The Advent of Laser Therapies in Dermatology and Urology: Underlying Mechanisms, Recent Trends and Future Directions

이호,정연욱,Kin F. Chan 한국광학회 2009 Current Optics and Photonics Vol.13 No.3

Following their applications in cardiology, ophthalmology and dentistry among others, the advent of lasers in dermatology and urology had become the success story of the past decade. Laser-assisted treatments in dermatology and urology are mainly based on the laser-induced tissue injury/coagulation and/or ablation, depending upon the desirable clinical endpoint. In this review, we discussed the underlying mechanisms of the laser induced tissue ablation. In any medical laser application, the controlled thermal injury and coagulation, and the extent of ablation, if required, are critical. The laser thermal mechanism of injury is intricately related to the selective absorption of light and its exposure duration, similarly to the laser induced ablation. The laser ablation mechanisms were categorized into four different categories (the photo-thermally induced ablation, the photo-mechanically induced ablation, the plasma induced ablation and the photoablation) and their fundamentals are herein described. The brief history of laser treatment modality in dermatology and urology are summarized.

A comparison of efficacy in ablative fractional laser assisted photodynamic therapy according to ablative depth for actinic keratosis

( Jeong-wan Seo ),( Yeo-rye Cho ),( Ho-jin Kim ),( Tae-hoon Kim ),( Ki-hoon Song ) 대한피부과학회 2017 대한피부과학회 학술발표대회집 Vol.69 No.2

Background: Er:YAG ablative fractional laser-assisted photodynamic therapy (AFL-PDT) has shown significant benefit for the treatment of actinic keratosis(AK). However, no comparison of the PDT efficacy with ablative laser parameters has been completed. Objectives: To investigate whether the use of increased laser depth affects the efficacy, side effects, cosmetic outcomes, and protoporphyrin IX(PPIX) accumulation of AFL-PDT for facial AK. Methods: 309 AK lesions of 36 patients were included. Patients were randomly allocated to the 150-μm, 350-μ m, and 500-μm laser depth groups. After AFL was performed with either different laser depth, all patients underwent one session of PDT. Patients were followed up with at 1week, 1month, and 3months post treatment. Efficacy, side effects, cosmetic outcomes, and accumulated levels of PPIX were assessed. Results: Increasing laser depth did not enhance PPIX fluorescence. However, three months after treatment, the treatment of the higher laser depth groups(500μm) appeared to be significantly more effective than that of the lower laser depth groups(150μm) in terms of the management of Olsen grade III AK lesions. No significant differences were found with respect to side effects, cosmetic outcomes and safety. Conclusion: Higher laser depth does not increase PPIX accumulation, but does improve the treatment effect of AFL-PDT for high-grade AK lesions. We recommend AFL-PDT using higher laser depth parameters in cases of high-grade AK lesions.

Study on effect of laser-induced ablation for Lamb waves in a thin plate

Lee, Sang Eon,Liu, Peipei,Ko, Young Woo,Sohn, Hoon,Park, Byeongjin,Hong, Jung-Wuk Elsevier 2019 Ultrasonics Vol.91 No.-

<P><B>Abstract</B></P> <P>In this paper, the effect of ablation on the shape of elastic waves generated by laser excitation is studied numerically and experimentally. Laser-induced ultrasound has been widely used in the nondestructive testing (NDT) field because it has the advantage that the sensor does not have to be directly attached to the target structure. In the safety assessment process, low energy excitation is used, and thus the structure is not damaged. Most studies related to laser ultrasound have focused on the method of detecting cracks within the elastic range, and there have been few studies on the effect of ablation. This research consists of experiments and numerical analyses. In experiments, elastic waves were generated in an aluminum plate by projecting laser pulses with different energy intensities. The velocities in the thickness direction were measured using a Laser Doppler Velocimeter (LDV) at a point 135 mm away from the excitation point.</P> <P>In the numerical study, two numerical simulations were carried out using heat flux and normal stress input to mimic laser pulse excitation. A thermo-mechanical simulation by heat flux was conducted to simulate thermal expansion by the laser pulse, and the normal stress was applied to reflect the effect of radiation pressure by ablation, respectively. Waveforms were synthesized by using different magnitude ratios of the obtained numerical responses and were compared with the experiment results. It is found that the effect of radiation pressure should not be neglected if the energy intensity is large although the effect of radiation pressure decreases as the energy intensity decreases. At the energy intensity with which ablation occurs, the effects of thermal expansion and radiation pressure exist simultaneously, and the contribution to the response depends on the energy intensity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of ablation on the shape of laser-induced elastic waves is studied. </LI> <LI> The elastic waves were generated and observed by projecting laser pulses. </LI> <LI> Two numerical simulations were performed using heat flux and normal stress input. </LI> <LI> The effects of thermal expansion and radiation pressure depend on energy intensity. </LI> </UL> </P>

