- Dr. Henry Ngai
Pico or Nano? Which is winning the laser match?
Q-switched lasers vs picosecond lasers
Q-switched lasers, which have been available to us for many years, is still the gold standard of choice in tattoo removal. Q-switched lasers are so called ultra-short-pulsed lasers because they emit light in a fraction of a second. Q-switched nanosecond laser emit light at about 0.000000005 second. A picosecond laser emits light over even a shorter duration at 1/10 of the duration of the nanosecond laser. The change in the physics of the light has important implication of what the laser can accomplish in industrial and medical use.
Short-pulsed lasers are effective in natural pigmentation
The discovery of nanosecond laser allows safe and selective removal of pigmented lesions on the skin. Prior technology using a continuous wave laser, such as CO2, causes non-specific tissue destruction and therefore increases the risk of scarring. Short pulsed duration lasers, such as devices in the millisecond (0.001sec) or microsecond (0.000001sec) domain, are effective in removing natural body pigmented lesions, like age spots. These skin pigment particles (melanin) are fairly large in size and the heat of treatment is mostly confined within the pigment particles and causes little collateral skin damage.
However, the pigmented particles in tattoo inks are much smaller. The laser energy from short-pulsed lases can no longer trap just within the lesion and the heat generated diffuses to the surrounding normal skin. Excessive heat in normal skin means burns and excessive inflammation.
Q-switched lasers & picosecond lasers are safe for tattoo removal
Both nanosecond and picosecond lasers are able to shatter tattoo ink particles. Because of the ultra-short-pulse, these devices minimize the heat from treatment diffusing to the surrounding skins. Therefore, side effects of treatment are reduced.
Is picosecond better than Q-switched?
Picosecond lasers are developed because nanosecond lasers are still limited in confining the heat damage within the smaller target particles ( photomechanical vs photothermal). In addition, a picosecond laser is able to generate higher shattering power (peak power) when it comes to breaking up finer tattoo ink.
Advantage of picosecond lasers
So what does this all means? Here the low-down on the advantage of picosecond lasers:
Faster tattoo removal – There is enough literature to support the removal of tattoo in fewer sessions
Non-specific targets – Picosecond lasers of a particular wavelength can remove more colors than the nanosecond laser. However, a color-specific picosecond laser is still better for tattoo removal.
Less tissue damage – The ability to generate a short pulse minimizes heat diffusion for the target pigments. As a result, there is less surface tissue disruption and more selective treatment.
Photorejuvenation – The higher power causes molecular ionization and tissue cavitation. This process is called LIOB (laser induced optical breakdown). Picosecond lasers cause little “explosion” with the dermis with subsequent tissue remodeling and new collagen production. This forms the basis of rejuvenation.
What can picosecond lasers treat?
Picosecond lasers have been used in scar revision, removal of birthmarks, treatment of acne scars etc. Many of these conditions are not amendable to nanosecond laser treatment.
Picosecond laser is still at the early stage of clinical use. It has several advantages over the nanosecond laser. However, the nanosecond is still very effective in treatment of most pigmented lasers and it is not necessarily inferior to the picosecond laser in many areas. It will require longer period of clinical use and gathering of clinical data from users around the world to see the full potential of this new picosecond technology.