Efficacy evaluation and treatment parameter optimization for laser surgery of Ota’s nevus based on an advanced non-equilibrium bio-tissue heat transfer model

Tian, Jing; Chen, Bin; Li, Dong

doi:10.1007/s10103-021-03262-9

Cited by 5 publications

(4 citation statements)

References 25 publications

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“…where µ a,mel (r, 0) represents the linear absorption coefficient of melanin and µ a,base (r, t) is the baseline absorption of epidermis, expressed as functions of wavelength λ, and f is the volume fraction of melanin (35%). 8,16 The absorption coefficients of the dermis and subcutaneous fat included blood absorption. The skin tissue model was vertically irradiated by laser pulse with a square pulse waveform and a uniform beam profile.…”

Section: Numerical Model Of Human Skin Tissuementioning

confidence: 99%

“…6,7 Differences in light distribution depending on pulse width have been evaluated based on the linear absorption of local fluence. [8][9][10] However, short-pulsed lasers usually cause nonlinear absorption by melanin inside cutaneous melanosomes owing to the high power density. Our previous study proposed a nonlinear absorption model of melanin based on sequential two-photon absorption and nonradiative decays.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative evaluation of light distribution in skin tissue for short-pulsed laser treatment using Monte Carlo simulation combined with nonlinear absorption model of melanin

Shimojo

Nishimura²,

Awazu³

2023

Optical Interactions With Tissue and Cells XXXIV

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The treatment effect of pigmented lesions with picosecond and nanosecond lasers is produced mainly from optical absorption by melanosomes. Differences in the treatment effect have been evaluated based on the linear absorption of local fluence. However, nonlinear absorption by melanin inside melanosomes occurs during shortpulsed laser propagation in skin tissue owing to the high power density. Our previous study demonstrated that a nonlinear absorption model based on sequential two-photon absorption and nonradiative decays was validated to describe nonlinear absorption by melanin. In this study, we comparatively evaluate light distributions in skin tissue with pigmented lesions irradiated with short-pulsed lasers using a Monte Carlo model combined with the nonlinear absorption model. Light distributions in a numerical model of human skin tissue with epidermal pigmented lesions were calculated for a single shot of 450-ps and 10-ns laser pulses at a wavelength of 532 nm, a fluence of 1 J/cm 2 , and a spot size of 3 mm. The computational simulations show that the penetration depth in the skin tissue was shorter for the picosecond laser. The simulation results suggested that picosecond lasers can reduce damage to surrounding tissue compared to nanosecond lasers. Although these results need to be validated by experiments, our simulations will provide a quantitative evaluation of the safety and efficacy of short-pulsed laser treatment of pigmented lesions.

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Section: Numerical Model Of Human Skin Tissuementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative evaluation of light distribution in skin tissue for short-pulsed laser treatment using Monte Carlo simulation combined with nonlinear absorption model of melanin

Shimojo

Nishimura²,

Awazu³

2023

Optical Interactions With Tissue and Cells XXXIV

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“…Melanosome disruption by a short‐pulsed laser is induced by converting the optical energy absorbed by the melanin into photothermal and photomechanical effects. This underlying treatment mechanism has been analyzed based on linear absorption of the local fluence 12–14 . However, melanin absorbs short‐pulsed laser in a nonlinear manner owing to the high‐power density 15 .…”

Section: Introductionmentioning

confidence: 99%

“…This underlying treatment mechanism has been analyzed based on linear absorption of the local fluence. [12][13][14] However, melanin absorbs short-pulsed laser in a nonlinear manner owing to the high-power density. 15 According to selective photothermolysis, 16 when pulse widths that satisfy the thermal confinement condition of melanosomes are used, an appropriate setting of fluence is required for safe and efficacious treatment.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear absorption‐based analysis of energy deposition in melanosomes for 532‐nm short‐pulsed laser skin treatment

et al. 2023

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Background and Objectives: The clinical use of 532-nm short-pulsed lasers has provided effective treatment of epidermal pigmented lesions. However, the detection of significant differences in treatment effects between picosecond and nanosecond lasers has still varied among clinical studies. For robust evaluation of the differences based on the treatment mechanism, this study presents a nonlinear absorption-based analysis of energy deposition in melanosomes for 532-nm shortpulsed laser treatment. Study Design/Materials and Methods: Nonlinear absorption by melanin is modeled based on sequential two-photon absorption. Absorption cross-sections and nonradiative lifetimes of melanin, which are necessary for the nonlinear absorption-based analysis, are determined from transmittance measurement. Using the model and parameters, energy deposition in melanosomes was calculated with varying fluence and pulse width settings, including actual clinical parameters.Results: The energy deposition in melanosomes increased with shorter laser pulses, and subnanosecond laser pulses were found to be most efficient. The comparison of energy deposition calculated using clinical parameters demonstrated the differences in treatment effects between picosecond and nanosecond lasers reported in clinical studies. Conclusion:The nonlinear absorption-based analysis provides quantitative evidence for the safety and efficacy evaluation of short-pulsed laser treatments, which may lead to the establishment of numerical indices for determining treatment conditions. Future studies considering the effects of the surrounding tissue on energy deposition in melanosomes will be needed.

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In Silico Evaluation of Nanosecond Laser Treatment of Pigmented Lesions Based on Skin Optical Properties Using a Model of Melanosome Disruption Threshold Fluence

Shimojo,

Nishimura,

Tsuruta

et al. 2024

Lasers Surg Med

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ObjectivesThis study aimed to evaluate the efficacy and safety of nanosecond laser treatment of pigmented lesions in silico using a model of melanosome disruption threshold fluence (MDTF) based on skin optical properties.MethodsParticle size analysis and scanning electron microscopy were performed to determine the threshold fluence for melanosome disruption using a nanosecond laser. By inputting the obtained threshold fluence into the MDTF model and considering the variability in skin optical properties, irradiation parameters were calculated and compared with the results from clinical studies.ResultsThe threshold fluences for 532 and 755 nm nanosecond laser irradiation were determined to be 3.0 and 15.0 J/cm2, respectively. In silico analysis showed that the incident fluence for moderately pigmented skin should be 1.2 times that for lightly pigmented skin, whereas it should be 50% lower than that for lightly pigmented skin to achieve the same level of energy deposition. Clinically applied fluences for moderately pigmented skin are at the low end of the calculated range of values, suggesting that the clinical fluence is chosen to minimize energy deposition in normal tissues.ConclusionsOur results showed that the MDTF model can be used to evaluate nanosecond laser treatments and provide clinical guidance on fluence settings based on laser–tissue interactions in moderately pigmented skin. The in silico method can, therefore, provide a robust and quantitative retrospective evaluation of the treatment effects that accounts for variation in irradiation parameters among patients by combining the MDTF model with the in vivo optical properties of individual skin types.

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Efficacy evaluation and treatment parameter optimization for laser surgery of Ota’s nevus based on an advanced non-equilibrium bio-tissue heat transfer model

Cited by 5 publications

References 25 publications

Quantitative evaluation of light distribution in skin tissue for short-pulsed laser treatment using Monte Carlo simulation combined with nonlinear absorption model of melanin

Quantitative evaluation of light distribution in skin tissue for short-pulsed laser treatment using Monte Carlo simulation combined with nonlinear absorption model of melanin

Nonlinear absorption‐based analysis of energy deposition in melanosomes for 532‐nm short‐pulsed laser skin treatment

In Silico Evaluation of Nanosecond Laser Treatment of Pigmented Lesions Based on Skin Optical Properties Using a Model of Melanosome Disruption Threshold Fluence

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