Laser Power Settings Research Articles

Potential Mechanisms of Intraocular Pressure Reduction by Micropulse Transscleral Cyclophotocoagulation in Rabbit Eyes.

PurposeTo evaluate the histological changes associated with, and the potential mechanisms of, intraocular pressure (IOP) reduction by micropulse cyclophotocoagulation (MP-CPC) in rabbit eyes.MethodsMP-CPC was performed on the right eyes of Dutch belted rabbits, whereas the left eyes served as controls. The laser power settings were 250, 500, 750, 1000, 1500, and 2000 mW, 10 seconds per sweep, 100 seconds in total. IOP, outflow facility, and uveoscleral outflow tract imaging, using a fluorescent tracer, were examined at one week after MP-CPC. Changes of morphology and protein expressions in the outflow tissues, conjunctiva, and sclera were also evaluated.ResultsSignificant reductions in IOP after MP-CPC were observed at 500 to 1000 mW (P = 0.036 and P = 0.014, respectively). The pre-MP-CPC IOP was 11.35 ± 0.41 mm Hg. At one week after surgery, the respective IOP values in the eyes treated at 500 mW and 1000 mW were 9.45 ± 0.49 mm Hg and 7.4 ± 0.27 mm Hg, respectively. Severe ciliary body damage was observed at 1500 to 2000 mW. MMP1–3 and fibronectin expression levels in the outflow tract and ciliary body were upregulated after MP-CPC. The α-smooth muscle actin (α-SMA) was upregulated at higher power levels. MP-CPC significantly increased uveoscleral outflow, whereas the outflow facility did not change. The α-SMA, collagen, and fibronectin were significantly upregulated in the subconjunctiva and sclera.ConclusionsReactive fibrotic responses were observed in the outflow tract, conjunctiva, and sclera after MP-CPC. A potential mechanism of IOP reduction by MP-CPC in pigmented rabbit eyes may involve increased uveoscleral outflow related to MMP upregulation.

What is the impact of pulse modulation technology, laser settings and intraoperative irrigation conditions on the irrigation fluid temperature during flexible ureteroscopy? An in vivo experiment using artificial stones.

To investigate the effect of different combinations of laser power settings and irrigation conditions using the pulse modulation technology of Quanta™ on irrigation fluid temperature (IFT) during FURS (flexible ureteroscopy) on an in-vivo porcine model with artificial stones. A female pig was used. Following the insertion of artificial stones (Begostone™, BEGO USA, Lincoln, RI), a K-type thermocouple was fixed to the created percutaneous access tract. Real-time recordings of IFT during FURS were performed without UAS (ureteral access sheath), with 10/12 UAS, 12/14 UAS and 14/16 UAS. Stone fragmentation was achieved using Quanta Litho Cyber Ho 150W™ (Samarate, Italy). The IFT was recorded for 30s, during laser activation, with power settings of 20, 40, 60, 75 and 100W under both manual pump and gravity irrigation. The IFT rise above 54°C was recorded above a power of 40W when gravity irrigation was used. The use of UAS prolonged the time for IFT to reach high values, although high power settings increase IFT within seconds from the laser activation. Under pump irrigation, only the 100W power setting without the use of UAS resulted in dangerous IFT after approximately 10s. The high-power Ho:YAG laser can cause a damaging thermal effect to the kidney exceeding the threshold of 54°C, under gravity irrigation. Lower power settings (up to 40W) can be used with safety. According to our experiment, when using high power settings, the use of UAS and manual pump irrigation, is the safest combination regarding renal thermal damage.

