LUCAS RAMOS DE PRETTO

LUCAS RAMOS DE PRETTO

Página do item completo

Resultados de Busca

Agora exibindo 1 - 10 de 24

Desenvolvimento de técnicas diagnósticas quantitativas baseadas em decorrelação de speckle presente nos sinais de Tomografia de Coerência Óptica
2019 - PRETTO, LUCAS R. de
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.
Terapia fotodinâmica antimicrobiana combinada ao tratamento periodontal em ratos
2016 - SOUZA, E.R.L.B. de; ALVARENGA, L.H.; LEAL, C.R.L.; LEITE, C.G.; PEREIRA, T.R.; VIEIRA, D.C.; PRETTO, L. de; FREITAS, A.Z. de; FERNANDES, A.U.; PRATES, R.A.
Introdução: A Terapia Fotodinâmica antimicrobiana (aPDT) vem sendo utilizada como adjuvante ao tratamento da periodontite. Ela combina um fotossensibilizador (FS) e fonte de luz para produzir espécies reativas de oxigênio e matar células microbianas [1]. A PpNetNI é um derivado da protoporfirina, e tem um sítio de ligação química no biofilme e grande afinidade às células microbianas. Este estudo tem como objetivo investigar os efeitos da aPDT como adjuvante ao tratamento da periodontite. Materiais e Métodos: Este estudo (aprovado pelo Comitê de Ética da UNINOVE AN0029/2015) incluiu 18 ratos machos Wistar saudáveis (Rattus norvegicus). A periodontite foi induzida pela inserção de uma ligadura de algodão em posição subgengival no primeiro molar inferior. O primeiro molar inferior contralateral não recebeu a ligadura ou nenhum tipo de tratamento, e foi utilizado como controle. Após 7 dias, a ligadura foi removida e todos animais receberam raspagem e alisamento radicular (RAR) [2]. Os grupos (n=3) foram então divididos em: 1) grupo RAR (receberá RAR e irrigação com PpNetNI, 10 μM, sem irradiação) e 2) grupo PDT (irrigado com PpNetNI 10 μM seguido de irradiação com LED durante 90 s). Para irradiação foi utilizado um LED emitindo comprimento de onda de 630 nm com potência radiante de 400 mW (irradiância - 200 mW/cm2; exposição radiante - 18 J/cm2). As avaliações foram realizadas 24 h, 48 h e 7 dias após a intervenção e para isto, 3 animais de cada grupo foram eutanasiados em cada momento experimental. A área de perda óssea na região vestibular do primeiro molar inferior foi avaliada por Tomografia de Coerência Óptica (OCT, THORLABS LTD., Ely, UK). Os dados foram submetidos à análise estatística (teste Mann-Whitney, p˂0.05). Até o momento foram avaliados 6 animais, que foram tratados conforme descrito e eutanasiados 7 dias após o término do tratamento. Resultados: Dentre os animais que foram eutanasiados 7 dias após o término do tratamento, os animais do grupo PDT mostraram um ganho ósseo de aproximadamente 30% quando comparados ao grupo RAR. A OCT foi capaz de detectar a perda óssea nas amostras e foi um método não destrutivo para este modelo experimental. Conclusões: Com os dados obtidos até o momento e com os parâmetros utilizados neste estudo podemos concluir que a aPDT foi uma alternativa eficaz em garantir a saúde periodontal e foi capaz de regenerar os tecidos de suporte periodontal.
Optical evaluation of polymer deposition for 3D printing
2019 - AMARAL, MARCELLO M.; PRETTO, LUCAS de; RAELE, MARCUS P.
3D printing is a technology that is revolutionizing the productive sector [1]. It allows the production of free- form components and systems. It may ¯nd application from biomedical to aerospace engineering, as well as in the production of unique and speci¯c components needed in basic science laboratories. One of the most common approaches for 3D printing is the fused deposition modeling were a plastic ¯lament is fused and the component shape is modeled by layers deposition [2]. The success in the manufacture of the component is related to the addition between successive deposited layers. Increasing the temperature of the ¯lament to ensure perfect adhesion may compromise the desired shape and function characteristics for the component. Scanning Electronic Microscopy (SEM) is the gold standard technique to ensure the ideal condition for the 3D printing and evaluate the bonding between successive layers [2]. However, in this context, SEM is a destructive technique and do not allow real time application. Low Coherence Interferometry (LCI) is an optical technique capable to performing non-destructive tomography evaluation of scatter medium [3]. Using a Michelson interferometer to measure the backscattered light intensity as a function of depth position associated to a lateral scanning it is possible to obtain a cross-section image of the sample [3]. It is non-invasive, relatively inexpensive technique and could allow real time application during manufacturing. The aim of this work was to investigate the use of low coherence interferometry to evaluate the adhesion of successive layers on 3D printed plastic material. A set of samples were manufactured using a 3D printing (Cliever CL1, Brazil), with layer thickness from 100¡250¹m using PLA ¯lament. The sample were evaluated using a SEM and a commercial LCI (OCP930SR - Thorlabs Inc.) and the images were compared. It was possible to observe a correlation on the observed fused ¯laments between the images acquired by SEM and LCI proving that it is possible to use the optical technique as a alternative for 3D printing quality evaluation.
Retinal nonperfusion relationship to arteries or veins observed on widefield optical coherence tomography angiography in diabetic retinopathy
