution on OCT profilometry measurements using harmonic artifacts. In: FUJIMOTO, JAMES G. (Ed.); IZZATT, JOSEPH A. (Ed.); TUCHIN, VALERY V. (Ed.) OPTICAL COHERENCE TOMOGRAPHY AND COHERENCE DOMAIN OPTICAL METHODS IN BIOMEDICINE, 19th, February 7, 2015, San Francisco, California, United States. Proceedings... Society of Photho-optical Instrumentation Engineers, 2015. p. 93123Q-1 - 93123Q-8. (SPIE Proceedings Series, 9312).

    Palavras-Chave: coherent radiation; interferometry; harmonics; resolution; images; fourier transformation; tomography; optical models

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  • IPEN-DOC 22440

    PRETTO, LUCAS R. de ; NOGUEIRA, GESSE E.C. ; FREITAS, ANDERSON Z. . Microfluidic volumetric flow determination using optical coherence tomography specke: An autocorrelation approach. Journal of Applied Physics, v. 119, n. 16, p. 163105-1 - 163105-5, 2016.

    Palavras-Chave: tomography; correlations; velocity; electrophoresis; walls; evaluation; comparative evaluations; fluid flow

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  • IPEN-DOC 21366

    PRETTO, LUCAS R. de ; NOGUEIRA, GESSE E.C. ; FREITAS, ANDERSON Z. . New speckle analysis algorithm for flow visualization in optical coherence tomography images. In: KURACHI, CRISTINA (Ed.); SVANBERG, KATARINA (Ed.); TROMBERG, BRUCE J. (Ed.); BAGNATO, VANDERLEI S. (Ed.) BIOPHOTONICS SOUTH AMERICA, May 23, 2015, Rio de Janeiro, Brasil. Proceedings... Bellingham, Washington USA: Society of Photo-optical Instrumentation Engineers, 2015. p. 95313O-1 - 95313O-8. (SPIE Proceedings Series, 9531).

    Palavras-Chave: images; algorithms; fluid flow; blood flow; optical systems; coherent radiation; tomography

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  • IPEN-DOC 21368

    PRETTO, LUCAS R. de ; NOGUEIRA, GESSE E.C. ; FREITAS, ANDERSON Z. . New speckle analysis method for optical coherence tomography signal based on autocorrelation. In: KURACHI, CRISTINA (Ed.); SVANBERG, KATARINA (Ed.); TROMBERG, BRUCE J. (Ed.); BAGNATO, VANDERLEI S. (Ed.) BIOPHOTONICS SOUTH AMERICA, May 23, 2015, Rio de Janeiro, Brasil. Proceedings... Bellingham, Washington USA: Society of Photho-optical Instrumentation Engineers, 2015. p. 95313P-1 - 95313P-9. (SPIE Proceedings Series, 9531).

    Palavras-Chave: tomography; signals; velocity; correlations; optical systems; coherent radiation

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  • IPEN-DOC 24779

    PRETTO, LUCAS R. de ; SAMAD, RICARDO E. ; ROSSI, WAGNER de ; FREITAS, ANDERSON Z. de . Optical coherence tomography characterization of femtosecond laser manufactured microfluidic circuits. In: GRAY, BONNIE L. (Ed.); BECKER, HOLGER (Ed.) MICROFLUIDICS, BIOMEMS, AND MEDICAL MICROSYSTEMS, 16th, January 27 - February 01, 2018, San Francisco, California, USA. Proceedings... Bellingham, WA, USA: Society of Photo-optical Instrumentation Engineers, 2018. p. 104911A-1 - 104911A-12. (SPIE Proceedings Series, 10491). DOI: 10.1117/12.2289937

