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Laser Tattoo Removal : How Q-Switching Works
Posted: Jan 08, 2014
How do you remove a tattoo? Removing a tattoo requires a laser to remove ink from the skin while preserving the surrounding tissue. Using a Q-switched laser causes a beam of light energy to interact with pockets of ink in the skin that comprise the tattoo. A "photo-acoustic" event occurs and light breaks apart the ink into smaller particles, small enough for the body to absorb. This process is repeated 4-8 times for full removal, and represents the only effective procedure to achieve tattoo removal.
What Exactly Is Going on Here?
Tattoo pigment in the skin is considered a very deep target. Tattoo ink creates "pockets" between the dermis and epidermis, which are deeper targets than others (sun damage, facial vessels), and which can be difficult to treat deeper pigment in skin (melasma). To fully remove a tattoo, the laser needs help from the healing system in the skin. The edema and swelling from tattoo removal treatment create a "wound healing response" in skin to absorb the smaller ink particles that result from treatment. The tattoo then begins to fade.
To complicate matters, different colors react in different ways. Black ink and darker colors are easier to remove with less post treatment healing required. More colorful tattoos will have longer healing times. Wavelengths used to remove more colorful inks interact more aggressively with the skin.
Technique Matters
The laser tattoo removal procedure needs to start with low energy, which is increased in each successive treatment. Practitioners should avoid over-treating. Additionally, R20 still being investigated and is not the "home run" many were hoping for. Practitioners will also want to avoid any epidermal disruption. This increases the potential for complication and long-term pigmentation issues.
Technology Matters
For the most effective treatment, a tattoo removal laser needs to be a high-energy system:
1J pulse energy or better
There are four different manufactures active in the US market, only two that are manufactured in USA
The laser should also be a "Active QS" and not a "Passive QS"
Active QS is a single pulse technology that delivers all energy in one pulse
Passive QS is electronically generated pulses that are delivered in a pulse train, which is made in China technology, not clinically effective and very cheap (in all senses of the word)
Lastly, multiple wavelengths are needed to remove multi-color tattoos.
What Type of Lasers Remove Tattoos?
Q-switched lasers remove tattoos and there are three main kinds:
Nd:YAG – considered the most effective by many
Ruby
Alex
"Q-switched" refers to "quality switched." In the dermatology and aesthetic field, Q-switched signifies "short pulse" or "nanosecond pulsed" lasers.
To remove multiple ink colors of a tattoo, different wavelengths must be used: 1064, 532, 585, 650, 755, 694. Long pulse lasers have been tried, and failed so we do not recommend them. Tattoo pigment absorbs energy from long pulse lasers too strongly, almost always causes a significant burn, and do not work either.
The light from a Q-switched laser is delivered in nanoseconds and delivers an acoustic pulse to the target. A nanosecond is one billionth of a second and photo-acoustic is a short pulse measured in seconds vs. photo-thermal, which is a long pulse measured in milliseconds.
What Is the Difference between Photothermal vs. Photoacoustic Tattoo Removal?
Photothermal
Millisecond energy is delivered over time to create a photothermal effect that produces heat to damage hair follicles or heat for rejuvenation. Lasers that deliver energy in milliseconds or thousandths of a second. This sounds fast but in the "laser world" this is a very long time. Long pulse lasers are millisecond pulsed lasers.
Photoacoustic
Nanosecond energy is delivered faster than the thermal relaxation time of cells. Cells cannot tolerate this energy and consequentially burst. This is more effective for laser tattoo removal.
Q-switched lasers deliver energy in nanoseconds, or a billionth of a second.
What Are the Alternatives to Laser Tattoo Removal?
While there are three main alternatives to removing tattoos with Q-switched lasers, none of them work nearly as well. Gels, creams and even "wrecking balm" at the most represent a low-grade chemical peel that will burn off a few layers of skin. Using chemical peels deep enough to reach tattoo ink packets will leave a serious scar. Long pulse and IPL lasers will burn the skin and make tattoo more difficult to eventually remove, as scar tissue will encapsulate ink packets. Surgery is acceptable only for very small tattoos and surgical tattoos. Thus, practitioners and patients alike will want to stick with laser tattoo removal with a q-switched laser.
John Lee is the author of this article on Tattoo Removal.