Objective　To obtain an objective assessment of the curative effectiveness of photodynamic therapy (PDT) for port wine stain (PWS), we investigate the relationship between the microvascular perfusion changes of PWS and the blanching of the lesions before and after PDT.
　　Methods　Twenty-four patients (18 females and 6 males with a total of 28 lesions) suffering from PWS were treated with PDT. The lesions of various extents were located on the face and neck. After intravenous injection of photosensitizer hepatoporphyrin derivative (HpD), the copper vapor laser was adopted as light source and the lesions of PWS were irradiated. The laser Doppler perfusion imager (LDI) was used to measure the microcirculatory perfusion of PWS before and after PDT and comparison with the normal skin was done.
　　Results　All the lesions showed remarkable decrease of tissue perfusion after PDT. It was shown that the mean, maximal and minimal values of tissue perfusion in the pre-treatment group were significantly higher than those in control group (P<0.01). Six months after PDT, the mean, maximal and minimal values of perfusion with the lesions were reduced, with significant difference from pre-treatment group (P<0.01), but no significant difference from control's. The colors of lesions were correlated with decrease of microcirculatory perfusion, which became lightened close to normal skin color without causing any scarring.
　　Conclusions　PDT is one of the most effective modalities for PWS. The microcirculation perfusion can reflect the degrees of PWS objectively. The curative effectiveness of PDT for PWS is due to tissue microcirculation response.

Chin Med J 1998; 111(2):136-138

　　Port wine stain (PWS) is a common skin disease of congenital vascular malformation,1　occurring in 0.3—0.5% of newborns.2　The disease presents erythema on the surface of the affected skin and often with acanthosis. On histology there are numerous ectatic vessels in the upper and mid-dermis.3　Several therapeutic modalities including cosmetic, X-ray, liquid nitrogen or dry ice, surgery, ultraviolet radiation, dermabrasion, tattooing, flashlamp-pumped pulsed dye laser,2　copper vapor laser　4 and argon laser　5,6 have been used to treat PWS. Few of them showed satisfactory effect without causing scarring.7

　　In our study a new method of photodynamic therapy (PDT) was first applied to treat PWS in our hospital. It can selectively destroy the ectatic capillaries in the dermis without damaging the overlaying normal epidermis. Therefore it does not cause any scarring of the skin.8　However, how to evaluate objectively the curative effectiveness of this new modality is an important problem. Although histological analysis of the treated area provides an objective means for evaluating treatment effect, its value is limited because the procedure is invasive, the histologic specimen does not necessarily represent the entire lesion, and the results may not correlate with the clinical appearance.3　Clinically the shades of the color of the lesion were taken as parameters, by either graded color charts or photographs of pre- and post-treatment, a matter of relative subjective perception and definition, which depends on the individual's interpretation of the color.9

　　Apfelberg et al 6　studied microvascular perfusion in PWS patients with laser Doppler flowmetry but were unable to predict the outcome of treatment. The reason may be attributed to the fact that the laser Doppler flowmetry (LDF) gives information about tissue perfusion at a single point, while the vascular architecture of PWS varies greatly even within the same area. In order to overcome the limitation of laser Doppler flowmetry, Nilsson et al developed a new type of device, the laser Doppler perfusion imager (LDI) that creates an image of tissue perfusion distribution.5　In order to reveal the change of blood flow in the microcirlculation and to obtain an objective assessment of the curative effectiveness of PDT for PWS, we applied LDI to investigate the relationship between the microvascular perfusion changes of PWS and the blanching of the lesions before and after PDT.

METHODS

Patients
　　Twenty-four patients (18 females and 6 males, with a total of 28 lesions) suffering from PWS were treated with PDT. The age range was from 2 to 35 years (mean 18.5). The lesions of various extents were located on the face and neck.

Photodynamic therapy (PDT)
　　After intravenous injection of photosensitizer HpD (hepatoporphyrin derivative) with a dosage of 5 mg/kg, the HpD appeared soon within the vascular endothelial cell and its concentration in the endothelium was proportional to that in the blood. Copper vapor laser with wavelengths of 510 and 577.8 nm was adopted as light source. All the PWS lesions were irradiated by the power and energy densities ranged 80—100 mW/cm2 and 180—360 J/cm2 respectively,9 while the normal skin surrounding the lesion was hidden by a black cloth.