Fusion enhancement of hollow tungsten arc coaxially assisted by fiber laser

Bead-on-plate experiment was performed on a continuous-mode fiber-laser hollow tungsten coaxial welding platform designed and built by us. The weld bead cross-section was observed by using a optics microscope, and the welding arc image was recorded by using a high-speed camera to track the welding process. The changes in the arc physical field after laser addition were analyzed by conducting numerical simulations to explore the mechanism of increasing the welding depth. The results showed that the coaxial hybrid of fiber laser and hollow tungsten arc can significantly increase the weld depth and thermal efficiency of hybrid arc. When the welding current remained constant at 70 A, the weld penetration increased with an increase in the laser power. However, the growth rate was different under different laser power settings and there were the upper and lower critical values of laser power which were 450 W and 60 W. When the laser power remained constant at 400 W, the weld penetration first increased and then remained constant with an increase in the current, and there was a current critical value of 170 A. The main reasons for the increase in the penetration depth were the increase in the arc temperature, arc pressure and thermal efficiency of hybrid welding.

Directed Energy Deposition roughness mitigation through laser remelting

One of the remaining challenges faced by Directed Energy Deposition is the poor surface finish induced by unmolten particles and the inherent superposition of layers during the process. The DED roughness levels are known to be significantly higher than for conventional parts and can become critical for the fatigue life and corrosion of the component. This is why the production of a DED part always requires a post-processing surface finishing step, which is known to be costly and to have a significant impact on the production time. This paper therefore presents an evaluation of single-track roughness induced by the DED process through transversal cross-sections, top-view micrographs, in situ process monitored images, laser triangulation, and contact-type measurements. The main DED process parameters defining the roughness are identified as being the particle diameter, laser beam diameter, and laser power. Finally, laser remelting during the production of cubic samples is proposed as a solution to further mitigate the roughness. Roughness levels on the top surface are reduced up to 86% with sufficiently high laser power settings. Laser remelting is therefore recommended to minimize the roughness, in combination with an optimal process parameter selection.

Influence of laser power in nanosecond laser texturing for a hydrophobic state on SS316L

The use of lasers in surface engineering has recently made significant progress. The hydrophobic surface is commonly studied because of the application in various fields, including vehicles, aerospace, biomedicine, etc. Since these laser methods require many combination parameters, such as laser power (P), frequency (ƒ), scan speed (ʋ) and laser beam diameter (D), the effect of the parameters must therefore be investigated to produce the hydrophobic condition. This research tries to relate the laser power with the morphological properties and contact angle of the SS316L surfaces. Samples are subjected to laser texturing with different laser power settings. The surface is then characterised by surface roughness, and the contact angle is measured according to a specific time interval. The laser power output and energy density function on the surface and contact angle were investigated in these contexts experimentally. Surface roughness was defined and validated to show that the laser parameters' effect is effective and controllable. This study shows that the laser output intensity significantly contributes to regulating surface roughness and the substrate's wetting activity. The 18W and 24W laser outputs produce a spiked surface with various peaks that cause the surface to become hydrophobic over time because of the air-trap that happens in the valley.

Fabricating plasma bonded microfluidic chips by CO2 laser machining of PDMS by the application of viscoelastic particle focusing and droplet generation

In this study, direct CO2 laser machining of microchannels onto PDMS slabs and plasma bonding for sealing have been shown to provide the fastest method to fabricate PDMS microfluidic chips. Due to resolidification, the ashes and dust remains that cover the PDMS slab surface following this ablation process change the surface chemistry and prevent plasma bonding. Removing these remnants on the surface has been shown to be only possible via attaching and detaching a tape to the surface. The effect of laser frequency, speed and power settings has been investigated over the entire possible range with regards to channel geometry. The best laser settings were determined and the resulting output channels were examined under SEM and optical microscopes. PDMS spin coating after laser machining has been proposed as a pre-treatment process to improve the geometrical features of the channel. Water-in-oil droplet generation in the T-junction, as well as microparticle focusing in viscoelastic fluid – used to sample enrichment– have been shown as examples of applications that benefit from precise direct laser machined microchannels.

MP65-03 DOES THE NOVEL THULIUM LASER GENERATE MORE HEAT THAN THE CONVENTIONAL HOLMIUM LASER?

