امروزه از لیزر و نور در درمان بسیاری از بیماری های پوستی استفاده می شود که می توان آنها را به دو گروه مجزا تقسیم نمود .گروه تخریبی و ترمیم.درگروه تخریبی لایه های سطحی پوست به علت انرژی بالای نور لیزر از بین می رود و در نوع ترمیمی بیشتر لایه های عمقی تحت تاثیر قرار می گیرد. هر لیزر دارای یک طول موج می باشد برای همین برای درمان های مختلف نیاز به لیزر های مختلف می باشد.و عملکرد لیزر بسیار انتخابی می باشد و در نوع تخریبی رنگ محل و ضایعه مورد نظر با انتخاب طول موج لیزر رابطه مستقیم دارد.
بررسی تمامی طول موج های لیزر نیاز به کتابی چند صد صفحه ائی دارد لذا سعی می کنیم بر اساس کاربرد مورد نیاز به بررسی طول موج لیزر مورد نیاز بپردازیم.
Laser Types for Different Cosmetic Uses
- Fine Lines and Wrinkles: For treating lines and wrinkles, a combination of skin resurfacing and skin-tightening procedures can be used or both can be accomplished with a more aggressive ablative laser, such as a CO2 (carbon dioxide) laser or Erbium YAG. The CO2 laser is also commonly used for the removal of warts and skin tags and for cutting skin in laser-assisted surgery. Pulsed dye lasers have also shown some success, along with less aggressive nonlaser, light-based treatments, such as IPL and LED photofacials. (See other light-based cosmetic applications below.)
- Skin Tightening: Most cosmetic laser procedures provide at least some level of superficial tightening because they produce a controlled injury of the skin, which encourages increased collagen production. For more significant tightening results, however, CO2 lasers are the laser of choice. In addition, there has been much success using nonlaser, light-based treatments, such as Titan infrared devices and Thermage radio-frequency based systems.
- Pigmented Lesions: The most commonly used lasers for the treatment of pigmented lesions, such as sun spots, age spots, melasma and other forms of hyperpigmentation are the pulsed dye, Nd:YAG, and fractional (Fraxel) lasers, along with nonlaser, light-based treatments, such as IPL.
- Precancerous Lesions: Almost all surgeons agree that cancerous lesions should be removed via scalpel (with a knife during surgery) to ensure clear borders and complete removal. In addition to making sure a skin cancer has “clear margins,” this assures that there is a sample for a pathologist to look at to determine exactly what the lesion was. By removing precancerous growths, such as actinic keratoses, before they have a chance to become malignant (squamous cell skin cancers), though, lasers are now routinely being used as a preventative measure. Ablative lasers, such as the CO2 and erbium:YAG, are generally chosen to remove these lesions.
- Vascular Lesions: Vascular lesions include broken blood vessels on the face, unsightly spider veins on the legs, spider nevi, hemangiomas, and certain birthmarks such as port wine stains. For these types of skin irregularities, IPL is a common choice, as it is minimally invasive. Also popular for treating these lesions are the pulsed dye, Nd:YAG and diode lasers.
- Tattoos: The CO2 laser and Nd:YAG remain popular for tattoo removal, although some success can also be had with the use of IPL.
- Hair Removal: The success and safety of laser hair removal is highly dependent on the pigment present in both the skin and the hair of the patient being treated. For darker-skinned patients, the Nd:YAG and diode lasers are often the lasers of choice, and for lighter-skinned patients, IPL has proved effective.
- Acne and Acne Scars: For deeper acne scars, the CO2 laser remains the gold standard, although more recent developments such as the erbium:YAG, fractional laser and certain nonablative lasers have shown considerable success with superficial acne scarring. For the treatment of active acne, LED technology has proven to be quite effective.
Other Light-Based Cosmetic Applications
There are many different modalities of light-based technology being used in the world of cosmetic surgery today. Though these methods are often referred to as “laser” procedures, the devices being used are not actually true lasers. These technologies include IPL, LED treatments, Titan and similar infrared energy-based technologies and radio-frequency based procedures, such as Thermage.
