Thermo-mechanical laser ablation of soft biological tissue: modeling the micro-explosions

Majaron, Boris; Plestenjak, Primoz; Lukač, Matjaž

doi:10.1007/s003400050772

Cited by 76 publications

(99 citation statements)

References 1 publication

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“…In contrast, deeper in the dermis the deposited heat accumulates due to much slower temperature relaxation in this region. As a result, theoretical models have predicted that collagen coagulation up to 200±300 mm deep could be achieved without exceeding the ablation temperature at the skin surface [12,22]. The present study demonstrates that repetitive Er:YAG irradiation can cause not only deep collagen coagulation, but also subsequent neo-collagen formation, very similar to that observed after CO 2 LSR.…”

Section: Discussionsupporting

confidence: 79%

“…Coagulation depths up to 260 mm (measured from the epidermal±dermal junction) were observed at pulsē uences around the ablation threshold, which matched well the results of an earlier published numerical model of thermo-mechanical laser ablation of skin [22,23]. At those¯uences, the dependence on the number of pulses in the sequence (between 5 and 10) was weak, and the in¯uence of the repetition rate (10 or 30 Hz) was found to be insigni®cant, in good agreement with predictions of the same theoretical model.…”

Section: Introductionsupporting

confidence: 87%

“…This ®nding is contrary to the notion that longer pulse durations should result in a greater degree of thermal damage. However, a previously published theoretical model of Er:YAG laser irradiation of human skin predicted that below the ablation threshold, the coagulation depth would increase only marginally with pulse duration at constant pulse¯uence [12,22]. According to this model, it is primarily the increase in ablation threshold that enables a larger heat deposition at longer pulse durations.…”

Section: Discussionmentioning

confidence: 96%

“…This effect results primarily from the very strong absorption of the 2.94-mm radiation in skin, which creates a very high temperature gradient in the super®cial interaction layer. As a result, the super®cial temperature rise relaxes very rapidly, which leads to a moderate surface temperature increase from pulse to pulse during repetitive laser exposure [12,22,31]. In contrast, deeper in the dermis the deposited heat accumulates due to much slower temperature relaxation in this region.…”

Section: Discussionmentioning

confidence: 99%

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Er:YAG laser skin resurfacing using repetitive long‐pulse exposure and cryogen spray cooling: I. Histological study*

et al. 2001

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Background and Objective: To evaluate histologically the characteristics of repetitive Er:YAG laser exposure of skin in combination with cryogen spray cooling (CSC), and its potential as a method of laser skin resurfacing. Study Design/Materials and Methods: Rat skin was irradiated in vivo with sequences of 10 Er:YAG laser pulses (repetition rate 20 Hz, pulse duration 150 or 550 ms, single-pulse¯uence 1.3±5.2 J/cm 2 ). In some examples, CSC was applied to reduce epidermal injury. Histologic evaluation was performed 1 hour, 1 day, 5 days, and 4 weeks post-irradiation. Results: A sequence of ten 550-ms pulses with¯uences around 2 J/cm 2 resulted in acute dermal collagen coagulation to a depth of approximately 250 mm, without complete epidermal ablation. CSC improved epidermal preservation, but also diminished the coagulation depth. Four weeks after irradiation, neo-collagen formation was observed to depths in excess of 100 mm. Conclusion: Dermal collagen coagulation and neo-collagen formation to depths similar to those observed after CO 2 laser resurfacing can be achieved without complete ablation of the epidermis by rapidly stacking long Er:YAG laser pulses. Application of CSC does not offer signi®cant epidermal protection for a given dermal coagulation depth.

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Section: Discussionsupporting

confidence: 79%

Section: Introductionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

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Er:YAG laser skin resurfacing using repetitive long‐pulse exposure and cryogen spray cooling: I. Histological study*

et al. 2001

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“…Strictly, this condition applies to spherical pores only (Majaron et al 1999), but it gives a useful guideline. Thus, for most of the situations we analyse, fracture creating fragments of enamel is not expected, and we can use the ultimate tensile strength as a simple guide to behaviour.…”

Section: The Physical Modelmentioning

confidence: 99%

The role of mesoscopic modelling in understanding the response of dental enamel to mid-infrared radiation

Verde¹,

Ramos²,

Stoneham³

2007

Phys. Med. Biol.

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Human dental enamel has a porous mesostructure at the nanometre to micrometre scales that affects its thermal and mechanical properties relevant to laser treatment. We exploit finite-element models to investigate the response of this mesostructured enamel to mid-infrared lasers (CO 2 at 10.6 µm and Er:YAG at 2.94 µm). Our models might easily be adapted to investigate ablation of other brittle composite materials. The studies clarify the role of pore water in ablation, and lead to an understanding of the different responses of enamel to CO 2 and Er:YAG lasers, even though enamel has very similar average properties at the two wavelengths. We are able to suggest effective operating parameters for dental laser ablation, which should aid the introduction of minimally-invasive laser dentistry. In particular, our results indicate that, if pulses of ≈10 µs are used, the CO 2 laser can ablate dental enamel without melting, and with minimal damage to the pulp of the tooth. Our results also suggest that pulses with 0.1-1 µs duration can induce high stress transients which may cause unwanted cracking.

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Nonablative Laser and Light Rejuvenation

Kelly

Majaron

Nelson

2001

Archives of Facial Plastic Surgery

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or centuries, patients and physicians have sought a safe and effective method for treating skin changes associated with photoaging. Currently, a variety of modalities are used to treat facial rhytids, including dermabrasion, chemical peels, and laser skin resurfacing (LSR). Although these modalities are relatively effective for rhytid reduction, epidermal disruption or removal results in an open wound that places the patient at risk for bacterial, viral, and fungal infections. Abnormal or delayed wound healing may result in skin dyspigmentation and scarring. In addition, the wound resolves with significant erythema that often lasts for weeks or months and is cosmetically troubling to patients (Figure 1). The ideal method of skin rejuvenation would achieve optimal cosmetic improvement of photodamage while minimizing wound care and the risk of adverse effects.

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Thermo-mechanical laser ablation of soft biological tissue: modeling the micro-explosions

Cited by 76 publications

References 1 publication

Er:YAG laser skin resurfacing using repetitive long‐pulse exposure and cryogen spray cooling: I. Histological study*

Er:YAG laser skin resurfacing using repetitive long‐pulse exposure and cryogen spray cooling: I. Histological study*

The role of mesoscopic modelling in understanding the response of dental enamel to mid-infrared radiation

Nonablative Laser and Light Rejuvenation

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