Impact of laser pulse width on laser ablation process of high performance PERC cells

Kim, M.,Kim, D.,Kim, D.,Kang, Y. Association for Applied Solar Energy ; Elsevier Sc 2014 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.110 No.-

This study quantitatively compares the characteristics of ablation processes using nanosecond (ns) and picosecond (ps) pulse width green (532nm) lasers. The laser ablation results are analyzed using Electron Probe Micro Analyzer (EPMA), quasi-steady-state photo-conductance (QSSPC) measurements and transmission electron microscopy (TEM). The ablated using the ns green laser is predominantly melted, due to the relatively longer pulse width, and laser damage is incurred to a depth of 2.5μm. Meanwhile, the laser ablation using the ps green laser precisely removes the thin layers on the surface without severely melting the sample and the observed laser damage depth is almost negligible. However, since the maximum damage depth (~2.5μm) using the ns laser is much shallower than the local contact depth (10-17μm), the passivated emitter and rear cell (PERC) efficiencies using the ns and ps pulse width lasers converge to a power conversion efficiency of 19.4%.

Digital selective laser methods for nanomaterials: From synthesis to processing

Hong, Sukjoon,Lee, Habeom,Yeo, Junyeob,Ko, Seung Hwan Elsevier 2016 Nano Today Vol.11 No.5

<P><B>Abstract</B></P> <P>Laser has long been used for material processing, and its applications to nanomaterials for their direct synthesis, positioning and processing are currently active fields of study. The main mechanism of typical laser processes is photothermal reaction by a focused laser that remotely generates confined temperature field at a desired position with high controllability. The laser-induced elevated temperature enables direct synthesis of nanomaterials in both gas and liquid environment as well as photophysical processing of nanomaterials through melting or vaporization, represented by laser sintering and ablation processes, in spatially selective manners. On the other hand, recent advances in laser process further incorporates not only different optical responses such as optical forces and photochemical reactions for more advanced manipulation of nanomaterials, but also the interaction between electromagnetic waves, nanostructures and underlying substrates to facilitate novel processing those cannot be achieved by any other means including laser nanowelding for percolation network and laser thinning for two dimensional nanomaterials. At the same time, the shortcomings of laser process in nanomaterial processing such as limited resolution and low throughput are tackled through introducing different optical schemes together with the integration with other systems. In this review, we summarize the development and current status of digital selective laser methods for nanomaterials in broad aspects that cover from nanomaterial synthesis to its processing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Digital selective laser processes for nanomaterials are summarized in this review. </LI> <LI> Nanomaterials are selectively synthesized, positioned, controlled and manipulated. </LI> <LI> These processes rely on photothermal, photochemical or photothermochemical reaction. </LI> <LI> More emphasis is placed on the processes for nanoparticles, nanowires and nanosheets. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Ablation efficiency and relative thermal confinement measurements using wavelengths 1,064, 1,320, and 1,444 nm for laser-assisted lipolysis

Youn, Jong-In,Holcomb, J. David Springer-Verlag 2013 Lasers in medical science Vol.28 No.2

