Study of Interaction of Laser with Tissue Using Monte Carlo Method for 1064nm Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) Laser

Introduction: Liposuction using laser is now one of the most common cosmetic surgery. This new method has minimized the disadvantages of the conventional liposuction including blood loss, skin laxity and long recovery time. Benefits of the new liposuction methods which include less trauma, bleeding and skin tightening prove the superiority of these methods over the traditional mechanical methods. Interaction of laser with fat tissue has the vital role in the development of these new procedures because this interaction simultaneously results in retraction of skin layers and coagulation of small blood vessels so skin tightening and less bleeding is achieved.Method: Laser lipolysis uses a laser fiber inserted inside a metal cannula of 1 mm delivering the laser radiation directly to the target tissue. Laser lipolysis has a wavelength dependent mechanism, tissue heating and therefor thermal effects are achieved through absorption of radiation by the target tissue cells, causing their temperature to rise and their volumes to expand. We used Monte Carlo (MC) method to simulate the photons propagation within the tissue. This method simulates physical variables by random sampling of their probability distribution. We also simulated temperature rise and tissue heating using Comsol Multiphysics software.Conclusion: Because optimum and safe laser lipolysis operation highly depends on optical characteristics of both tissue and laser radiation such as laser fluence, laser power and etc. having physical understanding of these procedures is of vital importance. In this study we aim to evaluate the effects of these important parameters.Results: Findings of our simulation prove that 1064 nm Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) has good penetration depth into fat tissue and can reach inside the deeper layers of fat tissue. We see that this wavelength also resulted in good temperature rise; after irradiation of fat tissue with this wavelength we observed that tissue heated in permitted values (50-65°C), this is why this wavelength is widely used in laser lipolysis operations.  

Grafting of a novel gold(III) complex on nanoporous MCM-41 and evaluation of its toxicity in Saccharomyces cerevisiae

The goal of this research was to investigate the potential of newly synthesized gold complex trichloro(2,4,6-trimethylpyridine)Au(III) as an anticancer agent. The gold(III) complex was synthesized and grafted on nanoporous silica, MCM-41, to produce AuCl3@PF-MCM- 41 (AuCl3 grafted on pyridine-functionalized MCM-41). The toxicity of trichloro(2,4,6- trimethylpyridine)Au(III) and AuCl3@PF-MCM-41 in Saccharomyces cerevisiae (as a model system) was studied. The gold(III) complex showed a mid cytotoxic effect on yeast viability. Using the drug delivery system, nanoporous MCM-41, the gold(III) complex became a strong inhibitor for growth of yeast cells at a very low concentration. Furthermore, the animal tests revealed a high uptake of AuCl3@PF-MCM-41 in tumor cells. The stability of the compound was confirmed in human serum

Investigation and development of mode-locking techniques of diode pumped solid-state lasers

Development of diode laser pumped mode-locked sources for use as short pulse oscillators for chirped pulse amplification (CPA) experiments using the VULCAN Nd:glass laser has been investigated. To achieve subpicosecond pulses we studied the performance of a recently reported laser crystal, NdxLa1-xMgAl11O19 (Nd:LMA). Using an active mode-locking technique (frequency modulation, or FM mode-locking) bandwidth-limited pulses of 16 W peak power and 14 psec duration were obtained. The pump source was a 0.5 W single stripe diode-laser. In order to obtain sub-picosecond pulses it was necessary to pump the Nd:LMA crystal with higher pump powers and use the more powerful mode-locking technique of additive-pulse mode-locking (APM). A detailed discussion is given of the performance of the Nd:LMA laser pumped with high power diode-lasers and also the pumping and cavity configurations which lead to successful laser operation. In free running operation up to 560 mW and 1.1 W output power was achieved in single and multi mode operation respectively when the crystal was pumped with a 3 W and two 3 W diode-lasers. A brief study is also made of the aspects of the thermal effects, such as thermal lensing and thermally induced birefringence, which may affect the laser performance.Both the Fabry-Perot and Michelson additive-pulse mode-locking configurations were used, and are discussed in detail. With the Fabry-Perot set up, transform-limited pulses of 420 fsec duration were obtained. The average output power was 18 mW, corresponding to an energy per pulse of 0.19 nJ. In the Michelson arrangement the average output power was 120 mW with nearly the same pulse duration which corresponds to a pulse energy of 1.6 nJ. The use of the additive pulse mode-locked laser-diode-pumped Nd:LMA laser as a seed source for the VULCAN Nd:glass amplifier system at the Rutherford Appleton Laboratory is discussed. Use of this seed source allowed the achievement of extremely high peak power (30 TW) sub-picosecond (800 fsec) pulses from this amplifier system. We also present detailed measurements of the main characteristics of this laser

