LUCAS RAMOS DE PRETTO

LUCAS RAMOS DE PRETTO

Página do item completo

Resultados de Busca

Agora exibindo 1 - 10 de 18

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.
New method for depth analysis of Y-TZP t-m phase transformation
2017 - ARATA, A.; PRETTO, L.R. de; USSUI, V.; LIMA, N.B.; FREITAS, A.Z.; MACHADO, J.P.B.; TANGO, R.N.; SOUZA, G.M. de; LAZAR, D.R.R.
Purpose/aim: The aim of this studywas to validate the optical coherence tomography (OCT) as a nondestructive method of analysis to evaluate the depth of tetragonal to monoclinic (t-m) transformed zone and to calculate the kinetics of phase transformation of a monolithic Y-TZP after hydrothermal aging. Specifically, to compare the activation energy of t-m transformation calculated by the depth of the transformed zone using scanning electron microscopy (SEM) and OCT. Materials and methods: Fully sintered (1450 ◦C/2 h) discs of dentalY-TZP (LAVAPLUS, 3M-ESPE)were aged in hydrothermal pressurized reactor to follow the phase transformation kinetics at 120 to 150 ◦C. Four samples per aging time were analyzed by OCT (OCP930SR, Thorlabs Inc.), = 930 nm, spectral bandwidth (FWHM) of 100 nm, nominal resolution of 6 m (lateral and axial) in air, declared digital resolution 3.09 m (axial). Three areas of 3mm (lateral) were observed to calculate the phase transformation depth (Image J). X-ray diffraction analysis (XRD) were performed, Cu-K , 20◦ to 80◦, 2 . The data were refined using the Rietveld method (GSAS). The transversal section of one specimen of each group was submitted to backscattered SEM analysis to calculate the phase transformation depth (Image J). The speed of the transformation zone front was determined plotting the phase transformation depth versus aging time. Results: XRD results indicated that Y-TZP that 66% is the maximum value of monoclinic phase concentration for all aged Y-TZP. The activation energy for the monolithic Y-TZP was 107.53 kJ/mol. One year and 5 years of hydrothermal aging at 37 ◦C will present approximately 4.21% and 15% of monoclinic phase, respectively. The comparison of the depth of the transformed zone using SEM and OCT were similar, showing a linear behavior and providing information that the opaque layer observed by OCT is related to the depth of the transformed zone (Fig. 1), any difference among the results could be a result of the refraction index correction. The energy of activation calculated by SEM and OCT were 114 kJ/mol and 100 kJ/mol, respectively. The speed calculated for the phase transformation into the bulk of the transformed zone estimated for 37 ◦C was 0.04 m/year (SEM) and 0.16 m/year (OCT). Conclusions: The results indicate that activation energy values determined by SEM and OCT observations were similar allowing the use of the OCT as a tool for monolithic Y-TZP t-m phase transformation kinetic evaluation. Moreover, OCT method has the advantage of a shorter analysis time, without the need of sample preparation steps.
Soldering mask laser removal from printed circuit boards aiming copper recycling
2017 - RAELE, MARCUS P.; PRETTO, LUCAS R. de; ZEZELL, DENISE M.
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.
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.