    Abstract: Dimensional characterization of microfluidic circuits were performed using three-dimensional models constructed from OCT images of such circuits. Were fabricated microchannels on the same BK7 glass plate, under different laser ablation conditions and substrate displacement velocity in relation to laser beam. Were used the following combination of energy, from 30 μJ to 60 μJ and velocity from 588 mm/min to 1176 mm/min, at 1 kHz laser repetition rate and 40 fs of pulse duration (FWHM). For OCT imaging we used an OCP930SR (Thorlabs System Inc) with 930 nm central wavelength, 6 μm of lateral and axial resolution, and image of 500 x 512 pixel corresponding to 2.0 mm x 1.6 mm of lateral and axial scans respectively at 8 frames per second. We also characterized devices like, micropumps, microvalves and microreactors. It was possible register the micropumps and valves in action in real time. Using the OCT images analyses was possible to select the best combination of laser pulse energy and substrate velocity. All the devices were made in raster protocol, where laser beam pass through the same path in a controlled number of times, and with each iteration more material is removed and deeper the channels remain. We found a deformation at the edge of fabricated structures, due to velocity reduction of substrate in relation to laser beam, which causes more laser pulses superposition in these regions, and more material is ablated. The technique was thus evaluated as a potential tool to aid in the inspection of microchannels.

    Palavras-Chave: tomography; optical systems; optical modes; scanning electron microscopy; electron scanning; computer codes; fluidic control devices; lasers

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  • IPEN-DOC 22842

    PRETTO, LUCAS R. de ; YOSHIMURA, TANIA M. ; RIBEIRO, MARTHA S. ; FREITAS, ANDERSON Z. de . Optical coherence tomography for blood glucose monitoring in vitro through spatial and temporal approaches. Journal of Biomedical Optics, v. 21, n. 8, p. 086007-1 - 086007-7, 2016. DOI: 10.1117/1.JBO.21.8.086007

    Abstract: As diabetes causes millions of deaths worldwide every year, new methods for blood glucose monitoring are in demand. Noninvasive approaches may increase patient adherence to treatment while reducing costs, and optical coherence tomography (OCT) may be a feasible alternative to current invasive diagnostics. This study presents two methods for blood sugar monitoring with OCT in vitro. The first, based on spatial statistics, exploits changes in the light total attenuation coefficient caused by different concentrations of glucose in the sample using a 930-nm commercial OCT system. The second, based on temporal analysis, calculates differences in the decorrelation time of the speckle pattern in the OCT signal due to blood viscosity variations with the addition of glucose with data acquired by a custom built Swept Source 1325-nm OCT system. Samples consisted of heparinized mouse blood, phosphate buffer saline, and glucose. Additionally, further samples were prepared by diluting mouse blood with isotonic saline solution to verify the effect of higher multiple scattering components on the ability of the methods to differentiate glucose levels. Our results suggest a direct relationship between glucose concentration and both decorrelation rate and attenuation coefficient, with our systems being able to detect changes of 65 mg∕dL in glucose concentration.

    Palavras-Chave: tomography; blood; glucose; in vitro; diabetes mellitus; mice; in vivo; animals

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  • IPEN-DOC 22984

    PRETTO, LUCAS R. de ; YOSHIMURA, TANIA M. ; RIBEIRO, MARTHA S. ; FREITAS, ANDERSON Z. de . Optical Coherence Tomography for blood glucose monitoring through signal attenuation. In: IZATT, JOSEPH A. (Ed.); FUJIMOTO, JAMES G. (Ed.); TUCHIN, VALERY V. (Ed.) OPTICAL COHERENCE TOMOGRAPHY AND COHERENCE DOMAIN OPTICAL METHODS IN BIOMEDICINE, 20th, February 13, 2016, San Francisco, California, USA. Proceedings... Bellingham, Washington USA: Society of Photo-optical Instrumentation Engineers, 2016. p. 96973F-1 - 96973F-9. (SPIE Proceedings Series, 9697).

