Treatment of a capillary hemangioma with the flashlamp pumped-dye laser.
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Fingers↗
Biomedical subjects
O T Tan
Publications and source records attributed to O T Tan.
585 nm for the treatment of port-wine stains.
Although the flashlamp-pulsed-dye laser has been successfully used for the treatment of port-wine stains (PWS) at 577 nm, a number of adult patients had incomplete clearance of their birthmarks with this treatment modality because of residual vessels lying beyond the 0.75-mm penetration depth of 577-nm irradiation. Fifteen adult patients, of whom nine were previously treated with limited success at 577 nm (group A), and six untreated patients (group B) were included in the study. For the group A patients, treatment with 585 nm produced successful clearance of the birthmark. For the six patients in group B, parallel treatment of different sites of the same lesion coupled with skin biopsies and histologic examination revealed that a change in the wavelength from 577 to 585 nm allowed the laser light to penetrate from the midreticular dermis into the subcutaneous fat. This explained the clearance achieved at 585 nm and not at 577 nm.
Adolescent↗
Treatment of children with port-wine stains using the flashlamp-pulsed tunable dye laser.
Thirty-five children, three months to 14 years of age, with disfiguring port-wine stains were treated with a flashlamp-pulsed tunable dye laser. All had complete clearing of the stains after an average of 6.5 laser treatments to each lesional area; skin over bony prominences required approximately half as many sessions as skin on the cheek. Children less than seven years old required fewer sessions (mean +/- SD, 5.8 +/- 1.1) than older children (7.1 +/- 1.1; P less than 0.05). Treated skin was identical in texture and color to adjacent normal skin in 33 (94.3 percent) of the children, whereas 2 (5.7 percent) had small, isolated, depressed scars in areas accidentally traumatized soon after laser treatment. The only other side effect was transient hyperpigmentation, which occurred in 20 patients (57 percent). These results can be attributed to two distinguishing characteristics of the flashlamp-pulsed tunable dye laser: an emission wavelength of 577 nm, theoretically ideal for selective absorption by the intravascular target oxyhemoglobin, and a pulse duration of 360 microseconds, which closely matches the thermal relaxation time for dermal blood vessels and hence avoids diffuse nonspecific thermal necrosis with subsequent scarring of the treated skin.
Adolescent↗
Action spectrum of vascular specific injury using pulsed irradiation.
It has been clearly demonstrated that cutaneous blood vessels will be selectively damaged by a laser whose wavelength matches one of the three absorption spectral peaks of the chromophore, oxyhemoglobin, for example, 577 nm. A restriction in the application of this wavelength for the treatment of benign cutaneous vascular tumors, such as portwine stains, has been the penetration depth of 577 nm irradiation of approximately 0.5 mm from the dermal epidermal junction (DEJ). This study was undertaken to establish whether it was possible to increase the penetration depth from 0.5 mm by changing the wavelength to beyond 577 nm in albino pig skin. Results from this study confirm that penetration depth increases from 0.5 to 1.2 mm by changing the wavelength from 577 to 585 nm at 4 J/cm2, while maintaining the same degree of vascular selectivity as that previously described after 577 nm irradiation. This occurred in spite of a mismatch in the wavelength between 585 nm and the oxyhemoglobin absorption peak of 577 nm. Unlike 585 nm irradiation and in contrast with theoretical predictions, 590 nm laser light did not penetrate as deeply as 585 nm. Not only was there a reduction in the penetration depth of the laser beam from 1.2 mm at 585 nm to 0.8 mm at 590 nm, at 4 J/cm2, but there was also a decrease in vascular selectivity in albino pig skin exposed to 590 nm irradiation.
Animals↗
Effect of wavelength on cutaneous pigment using pulsed irradiation.
Several reports have been published over the last two decades describing the successful removal of benign cutaneous pigmented lesions such as lentigines, café au lait macules' nevi, nevus of Ota, and lentigo maligna by a variety of lasers such as the excimer (351 nm), argon (488,514 nm), ruby (694 nm), Nd:YAG (1060 nm), and CO2 (10,600 nm). Laser treatment has been applied to lesions with a range of pigment depths from superficial lentigines in the epidermis to the nevus of Ota in the reticular dermis. Widely divergent laser parameters of wavelength, pulse duration, energy density, and spotsizes have been used, but the laser parameters used to treat this range of lesions have been arbitrary, with little effort focused on defining optimal laser parameters for removal of each type. In this study, miniature black pig skin was exposed to five wavelengths (504, 590, 694, 720, and 750 nm) covering the absorption spectrum of melanin. At each wavelength, a range of energy densities was examined. Skin biopsies taken from laser-exposed sites were examined histologically in an attempt to establish whether optimal laser parameters exist for destroying pigment cells in skin. Of the five wavelengths examined, 504 nm produced the most pigment specific injury; this specificity being maintained even at the highest energy density of 7.0 J/cm2. Thus, for the destruction of melanin-containing cells in the epidermal compartment, 504 nm wavelength appears optimal.