Laser Doppler perfusion Imager (LDI)
　　LDI that consists of laser scanner, computer system and color plotter is a system for totally non-invasive imaging of the superficial tissue perfusion. Light from a low power He-Ne laser is scattered onto the tissue by an optical system. The laser beam penetrating the tissue to a depth of within 1 mm, is controlled to move step by step over the object by the computer. A color-coded image which shows spatial distribution of the microcirculation perfusion is generated on the monitor by processing the data with the computer. Each of the six colors in the image corresponds to different microcirculation perfusion level. The recorded images can be stored in HD of a computer and printed by a color plotter.

Measurement
　　The patient lay on a bed in a temperature-controlled room (25℃) and the scanner of LDI was positioned 15 to 20 cm over the skin surface. Each scanning region by the LDI was 30×30 in format and about 3 cm2 in area. The tissue perfusion distribution was shown and observed within 1 minute on the monitor. The maximal, minimal, and mean values of each measurement were used for processing. Before the PDT a representative area of the lesion and a contralateral normal skin was measured. If PWS was bilateral, the normal skin near the lesion was taken as control measurement. Six months after PDT the same lesion area was measured again.

　　To compare the microcirculation perfusion of PWS at different period, the data were classified into three groups, control (the normal skin), pre-treatment and post-treatment (6 months after PDT), and statistical analysis was performed.

Statistics
　　The data were analyzed by the modified ANOVA test for multiple non-parametric comparison and according to the two sample tests. P value of less than 0.05 was considered significant.

RESULTS

　　The 24 tested patients presented similar changes of tissue perfusion of the PWS lesion and the outcome of PDT treatment. As shown by the color-coded image of one representative patient (a 30-year-old woman), the tissue perfusion of the PWS was unevenly distributed and the mean value was 2.03 v, 3.5 times of the mean value of the normal skin. Six months after PDT, the blood perfusion decreased to 0.68 v, close to the normal level (Fig. 1). All these color-coded images correlated well to the clinical appearance of the patients (Fig. 2). Besides, our results also showed that PDT is a new treatment modality with good and stable therapeutic outcome and no scarring.

　　Since all the patients showed remarkable decrease of

Fig. 1. Perfusion images of a woman of 30. A: Perfusion image of normal skin and the mean value; B: Perfusion image of PWS before PDT and the mean value; C: Six months after PDT the perfusion image of the lesion and the mean value.

Fig. 2. Photographs of the same patient. A: Appearance of PWS before PDT; B: Six months after PDT showing blanching of the lesion without scarring.

tissue perfusion after PDT, the data were pooled together and the average values of the mean, maximal and minimal were calculated to demonstrate a popular change of the perfusion. It showed that the maximal, minimal and mean values of tissue perfusion in the pre-treatment group were significantly higher than those in control group (P<0.01). Six months after PDT the mean, maximal and minimal values of perfusion were all reduced, with significant difference from pre-treatment group (P<0.01), but no significant difference from the control (Table).

Table. Perfusion of PWS before and after PDT
and control (±s)

Groups 　　Mean 　　Maximal 　　Minimal
Pre-treatment 2.485±1.108 8.339±2.195 0.697±0.430
Post-treatment 1.085±0.428* 5.570±2.439* 0.394±0.202*
Control 0.889±0.407* 5.083±3.051* 0.319±0.154*
　* P<0.01

DISCUSSION

　　As disclosed by histological study the main abnormality of the PWS is the malformation of blood vessels in the upper and mid-dermis with increased number and diameters of microvessels, which should certainly be reflected by the changes of blood flow and local perfusion and presents abnormal erythema. The indices of tissue perfusion should be the most objective parameter. In our present study the results showed there was significant difference of tissue perfusion between normal skin and PWS, which were consistent with the findings of Troilius et al, and indicated the involvement of whole microcirculatory disturbance, either structural or functional, in the pathogenesis of PWS. It also showed sensitive response of perfusion to the treatment and good correlation with the skin color.

　　The result showed the PDT is one of the most effective modalities for PWS. The curative effectiveness of PDT for PWS is due to tissue microcirculation response. As an assessment, the LDI is considered to be the best method to measure and compare the changes of the microcirculatory perfusion, with more objectiveness than reflectance photometer and photoelectric colorimeter.

　　The results also indicate that the microcirculation perfusion measured by LDI reflects the degree of PWS. Therefore it is possible to classify different types of PWS based on quantitative parameter of tissue perfusion which would be of great importance in determining the laser energy of PDT in clinical practice.
　Laboratory of Microcirculation (Jiang L, Li XH and Zhao XM), Department of Laser Medicine (Gu Y, Li JH, Wang K, Liang J, Pan YM and Zhang Y), Chinese PLA General Hospital, Beijing 100853, China　

REFERENCES


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