Successful Laser Research Articles

Evolution of middle cerebral artery peak systolic velocity after a successful laser procedure for iatrogenic twin anemia–polycythemia sequence

We report a case of twin anemia-polycythemia sequence (TAPS) treated by laser at 24 + 5 weeks' gestation, 7 weeks after a first laser procedure for twin-to-twin transfusion syndrome at 16 + 6 weeks. This management led to the birth of two healthy neonates by Cesarean section at 36 weeks. In this case, weekly measurement of the middle cerebral artery peak systolic velocity allowed us to monitor the twins after both laser treatments and, more specifically, to detect TAPS. Following delivery, placental injection showed a minuscule coagulated arteriovenous anastomosis. Intrauterine transfusion is generally chosen to manage TAPS, but the choice of therapy must consider gestational age, technical difficulties and disease severity. The laser procedure cannot be used as a curative treatment for TAPS in all cases. We propose a decisional algorithm to help clinicians select the appropriate treatment.

Selective Laser Sintering of Biopolymers with Micro and Nano Ceramic Additives for Medicine

Abstract Biocompatible oxide ceramics were added to bioresorbable polymeric powders for the laser-assisted fabrication of the porous tissue engineering scaffolds. The optimal regimes were determined for the Nd +3 YAG laser sintering. Microstructure researches of the sintered samples were carried out by means of the SEM equipped the EDX and the results were compared with those of the X-ray analysis. The observations showed that after a successful laser sintering the increase of the nano ceramic particles sizes was insignificantly. The results confirm the medical resource of the SLS-fabricated tissue engineering scaffolds.

Prospects for enhancement of ring laser gyroscopes using gaseous media

The most successful Ring Laser Gyroscopes (RLGs) are gas-laser based. It has been recently shown that the type of anomalous dispersion associated with fast light, when present inside an RLG, can increase its scale factor. We evaluate several proposed methods for realizing this appropriate dispersion in gas media, theoretically and experimentally. We find linear gas media in general to be unsuitable for this purpose, with mixed prospects for nonlinear effects.

How to Report Low-Level Laser Therapy (LLLT)/Photomedicine Dose and Beam Parameters in Clinical and Laboratory Studies

Dose and beam parameters are critical for successful laser, LED, and other light therapy treatments; however, in our experience, researchers frequently make critical errors and omissions when submitting papers for publication. Journals frequently publish studies with missing data, mathematical errors, and no reported verification of beam parameters. This makes reproducibility impossible, and further confounds an already complex subject. This article is intended to be a reference document for non-physicist researchers conducting low-level laser therapy (LLLT) laboratory studies and clinical trials to help them design and report the beam and dose aspects of their trials. It provides a checklist to help LLLT researchers understand and report all the necessary parameters for a repeatable scientific study. It includes the eight most important beam parameters to report, which are: wavelength, power, irradiation time, beam area at the skin or culture surface (this is not necessarily the same as the aperture size), pulse parameters, anatomical location, number of treatments, and interval between treatments. The three commonly used dose parameters are time, energy, and energy density. In addition, more thorough reporting would include coherence, application technique (contact, projection, scanning, pressure), beam profile, and spectral width, as these may also be considered important. Beam power often decreases as the device warms up and as the device ages; therefore, this should be checked routinely during an experiment/trial. Measurements of beam area and beam power require special instruments and trained technicians to operate them. Power measurements should be taken before, after, and at frequent intervals during research trials. Reviewers should insist that the minimum eight most important beam parameters are included, and authors should take care to measure and record these accurately before, during, and after an experiment or clinical trial.