<P>Laser-assisted lipolysis is routinely used for contouring the body and the neck while modifications of the technique have recently been advocated for facial contouring. In this study, wavelength-dependence measurements of laser lipolysis effect were performed using different lasers at 1,064, 1,320, and 1,444 nm wavelengths that are currently used clinically. Fresh porcine skin with fatty tissue was used for the experiments with radiant exposure of 5–8 W with the same parameters (beam diameter = 600 μm, peak power = 200 mJ, and pulse rate = 40 Hz) for 1,064, 1,320 and 1,444 nm laser wavelengths. After laser irradiation, ablation crater depth and width and tissue mass loss were measured using spectral optical coherence tomography and a micro-analytical balance, respectively. In addition, thermal temporal monitoring was performed with a thermal imaging camera placed over ex vivo porcine fat tissue; temperature changes were recorded for each wavelength. This study demonstrated greatest ablation crater depth and width and mass removal in fatty tissue at the 1,444 nm wavelength followed by, in order, 1,320 and 1,064 nm. In the evaluation of heat distribution at different wavelengths, reduced heat diffusion was observed at 1,444 nm. The ablation efficiency was found to be dependent upon wavelength, and the 1,444 nm wavelength was found to provide both the highest efficiency for fatty tissue ablation and the greatest thermal confinement.</P>

Treatment of Striae Distensae with Nonablative Fractional Laser versus Ablative CO2 Fractional Laser: A Randomized Controlled Trial

( You Jin Yang ),( Ga Young Lee ) 대한피부과학회 2011 Annals of Dermatology Vol.23 No.4

Background: Striae distensae are atrophic dermal scars with overlying epidermal atrophy causing significant cosmetic concern. Although a variety of laser and light sources have been used for the treatment of striae distensae, to date no definite ``gold standard`` treatment modality has been determined. Objective: To assess and compare the efficacy and safety of nonablative fractional photothermolysis and ablative CO2 fractional laser resurfacing in the treatment of striae distensae. Methods: Twenty-four ethnic South Korean patients with varying degrees of atrophic striae alba in the abdomen were enrolled in a randomized blind split study. The patients were treated with 1,550 nm fractional Er:Glass laser and ablative fractional CO2 laser resurfacing. Each half of the abdominal lesion was randomly selected and treated three times at intervals of 4-weeks using the same parameters. Digital photography was conducted and skin elasticity and the width of the widest striae in each subject were measured at the baseline and 4 weeks after the final treatment. Clinical improvement was assessed by comparing pre- and post-treatment clinical photographs by two blinded physicians and participant satisfaction rates were evaluated. Skin biopsies were taken from three participants. All adverse effects were reported during the study. Results: Although they do not statistically differ, both treatments with nonablative fractional laser and ablative CO2 fractional laser showed a significant clinical and histopathologic improvement of striae distensae over pretreatment sites. Conclusion: These results support the use of nonablative fractional laser and ablative CO2 fractional laser as effective and safe treatment modalities for striae distensae of Asian skin. However, neither treatment showed any greater clinical improvement than the other treatment. (Ann Dermatol 23(4) 481~489, 2011)

나노초 레이저를 이용한 PMMA의 습식 및 건식어블레이션 비교 연구

이호 한국산업융합학회 2019 한국산업융합학회 논문집 Vol.22 No.3

The nanosecond laser assisted ablation have been investigated. The biocompatable polymer PMMA was employed as the target material and the two distinctive surface conditions were test. The first surface condition is a dry surface for which the target surface is exposed to air and the second surface condition is the wet surface for which the target surface is covered with dehydrated water. The ablation volume, the laser induced acoustic wave, the laser induced plasma were investigated for both wet and dry condition. The nanosecond laser pulse ablatied more on the wet surface compared to the dry surface. The enhanced ablation of wet surface is attributed to the confined acoustic wave and the laser-induced plasma in the liquid layer.

