Laser and Light Treatment of Acquired and Congenital Vascular Lesions Flashcards
Lasers produce selective photocoagulation of vessels using wavelengths of light that are well absorbed by haemoglobin.
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Lasers produce selective photocoagulation of vessels using pulse durations equal to or longer than the thermal relaxation time (or cooling time) of the vessels.
F Equal to or shorter than thermal relaxation time.
Larger-diameter and deeper vessels require shorter wavelengths of light and shorter pulse durations.
F Longer wavelength and longer pulse durations.
Lasers and light devices used to treat vascular lesions include KTP, pulsed-dye, alexandrite, diodie and Nd:YAG lasers, in addition to IPL.
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Laser stands for Light Amplification by the Stimulated Emission of Radiation.
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Fluence is measured in J/cm2.
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The major chromophores in skin are haemoglobin and melanin.
F And water.
When targeting a vascular lesion, the wavelength of light chosen should be well absorbed by haemoglobin and poorly absorbed by melanin.
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Selective heating of the laser target is produced when the energy is deposited at a rate faster than the rate for cooling of the target structure.
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Pulsed KTP laser has a wavelength of 532nm.
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Pulsed dye laser has a wavelength of 595nm.
F 585nm (long-pulsed dye is 585-600nm).
Long-pulsed alexandrite laser has a wavelength of 755nm.
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Diode laser uses 800, 810 or 840nm wavelength.
F 800, 810 or 940nm.
Long-pulsed Nd:YAG laser has a wavelength of 1064nm.
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IPL uses a wavelength of 515-920nm.
F 515-1200nm.
For a given wavelength of light, the optical penetration into skin depends on absorption and scattering.
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The most penetrating wavelengths are in the 650-1200nm red and near-infrared region.
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Longer wavelengths (600-1200nm) penetrate deeper, but with more scattering
F Deeper with less scattering
The least penetrating wavelengths are in the far UV, where protein absorption dominates, and the far-infrared, where water absorption dominates.
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The depth of penetration gradually decreases with longer wavelengths.
F Increases with longer wavelengths.
With smaller spot sizes, a greater fraction of photons scatter outside the beam area and are rendered ineffective.
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Cooling the skin does not effect tissue injury caused by laser procedures.
F Cooling before/during/after reduces tissue injury.
Cooling can be achieved by using a liquid cryogen spray during treatments
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Pulsed-dye laser produces transient blue-black purpura due to haemorrhage and a delayed vasculitis.
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For v essels 10-50microm in diameter, the thermal relaxation time would be 0.1-10ms, with an average of 1.2ms
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Pulsed-KTP lasers emit in the green light spectrum.
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Longer pulse durations increase photomechanical injury and post-treatment purpura.
F Reduce.
Lasers with near-infrared wavelengths are not suitable for treating larger vascular anomalies or larger leg veins.
F Alexandrite, diode and Nd:YAG used for this.
Vascular lasers can be used for capillary malformations, haemangiomas, venous malformations, telangiectasias, facial erythema, cherry angiomas, venous lakes and poikiloderma of Civatte.
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Striae distensae cannot be treated with vascular laser.
F Striae rubra shows best response.
The hypopigmentation of striae distensae responds well to vascular laser.
F No effect.
Port wine stains can regress.
F Never regress.
Port wine stains darken in colour and become increasingly nodular with age.
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The hypertrophy or nodularity of a PWS are associated with a risk of spontaneous bleeding or haemorrhage with injury to the site.
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PWS should not be treated ideally until adulthood.
F Childhood better.
Treatment of PWS in early life enables more rapid clearing, however there may be partial return of the PWS 5-10 years after treatment.
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Greater PWS clearance in children is attributed to thinner skin allowing better laser penetration, smaller vessel diameter, and smaller lesional surface area.
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Gradual clearing of PWS is produced with successive PDL treatments usually performed at 2-4 week intervals.
F 4-6 week intervals.
PDL can be safely used in skin types I-IV.
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With PDL, longer wavelengths and longer durations improve PWS clearance.
T Longer wavelengths provide more deeply penetrating light to target deeper vessels.
The response of a PWS to PDL treatment depends on its size, anatomic location and the types of vessels that comprise the lesion
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PWS that are present in the central facial area or in a V2 dermatomal distribution respond faster than PWSs located elsewhere on the head and neck.
F More slowly.
PWS on extremities respond more slowly to laser therapy than lesions on the trunk, and lesions on the distal extremity respond the slowest.
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Smaller PWSs respond better to PDL.
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The best response to PDL is seen in PWSs located deeper, with smaller diameter vessels.
F Superficially located, larger-diameter vessels
Vessel morphology does not correlate with PWS colour.
F Pink = smaller vessel, purple = larger vessel.
Red PWS lesions are composed of more superficially located vessels than pink or purple ones.
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Red coloured PWSs respond poorly to laser, while pink coloured PWSs respond better.
F Red better, pink worse.
Even slowly responsive PWSs continue to clear with repetitive PDL treatment with no increased risk of adverse effects.
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PDL treatment for PWS during infancy is not recommended.
F Safe and rapid clearance possible.
Treatment of PWS with PDL is usually performed with the smallest spot size available to prevent reticulation.
F Largest spot size.
PDL treatment of PWS should be performed with the lowest fluence possible that produces purpura without tissue graying or whitening.
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Improved technology in skin cooling has been a major advancement in treatment of PWS
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Appropriate cooling can be achieved by applying millisecond-duration cryogen spurts, preceding each laser pulse with maintenance of the temperature of the laser-heated dermal vessels
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There may be a delayed final tissue reaction after PDL, so the patient should be observed for several minutes after treatment.
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Intense purpura develops 7-10 days after PDL.
F Immediately.
