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Laser in medicine

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on 11 November 2012

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Transcript of Laser in medicine

LASER in medicine LASER (Light Amplification by Stimulated Emission of Radiation) - device that emits light through a process of optical amplification based on the stimulated emission of photons.
spatial and temporal coherence
small beam divergence
big power density
three- or four-level
population inversion of states
big spatial density of photons What is LASER? angioplasty
cancer diagnosis and treatment
cosmetic applications (laser hair removal and tattoo removal)
medical imaging
ophthalmology (includes Lasik and laser photocoagulation)
optical coherence tomography
surgery Laser in medicine Photothermal Reactions
Photochemical Reactions
Photoablation Laser Tissue Interaction Laser light absorbed by chromophores in the tissue is converted into heat. A typical application is photocoagulation, where the laser light is absorbed by hemoglobin to stop bleeding or to seal blood vessels. Another example is thermal ablation when laser light vaporizes tissue water for tissue cutting. This interaction requires laser solutions that have high average power and a wavelength that matches the absorption levels of target tissue. Photothermal Reactions Photons absorbed by tissue molecules. Excited molecules can undergo chemical reactions. A prominent example is Photodynamic therapy (PDT) where a photosensitive drug is administered. Using specific wavelengths enables applications such as selective photo thermolysis. Tattoo removal is an example of this. This interaction requires laser solutions that have high average power and a wavelength defined by molecule absorption. Photochemical Reactions Laser light is used to break the molecular bonds in the tissue. Key applications include ophthalmology where UV laser light is used for refractive surgery of the cornea, as well as in lithotripsy where high energy laser pulses are used to generate plasma and shock waves that can break up kidney stones. Typical laser solutions operate in pulsed mode for high peak power and, depending on the type of tissue, have UV to NIR wavelengths. Photoablation refractive surgery - excimer laser based solutions for vision correction (LASIK).
retinalapplications - laser solutions for photocoagulation, an important application to treat wet form age related macular degeneration (AMD).
OpticallyPumped Semiconductor Lasers (OPSL):
wavelengths optimal for photocoagulation,
yellow light couples effectively with hemoglobin which enables more efficient sealing of blood vessels (photocoagulation),
more controlled healing effect and better patient comfort - minimized heat-load. Ophthalmology For surgical applications, CO2 lasers are used in a
number of laparoscopic applications. Fiber based beam delivery systems for urology applications enable the quick deployment of laser technologies
in surgery. Lasers are also used in laser liposuction.
The big advantage of using them is that surgeon avoids cutting tissue by scalpel or similar surgical instruments, what makes laser surgery less invasive. Surgical: Dermatology CO2 lasers and semiconductor diode lasers are widely adopted in the areas of tattoo removal and hair removal. In fractional skin resurfacing is used waveguide technology with CO2 lasers. More recently, clinics have begun to use visible OPSLs in the treatment of pigmentation, blood vessels or wrinkles because of its better absorption of yellow wavelengths
in melanin compared to legacy green laser solutions. Dentistry In dentistry several variants of dental laser are in use, with the most common being diode lasers, carbon dioxide lasers, and yttrium aluminium garnet laser. In the most common
- gum surgery there are used near infrared diode lasers. Types of lasers used in medicine Excimer Laser Excimer lasers are the leading UV laser solution in the medical
market, providing pulse energies at the mJ level and beyond. An excimer laser typically uses a combination of a noble gas (argon, krypton, or xenon) and a reactive gas (fluorine or chlorine). Under the appropriate conditions of electrical stimulation and high pressure, a pseudo-molecule called an excimer is created, which can only exist in an energized state and can give rise to laser light in the ultraviolet range. CO2 Laser The CO2 laser is a gas laser that produces a beam of infrared light with the principal wavelength bands centering around 9.4 and 10.6 micrometers. The filling gas within the discharge
tube consists primarily of:
Carbon dioxide (CO2) (around 10–20%)
Nitrogen (N2) (around 10–20%)
Hydrogen (H2) and/or xenon (Xe) (a few percent; usually only used in a sealed tube.)
Helium (He) (the remainder of the gas mixture) Semiconductor laser It is laser, whose active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current. Semiconductor lasers are widely used in lots of fields.
There are few types of this lasers:
Double heterostructure lasers
Quantum well lasers
Quantum cascade lasers
Separate confinement heterostructure lasers
Distributed feedback lasers
Vertical-cavity surface-emitting laser
Vertical-external-cavity surface-emitting-laser Thank you for your attention
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