Pediatric Etermatology Vol. 9 No. 4 358-360
Lasers for Vascular Lesions in Pediatric Dermatology O. T. Tan, M.D. In any discussion of lasers in dennatology, it would be impossible not to center the delivery on vascular lesions and the jjediatric population. In those fields in which the laser has proved a success and won itself a clear clinical role—ophthalmology, urology, and dennatology—one can see how certain quite distinct and special properties of this means of delivering energy have been specifically harnessed to particular tasks. In distinction, however, where the laser has been applied in a less sophisticated fashion, for example, as an ablating or cutting tool, success has been nowhere as clear cut. Looking at lasers in dermatology one could say that two factors characterize the field. First is the concentration on the treatment of vascular lesions. Despite recent promising innovations in pigmented lesions, it has been the high degree of focusing of effort on vascular abnonnalities and pathologies that has been instrumental in the key breakthrough of tissue selectivity. Second is the pediatric pattern of these lesions. Whereas distinct vascular pathologies are relevant to distinct age groups, and indeed the new lasers have been applied to many of these conditions at all age groups, it is true to say that it has been the congenital lesions, port-wine stains (PWS) and hemangiomas, that have been the stimuli of the new laser developments. Thus, in very large measure, the title of this article encompasses the major theme of success to date of lasers in dermatology. HISTORIC OVERVIEW Lasers have been used to treat benign cutaneous vascular lesions for nearly three decades (1-5). Several different lasers have been used during this time, some more suitable to treat these lesions than others (Table 1). All depend on the properties of monochromaticity (of a single wavelength) and coherence (photons within the beam are in phase).
358
Ruby Laser The ruby laser was the first laser introduced and used in the mid-1960s in dermatology to treat a variety of cutaneous lesions including benign cutaneous vascular lesions such as PWS (1). Unfortunately, the combination of its inherent properties of a fixed wavelength of 694 nm and exposure time of several nanoseconds to milliseconds emitted as a train of pulses produced results that were very similar to those achieved by other thermal sources such as electrocautery. Hence, the full potentials of the laser were not fully optimized to control the delivery of laser light specifically to destroy the abnormal blood vessels in these lesions. Ai^on Laser The next laser widely used in dermatology to treat benign cutaneous lesions was the argon laser (2,3). It appeared theoretically more suitable for these lesions because its emission wavelengths fall within the absorption spectrum of oxyhemoglobin and deoxyhemoglobin, which are endogenous pigments abundant in vascular lesions. Despite its improved characteristics, reports of clinical response to this laser were varied (2,3). Of significance were the results reported in children (3,6). The frequency of hypertrophic scar was as high as 41% in patients between ages 7 and 17 years (3). Scars were evident in 38% of children treated with the argon laser, compared with 24.6% for an overall group of 73 patients between 7 and 81 years (6). Scarring was attributed to nonspecific thermal injury of dermal collagen (7). This occurred because the pulse duration or the exposure time (the time during which the laser beam was exposed to the tissue at any one particular site) was "too long." It was sufficiently long to produce a whitening of the irradiated site, which has been correlated histologically to tissue necrosis. The degree and severity of such tissue damage is totally
Tan: Lasers for Vascular Lesions 359
TABLE 1. Lasers Used in Dermatology to Treat Benign Vascular Lesions Laser
Wavelength (nm)
Puise Duration
Lesions Treated
Ruby Argon
694 488,514
nsec-msec Continuous wave
PWS PWS Hemangioma Other PWS Hemangioma Other PWS Hemangioma Other PWS Hemangioma Other
Argon pumped dye Pulsed dye Copper vapor
577 577-585 578
dependent on the exposure time and fluence (dose) (7). Several investigators attempted to modify the argon laser. Amdt (8) shortened the exposure time to 50 and 200 msec and compared the effects of these two pulse durations with those produced by the continuous-wave (CW) argon laser, but was unable to demonstrate greater specificity of vessel injury using the pulsed modes. This was not surprising because these exposure times of 50 and 200 msec are still relatively long compared with the thermal relaxation times of individual dermal blood vessels that make up the vascular lesions. The thermal relaxation time, defined as the time it takes for the target to cool to 50% of its original temperature immediately after laser irradiation, has been used to calculate the exposure time or pulse duration necessary to confine the laser energy to the target. More recently, the hexascan was developed by Mordon et al (9) in another attempt to reduce the exposure time of the argon laser from continuous to several milliseconds. The addition of this handpiece to the end of the argon laser appears to have improved the clinical results of treatments. Unfortunately, only clinical reports have been published demonstrating the effectiveness of the hexascan (9). No histologic results have been published showing how this scanner injures the abnormal blood vessels in lesions such as PWS and the subsequent repair of the laser-irradiated skin.
