Notes

The "Laser"

I chuckle to myself when I think about lasers. I expect Austin Powers that will put air quotes round the word when I say it. I find that numerous people utilize the term just as if it had been a magical device that will do anything whatsoever - including make a scarless incision. It can't. Lasers are only a approach to apply energy to a spot. All you can change is the size of the area, the amount of time the laser is on, and also the color (and thereby the vitality) in the laser. That's basically it. (Physicists possess a term called fluence that measures how much energy delivered per unit area. Higher fluence = more energy. Don't understand that or men and women think you're a geek.)

My first knowledge about medical lasers was in 1984. I was a surgery intern and very happy to be watching a clear case of hemorrhoids (yes, hemorrhoids) being removed with a laser. The attending physician was proud to show me how his new toy worked. He pointed the hand piece of the laser with a wooden tongue depressor and stepped about the pedal. Sure enough - the lazer immediately went all the way through the wooden stick. Unfortunately it kept going, striking the paper drapes since the patients legs. Poof, a small fire started. find more information was totally calm and dumped a basin of water around the smoking paper. No harm done, but I remarked that this was not only a simple toy.

So what kinds of medical lasers are there and what are they employed for?

The fractional co2 laser was made at Bell Labs in 1964. It is an efficient laser that emits within the infrared part with the spectrum. The wavelength of the CO2 laser is absorbed by water and so heats tissue very well. It is used in facial resurfacing to eliminate wrinkles. By controlling the length of time the heart beat lasts as well as the pattern of pulses, very precise layers of skin can be taken off. It is often used using a computer pattern generator for perfect application of the pulses.

Nd:YAG is a form of laser also put together by Bell Labs inside same year. Nd means neodymium. The initials YAG is perfect for yttrium-aluminium-garnet. (Now you realise why we reference it by its initials.) This laser emits infrared light (1064 nm). It is employed in ophthalmology and may be used to take out skin cancers. Gynecologists put it to use during hysteroscopy to take care of certain uterine conditions. It's most common cosmetic use is good for laser treatment and to eliminate spider veins in the face and legs. It can also help with removing fungus from the fingernails and toenails.

Er:YAG can be a similar laser. Instead of neodymium, erbium is employed. This laser emits further into the infrared spectrum (2940 nm) and it is strongly absorbed by water. It is found in laser resurfacing in the skin to treat scarred tissues, wrinkles, and melasma (patchy pigmented areas of the skin). It also can be used to remove warts. Dentists and oral surgeons use this laser to cut bone.

Q-Switched Lasers - Alexandrite, Ruby, Nd:Yag, Tunable Dye. OK, another geeky term, but a really useful technique. Q-Switching allows the laser to possess high energy pulses rather than continuous beam. That makes these lasers ideal for tattoo removal. From the Wikipedia article on tattoo removal:



Q-switched Frequency-doubled Nd:Yag: 532 nm. This laser results in a green light which is highly absorbed by red and orange targets. Useful primarily for red and orange tattoo pigments, this wavelength is also highly absorbed by melanin (mit giving skin color or tan) that makes the laser wavelength also effective for age spot or sun spot removal.


Q-switched Ruby: 694 nm. This laser generates a red light which can be highly absorbed by green and dark tattoo pigments. Because it is more highly absorbed by melanin this laser may produce undesirable unwanted side effects like pigmentary changes for patients of most but white skin.


Q-switched Alexandrite: 755 nm. Similar to the Ruby laser, the alexandrite laser also creates a red light that is highly absorbed by green and dark tattoo pigments. However, the alexandrite laser color is slightly less absorbed by melanin, so this laser features a slightly lower incidence of unwanted pigmentation changes when compared to a ruby laser.


Q-switched Nd:YAG: 1064 nm. This laser creates a near-infrared light (invisible to humans) which is poorly absorbed by melanin, creating this the only real laser suited to darker skin. This laser wavelength is also absorbed by all dark tattoo pigments and will be the safest wavelength to use around the tissue as a result of low melanin absorption and low hemoglobin absorption. This wavelength will be the wavelength of choice for tattoo removal.


Dye modules are for sale for some lasers to convert 532 nm to 650 nm or 585 nm light. Which allows one laser system to soundly and effectively treat multi-color tattoo inks.



Dye lasers use an organic dye mixed using a solvent that's stimulated by an high energy external light source to lase. Mirrors are widely-used to increase the energy. Then cavities or resonators are employed to tune the output. By selecting different dyes the output color may be changed. They are frequently used to treat port-wine stains along with other pigmented lesions with the skin. The can also be used to decrease scarring and to make skin tone more even. By matching the dyes for the different ink colors they're able to also be useful for tattoo removal.

IPL is the last one to go over. Intense Pulsed Light is technically not just a laser. It produces extremely high intensity light in very short pulses. IPL is the most common way of techniques 'laser' and it is roughly as effective as the Nd:YAG stated earlier. It is also used to take care of rosacea, birth marks, sun damaged skin, and scarring.

And that will do it for today. You are now more educated. Enjoy!

Laser techniques

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