What is a KTP laser?
A KTP laser is a solid-state laser that uses a potassium titanyl phosphate (KTP) crystal as its frequencing doubling device. The KTP crystal is engaged by a beam generated by a neodynium:yitrium aluminium garnet (Nd: YAG) laser. This is directed through the KTP crystal to produce a beam in the green visible spectrum with a wavelength of 532 nm.
How does a KTP laser work?
- The KTP laser works on the principle of selective photothermolysis.
- The selected wavelength of laser light is absorbed to a high degree by the target structure (called a chromophore), and is absorbed less by surrounding tissue.
- The skin chromophores targeted by the KTP laser are melanin, oxyhaemoglobin and red tattoo pigment.
- The pulse duration of laser energy is shorter than the target structure’s thermal relaxation time (the time taken for the target to cool by 50% of its peak temperature after irradiation).
- This ensures that the impact of thermal energy is limited to the target structure and does not affect the surrounding tissue. Modern KTP lasers also have integrated cooling systems to help protect the epidermis, particularly when doing vascular work.
- When KTP laser light hits the skin, it is reflected, transmitted, or absorbed.
- Absorbed light energy is converted to thermal energy (heat) by the intended targets (chromophores), thereby killing the target cells.
- Complications result when energy intended for the target chromophore is nonselectively diffused and absorbed by surrounding tissues and structures. Because melanin is targeted by this wavelength, the KTP laser is rarely used in darker skin types.
- The effects of the KTP laser on the skin can be modified by altering the pulse width and degree of cooling. In the case of tattoo pigment, the pulse width is narrowed to nanoseconds (Q-switched KTP) and the clinical effect is photomechanical/acoustic. Picosecond lasers may be more effective for pigment fragmentation but at very short pulse widths, the creation of a plasma veil is a limiting factor.
Cutaneous vascular lesions
- KTP laser is useful in the treatment of some superficial port wine stains (vascular malformation) and a variety of acquired cutaneous vascular lesions, including telangiectasis, cherry angiomas and poikiloderma of Civatte.
- Light energy emitted by the Nd:YAG pumped KTP laser is primarily absorbed by oxyhemoglobin contained within blood vessels, thus minimising thermal damage to other structures.
- Laser treatment parameters are based on several factors, including lesion location, lesion morphology, and patient skin phototype.
- Lower energy densities are necessary in anatomic locations with an increased risk of scarring, such as the anterior chest, neck, and periorbital area. Skin cooling is essential.
- Only patients with Fitzpatrick skin types I to III are eligible.
- Successful treatment of poikiloderma of Civatte can be achieved with several treatment sessions. The KTP laser is particularly suited to treating facial telangiectasia.
Pigmented and non-vascular skin lesions
- KTP lasers can be effective for freckles, superficial dyspigmentation (eg epidermal melasma) and lentigos.
- In the removal of pigmentation, energy from KTP laser light is selectively absorbed by the melanin that causes pigmentation. Skin cooling is reduced resulting in a photo-thermal injury to the melanin.
- KTP lasers can be effective in erythematotelangiectatic rosacea.
- Used in the Q-switched mode, the KTP laser can be used to remove red-coloured tattoo ink (a cause of adverse tattoo reactions).
- The extremely short pulse width (ns) allows for vaporisation of the ink.
- Even though 532 nm wavelength of the KTP laser is well absorbed by other colours, the Nd:YAG (1,064 nm) and the alexandrite lasers (755 nm) penetrate better and result in a superior clinical result for dark-coloured (blue/black) tattoos.
What does the laser procedure involve?
The patient should wear eye protection, consisting of an opaque covering or goggles, throughout treatment.
- Treatment with the KTP laser consists of placing a hand piece against the surface of the skin and activating the laser. Many patients describe each pulse to feel like the snapping of a rubber band against the skin.
- Topical anaesthetic or forced air cooling may be applied to the area, but is not necessary if there is a cooling system.
- Immediately following treatment, an coolpack may be applied to soothe the treated area.
- Care should be taken in the first few days following treatment to avoid scrubbing the area, and/or use of abrasive skin cleansers.
- Following treatment, patients should protect the area from sun exposure to reduce the risk of postinflammatory pigmentation.
Are there any side effects from KTP laser treatment?
Side effects from KTP laser treatment are usually minor and may include:
- Pain – there may be some pain during treatment which can be reduced by contact cooling and if necessary, topical anaesthetic or forced air cooling or other analgesia.
- Redness and swelling – in rare instances soreness and redness may occur. Swelling is common especially on the upper cheeks and forehead and usually subsides in a few days. KTP laser is non-ablative treatment and there is usually no crusting or blistering
- Changes in skin pigmentation – Sometimes the pigment cells (melanocytes) can be damaged leaving darker (hyperpigmentation) or paler (hypopigmentation) patches of skin. Generally, cosmetic lasers will work better on people with lighter than darker skin tones.
- Bruising – rarely occurs.
- Bacterial infection – antibiotics may be prescribed to treat wound infection if epidermal disruption occurs.
- Scarring – is very rare and minor with KTP laser treatmetns.