Scanner 300-500 (isec Quasi-continuous
properties between this laser and those discussed above are its pulse duration, wavelength, and power. A combination of these properties made it possible, for the first time, to tEirget oxyhemoglobin specifically and damage the dermal blood vessels selectively, and at the same time spare injury to adjacent nonvascular structures such as dermal collagen and the epidermis (10-12). Skin exposed to this laser not only selectively destroyed the abnormal dermal blood vessels but left the irradiated site indistinguishable in color, texture, and markings from normal adjacent skin (2,1012). This laser was used initially to clear PWS in adults (7). The results were remarkable, and similar results are now being replicated in children of all ages with this birthmark (4,13). Copper Vapor Laser
This laser emits in the yellow range of the electromagnetic spectrum at 578 nm as well as in the green at 511 nm (5). Short powerfiil pulses in tens of nanoseconds are rapidly emitted, producing an effect described as quasi-continuous on the skin surface. Unlike the pulsed dye laser clinical end point of purpura (blue-gray discoloration) immediately after irradiation, either whitening or erythema follows copper vapor laser exposure. Good to excellent results have been reported after treatment of benign cutaneous vascular lesions using this laser.
Pulsed Dye Laser
VASCULAR LESIONS TREATED BY THE PULSED DYE LASER
The development of the flashlamp-pumped dye laser provided a means of selectively destroying the abnormal dermal blood vessels in benign cutaneous vessels such as PWS (10-12). The differences in
Not only are PWS being treated by the pulsed dye laser, but other vascular lesions such as hemangiomas are also being successfully treated by this modality (Table 2).
360 Pediatric Dermatology Vol. 9 No. 4 December 1992
TABLE 2. Benign Cutaneous Vascular lesions Treated by Pulsed Dye Laser Birthmarks Telangiectasias
Angiomas
PWS Hemangiomas: early proliferative phase incompletely involuted Facial telangiectasia Rosacea After skin graft After trauma Scars Spider Campbell de Morgan
3.
4.
5. 6.
Hemangioina Morelli et al (14) recently reported the effect of this laser on ulcerated hemangiomas. Of significance was their finding that pain, which is inherent in these lesions, disappeared after the first treatment in 6 of 10 hemangiomas. In addition, two healed after two treatments and the remaining two healed after three treatments. The questions that remain unanswered are how this laser achieves its results, what mechanism(s) are responsible for the observed clinical effects, when and how early should treatment be instituted, and the role of the pulsed dye laser in the spectrum of other treatment modalities. A national multicenter study group has been formed and collaborated on using a standard protocol aimed at addressing some of these questions. Results are atixiously awaited. REFERENCES 1. Goldman L, Blaney DJ, Kindel DJ, et al. Effect of the laser beam on the skin. J Invest Dermatol 1963;40: 121. 2. Apfelberg DB, Maser MR, Laser H. Argon laser
7.
8. 9.
10. 11. 12. 13.