High‐frequency ultrasound imaging of noninvasive laser coagulation of the canine vas deferens

A noninvasive approach to vasectomy may eliminate male fear of complications related to surgery (e.g., hematoma, infection, acute and chronic pain, sterilization failure) and increase its acceptance. Noninvasive laser thermal occlusion of the canine vas deferens has recently been reported. In this study, high-frequency ultrasound is used to confirm successful laser thermal coagulation and scarring of the vas in a short-term canine model. Bilateral noninvasive laser coagulation of the vas was performed in a total of nine dogs using a laser wavelength of 1,075 nm, incident power of 9.0 W, pulse duration of 500 milliseconds, pulse rate of 0.5 Hz, and 3-mm-diameter spot. Cryogen spray was used to cool the scrotal skin surface and prevent burns during the procedure. A clinical ultrasound system with a 13.2-MHz high-frequency transducer was used to image the vas before and after the procedure. Burst pressure measurements were performed on excised vas to confirm thermal occlusion. Day 0 and 28 burst pressures averaged 291 ± 31 mmHg and 297 ± 26 mmHg, respectively, significantly greater than ejaculation pressures of 136 ± 29 mmHg. Ultrasound showed a hyperechoic vas segment after thermal coagulation (Day 0) and scarring (Day 28). Doppler ultrasound showed normal blood flow through the testicular artery, indicating no collateral thermal damage to proximal structures. High-frequency ultrasound may be used as a noninvasive diagnostic tool to assist in determining successful short-term laser thermal coagulation and scarring of the vas.

Twin–twin transfusion syndrome treated with laser surgery: postnatal prevalence of congenital heart disease in surviving recipients and donors

To assess postnatal prevalence of congenital heart disease (CHD) in surviving twins treated for twin-twin transfusion syndrome (TTTS) with laser surgery. Patients who underwent laser surgery for TTTS at a single institution were prospectively enrolled between January 2009 and May 2010. Preoperative fetal echocardiography was performed. Perinatal outcomes were obtained via postnatal echocardiograms and review of medical records. CHD was defined as unequivocal structural cardiac pathology; patent foramen ovale and patent ductus arteriosus were excluded. Fifty pregnancies with TTTS were enrolled, with the following Quintero stage distribution: stage I, 10%; stage II, 22%; stage III, 50%; and stage IV, 18%. Of the 88 fetuses born alive, 84 patients (95.5%) completed postnatal cardiac evaluation. Overall postnatal prevalence of CHD was 15.5% (13 of 84): 15.6% of recipient twins and 15.4% of donor twins. Three patients required cardiac intervention during infancy. Among liveborn twins with CHD, the overall prenatal detection rate was 30.8% (4/13), comprising 16.7% (1/6) of donors compared with 42.9% (3/7) of recipients. Following successful laser surgery for TTTS, an increased and comparable postnatal prevalence of CHD occurs among both former recipients and donors.

Laser cleaning of 19th century Congo rattan mats

There is a growing interest by art conservators for laser cleaning of organic materials, such as wooden artworks, paper and textiles, since traditional cleaning with solvents can be a source of further decay and mechanical cleaning may be too abrasive for sensitive fibers. In this work we present a successful laser cleaning approach for 19th century rattan mats from the Brooklyn Museum collection of African Art, now part of the study collection at the Conservation Center in New York. Tests were carried out using the fundamental (1064nm) and second harmonic (532nm) wavelength of a Q-switched Nd:YAG laser to measure threshold values both for surface damage and color changes for different types of rattan samples. The irradiated substrates were investigated by optical microscopy, scanning electron microscopy and by UV–vis spectroscopy in order to determine the efficiency of laser cleaning and to assess possible deterioration effects that may have occurred as a result of laser irradiation. The study showed that by using the laser emission at 532nm, a wavelength for which photon energy is below the bond dissociation level of the main cellulosic compounds and the water absorption is negligible, it is possible to select a range of laser fluences to remove the black dust layer without damaging the rattan material.

Noninvasive laser coagulation of the human vas deferens: Optical and thermal simulations

