Q开关激光治疗人为皮肤色素沉着146例

目的　观察Q开关三种波长激光系统治疗人为皮肤色素沉着的临床效果。方法　根据皮损的颜色、部位 ,选用Q开关Nd :YAG激光 ,波长为 1 0 64nm ,Q开关翠绿宝石激光 ,波长为 755nm ,Q开关倍频Nd :YAG激光 ,波长为 532nm ,对人为皮肤色素沉着 1 4 6例患者进行治疗。色素沉着一次治疗未消退者可行多次治疗 ,每次治疗间隔 2～ 3个月。结果　经过 1～ 5次治疗达Ⅰ、Ⅱ级疗效者分别为 97例患者、36例患者 ,总有效率为 1 0 0 %。所有治疗后的患者 ,其皮损部位均未出现瘢痕。结论　Q开关三种波长激光系统治疗人为皮肤色素沉着安全性好 ,疗效佳     

Long-pulsed dye laser versus intense pulsed light for photodamaged skin: a randomized split-face trial with blinded response evaluation

OBJECTIVE: In a randomized controlled split-face trial to evaluate efficacy and adverse effects from rejuvenation with long-pulsed dye laser (LPDL) versus intense pulsed light (IPL). MATERIALS AND METHODS: Twenty female volunteers with Fitzpatrick skin types I-III, classes I-II rhytids, and symmetrical split-face photodamage were included in the study. Subjects received a series of three treatments at 3-week intervals with half-face LPDL (V-beam Perfecta, 595 nm, Candela Laser Corporation) and half-face IPL (Ellipse Flex, Danish Dermatologic Development); the interventions being randomly assigned to left and right sides. Primary end-points were telangiectasias, irregular pigmentation and preferred treatment. Secondary end-points were skin texture, rhytids, pain, and adverse effects. Efficacy was evaluated by patient self-assessments and by blinded clinical on-site and photographic evaluations at 1, 3, and 6 months postoperatively. Adverse effects were evaluated by blinded clinical on-site evaluations. RESULTS: Telangiectasia improved from LPDL and IPL treatments with superior vessel clearance from LPDL treatments (postoperative side-to-side evaluations, patient self-assessments, P相似文献   

CO2 laser-resurfacing: increased risk of side effects after uv-exposure-an experimental animal study

BACKGROUND AND OBJECTIVES: Carbon dioxide (CO(2)) laser resurfacing is primarily performed on photodamaged facial skin where patients are further exposed to ultraviolet radiation (UVR) postoperatively. We examined whether pre- and postoperative UVR influences the development of CO(2) laser-induced side effects. STUDY DESIGN/MATERIALS AND METHODS: Hairless mice (n = 211) were treated with a Sharplan CO(2) laser with FeatherTouch scanner. Simulated solar irradiation was administered either preoperatively or pre- and postoperatively. Skin end-points (wounds, texture changes, and pigmentary changes) were evaluated blinded by clinical evaluations, skin reflectance spectroscopy, and histological examinations. RESULTS: Pre- and postoperative UVR exposed mice obtained higher clinical scores of wounds (P < 0.02) and texture changes (P < 0.01) and developed more heavy fibrosis than mice treated with laser but no UVR. UVR exposure after CO(2) laser treatment induced significant hyperpigmentation compared to unexposed control mice (P < 0.003), whereas CO(2) laser treatment itself did not induce pigmentary changes. CONCLUSIONS: UVR increases in an animal model the occurrence of postoperative side effects from CO(2) laser resurfacing.     

Lactate dehydrogenase in laser incisions: a comparative analysis of skin wounds made with steel scalpel, electrocautery, superpulse--continuous wave mode carbon-dioxide lasers, and contact Nd:YAG laser

A histochemical method for demonstrating lactate dehydrogenase activity was used in addition to standard Van Gieson stain to study early alterations near wounds made in pig skin by steel scalpel, electrocautery, two modes of CO2 laser (the rapid super-pulse mode and the continuous wave mode), and contact Nd:YAG laser. The enzyme-free zone near the wounds made using the thermal knives appeared to be twice as wide as the necrotic zone observed with Van Gieson stain. In polarized light, the enzyme-free area showed two zones of equal width with respect to birefringence of collagen fibers. The zone lacking birefringence correlated well with that observed with Van Gieson stain. The birefringent zone represented functionally damaged tissue with more or less normal structures by light microscopy. The damage to adjacent tissue caused with the thermal knives seems to be considerably larger than has usually been reported.     

The effect of epidermal pigmentation on selective vascular effects of pulsed laser

The effect of epidermal pigmentation on the threshold exposure dose for inducing purpura with a tunable dye laser at 577 nm, 1.5 microseconds pulse duration, was studied in 21 human volunteers with varied genetically determined amounts of melanin. More laser energy was required to produce purpura as constitutive skin pigmentation increased. Histology showed that, in lighter skin, the laser threshold dose produced the most specific vascular injury with no disruption of surrounding structures. In more pigmented skin, damage occurred in the epidermal basal layer and very few changes were seen in blood vessels below.     

Histologic comparison of the pulsed dye laser and copper vapor laser effects on pig skin

Albino pig skin was exposed to the copper vapor (CVL) and flash-lamp pulsed dye (PDL) lasers at 578 nm with a 3 mm diameter spotsize over a range of fluences until purpura and whitening were first established. The total irradiation time was the parameter that was varied in order for the CVL to reach the desired fluence. The lowest fluence producing each clinical endpoint was designated the threshold fluence: 34 J/cm2 was required to produce purpura using the CVL compared to 7.5 J/cm2 with the PDL laser. Histologically, skin exposed to purpura fluences from the CVL revealed the presence of constricted, disrupted papillary dermal blood vessels with trapped RBC's within them which were unlike those exposed to PDL where the irradiated vessels were dilated and packed with masses of intravascular agglutinated RBC's. The whitening threshold fluences for the CVL and PDL lasers were 67 J/cm2 and 29 J/cm2, respectively. Streaming of epidermal cells and dermal collagen denaturation were observed in CVL irradiated skin, compared to occasional dyskeratotic epidermal cells and focal dermal collagen denaturation following PDL exposure. The mechanisms responsible for the clinical and histologic changes produced by the two laser systems are discussed.     

