Pulsed Laser Ablation of Soft Biological Tissues

Vogel, Alfred; Venugopalan, Vasan

doi:10.1007/978-90-481-8831-4_14

Cited by 25 publications

(20 citation statements)

References 211 publications

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“…The complete energy deposition is required until ablation is initiated. The blow‐off model predicts the etch depth according to [22]

δ = \frac{1}{μ_{a}} \ln true(\frac{H_{0}}{H_{italicth}} true) = \frac{1}{μ_{a}} \ln true(\frac{I_{0} τ}{H_{italicth}} true),

where μ a is the absorption coefficient, H 0 = I 0 τ is the radiant exposure, I 0 is the irradiance, τ is the pulse duration, and H th is the threshold of ablation. The ablation threshold is defined as the minimum radiant exposure required for tissue ablation to occur [23].…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

First Assessment of a Carbon Monoxide Laser and a Thulium Fiber Laser for Fractional Ablation of Skin

Jaspan²,

Welford³

et al. 2020

Lasers Surg Med

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Background and Objectives A recent generation of 5,500 nm wavelength carbon monoxide (CO) lasers could serve as a novel tool for applications in medicine and surgery. At this wavelength, the optical penetration depth is about three times higher than that of the 10,600 nm wavelength carbon dioxide (CO2) laser. As the amount of ablation and coagulation is strongly influenced by the wavelength, we anticipated that CO lasers would provide extended coagulation zones, which could be beneficial for several medical applications, such as tissue tightening effects after laser skin resurfacing. Until now, the 1,940 nm wavelength thulium fiber (Tm:fiber) laser is primarily known as a non‐ablative laser with an optical penetration depth that is eight times higher than that of the CO2 laser. The advantage of lasers with shorter wavelengths is the ability to create smaller spot sizes, which has a determining influence on the ablation outcome. In this study, the ablation and coagulation characteristics of a novel CO laser and a high power Tm:fiber laser were investigated to evaluate their potential application for fractional ablation of the skin. Study Design/Materials and Methods Laser‐tissue exposures were performed using a novel CO laser, a modified, pulse‐width‐modulated CO2 laser, and a Tm:fiber laser. We used discarded ex vivo human skin obtained from abdominoplasty as tissue samples. Similar exposure parameters, such as spot size (108–120 μm), pulse duration (2 milliseconds), and pulse energy (~10–200 mJ) were adjusted for the different laser systems with comparable temporal pulse structures. Laser effects were quantified by histology. Results At radiant exposures 10‐fold higher than the ablation threshold, the CO laser ablation depth was almost two times deeper than that of the CO2 laser. At 40‐fold of the ablation threshold, the CO laser ablation was 47% deeper. The ablation craters produced by the CO laser exhibited about two times larger coagulation zones when compared with the CO2 laser. In contrast, the Tm:fiber laser exhibited superficial ablation craters with massive thermal damage. Conclusions The tissue ablation using the Tm:fiber laser was very superficial in contrast to the CO laser and the CO2 laser. However, higher etch depths should be obtainable when the radiant exposure is increased by using higher pulse energies and/or smaller spot sizes. At radiant exposures normalized to the ablation threshold, the CO laser was capable of generating deeper ablation craters with extended coagulation zones compared with the CO2 laser, which is possibly desirable depending on the clinical goal. The effect of deep ablation combined with additional thermal damage on dermal remodeling needs to be further confirmed with in vivo studies. Lasers Surg. Med. © 2020 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

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“…The complete energy deposition is required until ablation is initiated. The blow‐off model predicts the etch depth according to [22]

δ = \frac{1}{μ_{a}} \ln true(\frac{H_{0}}{H_{italicth}} true) = \frac{1}{μ_{a}} \ln true(\frac{I_{0} τ}{H_{italicth}} true),

Section: Methodsmentioning

confidence: 99%

“…However, the steady‐state model assumes that heat diffusion occurs during irradiation and that tissue removal occurs at the beginning of the laser pulse, which continues during the whole irradiation. The steady‐state model anticipates an etch depth as follows [22]:

δ = \frac{H_{0} {- H}_{italicth}}{μ_{a} H_{italicth}} = \frac{I_{0} {τ - H}_{italicth}}{μ_{a} H_{italicth}} .