14.
treatment of cutaneous vascular abnormalities: progress report. Ann Plast Surg !978;1:14-18. Noe JM, Barsky SH, Geer DE, et al. Portwine stains and the response to argon laser therapy: successful treatment and the predictive roie of color, age and biopsy. Plast Reconstr Surg 1980;65:130-136. Tan OT, Sherwood K, Gilchrest BA. Treatment of children with port-wine stains using the flashlamppumped tunable dye laser. N Engl J Med 1989;320: 416-421. Walker EP, Butler PH, Pickering JW. Histology of portwine stains of the copper vapor laser treatment. BrJ Dermatol 1989; 121:217-223. Dixon JA, Huether SE, Rotering R. Hypertrophic scarring in argon laser treatment of portwine stains. Plast Reconstr Surg 1984;73:771-779. Tan OT, Carney M, Margoiis R, et al. Histologic responses of portwine stains treated by argon, carbon dioxide and dye lasers: a preliminary report. Arch Dermatol 1986;122:1016-1022. Arndt KA. Treatment techniques in argon laser therapy. J Am Acad Dermatol 1984;11:90-97. Morden S, Rotteleur G, Buys B, Brunetaud JM. Comparative study on the "point by point" technique and the "scanning" technique for laser treatment of the portwine stains. Lasers Surg Med 1989; 9:398-404. Garden JM, Tan OT, Kerschmann R, et a!. Effect of dye laser pulse duration on selective cutaneous vascular injury. J Invest Dermatol 1986;87:653-657. Tan OT, Motemedi M, Welch AJ, Kurban AK. Spotsize effects on guinea pig skin following pulsed irradiation. J Invest Dermatol 1988;90:877-881. Tan OT, Murray S, Kurban AK. Action spectrum of vascular-specific injury using pulsed irradiation. J Invest Dermatol 1989 ;92:868-871. Ashinoff R, Geronemus RG. Flashlamp-pumped pulsed dye laser for port wine stains in infancy: early versus later treatment. J Acad Dermatol 1991 ;24:467472. Morelli JG, Tan OT, Weston WL. Treatment of ulcerated hemangiomas with the pulsed tunable dye laser. Am J Dis Child 1991;145:1062-1064.
Lasers for Vascular Lesions in Pediatric Dermatology O. T. Tan, M.D. In any discussion of lasers in dennatology, it would be impossible not to center the delivery on vascular lesions and the jjediatric population. In those fields in which the laser has proved a success and won itself a clear clinical role—ophthalmology, urology, and dennatology—one can see how certain quite distinct and special properties of this means of delivering energy have been specifically harnessed to particular tasks. In distinction, however, where the laser has been applied in a less sophisticated fashion, for example, as an ablating or cutting tool, success has been nowhere as clear cut. Looking at lasers in dermatology one could say that two factors characterize the field. First is the concentration on the treatment of vascular lesions. Despite recent promising innovations in pigmented lesions, it has been the high degree of focusing of effort on vascular abnonnalities and pathologies that has been instrumental in the key breakthrough of tissue selectivity. Second is the pediatric pattern of these lesions. Whereas distinct vascular pathologies are relevant to distinct age groups, and indeed the new lasers have been applied to many of these conditions at all age groups, it is true to say that it has been the congenital lesions, port-wine stains (PWS) and hemangiomas, that have been the stimuli of the new laser developments. Thus, in very large measure, the title of this article encompasses the major theme of success to date of lasers in dermatology. HISTORIC OVERVIEW Lasers have been used to treat benign cutaneous vascular lesions for nearly three decades (1-5). Several different lasers have been used during this time, some more suitable to treat these lesions than others (Table 1). All depend on the properties of monochromaticity (of a single wavelength) and coherence (photons within the beam are in phase).