Selective photothermolysis (fō’tō-thĕrm-ol’i-sis) is a precise microsurgery technique used to target tissue in a specific area. It matches the specific wavelength of light and heats the tissue and destroys it with a laser without affecting or damaging surrounding tissue. The targeted cells are destroyed by the absorption of light and transfer of energy.
While the term “selective photothermolysis” may sound like a high school physics concept you never understood, the term is really quite easy to understand when broken down. Selective means just that. The procedure “selects” an abnormal area to treat in contrast to surrounding normal tissue. Photo refers to light. The laser sends out light. Thermo refers to heat. So the light now creates heat. Finally, lysis refers to destruction. All in all, selective photothermolysis refers to using light to heat and destroy tissue in a selective area of the body.
Decreasing a lasers pulse time allows surgeons to provide short bursts of energy to the tissue. The pulse limits peripheral damage yet creates enough power to affect the targeted area.
The target of the laser is determined by its color. For instance, when selective photothermolysis is used in laser tattoo removal, the laser targets specific colors. Different lasers, or different settings on the same laser, are then used to break up different colors of the ink of the tattoo.
Selective photothermolysis was first developed for the process of laser hair removal but has since been used in the treatment of the following conditions:
- Severe inflammatory acne (light-absorbing particles are delivered into enlarged sebaceous glands.)
- Laser hair removal (photoepilation.)
- Tattoo removal.
- Port wine stains – A port wine stain may occur as an isolated condition, or may be part of a condition such as Sturge-Weber syndrome or Klippel-Trenaunay-Weber syndrome. Port wine stains are pink to reddish patches of skin (“birthmarks”) which occur in 0.3 to 0.5 percent of the population. In addition to being disturbing cosmetically, these lesions can darken as people age, sometimes developing into pyogenic granulomas.
- Spider veins.
- Photoaging of the skin (aging changes.)
How Selective Photothermolysis Works in These Conditions
The light energy that is emitted by the laser is absorbed by the molecules responsible for its color, and precisely targets and destroys molecules responsible for the color.
For hair removal, the molecules would be melanin. For port wine stains, the molecules would be hemoglobin. With port-wine stains, the blood inside the blood vessels is heated due to the selective absorption of the laser energy.
The laser’s wavelength and the length of its pulse will determine the effectiveness of treatment.
You may wish to learn more about the different types of lasers and how they work.
Selective photothermolysis is the reason why a pale-skinned patient with a black tattoo will achieve better and fastest results. The laser breaks down the dark ink leaving the pale skin around it intact. Black is the easiest color to remove, followed by red, and then green and blue. It also explains why ink colors which are closer to skin colors, such as brown, yellow, or pink, are more challenging to remove.
Goodbye to Tattoos
If you are considering having a tattoo removed, it can be helpful to learn some of the history and basics about tattoo removal. Unlike the sometimes impulsive decision, followed by a few hour procedure (or less) process of getting a tattoo, removing a tattoo requires a commitment to time and often multiple visits. From the length of time you will need to wait between treatments, you should learn about which type of tattoos are the easiest to remove, and even a discussion about how painful these procedures may be.
The most common “complication” of selective photothermolysis is the inability to resolve the pigmented skin lesion completely. The procedure works best when there is a significant contrast between the color of the skin and the normal surrounding skin. The procedure is also limited to what can be accomplished by the laser surgery. For example, selective photothermolysis may resolve some skin changes secondary to aging or treat some problems related to inflammatory acne, but certainly not all.
As with any laser technique, there can be damage (burns) to surrounding normal tissues in some cases.
The Bottom Line
Procedures such as selective photothermolysis provide another method for people to treat skin conditions ranging from unwanted tattoos to congenital port wine stains, to changes related to inflammatory acne. It’s likely that with current knowledge, procedures such as this will continue to improve in ways which help physicians treat unwanted skin coloring without harming nearby tissues.