    Abstract: Development of non-invasive techniques for glucose monitoring is crucial to improve glucose control and treatment adherence in patients with diabetes. Hereafter, Optical Coherence Tomography (OCT) may offer a good alternative for portable glucometers, since it uses light to probe samples. Changes in the object of interest can alter the intensity of light returning from the sample and, through it, one can estimate the sample's attenuation coefficient (μt) of light. In this work, we aimed to explore the behavior of μt of mouse’s blood under increasing glucose concentrations. Different samples were prepared in four glucose concentrations using a mixture of heparinized blood, phosphate buffer saline and glucose. Blood glucose concentrations were measured with a blood glucometer, for reference. We have also prepared other samples diluting the blood in isotonic saline solution to check the effect of a higher multiple-scattering component on the ability of the technique to differentiate glucose levels based on μt. The OCT system used was a commercial Spectral Radar OCT with 930 nm central wavelength and spectral bandwidth (FWHM) of 100 nm. The system proved to be sensitive for all blood glucose concentrations tested, with good correlations with the obtained attenuation coefficients. A linear tendency was observed, with an increase in attenuation with higher values of glucose. Statistical difference was observed between all groups (p<0.001). This work opens the possibility towards a non-invasive diagnostic modality using OCT for glycemic control, which eliminates the use of analytes and/or test strips, as in the case with commercially available glucometers.

    Palavras-Chave: tomography; optical systems; coherence length; attenuation; in vitro; diabetes mellitus; hyperglycemia; blood; glucose; monitoring

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  • IPEN-DOC 26892

    ALIBHAI, A.Y.; PRETTO, LUCAS R. de ; MOULT, ERIC M.; OR, CHRIS; ARYA, MALVIKA; MCGOWAN, MITCHELL; CARRASCO-ZEVALLOS, OSCAR; LEE, BYUNGKUN; CHEN, SIYU; BAUMAL, CAROLINE R.; WITKIN, ANDRE J.; REICHEL, ELIAS; FREITAS, ANDERSON Z. de ; DUKER, JAY S.; FUJIMOTO, JAMES G.; WAHEED, NADIA K.. Quantification of retinal capillary nonperfusion in diabetics using wide-field optical coherence tomography angiography. RETINA, The Journal of Retinal and Vitreous Diseases, v. 40, n. 3, p. 412-420, 2020. DOI: 10.1097/IAE.0000000000002403

    Abstract: Purpose: To combine advances in high-speed, wide-field optical coherence tomography angiography (OCTA) with image processing methods for semiautomatic quantitative analysis of capillary nonperfusion in patients with diabetic retinopathy (DR). Methods: Sixty-eight diabetic patients (73 eyes), either without retinopathy or with different degrees of retinopathy, were prospectively recruited for volumetric swept-source OCTA imaging using 12 mm · 12 mm fields centered at the fovea. A custom, semiautomatic software algorithm was used to quantify areas of capillary nonperfusion. Results: The mean percentage of nonperfused area was 0.1% (95% confidence interval: 0.0–0.4) in the eyes without DR; 2.1% (95% confidence interval: 1.2–3.7) in the nonproliferative DR eyes (mild, moderate, and severe), and 8.5% (95% confidence interval: 5.0–14.3) in the proliferative DR eyes. The percentage of nonperfused area increased in a statistically significant manner from eyes without DR, to eyes with nonproliferative DR, to eyes with proliferative DR. Conclusion: Capillary nonperfusion area in the posterior retina increases with increasing DR severity as measured by swept-source OCTA. Quantitative analysis of retinal nonperfusion on wide-field OCTA may be useful for early detection and monitoring of disease in patients with diabetes and DR.

    Palavras-Chave: tomography; coherent radiation; optical activity; optical properties; computerized tomography; ischemia; retina; diabetes mellitus; patients; perfused organs; capillaries; statistical data

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  • IPEN-DOC 25645

    ALIBHAI, A.Y.; PRETTO, LUCAS R. de ; MOULT, ERIC; SCHOTTENHAMML, JULIA; OR, CHRIS; ARYA, MALVIKA; MCGOWAN, MITCHELL; BAUMAL, CAROLINE; WITKIN, ANDRE J.; DUKER, JAY S.; FUJIMOTO, JAMES G.; WAHEED, NADIA K.. Quantitative analysis of capillary non-perfusion in diabetic retinopathy using widefield OCT-angiography. Investigative Ophthalmology & Visual Science, v. 59, n. 9, 2018.