358
Ruby Laser The ruby laser was the first laser introduced and used in the mid-1960s in dermatology to treat a variety of cutaneous lesions including benign cutaneous vascular lesions such as PWS (1). Unfortunately, the combination of its inherent properties of a fixed wavelength of 694 nm and exposure time of several nanoseconds to milliseconds emitted as a train of pulses produced results that were very similar to those achieved by other thermal sources such as electrocautery. Hence, the full potentials of the laser were not fully optimized to control the delivery of laser light specifically to destroy the abnormal blood vessels in these lesions. Ai^on Laser The next laser widely used in dermatology to treat benign cutaneous lesions was the argon laser (2,3). It appeared theoretically more suitable for these lesions because its emission wavelengths fall within the absorption spectrum of oxyhemoglobin and deoxyhemoglobin, which are endogenous pigments abundant in vascular lesions. Despite its improved characteristics, reports of clinical response to this laser were varied (2,3). Of significance were the results reported in children (3,6). The frequency of hypertrophic scar was as high as 41% in patients between ages 7 and 17 years (3). Scars were evident in 38% of children treated with the argon laser, compared with 24.6% for an overall group of 73 patients between 7 and 81 years (6). Scarring was attributed to nonspecific thermal injury of dermal collagen (7). This occurred because the pulse duration or the exposure time (the time during which the laser beam was exposed to the tissue at any one particular site) was "too long." It was sufficiently long to produce a whitening of the irradiated site, which has been correlated histologically to tissue necrosis. The degree and severity of such tissue damage is totally
Tan: Lasers for Vascular Lesions 359
TABLE 1. Lasers Used in Dermatology to Treat Benign Vascular Lesions Laser
Wavelength (nm)
Puise Duration
Lesions Treated
Ruby Argon
694 488,514
nsec-msec Continuous wave
PWS PWS Hemangioma Other PWS Hemangioma Other PWS Hemangioma Other PWS Hemangioma Other
Argon pumped dye Pulsed dye Copper vapor
577 577-585 578
dependent on the exposure time and fluence (dose) (7). Several investigators attempted to modify the argon laser. Amdt (8) shortened the exposure time to 50 and 200 msec and compared the effects of these two pulse durations with those produced by the continuous-wave (CW) argon laser, but was unable to demonstrate greater specificity of vessel injury using the pulsed modes. This was not surprising because these exposure times of 50 and 200 msec are still relatively long compared with the thermal relaxation times of individual dermal blood vessels that make up the vascular lesions. The thermal relaxation time, defined as the time it takes for the target to cool to 50% of its original temperature immediately after laser irradiation, has been used to calculate the exposure time or pulse duration necessary to confine the laser energy to the target. More recently, the hexascan was developed by Mordon et al (9) in another attempt to reduce the exposure time of the argon laser from continuous to several milliseconds. The addition of this handpiece to the end of the argon laser appears to have improved the clinical results of treatments. Unfortunately, only clinical reports have been published demonstrating the effectiveness of the hexascan (9). No histologic results have been published showing how this scanner injures the abnormal blood vessels in lesions such as PWS and the subsequent repair of the laser-irradiated skin.
Scanner 300-500 (isec Quasi-continuous
properties between this laser and those discussed above are its pulse duration, wavelength, and power. A combination of these properties made it possible, for the first time, to tEirget oxyhemoglobin specifically and damage the dermal blood vessels selectively, and at the same time spare injury to adjacent nonvascular structures such as dermal collagen and the epidermis (10-12). Skin exposed to this laser not only selectively destroyed the abnormal dermal blood vessels but left the irradiated site indistinguishable in color, texture, and markings from normal adjacent skin (2,1012). This laser was used initially to clear PWS in adults (7). The results were remarkable, and similar results are now being replicated in children of all ages with this birthmark (4,13). Copper Vapor Laser
This laser emits in the yellow range of the electromagnetic spectrum at 578 nm as well as in the green at 511 nm (5). Short powerfiil pulses in tens of nanoseconds are rapidly emitted, producing an effect described as quasi-continuous on the skin surface. Unlike the pulsed dye laser clinical end point of purpura (blue-gray discoloration) immediately after irradiation, either whitening or erythema follows copper vapor laser exposure. Good to excellent results have been reported after treatment of benign cutaneous vascular lesions using this laser.