You have accessJournal of UrologyStone Disease: Surgical Therapy V (MP65)1 Sep 2021MP65-03 DOES THE NOVEL THULIUM LASER GENERATE MORE HEAT THAN THE CONVENTIONAL HOLMIUM LASER? Joshua D. Belle, Nathaniel Srikureja, Natalie Chen, Mohamed Keheila, Akin S. Amasyali, Jenna Lee, Mohammad Hajiha, and D. Duane Baldwin Joshua D. BelleJoshua D. Belle More articles by this author , Nathaniel SrikurejaNathaniel Srikureja More articles by this author , Natalie ChenNatalie Chen More articles by this author , Mohamed KeheilaMohamed Keheila More articles by this author , Akin S. AmasyaliAkin S. Amasyali More articles by this author , Jenna LeeJenna Lee More articles by this author , Mohammad HajihaMohammad Hajiha More articles by this author , and D. Duane BaldwinD. Duane Baldwin More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002105.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The novel thulium fiber laser (TFL) has been shown to break stones more rapidly than the traditional holmium:YAG laser (HL). However, some evidence suggests that the TFL may generate comparatively more heat. The purpose of this study is to compare ureteral temperatures generated by these lasers during flexible ureteroscopic laser lithotripsy in a benchtop model. METHODS: A 1-cm BegoStone (CaOx monohydrate consistency) was manually impacted in the proximal ureter of a 3D printed kidney-ureter model and submerged in 35°C saline. Lithotripsy was performed with a flexible ureteroscope and a 200 μm laser fiber without a ureteral access sheath. Three lasers were compared (Dornier 30W HL, Olympus 100W HL, and Olympus 60W TFL). A needle thermocouple to measure temperature was inserted 2 mm from the laser tip. Irrigation was maintained at 35cc/min at room temperature using the Thermedx FluidSmart System. Intraluminal temperature was continuously recorded for 60 seconds of laser activation. Time was given between each trial for the intraureteral fluid to return to room temperature. 5 trials were performed for each of 4 different power settings: 3.6, 10, 20, and 30 Watts. ANOVA and Mann-Whitney U tests were performed, with p<0.05 considered significant. RESULTS: Intraureteral fluid temperature increased as laser power settings increased for all lasers trialed (p<0.05, table 1). The TFL produced significantly higher temperatures at both 3.6W (26.36°C vs. 24.57°C (Dornier) and 23.23°C (Empower); p<0.05) and 30W (41.76°C vs. 37.28°C (Empower); p<0.05). There was no difference in intraureteral temperature between lasers at the 10W and 20W settings. At 30W, the TFL generated supraphysiologic intraluminal temperature. CONCLUSIONS: The TFL generated significantly more heat at both the 3.6W and 30W settings. Supraphysiologic ureteral temperatures may be generated by the TFL with extended use at high energy settings and low irrigation rates. Understanding the heat generation properties of both the Holmium and Thulium lasers during ureteroscopy could help improve the safety of ureteroscopic laser lithotripsy. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e1119-e1119 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Joshua D. Belle More articles by this author Nathaniel Srikureja More articles by this author Natalie Chen More articles by this author Mohamed Keheila More articles by this author Akin S. Amasyali More articles by this author Jenna Lee More articles by this author Mohammad Hajiha More articles by this author D. Duane Baldwin More articles by this author Expand All Advertisement Loading ...