Animals↗
Ultrastructural changes in red blood cells following pulsed irradiation in vitro.
The careful choice of a combination of laser parameters such as wavelength, pulse duration, and dose has provided a means for confining laser energy to specific targets within tissue such as oxyhemoglobin within the cutaneous microvasculature. In the process of achieving such vascular selectivity, certain ultrastructural changes in red blood cell (RBC) cytoplasm have been observed, such as the generation of intracytoplasmic electron-lucent spherical structures. These structures, ranging in size from 80 to 1000A, were seen in RBCs exposed to laser doses at and above threshold, and appeared to represent a morphologically novel form of highly-specific tissue injury. This in vitro study using RBC in phosphate buffered saline (PBS) was undertaken to better understand the mechanism(s) that could have been responsible for these unique morphologic changes. We conclude that the intracytoplasmic electron-lucent spherical structures seen within RBCs were heat-fixed molds formed around vaporized water bubbles and were not produced by the release of oxygen from the oxyhemoglobin moiety during 577-nm laser irradiation.
Erythrocytes↗
Factitious dermatosis masquerading as recurrent herpes zoster.
A 35-year-old nurse's aide presented with monthly episodes, during her menses, of self-induced cutaneous lesions intended to simulate recurrent herpes zoster. Features of the clinical presentation that prompted the correct diagnosis are discussed.
Adult↗
Selective vascular coagulation of rabbit colon using a flashlamp-excited dye laser operating at 577 nanometers.
Previous studies have demonstrated that brief pulses of selectively absorbed optical radiation can be used to confine thermal injury to pigmented targets within tissues. We performed studies in rabbits to assess the usefulness of this technique for selectively coagulating the colonic vasculature. By measuring the optical absorbance of rabbit colon with a spectrophotometer, it was determined that hemoglobin exhibits strong absorption relative to the rabbit colon at a wavelength of 577 nm. Because light must be absorbed to affect tissue, it was hypothesized that laser pulses of this wavelength would selectively damage blood vessels. This hypothesis was tested by examining the effect of 300-microseconds-long 577-nm laser pulses on rabbit colon in vivo. For delivered radiant exposures between 4 and 8 J/cm2, selective coagulation of the colonic vasculature could be produced without damage to the surrounding colon. At greater radiant exposures, vessel hemorrhage was occasionally noted but no transmural thermal injury was produced with delivered radiant exposures as high as 22 J/cm2. This technique may form the basis of a safe and simple treatment of vascular lesions of the colon such as angiodysplasia.
Animals↗
Pulsed dye laser (577 nm) treatment of portwine stains: ultrastructural evidence of neovascularization and mast cell degranulation in healed lesions.
Portwine stains were examined before, immediately after, and 1 yr after successful clearance by a pulsed dye laser (577 nm) using ultrastructural techniques. Dilated vascular channels and mast cell hypoplasia characterized lesional skin before treatment. Immediately after treatment, widespread selective vessel necrosis, similar to changes previously described, was observed. One year after laser irradiation, the abnormally ectatic portwine stain vessels had been replaced by small venules and arterioles, similar in number and diameter to blood vessels in normal skin; the only difference noted was that these new vessels were surrounded by easily identifiable mast cells. Many of these mast cells exhibited evidence of activation and degranulation. We conclude that mast cells may play an important role in the neovascularization of portwine stains treated by 577-nm dye laser irradiation.
Adolescent↗
Spotsize effects on guinea pig skin following pulsed irradiation.
Laser irradiation parameters such as wavelength, irradiance (W/cm2), and pulse duration have been clearly shown to influence the extent to which tissue is damaged. The careful choice of these parameters can result in confining laser injury to specific targets in tissue. Spotsize, a parameter not commonly appreciated in the application of lasers to medicine and surgery, has been shown, in this study, to contribute to the ultimate outcome of laser effects in tissue. A series of histological events occurring in the skin are demonstrated to be directly related to the effects of spotsize on tissue at a fixed exposure time and wavelength. Many of these changes could contribute to unwanted adverse effects, such as scarring, which occur following certain laser therapies.
Animals↗
193 nm excimer laser selective ablation of in vivo guinea pig epidermis.
We have previously shown that 193 nm excimer laser irradiation cleanly and effectively ablates avascular tissue with minimal thermal damage to surrounding adjacent structures. In this study, the 193 nm excimer laser is used to remove guinea pig epidermis in vivo. The epidermis can be totally ablated with thermal damage extending only superficially into the dermis. Reepitheliazation of the ablated area takes place in 1 week or less. This technique may be applicable to the removal of benign epidermal lesions.
Animals↗
Congo red binding of elastin in aortic smooth muscle cell cultures.