…”

Section: Methodsmentioning

confidence: 99%

First Assessment of a Carbon Monoxide Laser and a Thulium Fiber Laser for Fractional Ablation of Skin

Jaspan²,

Welford³

et al. 2020

Lasers Surg Med

View full text Add to dashboard Cite

show abstract

“…The high efficiency makes it possible to perform intracellular and intratissue surgery, dissection and optical knock-out of cells [16][17][18][19][20][21] as well as targeted transfection by transient opening of the cellular membrane [22,23] using very low mean laser powers. This ensures to avoid collateral damage in the microenvironment due to photodisruptive effects based on the formation of bubbles and shock waves [24,25]. Formerly, using longer pulses mean powers of about 100 mW (~1 nJ) were required to induce transient holes [26][27][28].…”

Section: Methodsmentioning

confidence: 99%

Trafficking of Mature miRNA-122 into the Nucleus of Live Liver Cells

Földes-Papp¹,

König²,

Studier³

et al. 2009

CPB

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The binding of superquencher molecular beacon (SQMB) probes to human single-stranded cellular miRNA-122 targets was detected in various single live cells with femtosecond laser microscopy. For delivery of the SQMB-probes, 3D-nanoprocessing of single cells with sub-15 femtosecond 85 MHz near-infrared laser pulses was applied. Transient nanopores were formed by focusing the laser beam for some milliseconds on the membrane of a single cell in order to import of SQMB-probes into the cells. In single cells of the human liver cell lines Huh-7D12 and IHH that expressed miRNA-122, we measured target binding in the cytoplasm by two-photon fluorescence imaging. We found increased fluorescence with time in a nonlinear manner up to the point where steady state saturation was reached. We also studied the intracellular distribution of target SQMB and provide for the first time strong experimental evidence that cytoplasmic miRNA travels into the cell nucleus. To interpret nonlinear binding, a number of individual miRNA-122 positive cells (Huh-7D12 and IHH) and negative control cells, human VA13 fibroblasts and Caco-2 cells were analyzed. Our experimental data are consistent with the cytoplasmic assembly of nuclear miRNA and provide further mechanistic insight in the regulatory function of miRNAs in cellular physiology. An open issue in the regulation of gene expression by miRNA is whether miRNA can activate gene expression in addition to the well-known inhibitory effect. A first step for such a regulatory role could be the travelling of miRNA-RISC into the nucleus.

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“…While testing the described experimental setup directly on a real world sample might seem hasty at rst, it has to be considered that the basic mechanisms of LAESI have already been explored and published in greater detail. 1,2,[17][18][19] The methodology to be validated was in fact not the LAESI concept but focusing a laser onto an undisturbed surface of a biological sample. By demonstrating consistent laser focus on a real world sample while detecting the mass features expected to be found in said sample validated the feasibility of the experimental setup.…”

Section: Discussionmentioning

confidence: 99%

Mapping metabolites from rough terrain: laser ablation electrospray ionization on non-flat samples

et al. 2017

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Established laser-based ionization experiments require the surface of a sample to be as flat as possible to guarantee optimal laser focus. A laser ablation electrospray ionization (LAESI) source was custom-built to accommodate the topography of non-flat sample surfaces. Employing a confocal distance sensor, a height profile of the surface in question was recorded prior to the actual ionization experiment. The robustness of the system was evaluated by the metabolic profiling of radish (Raphanus sativus) leaves, chosen due to their pronounced surface features and known content of specialized metabolites. After the ionization experiments, light microscopy imaging was performed to evaluate ablation crater size and position. Reproducible ablation mark diameters of 69 7 mm in average have been achieved. Mass spectrometric imaging capability has been proven on R. sativus leaf samples as well

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Pulsed Laser Ablation of Soft Biological Tissues

Cited by 25 publications

References 211 publications

First Assessment of a Carbon Monoxide Laser and a Thulium Fiber Laser for Fractional Ablation of Skin

First Assessment of a Carbon Monoxide Laser and a Thulium Fiber Laser for Fractional Ablation of Skin

Trafficking of Mature miRNA-122 into the Nucleus of Live Liver Cells

Mapping metabolites from rough terrain: laser ablation electrospray ionization on non-flat samples

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