PD26-07 IMAGE DISTORTION DURING FLEXIBLE URETEROSCOPY: A LABORATORY MODEL COMPARING SUPER PULSE THULIUM FIBER (SPTF) LASER VS HIGH POWER HO:YAG LASER

You have accessJournal of UrologyStone Disease: Surgical Therapy III (PD26)1 Sep 2021PD26-07 IMAGE DISTORTION DURING FLEXIBLE URETEROSCOPY: A LABORATORY MODEL COMPARING SUPER PULSE THULIUM FIBER (SPTF) LASER VS HIGH POWER HO:YAG LASER Caleb S Miller, Bristol B Whiles, David A Duchene, Donald A Neff, and Wilson R Molina Caleb S MillerCaleb S Miller More articles by this author , Bristol B WhilesBristol B Whiles More articles by this author , David A DucheneDavid A Duchene More articles by this author , Donald A NeffDonald A Neff More articles by this author , and Wilson R MolinaWilson R Molina More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002019.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Digital ureteroscopes employ “chip on the tip” technology which allows significant improvement in image resolution. However, image distortion often occurs during laser lithotripsy due to acoustic wave production. We sought to compare the Super Pulse Thulium Fiber (SPTF) laser with the high power Holmium (Ho:YAG) laser in terms of image distortion using variable laser power settings and laser fiber tip distance from the scope’s tip. METHODS: Utilizing a silicone renal model fitted with a 12/14F access sheath, we developed a laboratory model to simulate ureteroscopy. The LithoVue (Boston Scientific), disposable digital flexible ureteroscope was used with 200 micron laser fibers for both the SPTF (Soltive-Olympus) and High power Ho:YAG laser (P120-Lumenis). At defined laser parameters (10, 20, 30, and 40W; short pulse) the laser fiber was slowly retracted toward the tip of the scope during laser activation. Image distortion was identified, and distance from the laser tip to the scope tip was determined. Data from the two lasers were compared utilizing a paired t-test. RESULTS: Image distortion occurred at greater distance with the Ho:YAG compared to SPTF at all laser settings (Table 1). Additionally, higher power (W) was associated with image distortion occurring further from the tip of the scope (p<0.01 for Ho:YAG; p=0.02 for SPFT). At the same power (W) with either 1J or 0.5J, there was no difference in distance for image distortion for the Ho:YAG, but distortion occurred differently with the SPTF (20 and 40W; p<0.01 and p=0.02, respectively). CONCLUSIONS: Increased total power as well as decreased distance between the scope and laser fiber tip results in image distortion during flexible ureteroscopy. Image distortion occurs at a greater distance with the Ho:YAG laser than with SPTF fibers at the same laser settings. SPTF seems to have a better safety profile in terms image distortion and potential scope damage. Further evaluation utilizing Ho:YAG on modulated pulse mode is warranted. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e440-e440 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Caleb S Miller More articles by this author Bristol B Whiles More articles by this author David A Duchene More articles by this author Donald A Neff More articles by this author Wilson R Molina More articles by this author Expand All Advertisement Loading ...

Improving surface quality in selective laser melting based tool making

In the last years, Additive Manufacturing, thanks to its capability of continuous improvements in performance and cost-efficiency, was able to partly replace and redefine well-established manufacturing processes. This research is based on the idea to achieve great cost and operational benefits especially in the field of tool making for injection molding by combining traditional and additive manufacturing in one process chain. Special attention is given to the surface quality in terms of surface roughness and its optimization directly in the Selective Laser Melting process. This article presents the possibility for a remelting process of the SLM parts as a way to optimize the surfaces of the produced parts. The influence of laser remelting on the surface roughness of the parts is analyzed while varying machine parameters like laser power and scan settings. Laser remelting with optimized parameter settings considerably improves the surface quality of SLM parts and is a great starting point for further post-processing techniques, which require a low initial value of surface roughness.

Spectrophotometric evaluation of the effectiveness of Er,Cr:YSGG laser-assisted intracoronal tooth bleaching treatment using different power settings