    Abstract: Purpose : Several OCT angiography (OCTA) studies suggest an association between capillary non-perfusion, a surrogate for retinal ischemia, and diabetic retinopathy (DR) severity. However, due to technical limitations, these studies focused on either 3x3mm or 6x6mm fields of view centered on the macula. In contrast, widefield fluorescein angiography (FA) studies suggest that the majority of capillary non-perfusion in early DR occurs outside of the macular region. The recent development of high-speed, widefield OCTA systems, has for the first time allowed non-invasive visualization of retinal vasculature over wider fields of view—a functionality that, in light of previous widefield FA studies, may be promising for early detection and monitoring of DR. This study aims to couple the recent technological advances in high-speed, widefield OCTA with image processing methods to allow for semi-automatic quantitative analysis of capillary non-perfusion of widefield OCTA images of diabetic eyes. Methods : A semi-automatic, texture-based algorithm that detects areas of non-perfusion on 12x12mm SS-OCTA images from the Zeiss PlexElite™ system was developed. We tested the algorithm on a series of patients with diabetes without DR (28 eyes, 21 subjects; 54.8 ± 10.9 y/o), eyes with non-proliferative DR (NPDR) (24 eyes, 16 subjects; 62.1 ± 13.2 y/o) and eyes with proliferative DR (PDR) (21 eyes, 14 subjects; 52.2 ± 12.7 y/o). Results : There was a general trend of increasing capillary non-perfusion with increasing DR severity; however, there was significant overlap between patients having different DR severities (Fig. 1). Conclusions : Quantitative analysis of widefield OCTA images may be useful for early detection and monitoring for diabetic retinopathy progression in diabetics. Additional work is needed to determine the added value of widefield OCTA.

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  • IPEN-DOC 26682

    ISHIBAZAWA, AKIHIRO; PRETTO, LUCAS R. de ; ALIBHAI, A. YASIN; MOULT, ERIC M.; ARYA, MALVIKA; SOROUR, OSAMA; MEHTA, NIHAAL; BAUMAL, CAROLINE R.; WITKIN, ANDRE J.; YOSHIDA, AKITOSHI; DUKER, JAY S.; FUJIMOTO, JAMES G.; WAHEED, NADIA K.. Retinal nonperfusion relationship to arteries or veins observed on widefield optical coherence tomography angiography in diabetic retinopathy. Investigative Ophthalmology & Visual Science, v. 60, n. 13, p. 4310-4318, 2019. DOI: 10.1167/iovs.19-26653

    Abstract: PURPOSE. To evaluate whether retinal capillary nonperfusion is found predominantly adjacent to arteries or veins in eyes with diabetic retinopathy (DR). METHODS. Sixty-three eyes from 44 patients with proliferative DR (PDR) or non-PDR (NPDR) were included. Images (12 3 12-mm) foveal-centered optical coherence tomography (OCT) angiography (OCTA) images were taken using the Zeiss Plex Elite 9000. In 37 eyes, widefield montages with five fixation points were also obtained. A semiautomatic algorithm that detects nonperfusion in full-retina OCT slabs was developed, and the percentages of capillary nonperfusion within the total image area were calculated. Retinal arteries and veins were manually traced. Based on the shortest distance, nonperfusion pixels were labeled as either arterial-side or venous-side. Arterial-adjacent and venous-adjacent nonperfusion and the A/V ratio (arterial-adjacent nonperfusion divided by venous-adjacent nonperfusion) were quantified. RESULTS. Twenty-two eyes with moderate NPDR, 16 eyes with severe NPDR, and 25 eyes with PDR were scanned. Total nonperfusion area in PDR (median: 8.93%) was greater than in moderate NPDR (3.49%, P < 0.01). Arterial-adjacent nonperfusion was greater than venousadjacent nonperfusion for all stages of DR (P < 0.001). The median A/V ratios were 1.93 in moderate NPDR, 1.84 in severe NPDR, and 1.78 in PDR. The A/V ratio was negatively correlated with the total nonperfusion area (r ¼ 0.600, P < 0.0001). The results from the widefield montages showed similar patterns. CONCLUSIONS. OCTA images with arteries and veins traced allowed us to estimate the nonperfusion distribution. In DR, smaller nonperfusion tends to be arterial-adjacent, while larger nonperfusion tends toward veins.