2019 - 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.
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.
Controlling for artifacts in widefield optical coherence tomography angiography measurements of non-perfusion area
2019 - 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.
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.
Focus tracking system for femtosecond laser machining using low coherence interferometry
2019 - RAELE, MARCUS P.; DE PRETTO, LUCAS R.; ROSSI, WAGNER de; VIEIRA JUNIOR, NILSON D.; SAMAD, RICARDO E.
We designed a real time, single-laser focus tracking system using low coherence properties of the machining femtosecond laser itself in order to monitor and correct the sample position relative to the focal plane. Using a Michelson Interferometer, the system collects data arising from part of the beam backscattered at the ablation spot. The data is analyzed by a custom software for position correction (employing an XYZ automated translation stage). With the focus tracking enabled we were able to etch channels with a stable cross-section profile on a bovine tooth with relief amplitude tens of times greater than the Rayleigh length of the system, keeping the sample inside the confocal parameter during most of the processing time. Moreover, the system is also capable of monitoring crater depth evolution during the ablation process, allowing for material removal assessment.
Quantitative analysis of capillary non-perfusion in diabetic retinopathy using widefield OCT-angiography
2018 - 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.
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.
Backscattered light properties during femtosecond laser ablation and development of a dynamic interferometric focusing system
2018 - RAELE, MARCUS P.; SAMAD, RICARDO E.; FREITAS, ANDERSON Z.; PRETTO, LUCAS de; AMARAL, MARCELLO M.; VIEIRA JUNIOR, NILSON D.; WETTER, NIKLAUS U.
The backscattered light originated when machining with femtosecond laser pulses can be used to accurately measure the processed surface position through an interferometer, as recently demonstrated by our group, in a setup that uses the same laser beam for ablation and inspection. The present work explores the characteristics of the laser light reflected by the target and its interaction with the resulting plasma to better understand its propagation physics and to improve the dynamic focusing system. The origin of this returning radiation was studied and has been traced, mainly, from the peripheral area of the focal spot (doughnut-like). By means of a Mach-Zehnder setup, the interferometric pattern was measured and analyzed aiming to access the influences of the plasma on the laser beam properties, and therefore on the retrieved information. Finally, the wavefront of the laser that creates and propagates through the plasma was characterized using a Shack-Hartmann sensor.
Optical coherence tomography characterization of femtosecond laser manufactured microfluidic circuits
2018 - PRETTO, LUCAS R. de; SAMAD, RICARDO E.; ROSSI, WAGNER de; FREITAS, ANDERSON Z. de
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.
Periodontal treatment combined to antimicrobial photodynamic therapy
2017 - GODOY-MIRANDA, BIANCA; BELINELLO-SOUZA, ESTEFANI; ALVARENGA, LETICIA; LEAL, CINTIA; LEITE, CAROLINA; LIMA, TAIRINE; PREVIATI-OLIVEIRA, JHOSEPHER; FREITAS, ANDERSON; PRETTO, LUCAS de; FERNANDES, ADJACI; PRATES, RENATO
Background: Antimicrobial photodynamic therapy (APDT) has been used as an adjuvant treatment for periodontitis. It combines a photosensitizer (PS) with a light source to induce reactive oxygen species (ROS) and kill microbial cells. PpNetNI is a protoporphyrin derivate, and it has a chemical binding site at biofilm and great affinity to microbial cells. The aim of this study was to investigate the effects of APDT as an adjuvant treatment for periodontitis. Study: Ten healthy male rats Wistar (Rattus norvegicus) were used in this study (Approved by UNINOVE Ethical committee AN0029/2015). Periodontitis was induced by placing a cotton ligature around the first mandibular molar in a subgingival position. The contralateral mandibular first molar received neither a ligature nor any treatment, and was used as a control. After 7 days, the ligature was removed and all animals received scaling and root planning (SRP) and were divided according to the following treatments: SRP group (received SRP and irrigation with PpNetNI, 10 mM) and PDT group (PpNetNI 10 mM followed by LED irradiation). PDT was performed with a LED (630 nm) with an output power of 400mW (fluence-rate 200mW/cm2; fluence 18 J/cm2). Rats were euthanized at 7 days postoperatively. The bone loss was measured by Optical Coherence Tomography (OCT, THORLABS LTD., Newton, US). Data were analyzed statistically (Mann-Whitney test, p<0.05). in vestibular region of the first molar Results: The animals treated by APDT showed a bone gain of approximately 30% compared to the SRP group following 7 days from the treatment. OCT was able to detect bone loss in the samples and it was nondestructive method for this experimental model. Conclusion: In conclusion, within the parameters used in this study, APDT was an effective alternative to held periodontal health after treatment, and it was able to regenerate supportive periodontal tissue.