BackgroundNon-vital tooth discoloration is a common condition in dental practice. The aim of this in vitro study was to evaluate the efficacy of intracoronal bleaching treatments of non-vital teeth either activated or not by Er,Cr:YSGG laser (2780 nm) operating at 1.25 or 2.5 W. MethodsTwenty four human canines were artificially stained after implementation of root canal treatment. Subsequently, the teeth were randomly divided into three groups (n = 8): Group 1 (control) received intracoronal bleaching treatment with a bleaching gel containing 35 % hydrogen peroxide for 40 min, Group 2 received the same treatment assisted with Er,Cr:YSGG laser (2780 nm) operating at 1.25 W average power for 30 s and Group 3 received the same treatment with Group 2, but the average power was adjusted to 2.5 W. The bleaching treatments repeated after one week. Spectrophotometric analysis of tooth color change (ΔE) was implemented 7 days after both bleaching sessions. ResultsThe results of two-way ANOVA revealed that there was a tendency of no significant difference in color change between the three experimental groups (p = 0.063). However, the between-group comparisons showed that laser 2.5 W group had significantly higher ΔE than the control group after the first bleaching session. Moreover, a significant interaction between bleaching treatment and number of applications was detected (p = 0.026). ConclusionsEr,Cr:YSGG laser irradiation significantly increased ΔE only after the first bleaching session when operating at 2.5 W. After the second bleaching session ΔE was not different compared to the control group, irrespectively of the laser power settings.

Heterogeneous sensing and scientific machine learning for quality assurance in laser powder bed fusion – A single-track study

Laser Powder Bed Fusion (LPBF) is the predominant metal additive manufacturing technique that benefits from a significant body of academic study and industrial investment given its ability to create complex geometry parts. Despite LPBF’s widespread use, there still exists a need for process monitoring to ensure reliable part production and reduce post-build quality assessments. Towards this end, we develop and evaluate machine learning-based predictive models using height map-derived quality metrics for single tracks and the accompanying pyrometer and high-speed video camera data collected under a wide range of laser power and laser velocity settings. We extract physically intuitive low-level features representative of the meltpool dynamics from these sensing modalities and explore how these vary with the linear energy density. We find our Sequential Decision Analysis Neural Network (SeDANN) model – a scientific machine learning model that incorporates physical process insights – outperforms other purely data-driven black box models in both accuracy and speed. The general approach to data curation and adaptable nature of SeDANN’s scientifically informed architecture should benefit LPBF systems with an evolving suite of sensing modalities and post-build quality measurements.

Effects of irrigation parameters and access sheath size on the intra-renal temperature during flexible ureteroscopy with a high-power laser.

To investigate the effect of different laser power settings on intra-renal temperature (IRT) under different irrigation conditions during flexible ureteroscopy (FURS) in a live-anesthetized porcine model. Following ethics approval, 2 female pigs weighing ~ 28kg were used. Under general anesthesia, a percutaneous access was obtained to fix a K-type thermocouple inside the pelvi-calyceal system for real-time recording of IRT during FURS without UAS, UAS-10/12, UAS-12/14, and UAS-14/16F. A high-power holmium laser was used and the IRT was recorded during laser activation for up to 60s at a laser power of 20W, 40W, and 60W under gravity irrigation and manual pump irrigation. Under gravity irrigation, FURS without UAS was associated with hazardous IRT at a laser power as low as 20W for as short as 20s of laser activation. The IRT was rendered borderline when UAS was used. This UAS buffering effect disappeared with the use of higher laser-power settings (40W and 60W) with the maximal IRT exceeding 60°C. Moreover, laser activation at 60W was associated with very rapid increase in IRT within few seconds. Under pump irrigation, laser activation at the highest power setting (60W) for 60s was associated with a safe IRT, even without the use of UAS. The maximal IRT was below 45°C. The use of high-power Ho:YAG laser carries potentially harmful thermal effect when used under gravity irrigation, even when large-diameter UAS is used. High-power settings (> 40W) require high irrigation flow. The use of UAS is advisable to reduce the IRT and balance any intra-renal pressure increase.