These studies demonstrate that the strong binding capacity of elastin for Congo red can be used to advantage in aortic smooth muscle cell cultures. A fibrous elastin network fluoresces when Congo red is added. Congo red does not alter accumulation of elastin or of total protein, even when the cells are grown in the presence of the dye for long periods of time, indicating that it is not toxic. Porcine pancreatic elastase was used to solubilize elastin in these cultures, to determine the molar ratio of Congo red to elastin, thus making it possible to estimate the amount of elastin solubilized when the cultures are injured. Congo red binding to elastin will be useful in studying elastin accumulation and/or degradation in vitro and in vivo.
Animals↗
Laser therapy for selected cutaneous vascular lesions in the pediatric population: a review.
Three cutaneous vascular lesions of childhood (the spider angioma [nevus araneus], the strawberry hemangioma, and the port wine stain) are reviewed, with particular emphasis on the present and future role of laser therapy in their management.
Adolescent↗
The treatment of port-wine stains by the pulsed dye laser. Analysis of pulse duration and long-term therapy.
A flashlamp-pumped pulsed dye laser at 577 nm was evaluated in the treatment of port-wine stains. The degree of lesional lightening was compared following laser exposure with pulse durations of 20 and 360 microseconds. In addition, lesional therapy using the 360-microseconds pulse duration was evaluated for lightening and side effects following long-term patient observation and after repeated treatments of the same site. A total of 52 patients with port-wine stain were treated; their average age was 29 years, with eight patients less than 18 years, of whom 29 had comparative test site placement for the different pulse durations. Of these 29 patients, 25 demonstrated greater lightening at the 360-microseconds pulse duration test site. All 52 patients proceeded to receive full treatment placement with the 360-microseconds pulse duration, which resulted in an overall lightening of 42% after the initial treatment and 68% after re-treatment sessions. Forty-four percent of the patients had equal to or greater than 75% lesional lightening. Pretreatment anesthesia was unnecessary and only minimum posttreatment care was required. Mild adverse effects of epidermal change, depression, or pigmentary change appeared in only four cases and was limited to less than a 2% area in each of these lesions. These side effects did not recur when the lesions were re-treated at lower energy dosages. No posttreatment sclerosis or scarring appeared, even after multiple retreatment sessions to the same area, regardless of the anatomic location, color of the lesion, or age of the patient.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Limitations of carbon dioxide lasers for treatment of port-wine stains.
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Carbon Dioxide↗
Pruritic, pink, papular eruption. Generalized granuloma annulare (GA).
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Diagnosis, Differential↗
Ultrastructure: effects of melanin pigment on target specificity using a pulsed dye laser (577 nm).
It has been shown recently that brief pulses of 577 nm radiation from the tunable dye laser are absorbed selectively by oxyhemoglobin. This absorption is associated with highly specific damage to superficial vascular plexus blood vessels in those with lightly pigmented (type I-II) skin. To determine whether pigmentary differences in the overlying epidermis influence this target specificity, we exposed both type I (fair) and type V (dark) normal human skin to varying radiant exposure doses over 1.5-microsecond pulse durations from the tunable dye laser at a wavelength of 577 nm. Using ultrastructural techniques, we found in type I skin that even clinical subthreshold laser exposures caused reproducible alterations of erythrocytes and adjacent dermal vascular endothelium without comparable damage to the overlying epidermis. In contrast, degenerated epidermal basal cells represented the predominant form of cellular damage after laser exposure of type V skin at comparable doses. We conclude that epidermal melanin and vascular hemoglobin are competing sites for 577 nm laser absorption and damage, and that the target specificity of the 577 nm tunable dye laser is therefore influenced by variations in epidermal pigmentation. This finding is relevant to the clinical application of the tunable dye laser in the ablative treatment of vascular lesions. We also found on ultrastructure that the presence of electron-lucent circular structures of approximately 800 A in diameter were observed only at and above clinical threshold doses in those with type I skin and at the highest dose of 2.75 J/cm2 in type V skin. It has been proposed that these structures might be heat-fixed molds of water vapor. Both this and ultrastructural changes of epidermal basal cells demonstrate mechanisms responsible for alteration of tissue after exposure to 577 nm, which are discussed.
Animals↗
Ultraviolet excimer laser ablation: the effect of wavelength and repetition rate on in vivo guinea pig skin.
Multiple dermatologic conditions that are currently treated with traditional cold-knife surgery are amenable to laser therapy. The ideal surgical treatment would be precise and total removal of abnormal tissue with maximal sparing of remaining structures. The ultraviolet (UV) excimer laser is capable of such precise tissue removal due to the penetration depth of 193 nm and 248 nm irradiation of 1 micron per pulse. This type of ablative tissue removal requires a high repetition rate for efficient lesional destruction. Excimer laser radiation at 193 nm is capable of high repetition rates, which are necessary while 248 nm radiation causes increasing nonspecific thermal injury as the laser repetition rate is increased.
Animals↗