LUCAS RAMOS DE PRETTO

LUCAS RAMOS DE PRETTO

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Nondestructive evaluation of fused filament fabrication 3D printed structures using optical coherence tomography
2020 - DE PRETTO, LUCAS R.; AMARAL, MARCELO M.; FREITAS, ANDERSON Z. de; RAELE, MARCUS P.
Purpose – The quality of components under fused filament fabrication (FFF) is related to the correct filament spacing and bonding of successively deposited layers and is evaluated mainly by scanning electron microscopy (SEM). However, it is a destructive technique and real-time evaluation is not possible. Optical coherence tomography (OCT), on the other hand, is an optical method that acquires cross-sectional images non-invasively and in real-time. Therefore, this paper aims to propose and validate the use of OCT as a non-destructive quality evaluation tool for FFF using Polylactic Acid (PLA) filaments. Design/methodology/approach – PLA three-dimensional (3D) printed samples were made in a variety of nozzle temperatures and mesh spacing. These samples were fractured in liquid nitrogen and inspected using SEM (as a gold standard) to evaluate dimensions and morphology, then the samples were evaluated by OCT in the same area, allowing the results confrontation. Findings – Our results indicate a good correlation between OCT and SEM for the dimensional assessment of layers. When the filament was extruded in lower temperatures, the OCT images presented sharply defined interfaces between layers, in contrary to higher nozzle temperatures, denoting better fusion between them. However, higher extruding temperatures are incurred in greater deviations from nominal dimensions of the mesh. Finally, we demonstrate the advantage of a full 3D tomographic reconstruction to inspect within a FFF sample, which enabled the inspection of “hidden” information, not visible on a single cross-sectional cut. Originality/value – This paper proposes OCT as a novel and nondestructive evaluation tool for FFF.
Quantification of retinal capillary nonperfusion in diabetics using wide-field optical coherence tomography angiography
2020 - 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.
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.
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.
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.
Antimicrobial photodynamic therapy combined to periodontal treatment: experimental model
2017 - BELINELLO-SOUZA, ESTEFANI L.; ALVARENGA, LETICIA H.; LIMA-LEAL, CINTIA; ALMEIDA, PATRICIA; LEITE, CAROLINA G.; LIMA, TAIRINE R.; GODOY-MIRANDA, BIANCA; PREVIATI-OLIVEIRA, JHOSEPHER; PRETTO, LUCAS de; FREITAS, ANDERSON Z. de; FERNANDES, ADJACI U.; MARCOS, RODRIGO L.; PRATES, RENATO A.
tBackground: Antimicrobial photodynamic therapy (aPDT) has been used as an adjuvant treatment forperiodontitis. It combines a photosensitizer with a light source to induce reactive oxygen species and killmicrobial cells. PpNetNI is a protoporphyrin derivative, and it has a chemical binding site at biofilm andgreat affinity to microbial cells. The aim of this study was to investigate the effects of aPDT as an adjuvanttreatment for periodontitis.Methods: Thirty healthy male rats Wistar (Rattus norvegicus) were used in this study (Approved by UNI-NOVE Ethical committee AN0029/2015). Periodontitis was induced by placing a cotton ligature aroundthe first mandibular molar in a subgengival position. The contralateral mandibular first molar receivedneither a ligature nor any treatment, and was used as a control. After 7 days, the ligature was removedand all animals received scaling and root planing (SRP) and were divided according to the following treat-ments: SRP group (received SRP and irrigation with PpNetNI, 10 M) and aPDT group (PpNetNI 10 Mfollowed by LED irradiation). aPDT was performed with a LED (630 nm) with an output power of 400 mW(fluence-rate 200 mW/cm2; fluence 18 J/cm2). Rats were euthanized at 24 h, 48 h and 7 days postopera-tively. The area of bone loss in vestibular region of the first molar was evaluated by Optical CoherenceTomography (OCT, THORLABS LTD., Ely, UK). Data were analyzed statistically (ANOVA and Tukey tests,p < 0.05).Results: The animals treated by aPDT showed bone gain of approximately 30% compared to the SRP groupfollowing 7 days from the treatment.Conclusion: aPDT promoted bone recovery 7 days after periodontal intervention.
Optical coherence tomography for blood glucose monitoring in vitro through spatial and temporal approaches
2016 - PRETTO, LUCAS R. de; YOSHIMURA, TANIA M.; RIBEIRO, MARTHA S.; FREITAS, ANDERSON Z. de
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.