    Palavras-Chave: tomography; optical modes; optical equipment; diabetes mellitus; blood vessels; ischemia; retina; veins

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  • IPEN-DOC 23101

    RAELE, MARCUS P. ; PRETTO, LUCAS R. de ; ZEZELL, DENISE M. . Soldering mask laser removal from printed circuit boards aiming copper recycling. Waste Management, v. 68, p. 475-481, 2017. DOI: 10.1016/j.wasman.2017.07.019

    Abstract: Management of waste of electric and electronic equipment (WEEE) is a key issue for modern societies; furthermore, it contains valuable materials that can be recycled, especially in printed circuit boards (PCB), which have approximately one-third of their weight in copper. In this study we demonstrated the use of laser to strip the covering soldering mask on PCB’s, thus exposing the copper underneath so that extraction techniques may take place. Using a Q-Switched Nd:YAG laser operating at 1064 nm and 532 nm we tested the procedure under different energy conditions. The laser stripping of the soldering mask was achieved with satisfactory results by irradiation with 225 mJ at 1064 nm. However, when using similar parameters at 532 nm the process of the coating ejection was not promoted properly, leading to a faulty detachment. Infrared laser PCB stripping presents itself to be technically viable and environmental friendly, since it uses no chemicals inputs, offering one more option to WEEE treatment and recycling.

    Palavras-Chave: copper; electronic equipment; electronic wastes; neodymium lasers; printed circuits; pulsed irradiation; recycling; removal; removal; respirators; soldering; testing; waste management

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ATENÇÃO!

ESTE TEXTO "AJUDA" ESTÁ SUJEITO A ATUALIZAÇÕES CONSTANTES, A MEDIDA QUE NOVAS FUNCIONALIDADES E RECURSOS DE BUSCA FOREM SENDO DESENVOLVIDOS PELAS EQUIPES DA BIBLIOTECA E DA INFORMÁTICA.

O gerenciamento do Repositório está a cargo da Biblioteca do IPEN. Constam neste RI, até o presente momento 20.950 itens que tanto podem ser artigos de periódicos ou de eventos nacionais e internacionais, dissertações e teses, livros, capítulo de livros e relatórios técnicos. Para participar do RI-IPEN é necessário que pelo menos um dos autores tenha vínculo acadêmico ou funcional com o Instituto. Nesta primeira etapa de funcionamento do RI, a coleta das publicações é realizada periodicamente pela equipe da Biblioteca do IPEN, extraindo os dados das bases internacionais tais como a Web of Science, Scopus, INIS, SciElo além de verificar o Currículo Lattes. O RI-IPEN apresenta também um aspecto inovador no seu funcionamento. Por meio de metadados específicos ele está vinculado ao sistema de gerenciamento das atividades do Plano Diretor anual do IPEN (SIGEPI). Com o objetivo de fornecer dados numéricos para a elaboração dos indicadores da Produção Cientifica Institucional, disponibiliza uma tabela estatística registrando em tempo real a inserção de novos itens. Foi criado um metadado que contém um número único para cada integrante da comunidade científica do IPEN. Esse metadado se transformou em um filtro que ao ser acionado apresenta todos os trabalhos de um determinado autor independente das variáveis na forma de citação do seu nome.

A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

1. Portaria IPEN-CNEN/SP nº 387, que estabeleceu os princípios que nortearam a criação do RDI, clique aqui.


2. A experiência do Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP) na criação de um Repositório Digital Institucional – RDI, clique aqui.