Flashcards in Laser treatment of tattoos and pigmented lesions Deck (124):
Q-switched lasers with extremely short pulse durations are best suited for the selective destruction of most pigmented lesions.
The main chromophores in skin are melanin in pigmented lesions, oxyhaemoglobin in vascular lesions and water in all cells.
By limiting the pulse duration (ie. the time that the laser is fired into the chromophore), it is possible to contain damage to the selected chromophore.
If the laser is fired in a time longer than the target’s thermal relaxation time, the generated heat will cause selective damage to the target chromophore.
F Shorter than the target’s thermal relaxation time (the time required for the target to lose 50% of heat)
If the laser pulse duration is too short, the heat produced in the chromophore will have time to spread to the surrounding structures, cause non-selective damage that may lead to scarring.
F This is true with pulse durations that are too long.
Since melanosomes are quite large, they cool very slowly when heated (ie. they have a longer thermal relaxation time).
F Melanosomes are small, cool very quickly when heated, short thermal relaxation time.
The estimated thermal relaxation time of a melanosome is approximately 250-1000 nanoseconds.
Lasers with very short pulse durations, in the nanosecond domain, are ideally suited to target the small melanosome chromophore.
Short pulse lasers are called Q-switched (QS) lasers, indicating quality-switched.
The delivery of an exceptionally high-energy laser pulse within a long time span results in rapid heating of the target melanosome, causing it to explode.
F Short time span.
Melanin has a narrow absorption spectrum.
F Broad – UV, visible and near-infrared light.
Ideal wavelengths to treat pigmented lesions would be those with greater absorption by melanin than by oxyhaemoglobin.
Melanin light absorption decreases with decreasing wavelength.
F Decreases with increasing wavelength.
Lasers with shorter wavelengths (eg. pulsed-dye, QS KTP and QS ruby) are typically used for lentigines, given that the pigment is superficial.
Lentigines are successfully treated with various types of laser sources
QS lasers including the 694nm QS Ruby, 755nm QS alexandrite and the 532nm frequency-doubled Nd:YAG lasers are most commonly used for the treatment of individual lentigines
Shorter wavelengths are also optimal for the treatment of dermal pigmented lesions or deeper vascular lesions.
F Not optimal.
Longer wavelength pigment lasers (eg QS Nd:YAG) are used where the pigment is located in the dermis, such as naevus of Ota and tattoos.
QS alexandrite lasers, with an intermediate wavelength, may be used for both superficial and deep pigment.
Longer pulse width ruby, alexandrite and Nd:YAG lasers, predominantly used for hair removal, do not have the same wavelength as the QS versions used in the treatment of pigmented lesions.
F Do have same wavelength.
Intense pulsed light is not a suitable option for the treatment of superficial pigmented lesions.
With intense pulsed light, polychromatic light ranging from 515-1200nm is emitted with filters to cut off light above a predetermined wavelength.
F Below a predetermined wavelength.
Ablative lasers can be used to non-selectively eliminate pigment as a secondary event, eg. CO2, Er:YAG, YSGG and the fractional lasers.
For treating pigmented lesions, higher fluences should be used in the treatment of patients with darker skin types, since the threshold response will likely occur at a higher fluence.
F Lower fluences.
Patients with darker skin are at greater risk for post-operative hyper or hypopigmentation.
It is preferable to use a longer wavelength device in patients with darker skin, since longer wavelengths penetrate more deeply than shorter wavelengths and produce relatively less epidermal damage with the same dermal effect.
Patients with suntans can be treated with pigment lasers. .
F Shouldn’t be treated
QS lasers are not helpful in the treating naevus of Ota
F Are extremely helpful
Prolonged scarring can develop in patients who have used isotretinoin at any time in the past.
F Within preceding 6 months.
Retinal injury is only a hazard the patient undergoing laser.
F All personnel in the room.
Placement of intraocular metal eye shields should be considered when treatment is in the immediate periocular area.
Reflective surfaces and windows should be covered, no flammable materials should be present, and access to the procedure room should be limited during laser treatment.
QS lasers do not generally cause tissue or blood spatter.
F Can cause some tissue and blood splatter.
The use of alcohol in the cleaning area prior to laser treatment does not pose any safety hazard.
F Alcohol must not be present on the skin at time of laser delivery (risk flash fire).