Modeling optical and thermal distributions in tissue during laser irradiation

The propagation of light energy in tissues is an important problem in phototherapy, especially with the increased use of lasers as light sources. Often a slight difference in delivered energy separates a useless, efficacious, or disastrous treatment. Methods are presented for experimental characterization of the optical properties of a tissue and computational prediction of the distribution of light energy within a tissue. A standard integrating sphere spectrophotometer measured the total transmission, Tt, total reflectance, Rt, and the on-axis transmission, Ta, for incident collimated light that propagated through the dermis of albino mouse skin, over the visible spectrum. The diffusion approximation solution to the one-dimensional (1-D) optical transport equation computed the expected Tt and Rt for different combinations of absorbance, k, scattering, s, and anisotropy, g, and by iterative comparison of the measured and computed Tt and Rt values converged to the intrinsic tissue parameters. For example, mouse dermis presented optical parameters of 2.8 cm-1, 239 cm-1, and 0.74 for k, s, and g, respectively, at 488 nm wavelength. These values were used in the model to simulate the optical propagation of the 488-nm line of an argon laser through mouse skin in vivo. A 1-D Green's function thermal diffusion model computed the temperature distribution within the tissue at different times during laser irradiation. In vitro experiments showed that the threshold temperature range for coagulation was 60 degrees-70 degrees C, and the kinetics were first order, with a temperature-dependent rate constant that obeyed an Arrhenius relation (molar entropy 276 cal/mol-degrees K, molar enthalpy 102 kcal/mol). The model simulation agreed with the corresponding in vivo experiment that a 2-s pulse at 55 W/cm2 irradiance will achieve coagulation of the skin.     

Clinical effects of dynamic cooling during pulsed laser treatment of port-wine stains

Pulsed dye lasers permit effective treatment of port-wine stains without a significant risk of complications. However, epidermal damage manifested by weeping or crusting of the treated area have been reported in 48—83% of patients, and transient hyperpigmentation after treatment is observed in 10–57%. Theoretically, the epidermis can be protected from thermal damage with the use of the concept of selective epidermal cooling. This study examined the clinical effects of rapid cooling of the epidermis with a liquid refrigerant R-134a (boiling point — 26.5 ‡C) during pulsed dye laser therapy. In 23 patients with port-wine stains, a 50-ms-long cooling pulse delivered immediately prior to laser irradiation with a fluence of 6.0 J cm^-2 significantly reduced the pain, and shortened the period with purpura without compromising the clinical blanching. Cooling periods longer than 60 ms, as well as additional cooling pulses immediately after laser exposure, reduced the blanching in areas irradiated with 6.0 J cm^-2. Post-treatment hyperpigmentation was not prevented with dynamic cooling.     

Impact of gastrointestinal-related side effects on mycophenolate mofetil dosing and potential therapeutic strategies

In renal transplant patients receiving mycophenolate mofetil (MMF), maintaining an adequate dosing regimen has been shown to maximize short- and long-term outcomes. Gastrointestinal (GI) adverse events associated with MMF are frequent, and lead to MMF dose reduction or withdrawal in 40-50% of cases. Among MMF-treated patients experiencing GI complications, one analysis has reported MMF discontinuation to be associated with almost a threefold increase in risk of graft loss, while a dose reduction > or = 50% carried over a twofold increase in risk. If GI symptoms improve and the pre-reduction MMF dose is resumed the increased risk of graft loss may be reversed, but continuing intolerance can make this difficult to achieve. Investigation of contributing factors is important and may alleviate symptoms. Conversion to enteric-coated mycophenolate sodium (EC-MPS) may be an effective option. Two open-label studies using patient-reported outcomes data have shown a significant and clinically relevant benefit in GI-related symptom burden after conversion from MMF to EC-MPS. In conclusion, monitoring of GI complications is essential following renal transplantation, and maintaining adequate mycophenolic acid exposure should be a priority when considering treatment options.     

Differential effects of short- and long-pulsewidth laser exposures on retinal ganglion cell response

Time-dependent effects of laser exposures on rhesus monkey retinal ganglion cells were studied with a Q-switched, doubled Nd:glass laser, which produced 20 nsec pulses of 530-nm light, and a continuous-wave (CW) argon laser (514.5 nm), which produced exposures of 0.1-msec to 0.1-sec duration. Ganglion cell activity was recorded in situ by means of an intraocular electrode. Ganglion cells exposed to a single 20-nsec exposure, at a sublesion intensity, produced a 60-90 sec discharge of action potentials and exhibited a 2 log or greater elevation of light threshold, depending on beam size and intensity. At equivalent energy levels, the longer exposures produced the same or slightly weaker effects. This result is not as straightforward as it seems. Submillisecond flashes bleach no more than 50% of the visual pigment because of photoregeneration. The Dowling-Rushton relation predicts that a 50% bleach should produce only a 1.5 log loss of cone sensitivity. Exposures longer than 1 msec should not photoregenerate pigment (ie, more pigment will be bleached for a given exposure intensity). In view of the probable differences in pigment bleaching, it appears that the Q-switched laser light adapts the cells out of proportion to the visual pigment actually bleached--a single-cell analogue of Rushton's "theta" effect.