Successful noninvasive laser coagulation of the canine vas deferens, in vivo, has been previously reported. However, there is a significant difference between the optical properties of canine and human skin. In this study, Monte Carlo (MC) simulations of light transport through tissue and heat transfer simulations are performed to determine the feasibility of noninvasive laser vasectomy in humans. A laser wavelength of 1,064 nm was chosen for deep optical penetration in tissue. MC simulations determined the spatial distribution of absorbed photons inside the tissue layers (epidermis, dermis, and vas). The results were convolved with a 3-mm-diameter laser beam, and then used as the spatial heat source for the heat transfer model. A laser pulse duration of 500 milliseconds, pulse rate of 1 Hz, and cryogen spray cooling were incident on the tissue for 60 seconds. Average laser power (5-9 W), cryogen pulse duration (60-100 milliseconds), cryogen cooling rate (0.5-1.0 Hz), and increase in optical transmission due to optical clearing (0-50%) were studied. After application of an optical clearing agent (OCA) to increase skin transmission by 50%, an average laser power of 6 W, cryogen pulse duration of 60 milliseconds, and cryogen cooling rate of 1 Hz resulted in vas temperatures of approximately 58°C, sufficient for thermal coagulation, while 1 mm of the skin surface (epidermis and dermis) remained at a safe temperature of approximately 45°C. MC and heat transfer simulations indicate that it is possible to noninvasively thermally coagulate the human vas deferens without adverse effects (e.g., scrotal skin burns), if an OCA is applied to the skin prior to the procedure.

Two-Step Matrix Application for the Enhancement and Imaging of Latent Fingermarks

Matrix deposition is a crucial aspect for successful matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) analysis. The search for more efficient protocols over the years has resulted in the devising of "dry matrix methods" in which the matrix is solely or preliminarily deposited as powder and acts in most cases as a seeding agent. Although not fully embraced by the MALDI MSI community, these methods have proven to be more efficient in terms of ion intensity, ion abundance, and ion images in the experimental circumstances they were employed. Here we report a novel two-step matrix application method, that we have named the "dry-wet" method, where the matrix is dusted onto the sample followed by solvent spray using a robotic device. The new method has been successfully applied to the detection and mapping of several analyte classes within latent fingermarks. Dusting the matrix generated the added advantage of enhancing the latent fingermarks which are invisible. This allows not only for an optical image to be taken of the fingermark in situ but also bridges the gap in the application of MALDI MSI technology in this field; with the use of the methodology reported, fingermark enhancement, recovery, and analysis from different surfaces is now compatible with subsequent MALDI MSI analysis thus allowing visual and chemical information to be obtained simultaneously.

Effect of pan retinal photocoagulation on the serum levels of vascular endothelial growth factor in diabetic patients

This study tests the hypothesis that subjects with proliferative diabetic retinopathy (PDR) have a detectable rise in levels of serum vascular endothelial growth factor (VEGF), which is an important regulator of angiogenesis. Our investigation aims to evaluate plasma VEGF changes after pan-retinal photocoagulation (PRP) in diabetic patients. Twenty-nine type two diabetic patients (17 male, 12 female: mean age 53.13±12.22 years) with PDR secondary to diabetes were studied. Blood samples were obtained before and at 2 months after the last PRP session. Serum VEGF levels were measured by ELISA. After PRP, the mean serum VEGF decreased, but this reduction was not remarkable (88.68±71.09 vs. 77.01±60.33 ng/ml) (P=0.18). There was a statistically significant difference in serum VEGF changes between patients who had regressed PDR with patients who had progressed PDR (-25.98±47.37 vs. 56.44±31.7 ng/ml) (P=0.003). Our results showed a significant reduction in levels of serum VEGF in the patients who had successful laser treatment. Our findings suggest that serum VEGF levels could be used for monitoring diabetic retinopathy outcome.

Successful laser lithotripsy using peroral SpyGlass cholangioscopy in a patient with Mirizzi syndrome

Successful laser lithotripsy using peroral SpyGlass cholangioscopy in a patient with Mirizzi syndrome

Separation of Thin GaN from Sapphire by Laser Lift-Off Technique

Laser lift-off of GaN from sapphire substrates has become a viable technique to increase the brightness of GaN-based light-emitting diodes (LEDs). The LEDs free from sapphire exhibit high luminous efficiency by placing highly reflective electrode on the back side. The devices serve low series resistance together with low thermal resistance taking advantages of the vertical structure. Thinner epitaxial structure is desired to serve better device performance, however, cracks in the film after the lift-off limits the minimum thickness. In this paper, successful laser lift-off of very thin GaN with the thickness down to 4 µm is described. The established laser lift-off system utilizes homogenized beam-profile of the employed neodymium-doped yttrium aluminium garnet (Nd:YAG) third harmonic laser in which optimization of the laser fluence minimizes the thickness of the decomposed GaN. It is also revealed by calculation that the compressive stress in the thin GaN is increased by reducing the thickness. It is demonstrated that the lattice of the GaN is relaxed after the laser lift-off, which is confirmed by photoluminescence (PL) and X-ray diffraction (XRD) measurements. In addition, reduction of the wafer bowing of GaN on sapphire is experimentally confirmed after the laser irradiation with the formation of metal Ga in between the interface.