Clearance of 70% of melanocytic lesions is reported in patients treated at least 5 times with the QS ruby laser
A study of QS Nd:YAG treatment for acquired nevus of Ota-like macules suggests that epidermal cooling may be associated with an increased risk or post-inflammatory hyperpigmentation
Following irradiation with QS laser light, sublethal laser damage may increase DNA damage leading to an increase in p16 expression
There are several reported cases of true malignant transformation of benign pigmented lesions following laser treatment
F There has never been a reported case, despite the fact that benign-appearing nevi that recur following laser treatment may show new-found atypia
Red-brown tattoo colour contains pigment Iron oxide and is treated with QS Ruby laser
F QS KTP laser
For the treatment of large tattoos, lesions containing large amounts of dermal pigment, or when ablative lasers are used, infiltrative local anaesthesia or regional nerve blocks should be used.
Shorter wavelength lasers are generally well suited for the treatment of dermal lesions as a result of their high absorption by melanin and limited depth of penetration.
F True for epidermal lesions.
Longer wavelength lasers penetrate deeper into the skin for dermal lesions but have less melanin absorption.
Fair-skinned photodamaged patients with both mild vascular and pigmentary changed are best suited for treatment with intense pulsed light devices.
The most effective lasers for deeper dermal and pigment tattoos are IPL, KTP and QS ruby lasers.
F QS alexandrite and Nd:YAG.
With any modality, the degree of lightening is usually directly proportional to the number of treatments performed.
Laser treatment of melanocytic naevi is completely safe and recommended for those lesions which are cosmetically bothersome.
F Controversial – unclear whether laser has any potential to induce malignant change in naevus cells.
Benign appearing naevi that tend to recur following laser treatment may show new-found clinical and histologic atypia, referred to as pseudomelanoma.
There has never been a report of true malignant transformation of a benign pigmented lesion following laser treatment.
QS laser treatment is recommended as first-line treatment of melasma or postinflammatory pigmentation.
F Often paradoxically increases dermal melanophages.
Repeated fractional photothermolysis utilising the 1550nm laser (Fraxel) has shown some benefit for melasma.
Dermal drug-induced hyperpigmentation does not generally respond to treatment with QS lasers.
In amateur tattoos, pigment is typically present in lower concentrations and located in various levels of the dermis.
In professional tattoos, there is dense pigment implanted at the epidermal-dermal junction.
F Junction of the papillary and reticular dermis.
In professional tattoos, the pigments cinnabar and cadmium red and commonly used to produce red colour.
In professional tattoos, the pigment cadmium sulphate is commonly used to produce green colour.
In professional tattoos, chromium salts are commonly used to produce a yellow colour.
In professional tattoos, titanium dioxide is commonly used to produce a white colour.
In professional tattoos, iron oxide is commonly used to produce a dark blue colour.
F Red-brown colour. Dark blue is produced by cobalt salts.
All tattoos contain carbon, which adds to the dark hue of tattoos, and is the most responsive part of the pigment to laser treatment.
Carbon pigment by itself produces a black tattoo colour.
QS lasers lighten the majority of tattoos, but clearance is related to density, colour, and composition of the tattoo.
Typically, amateur, dark, uniformly-coloured tattoos do not respond predictably, even after more than ten laser treatments.
F Clear with some reliability after 3-5 treatments.
Professional multi-coloured tattoos respond with some reliability to QS lasers.
F Don’t respond predictably, may not clear completely even after > 10 treatments.
Tattoos with red, yellow and orange are particularly difficult to completely clear with most tattoo lasers.
Older tattoos tend to require an increased number of laser treatments for their removal.
Tattoos on distal extremities tend to be more resistant to laser treatment as a result of decreased lymphatic drainage.
The possible fate of tattoo ink particles after laser irradiation includes direct fragmentation of ink particles.
The possible fate of tattoo ink particles after laser irradiation includes release of ink into the extracellular dermal space.
The possible fate of tattoo ink particles after laser irradiation includes partial elimination of ink in a scale crust.
The possible fate of tattoo ink particles after laser irradiation includes rephagocytosis of laser-altered residual tattoo ink particles.
The possible fate of tattoo ink particles after laser irradiation includes increased ink elimination via the lymphatics.
Red tattoo colour is best treated with any QS laser.
F QS 510nm pulsed-dye/QS KTP
Red-brown tattoo colour is best treated with QS KTP laser.
Yellow tattoo colour is best treated with QS ruby/QS alexandrite laser.
F QS KTP
Green tattoo colour is best treated with QS KTP laser.
F QS ruby/QS alexandrite
Dark blue tattoo colour is best treated with QS ruby/QS alexandrite/QS Nd:YAG laser.
Black tattoo colour is best treated with any QS laser.
F QS ruby/QS alexandrite/QS Nd:YAG
White tattoo colour is best treated with any QS laser.
When treating pigmented lesions, QS lasers do not cause an immediate sign at the site of impact.