Thermal effect of holmium laser during ureteroscopic lithotripsy

BackgroundHolmium laser lithotripsy is the most common technique for the management of ureteral stone. Studies founded that holmium laser firing can produce heat which will cause thermal injury towards ureter. The aim of our current study is to explore factors affecting thermal effect of holmium laser during ureteroscopic lithotripsy.MethodsAn in vitro experimental model is design to simulate the ureteroscopic lithotripsy procedure. Different laser power settings (10w (0.5JX20Hz, 1.0 JX10Hz), 20w (1.0 JX20Hz, 2.0 JX10Hz), 30w (1.5JX20Hz, 3.0 JX10Hz)) with various firing time (3 s, 5 s, 10s) and irrigation flow rates(10 ml/min, 15 ml/min, 20 ml/min and 30 ml/min) were employed in the experiment. The temperature around the laser tip was recorded by thermometer.ResultsThe temperature in the “ureter” rises significantly with the increasing laser power, prolonging firing time and reducing irrigation flow. The highest regional temperature is 78.0 °C at the experimental set-up, and the lowest temperature is 23.5 °C. Higher frequency setting produces more heat at the same power. Laser power < =10w, irrigation flow> = 30 ml/min and “high-energy with low-frequency” can permit a safe working temperature.ConclusionWe clarify that the thermal effect of holmium laser is related with both laser working parameters and irrigation flow. The proper setting is the key factor to ensure the safety during ureteroscopic holmium laser lithotripsy.

Effect of Er:YAG Laser Etching on the Shear Bond Strength and Microleakage of Self-Glazed Zirconia Ceramics.

Objective: To investigate the effect of Er:YAG laser irradiation on the shear bond strength (SBS) and microleakage of self-glazed zirconia (SZ) ceramics. Background: SZ is a novel type ceramic; laser irradiation has started to be used in the surface treatment of different ceramics, while SZ has been rarely studied to improve the bond quality. Methods: One hundred twenty blocks (5 mm × 5 mm × 5 mm) of SZ ceramics were produced and split into eight groups following different surface treatments (n = 15): Group A: no treatment; Group B: standard grid processing; and Group C-H: different Er:YAG laser power settings (100, 200, 300, 400, 500, and 600 mJ). Ten blocks of each group received the measurement of SBS and fracture mode analysis, three blocks underwent the evaluation of the microleakage depths, and the other two blocks were observed under the scanning electronic microscopy (SEM). Results: Group F obtained the highest SBS and the lowest microleakage depth without damaging the ceramic surface structure, which was statistically significant compared with the control group and gridding group (p < 0.05), whereas the difference was not statistically significant (p > 0.05) between group E and group F. The results of bonding performance were consistent with failure types and observation of surface characterizations in SEM images. Conclusions: According to the results here, Er:YAG irradiation had effect on surface treatment. In addition, 400 mJ Er:YAG could increase the SBS and decrease the microleakage depth on SZ ceramics without damaging the surface structure.

The Rise and Fall of High Temperatures During Ureteroscopic Holmium Laser Lithotripsy.

Introduction: Temperatures over 43°C-the threshold for cellular injury-may be achieved during ureteroscopic holmium laser lithotripsy. The time to reach and subsequently clear high temperatures at variable laser power settings and irrigation pressures has not been studied. Methods: A flexible or semirigid ureteroscope was placed within an 11/13 F ureteral access sheath inserted into a 250-mL saline bag simulating a normal-caliber ureter, renal pelvis reservoir, and antegrade irrigation flow. A thermocouple was placed adjacent to a 365 μm fiber fired for 45 seconds at 0.6 J/6 Hz, 0.8 J/8 Hz, 1 J/10 Hz, 1 J/20 Hz, and 0.2 J/80 Hz. Irrigation pressures of 200, 100, and 0 mm Hg were tested. Mean temperature changes were recorded with 6°C increase as a threshold for injury (as body temperature is 6°C below 43°C). Results: Semirigid scope: At 200 mm Hg no temperature changes >6°C were observed. At 100 mm Hg, changes >6°C occurred with 1 J/20 Hz within 1 second of activation and returned to ≤6°C within 1 second of cessation. At 0 mm Hg, changes >6°C occurred with all settings; within 1 second at power ≥10 W. Temperatures returned to ≤6°C within 5-10 seconds. Flexible scope: At 200 mm Hg, changes >6°C occurred at 1 J/10 Hz (15 seconds), 0.2 J/80 Hz (3 seconds), and 1 J/20 Hz (2 seconds). Temperatures returned within 6°C of baseline within 2 seconds. At 100 mm Hg, changes >6°C occurred in all but 0.6 J/6 Hz. Temperatures returned to ≤6°C in 5-10 seconds. At 0 mm Hg, all settings produced changes >6°C within 3 seconds, except 0.6 J/6 Hz (35 seconds). Temperatures returned to ≤6°C in under 10 seconds. Conclusions: High temperatures were achieved in our in vitro model in as little as 1 second at common irrigation pressures and laser settings, particularly with a flexible ureteroscope and power ≥10 W. However, with laser cessation, temperatures quickly returned to a safe level at each irrigation pressure.