Successful Laser Treatment of Vandetanib-Associated Cutaneous Pigmentation

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Combining Laser Ablation/Liquid Phase Collection Surface Sampling and High-Performance Liquid Chromatography−Electrospray Ionization-Mass Spectrometry

This letter describes the coupling of ambient pressure transmission geometry laser ablation with a liquid phase sample collection method for surface sampling and ionization with subsequent mass spectral analysis. A commercially available autosampler was adapted to produce a liquid droplet at the end of the syringe injection needle while in close proximity to the surface to collect the sample plume produced by laser ablation. The sample collection was followed by either flow injection or a high-performance liquid chromatography (HPLC) separation of the extracted components and detection with electrospray ionization mass spectrometry (ESI-MS). To illustrate the analytical utility of this coupling, thin films of a commercial ink sample containing rhodamine 6G and of mixed isobaric rhodamine B and 6G dyes on glass microscope slides were analyzed. The flow injection and HPLC-ESI-MS analysis revealed successful laser ablation, capture, and with HPLC, the separation of the two compounds. The ablated circular area was about 70 μm in diameter for these experiments. The spatial sampling resolution afforded by the laser ablation, as well as the ability to use sample processing methods like HPLC between the sample collection and ionization steps, makes this combined surface sampling/ionization technique a highly versatile analytical tool.

Clinical Summaries

Fractures of pace-sense electrodes in implantable cardioverter-defibrillator patients are a common cause of inappropriate shocks. To reduce inappropriate shocks, we developed a lead-integrity alert (LIA) triggered by either oversensing or high impedance that can be downloaded into previously implanted implantable cardioverter-defibrillators. This prospective study tested the hypothesis that the LIA would reduce the percentage of patients who receive inappropriate shocks compared with a concurrent control group monitored by impedance only. Each group included a prospectively determined sample size of 213 consecutive patients with fractures confirmed by structural analysis of explanted leads. The LIA group had a 46% relative reduction (95% confidence interval 34% to 55%) in the percentage of patients with ≥1 inappropriate shock (LIA 38% versus control 70%, P <0.001) and a 50% relative reduction (95% confidence interval 33% to 61%) in the percentage with ≥5 shocks (25% versus 50%, P <0.001). These data show that a software download that upgrades previously implanted implantable cardioverter-defibrillators without surgical revision reduces inappropriate shocks caused by lead fractures. See p 1449. Twin-twin transfusion syndrome is an important cause of perinatal mortality in monochorionic twins, often because of cardiovascular compromise associated with increased intravascular volume in the recipient twin. In this autopsy study of 11 sets of twins with the condition, 4 recipient twins had anomalous mitral arcade, a rare fibrotic valve lesion that is associated with regurgitation. Previously unrecognized in twin-twin transfusion syndrome, anomalous mitral arcade may explain many of the progressive hemodynamic abnormalities in this condition. From this retrospective clinicopathological correlation study, ultrasound/echocardiographic evidence of left atrial dilation and significant mitral regurgitation in the recipient should raise suspicion for anomalous mitral arcade, a structural lesion that likely will not reverse after successful laser treatment or delivery of the fetus, as other hemodynamic and functional abnormalities often do. Thus, for perinatologists …