F Immediate ash-white colour.
The cause of ash-white colour at the site of laser impact is due to heat-induced stream cavities in melanosomes, which cause scattering of visible light producing a white colour.
The ash-white colour at the site of laser impact gradually disappears over 20 hours.
F 20 minutes.
The adequate laser exposure does for melanosome damage correlates well with the clinical threshold for immediate skin whitening.
If clinical ash-white colour is not visible, the laser exposure dose is sufficient.
F Laser dose is not sufficient.
Darker skin has a higher threshold for whitening due to a higher epidermal melanin content.
F Lower threshold for whitening.
With higher fluences, solid whitening with epidermal disruption and pinpoint bleeding may occur.
If the fluence is too high, whitening may be imperceptible.
F Fluence too low.
At fluences less than threshold, paradoxical hyperpigmentation may occur as a result of melanocyte stimulation.
Excessive fluences can result in a thermal burn with tissue sloughing, prolonged wound healing, hypo/hyperpigmentation, textural changes and scarring.
For darker phototypes, higher fluences with a test spot should be employed.
F Lower fluences.
Laser treatments for superficial pigment are generally spaced 4-8 weeks apart.
Laser treatments for tattoos are ideally spaced 4-8 weeks apart.
F 6-12 weeks.
For epidermal lesions, Er:YAG carries a higher risk of scarring than treatment with more selective QS lasers.
For IPL, cooling is vitally important to minimise the risk of significant epidermal injury.
For IPL, areas should not be treated with more than one pulse.
F Area may be single, double or triple pulsed.
Generally, lower fluences are employed for dermal lesions than for epidermal lesions.
F Higher fluences.
Uniform whitening is the desired end point after laser treatment with an approximately 10% overlap for dermal lesions.
Darker phototypes are probably best treated with longer wavelength lasers such as the 1064nm Nd:YAG.
The clearing of dermal pigment occurs quickly after laser treatment, typically within 2-4 weeks.
F Clearing is slow and gradual – may occur for many months post treatment.
Occlusive dressings can be used over tattoos during laser treatment
Pulses should not be overlapped during laser treatment of tattoos.
For tattoo removal, treatment with the lowest possible fluence is generally recommended.
F Highest possible fluence.
The desired response for laser tattoo removal is immediate, bright tissue whitening.
For tattoos with darker, dense pigment, lower laser fluences are recommended for initial treatments. As the pigment lightens, higher fluences can be used.
In darker skinned patients, the 1064nm Nd:YAG laser is recommended for blue or black pigment.
Tattoo pigment may lighten for several months following treatment.
Cosmetic tattoos may contain iron oxide or titanium dioxide when can be treated safely with an QS laser.
F Risk of immediate irreversible darkening of the pigment.
The use of occlusive dressings should be avoided after laser treatments.
F This can provide some pain relief
Some patients may develop an urticarial reaction after laser with oedema and pruritus, which will subside within the hour.
Areas treated with laser may appear darker and develop crusting in the first 7-10 days after treatment.
After laser, patients should be instructed to gently clean treated areas daily, apply occlusive emollient ointments to hasten healing, and remove crusts actively.
F Allow crusts to slough on their own.
There is no need to avoid sun exposure after laser treatment.
Patients treated with 532nm KTP or 510nm pulse dye lasers may develop purpura for 7-10 days as a result of the significant absorption of haemoglobin at these wavelengths.
The post-operative changes tend to be more pronounced after treatment of epidermal lesions versus dermal lesions and tattoos.
F Dermal lesions and tattoos more pronounced.
Vesiculation may occur with shorter wavelength QS laser treatment of tattoos, but typically heal without scarring or textural changes
The development of blistering in the treatment of dermal lesions is typically of a normal expected reaction.
F Indicates the use of excessive fluences.
Factors that may increase risk of scarring and permanent hypopigmentation include excessive fluences using small spot sizes.
Factors that may increase risk of scarring and permanent hypopigmentation include non-overlapping, separate pulses.
F Pulse stacking.
Factors that may increase risk of scarring and permanent hypopigmentation include tattoos with ‘double ink’ (ie. two tattoos on top of one another).
Factors that may increase risk of scarring and permanent hypopigmentation include too frequent treatments.
Factors that may increase risk of scarring and permanent hypopigmentation include treatment of areas such as the ankle, deltoid and chest.
T These areas are more prone to scarring.
IPL devices tend to cause more pronounced postoperative reactions compared with lasers.
F Less pronounced.
Pigmented lesions will darken for up to 1 week following IPL.
Similar to IPL devices, there is also minimal recovery time with fractional thermolysis.