Chromosome Analysis Using Benchtop Flow Analysers and High Speed Cell Sorters.

The use of the DNA dyes Hoechst (HO) and chromomycin A3 (CA3) has become the preferred combination for the bivariate analysis of chromosomes from both human and animals. This analysis requires a flow cytometer equipped with lasers of specific wavelength and of higher power than is typical on a conventional bench top flow cytometer. In this study, we have investigated the resolution of chromosome peaks in a human cell line with normal flow karyotype using different combinations of DNA dyes on a number of flow cytometers available in a flow cytometry core facility. Chromosomes were prepared from the human cell line using a modified polyamine isolation buffer. The bivariate flow karyotypes of different DNA dyes combination; 4′‐6‐diamidino‐2‐phenylindole (DAPI) or Hoechst with propidium iodide (PI), obtained from different flow cytometers were compared to the reference flow karyotype of DAPI or Hoechst with chromomycin A3, generated from a Mo‐Flo cell sorter using laser power settings of 300 mW each of UV and 457 nm. Good chromosome separation was observed in most of the flow cytometers used in the study. This study demonstrates that chromosome analysis and sorting can also be performed on benchtop flow cytometers equipped with the standard solid state 488 and 355 nm lasers, using a DNA dye combination of DAPI or Hoechst with PI. © 2018 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Fluorometric Quantification of Single-Cell Velocities to Investigate Cancer Metastasis.

Hematogenous metastasis is a multistep, selectin-regulated process whose mechanisms remain poorly understood. To investigate this biological pathway of cancer dissemination and better understand circulating cancer cells, we developed a high-throughput methodology that integrates organ-on-chip-like microfluidic and photoconvertible protein technologies. Our approach can ascribe single-cell velocity as a traceable cell property for off-chip analysis of the direct relationships between cell molecular profiles and adhesive phenotypes in the context of physiologically relevant fluid flow. We interrogate how natively expressed selectin ligands relate to colon cancer cell rolling frequencies and velocities and provide context for previously reported disparities in invitro and invivo models of selectin-mediated adhesion and metastasis. This integrated methodology represents a versatile approach for the development of anti-metastatic therapeutics as well as to generate and test mechanistic hypotheses regarding spatiotemporal processes that occur over timescales of seconds to hours with single-cell resolution.

A three-dimensional transient computational study of 532-nm laser thermal ablation in a geometrical model representing prostate tissue

