The optimal treatment of port-wine stains is laser-induced selective photothermolysis. Lesion color and location and the age of the patient are reported to influence the therapeutic outcome. This study was initiated to analyze the outcome not only by the clinical response of lightening, but also in terms of photothermally induced necrosis to the vessel wall. Punch biopsy specimens were taken from 51 patients before treatment. Post-treatment biopsies were taken after exposure to a pulsed dye laser (585-nm wavelength, 0.45-ms pulse length) with an irradiant fluence of 6.5 J/cm2. Vessel diameter, depth, and wall thickness were measured in all histologic slides. The viability of the vessel walls was evaluated using an enzyme histochemical method. Port-wine stains with good blanching had significantly more superficially located vessels than the moderate and poor responders (p < 0.000). The moderate and good responding lesions consisted of moderate-sized vessels with diameters of 38 +/- 17 micrometers and 38 +/- 19 micrometers (mean +/- SD), respectively. The lesions showing poor blanching had significantly smaller vessels, with a diameter of 19 +/- 6.5 micrometers < 0.000). Analyses of the post-treatment specimens showed that coagulated vessels were superficially located and of moderate size, whereas the viable vessels were small with a median diameter of 14 micrometers. The probability of coagulation correlated with the thickness of the vessel wall. These data indicate that the therapeutic outcome of port-wine stains can be improved by using the lesional vessel parameters to select the optimal laser wavelength, pulse duration, and dose.

Abstract. Selective photothermolysis with pulsed lasers is presumably the most successful therapy for port-wine stain birthmarks (flammeus nevi). Selectivity is obtained by using an optical wavelength corresponding to high absorption in blood, together with small absorption in tissues. Further on, the pulse length is selected to be long enough to allow heat to diffuse into the vessel wall, but simultaneously short enough to prevent thermal damage to perivascular tissues. The optical wavelength and pulse length are therefore dependent on vessel diameter, vessel wall thickness and depth in dermis. The present work demonstrates that in the case of a 0.45 ms long pulse at 585 nm wavelength, vessels of 40~0 Fm require minimum optical fluence. Smaller vessels require higher fluence because the amount of heat needed to heat the wall becomes a substantial fraction of the absorbed optical energy. Larger vessels also require a higher dose because the attenuation of light in blood prevents the blood in the centre of the lumen from participating in the heating process. It is shown that the commonly used optical dose in the range of 6-7 J cm-2 is expected to inflict vessel rupture rather than thermolysis in superficially located vessels. The present analysis might serve to draw guidelines for a protocol where the optical energy, wavelength and pulse length are optimized with respect to vessel diameter and depth in dermis.

Thirty patients were treated with a flashlamp-pumped pulsed dye laser, with 0.45 ms pulse width and 585 nm wavelength. Punch biopsies were taken prior to treatment, and the biopsies were examined morphometrically. Three different test sites were exposed to laser light of fluence 5.25, 6.50 and 7.75 J/cm2. The degree of blanching was examined 6-8 weeks after treatment, and each site was retreated four times. Six patients (20%) achieved poor blanching, eight patients (27%) obtained moderate lightening and 16 patients (53%) showed good response. The vessels of the good responders were located significantly more superficially than the vessels of the moderate and poor responders (P < 0.05). The poor responders had significantly smaller vessels than the moderate and good responders (P < 0.01). The moderate responders had deeper, but larger vessels, than the poor responders. Hence, an increasing vessel diameter reduces the negative outcome of increasing vessel depth. The vessel diameter was correlated to the colour (P < 0.01), e.g. the mean vessel diameter was increasing from 16.5 microns in pink lesions to 51.2 microns in purple lesions. The vessel depth was partly reflected in the lesional colour, as the pink and purple lesions had significantly deeper vessels than the red ones (P = 0.02). These results indicate that pink lesions predict poor blanching due to deeply located small vessels, while red lesions predict a good therapeutic result because of more superficially located vessels.

Thirty patients were treated with a flashlamp-pumped pulsed dye laser, with 0.45 ms pulse width and 585 nm wavelength. Punch biopsies were taken prior to treatment, and the biopsies were examined morphometrically. Three different test sites were exposed to laser light of fluence 5.25, 6.50 and 7.75 J/cm2. The degree of blanching was examined 6-8 weeks after treatment, and each site was retreated four times. Six patients (20%) achieved poor blanching, eight patients (27%) obtained moderate lightening and 16 patients (53%) showed good response. The vessels of the good responders were located significantly more superficially than the vessels of the moderate and poor responders (P < 0.05). The poor responders had significantly smaller vessels than the moderate and good responders (P < 0.01). The moderate responders had deeper, but larger vessels, than the poor responders. Hence, an increasing vessel diameter reduces the negative outcome of increasing vessel depth. The vessel diameter was correlated to the colour (P < 0.01), e.g. the mean vessel diameter was increasing from 16.5 microns in pink lesions to 51.2 microns in purple lesions. The vessel depth was partly reflected in the lesional colour, as the pink and purple lesions had significantly deeper vessels than the red ones (P = 0.02). These results indicate that pink lesions predict poor blanching due to deeply located small vessels, while red lesions predict a good therapeutic result because of more superficially located vessels.

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