Interaction of Er,Cr:YSGG laser with dental hard tissue

Background and Aims: Nowadays lasers are used as alternatives to the tooth preparation because of reducing pain, bloodshed and stress. The aim of this study was to observe the effect of Er,Cr:YSGG laser on the dental hard tissues. Materials and Methods: For this studty, molar teeth with no caries or dental restoration and enamel cracks were used. The laser power were taken from 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 up to 6 Watts for enamel and 0.5, 1, 1.5, 2, 2.5, 3, 3.5 and 4 Watts for dentine simultaneously with water spray. The ablation effect was observed on both enamel and dentine. Finally, by use of a CCD camera connected to the computer, the dimensions of ablated areas were measured and results were applied in graphs. Results: Volume of ablation was increased by increasing laser power. Also, by increasing energy value in each stage, the depth of ablation was increased for enamel and dentine. SEM images of ablations by 3.5 and 4 Watts on enamel and 1 and 1.5 Watts on dentine did not show any sharp edges. Conclusion: The ablation volumes and depth increased by increasing the energy of laser pulses power. The reason for this trend was due to the water spray while irradiating and good absorption of water by laser beam

Acoustic and optoacoustic stimulations in auditory brainstem response test in salicylate induced tinnitus

Abstract As a common debilitating disorder worldwide, tinnitus requires objective assessment. In the auditory brainstem response (ABR) test, auditory potentials can be evoked by acoustic or optoacoustic (induced by laser light) stimulations. In order to use the ABR test in the objective assessment of tinnitus, in this study, acoustic ABR (aABR) and optoacoustic ABR (oABR) were compared in the control and tinnitus groups to determine the changes caused by sodium salicylate (SS)-induced tinnitus in rat. In both aABR and oABR, wave II was the most prominent waveform, and the amplitude of wave II evoked by oABR was significantly higher than that of aABR. Brainstem transmission time (BTT), which represents the time required for a neural stimulation to progress from the auditory nerve ending to the inferior colliculus, was significantly shorter in oABR. In the tinnitus group, there was a significant increase in the threshold of both ABRs and a significant decrease in the amplitude of wave II only in the oABR. Based on our findings, the ABR test has the potential to be used in the assessment of SS-induced tinnitus, but oABR has the advantages of producing more prominent waveforms and significantly reducing the amplitude of wave II in tinnitus

Effect of Gamma Irradiation on Structural and Biological Properties of a PLGA-PEG-Hydroxyapatite Composite

Gamma irradiation is able to affect various structural and biological properties of biomaterials In this study, a composite of Hap/PLGA-PEG and their ingredients were submitted to gamma irradiation doses of 25 and 50 KGy. Various properties such as molecular weight (GPC), thermal behavior (DSC), wettability (contact angle), cell viability (MTT assay), and alkaline phosphatase activity were studied for the composites and each of their ingredients. The results showed a decrease in molecular weight of copolymer with no change in the glass transition and melting temperatures after gamma irradiation. In general gamma irradiation can increase the activation energy ΔH of the composites and their ingredients. While gamma irradiation had no effect on the wettability of copolymer samples, there was a significant decrease in contact angle of hydroxyapatite and composites with increase in gamma irradiation dose. This study showed an increase in biocompatibility of hydroxyapatite with gamma irradiation with no significant effect on cell viability in copolymer and composite samples. In spite of the fact that no change occurred in alkaline phosphatase activity of composite samples, results indicated a decrease in alkaline phosphatase activity in irradiated hydroxyapatites. These effects on the properties of PLGA-PEG-hydroxyapatite can enhance the composite application as a biomaterial

Synthesis and Preclinical Studies of [61Cu]-N-(2-hydroxyacetophenone)glycinate as a Possible PET Radiopharmaceutical

[61Cu]-N-(2-hydroxyacetophenone)glycinate ([61Cu]NHAG) was prepared using in house-made NHAG ligand and [61Cu]CuCl2 produced via the natZn(p,x)61Cu (180μA proton irradiation, 22MeV, 3.2h) and purified by a ion chromatography method. [61Cu]NHAG radiochemical purity was >98% and >99.9% by RTLC and HPLC methods respectively after purification by SPE. [61Cu]NHAG was administered into normal and tumor bearing mice followed by biodistribution studies up to 180 minutes. The best tumor accumulation was observed by animal sacrification after 120 min (tumor/muscle and tumor/blood ratios were 25.6 and 3.4 respectively). [61Cu]NHAG is a potential PET radiotracer for tumor imaging