Plume dynamics and shielding by the ablation plume during Er:YAG laser ablation
| Autor: | Alfred Vogel, Kester Nahen |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Optics and Photonics
Materials science Infrared Rays medicine.medical_treatment Dermatologic Surgical Procedures Biomedical Engineering In Vitro Techniques law.invention Biomaterials Optics Radiation Protection law Schlieren Vaporization medicine Animals Humans Laser ablation business.industry Lasers Pulse duration Water Ablation Laser Atomic and Molecular Physics and Optics Electronic Optical and Magnetic Materials Plume Gelatin Laser Therapy business Er:YAG laser |
| Zdroj: | Journal of biomedical optics. 7(2) |
| ISSN: | 1083-3668 |
| Popis: | Free-running Er:YAG lasers are used for precise tissue abla- tion in various clinical applications. The ablated material is ejected into the direction perpendicular to the tissue surface. We investigated the influence of shielding by the ablation plume on the energy depo- sition into an irradiated sample because it influences the ablation dy- namics and the amount of material ablated. The investigations were performed using an Er:YAG laser with a pulse duration of 200 ms for the ablation of gelatin with different water contents, skin, and water. Laser flash photography combined with a dark field Schlieren tech- nique was used to visualize gaseous and particulate ablation prod- ucts, and to measure the distance traveled by the ablating laser beam through the ablation plume at various times after the beginning of the laser pulse. The temporal evolution of the transmission through the ablation plume was probed using a second free running Er:YAG laser beam directed parallel to the sample's surface. The ablation dynamics was found to consist of a vaporization phase followed by material ejection. The observation of droplet ejection during water ablation provided evidence that a phase explosion is the driving mechanism for material ejection. The laser light transmission was only slightly reduced by the vapor plume, but decreased by 25%-50% when the ejected material passed the probe beam. At radiant exposures '10 times above the ablation threshold, the laser energy deposited into the sample amounted to only 61% of the incident energy for gelatin samples with 90% water content and to 86% for skin samples. For free-running Er:YAG laser pulses shielding must therefore be consid- ered in modeling the ablation dynamics and determining the dosage for clinical applications. © 2002 Society of Photo-Optical Instrumentation Engineers. |
| Databáze: | OpenAIRE |
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