Evaluation of laser cleaning of ancient Greek, Roman and Byzantine coins

AbstractLaser cleaning tests were performed on ancient coins, which belong to the collection of the Numismatic Museum of Athens, Greece. Silver and copper alloy coins with various types of surface corrosion and ground deposits were studied, using Q‐switched (QS), long pulse (LP) and free‐running (FR) Nd:YAG lasers and a range of laser‐pulsing parameters on wet surfaces. A comparison among the different laser types was made, cleaning with an optical fibre delivery system and an optical focusing subassembly, or with the help of x‐y microadjustable stage. It was discovered that the results of laser cleaning was influenced by the type of corrosion and the corrosion products or the ground deposits on the surface of the coins. The results, evaluated by objective and SEM‐EDX observations, indicated that on silver alloy coins, different wavelengths could achieve a successful laser cleaning for several types of corrosion. On the other hand, laser cleaning could result in loss of the original surface in various cases of copper alloy coins, followed by frequent appearance of the oxidation layer underneath and partial removal of corrosion products and ground deposits. The optimum laser cleaning procedure was associated with the different types of coin corrosions. Special emphasis was stressed on the side effects of the procedures and, in particular, on the minimization of any chemical modifications and thermal results induced to the original surface of the coins. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Effect of pan-retinal laser photocoagulation on plasma VEGF, endothelin-1 and nitric oxide in PDR.

To study plasma levels of vascular endothelial growth factor (VEGF), endothelin-1(ET-1) and nitric oxide (NO) in patients with proliferative diabetic retinopathy (PDR) before and after pan-retinal photocoagulation (PRP). Forty patients (23 females and 17 males, mean age 48.5±12.2 years) with PDR without previous PRP therapy were studied. Blood samples were obtained before and 3 months after the last PRP session. Baseline (prelaser) plasma levels of VEGF, ET-1 and NO were compared with their levels in 30 healthy age- and sex- matched controls and also with plasma levels 3 months post-PRP. Patients with PDR had significantly raised plasma VEGF (375±89ng/L), ET-1(20±5ng/L) and NO (135±53µmol/L) when compared with healthy control group (P<0.01). After PRP, there was a significant reduction in plasma VEGF (179±66ng/L), ET-1 (11±5ng/L) and NO (91±49µmol/L) levels at 3 months' follow-up but still significantly higher than healthy controls. Patients with PDR demonstrate elevated VEGF, ET-1 and NO, which decrease after successful laser treatment.

Argon Laser Photocystotomy of a Vitreous Cyst.

Free-floating idiopathic vitreous cysts are rare entities. For symptomatic patients, treatment options include laser photocystotomy or pars plana vitrectomy (PPV) with cyst excision. Historically, size of the cyst impacted treatment approaches. Laser treatments have been used for smaller cysts ranging 3 to 5 mm in diameter. PPV has been utilized for cysts larger than 4 mm. Successful laser photocystotomy has been reported, utilizing both argon and Nd: YAG lasers. Herein, we present a case of successful argon laser photocystotomy of a 7.1 mm diameter vitreous cyst, the largest documented cyst ever treated. Treatment should be individualized based on patient age, ability to cooperate in an office setting, phakic status, status of the posterior hyaloid, cyst morphology, and location. In our case, because of pigment on the anterior cyst surface, and the presence of an attached posterior hyaloid, the argon green laser was used.

Successful CO2 laser treatment of naevus lipomatosus cutaneous superficialis

Successful CO2 laser treatment of naevus lipomatosus cutaneous superficialis

Assessment of Long Range Laser Weapon Engagements: The Case of the Airborne Laser

This article presents a method developed to assess laser Directed Energy Weapon engagements. This method applies physics-based models, which have been validated by experiments. It is used to assess the capabilities of the Airborne Laser (ABL), a system for boost phase missile defense purposes, which is in development under supervision of the U.S. missile defense agency. Implications for international security are presented. The article begins with a general introduction to laser Directed Energy Weapons (DEW). It is notable that several laser directed energy weapon prototypes have recently become operational for testing. One of them is the ABL, a megawatt-class laser installed into a cargo aircraft. It is concluded that only the ABL could have significant political impact on an international scale at the moment. Hence, the remainder of the article focuses on the assessment of that system. The laser intensity, the induced temperature increase of a target and the impact of this temperature increase on the mechanical properties of the target are calculated for different scenarios. It is shown that the defensive capability of the ABL against ballistic missiles is limited. Even a successful laser engagement that deflects a missile trajectory from its intended target can have negative impact for third parties, as missile warheads will most likely not be destroyed.