Pulsed Dye Laser
VASCULAR LESIONS TREATED BY THE PULSED DYE LASER
The development of the flashlamp-pumped dye laser provided a means of selectively destroying the abnormal dermal blood vessels in benign cutaneous vessels such as PWS (10-12). The differences in
Not only are PWS being treated by the pulsed dye laser, but other vascular lesions such as hemangiomas are also being successfully treated by this modality (Table 2).
360 Pediatric Dermatology Vol. 9 No. 4 December 1992
TABLE 2. Benign Cutaneous Vascular lesions Treated by Pulsed Dye Laser Birthmarks Telangiectasias
Angiomas
PWS Hemangiomas: early proliferative phase incompletely involuted Facial telangiectasia Rosacea After skin graft After trauma Scars Spider Campbell de Morgan
3.
4.
5. 6.
Hemangioina Morelli et al (14) recently reported the effect of this laser on ulcerated hemangiomas. Of significance was their finding that pain, which is inherent in these lesions, disappeared after the first treatment in 6 of 10 hemangiomas. In addition, two healed after two treatments and the remaining two healed after three treatments. The questions that remain unanswered are how this laser achieves its results, what mechanism(s) are responsible for the observed clinical effects, when and how early should treatment be instituted, and the role of the pulsed dye laser in the spectrum of other treatment modalities. A national multicenter study group has been formed and collaborated on using a standard protocol aimed at addressing some of these questions. Results are atixiously awaited. REFERENCES 1. Goldman L, Blaney DJ, Kindel DJ, et al. Effect of the laser beam on the skin. J Invest Dermatol 1963;40: 121. 2. Apfelberg DB, Maser MR, Laser H. Argon laser
7.
8. 9.
10. 11. 12. 13.
14.
treatment of cutaneous vascular abnormalities: progress report. Ann Plast Surg !978;1:14-18. Noe JM, Barsky SH, Geer DE, et al. Portwine stains and the response to argon laser therapy: successful treatment and the predictive roie of color, age and biopsy. Plast Reconstr Surg 1980;65:130-136. Tan OT, Sherwood K, Gilchrest BA. Treatment of children with port-wine stains using the flashlamppumped tunable dye laser. N Engl J Med 1989;320: 416-421. Walker EP, Butler PH, Pickering JW. Histology of portwine stains of the copper vapor laser treatment. BrJ Dermatol 1989; 121:217-223. Dixon JA, Huether SE, Rotering R. Hypertrophic scarring in argon laser treatment of portwine stains. Plast Reconstr Surg 1984;73:771-779. Tan OT, Carney M, Margoiis R, et al. Histologic responses of portwine stains treated by argon, carbon dioxide and dye lasers: a preliminary report. Arch Dermatol 1986;122:1016-1022. Arndt KA. Treatment techniques in argon laser therapy. J Am Acad Dermatol 1984;11:90-97. Morden S, Rotteleur G, Buys B, Brunetaud JM. Comparative study on the "point by point" technique and the "scanning" technique for laser treatment of the portwine stains. Lasers Surg Med 1989; 9:398-404. Garden JM, Tan OT, Kerschmann R, et a!. Effect of dye laser pulse duration on selective cutaneous vascular injury. J Invest Dermatol 1986;87:653-657. Tan OT, Motemedi M, Welch AJ, Kurban AK. Spotsize effects on guinea pig skin following pulsed irradiation. J Invest Dermatol 1988;90:877-881. Tan OT, Murray S, Kurban AK. Action spectrum of vascular-specific injury using pulsed irradiation. J Invest Dermatol 1989 ;92:868-871. Ashinoff R, Geronemus RG. Flashlamp-pumped pulsed dye laser for port wine stains in infancy: early versus later treatment. J Acad Dermatol 1991 ;24:467472. Morelli JG, Tan OT, Weston WL. Treatment of ulcerated hemangiomas with the pulsed tunable dye laser. Am J Dis Child 1991;145:1062-1064.
