Lý tưởng nhất, một nguồn ánh sáng cần phải có một thời gian xung sẽ cho phép năng lượng ánh sáng để xây dựng tàu mục tiêu để toàn bộ đường kính của nó là thermocoagulated. T | 158 Clinical procedures in laser skin rejuvenation Wavelength nm Fig. Oxygenated and deoxygenated hemoglobin. Water and melanin absorption curves as a function of wavelength. Adaptedfrom Boulnois JL. Lasers Med Sci 1986 and reproduced with permission from Sclerotherapy Treatment of Varicose and Telangiectatic Leg Veins 4th edn. Goldman MP Bergan JB Guex JJ eds. Elsevier London 2006. nm. Ideally for wavelengths between 600 and 1064 a light source should have a pulse duration that would allow the light energy to build up in the target vessel so that its entire diameter is thermocoagulated. Optimal pulse durations have been calculated for blood vessels of various diameter Table . During the process of delivering a sufficient amount of energy to thermocoagulate the target vessel the overlying epidermis and perivascular tissue should be unharmed. This selective preservation of tissue requires some form of epidermal cooling. A number of different laser and IPL systems have been developed toward this end and are discussed in subse quent sections. Table Thermal relaxation times of blood vessels Vessel diameter mm Relaxation time s Patients seek treatment for leg veins mostly for cos- metic reasons and any treatment that is effective should be relatively free of adverse Bernstein 3 for example evaluated the clinical characteristics of 500 consecutive patients presenting for removal of Treatment of leg telangiectasia with laser and pulsed light 159 lower extremity spider veins. Patients ranged in age from 20 to 70 years and had had noticeable spider veins for an average of 14 years 28 had leg veins less than mm in diameter and 39 veins less than mm in diameter. Interestingly regardless of exactly how sclerotherapy was performed more than half 56 of patients developed TM. Recent advances in laser and IPL treatments for treating telangiectatic vessels if used appropriately assure minimal if any .