Objective: Laser with 532-nm wavelength (GreenLightTM) is clinically approved to treat benign prostatic hyperplasia (BPH). However, low rate of tissue ablation and excessive thermal coagulation are shortcomings of this therapy. The goal of this study was to use a mathematical model to identify clinically viable laser settings that have the potential to improve treatment time and outcomes.Methods: A three-dimensional transient computational model was developed, validated against analytical and experimental results, and utilized to investigate the response of tissues subjected to continuous-wave and pulsed lasers emitting 532-nm light (GreenLightTM laser). The impact of laser power (10–125 W), pulse duration (100 ns and 100 µs) and pulse frequency (10 and 100 Hz) on tissue ablation and coagulation rates and sizes was explored.Results: Good agreement between the computational model and analytical and experimental results was found. Continuous-wave laser results in 13% less coagulation zone thickness and 10% higher ablation rate than the low frequency pulsed laser. With increasing laser power; ablation rate is expected to increase linearly, while coagulation zone thickness is expected to increase asymptotically. Pulse frequency influence on tissue ablation and coagulation is relevant at high power, but pulse duration is found to have minimal effect at all powers.Conclusions: Laser thermal tissue ablation employing continuous wave mode lasers outperforms that employing pulsed mode lasers. Laser power settings should be carefully selected to maximize the rate of tissue ablation and minimize tissue coagulation.

Holmium-YAG laser: impact of pulse energy and frequency on local fluid temperature in an in-vitro obstructed kidney calyx model.

During laser lithotripsy, energy is transmitted to both the stone and the surrounding fluid. As the energy is delivered, the temperature will rise. Temperatures ≥60 ° C can cause protein denaturation. The objective of this study is to determine the time it takes from body temperature (37°C) to 60°C at various laser power settings. A Flexiva TracTip 200 optical fiber was submerged alongside a negative temperature coefficient-type thermistor in 4mL of saline in a glass test tube. A Lumenis VersaPulse Powersuite 100-W holmium:yttrium aluminum garnet laser was activated at 0.2- to 1.5-J pulse energies, 6- to 50-Hz frequencies, and 2- to 22.5-W average power. Temperature readings were recorded every second from 37°C until 60°C. Time and heating rate were measured. The procedure was repeated three times for each setting. Average time from 37°C to 60°C for settings (1)0.2J/50Hz, (2)0.6J/6Hz, (3)1J/10Hz, and (4)1.5J/10Hz was 60.3, 172.7, 58, and 43.3s, respectively. Time from 37°C to 60°C decreased as frequency increased for every given pulse energy. Average heating rate increased proportionally to power from 0.06°C/s at 2 W to 0.74°C/s at 22.5 W. During laser lithotripsy, there is a rapid increase in the temperature of its surrounding fluid and temperatures ≥60 ° C may be reached. This could have local tissue effects and some caution with higher power settings should be employed especially where irrigation is limited. Further studies incorporating irrigation and live tissue models may aid to further define the risks.

Shear Bond Strength of Different CAD/CAM Ceramics: Acid vs Er:YAG Laser Etching.

To evaluate whether Er:YAG laser etching could be an alternative surface treatment to hydrofluoric (HF) acid etching. Surface treatment is important to bonding properties and utility times of computer aided design/computer aided manufacture (CAD/CAM) dental ceramics. The traditional method of HF acid etching is harmful to humans if not handled properly. Four different CAD/CAM ceramics (Vita Mark II, IPS Empress CAD, IPS e.max CAD, and Vita Enamic) were cut into 72 blocks and divided into 6 groups according to different surface treatments (n = 12): Group A: no treatment; Group B: HF acid; and Group C to F: different Er:YAG laser power settings (300, 400, 500, and 600 mJ). Ten blocks of each group were measured for shear bond strength (SBS) and the failure modes were evaluated; the rest blocks were observed by scanning electronic microscopy (SEM). HF acid etching resulted in the highest SBS for Vita Mark II, IPS Empress CAD, and Vita Enamic; however, the difference was not statistically significant (p > 0.05) compared to the second highest group of laser with 600 mJ in IPS Empress CAD. For IPS e.max CAD, the highest SBS was obtained from laser group with 400 mJ. The SBS results were consistent with failure modes and surface characterizations in SEM images. Our results showed that Er:YAG laser had little impact on Vita Mark II and Vita Enamic; but proper power settings could be an alternative surface treatment to HF acid etching (600 mJ for IPS Empress CAD and 400 mJ for IPS e.max CAD).