Micro Sampling System for Highly Radioactive Specimen by Laser Ablation

Sun-Ho Han,Yeong-Keong Ha,Ki-Chul Han,Yang-Soon Park,Kwang Youg Jee,Won Ho Kim 한국방사성폐기물학회 2005 방사성폐기물학회지 Vol.3 No.1

방사선차폐 laser ablation 시스템을 레이저, 미세영역의 영상 확인을 위한 이미지 시스템, XYZ 이동장치와 조절기, ablation chamber, manipulator 및 여러 가지 광학부품들로 구성하였다. Ablation용 레이저는 UOB 및 tircaloy 시편으로부터 효율적으로 시료를 채취할 수 있도록 266 nm(6 mJ)까지 파장 변환이 가능한 Nd:YAG 레이저를 선정하였으며, 이미지 시스템은 직경 50 m 크기의 crater를 판별할 수 있는 200 배율 이상의 규격을 갖춘 CCD 카메라로 선정하였다. 시편 미세이동장치는 XYZ방향으로 시편이동이 가능하고 최대 이동거리가 50 mm까지 , 그리고 최소 1m 씩 정확하게 움직일 수 있는 장치로 선정하였다. 구성된 각 단위기기들에 대하여 광학 정렬을 수행한 후, 시료채취 부위를 50 m씩 정확하게 이동하면서 레이저로 조사시킨 시료 표면을 CCD 카메라를 통하여 관찰한 결과, 표면에 생성된 crater는 원형임을 확인함으로써 단위기기별 성능을 확인할 수 있었다. Shielded laser ablation system composed of laser system, image analyser, XYZ translator with motion controller, ablation chamber, manipulator and various optics was designed. Nd:YAG laser which can be tunable from 1064 nm to 266 m was selected as light source. CCD camera(< 200) was chosen to analyze a crater less than 50 un in diameter. XYZ translator was composed of three linear stage which can travel 50 w with a minimum movement of 1 um and motion controller. Before the performance test, each part of system was optically aligned. To perform the ablation test, the specimen was ablated by 50 um interval and observed by image analyser The shape of crater was almost round, indicating laser beam has homogeneous energy distribution. The resolution and magnification of image system were compatible with the design.

MEL-80으로 라섹수술 시 라식 모드 절삭과 PRK 모드 절삭의 임상적 유용성 비교

김영돈,이담호,경학수,Youngdon Kim,Damho Lee,Haksu Kyung 대한안과학회 2014 대한안과학회지 Vol.55 No.11

Purpose: We compared laser assisted in situ keratomileusis (LASIK) mode and photorefractive keratectomy (PRK) mode ablation methods in laser subepithelial keratomileusis (LASEK) surgery using the MEL-80 excimer laser.Methods: All patients were followed up for a minimum of 1 year. The PRK mode group consisted of 46 eyes of 23 patients and the LASIK mode group consisted of 97 eyes of 56 patients. The central corneal thickness (CCT), ablation thickness, manifest refractive error and uncorrected visual acuity were compared preoperatively, 1 month and 1 year postoperatively. Spherical equivalent (SE) of cycloplegic refraction at postoperative 1 month and the uncorrected visual acuity (UCVA) ratios of 1.0 or better at postoperative 1 year were compared between the two groups to evaluate clinical efficacy. Results: The SE of refractive error, CCT and target corneal ablation thickness of the two groups were not significantly different preoperatively. The PRK mode group obtained an actual ablation mean thickness of 82.8% of the target and the LASIK mode group obtained an actual ablation mean thickness of 94.1% of the target at postoperative 1 month. In each group, a statistically significant difference was observed between the actual corneal ablation thickness and target corneal ablation thickness. In the PRK mode group, the mean SE of postoperative 1 month cycloplegic refraction was +0.24 ± 0.47 D and in the LASIK mode group, +0.87 ± 0.54 D, indicating a statistically significant difference between the two groups. One year postoperatively, the UCVA ratios of 1.0 or better were 83% in the PRK mode group and 96% in the LASIK mode group, showing a statistically significant difference between the two groups. However, SE of manifest refractive error and CCT in the two groups were not statistically different at postoperative 1 year. Conclusions: The LASIK mode ablation method showed better results than the PRK mode ablation method in postoperative UCVA prognosis after LASEK surgery using the MEL-80 excimer laser. J Korean Ophthalmol Soc 2014;55(11):1625-1630