Blood flow dynamics after laser therapy of port wine stain birthmarks

Abstract

Background and objective: During laser therapy of port wine stain (PWS) birthmarks, regions of perfusion may persist. We hypothesize that such regions are not readily observable even when laser surgery is performed by highly experienced clinicians. The objective of this study was to use objective feedback to assess the acute vascular response to laser therapy.

Study design/materials and methods: A clinic-friendly laser speckle imaging (LSI) instrument was developed to provide the clinician with real-time images of blood flow during laser therapy. Images were acquired from patients undergoing laser therapy of PWS birthmarks at Scripps Clinic and the Beckman Laser Institute and Medical Clinic. Blood flow maps were extracted from the acquired imaging data. Histogram-based analysis was applied in grading the degree of heterogeneity present in the blood flow maps after laser therapy.

Results: Collectively, two types of patient responses were observed in response to laser exposure: (1) an immediate increase in perfusion within minutes after laser therapy; and (2) an overall decrease in blood perfusion approximately 1 hour after laser therapy, with distinct regions of persistent perfusion apparent in the majority of post-treatment blood-flow images. A comparison of blood flow in PWS and adjacent normal skin demonstrated that PWS blood flow can be greater than, or sometimes equivalent to, that of normal skin.

Conclusion: In general, a decrease in skin perfusion is observed during pulsed laser therapy of PWS birthmarks. However, a heterogeneous perfusion map was frequently observed. These regions of persistent perfusion may be due to incomplete photocoagulation of the targeted vessels. We hypothesize that immediate retreatment of these regions identified with LSI, will result in enhanced removal of the PWS vasculature. Lasers Surg. Med. 41:563-571, 2009. (c) 2009 Wiley-Liss, Inc.

Fig. 1

A: Schematic of clinical LSI instrument, first described in Ref. [12]. B, C: Clinical LSI instrument in action.

Fig. 2

Persistent perfusion after laser therapy. Top: Photograph of user-specified region of interest (ROI) identified on a female Caucasian patient with a facial PWS birthmark. A, B: Grayscale and (C, D) corresponding SFI maps of ROI treated with a PDL. Images were acquired (A, C) immediately before, and (B, D) 40 minutes after, treatment. With the exception of the nose and lips, the entire region shown in A was treated. Purpura formation was evident throughout the treated region. The regions enclosed in dashed lines (D) correspond to regions of persistent perfusion, despite the formation of purpura.

Fig. 3

Based on SFI images collected before and 40 minutes after laser treatment, over 76 treatment sessions, we postulate that the acute vascular response to laser therapy varies considerably. A perfusion reduction > 20% (i.e., left of the dashed line) was observed in 71% of the treatment sessions. In contrast, in 12% of the treatment sessions, an increase in mean SFI was observed.

Fig. 4

Example of moderate DoH achieved after laser therapy. Top: Photograph of user-specified region of interest (ROI) identified on a female Caucasian patient with a facial PWS birthmark. A, B: Grayscale and (C, D) corresponding SFI maps of ROI treated with a PDL. Images were acquired (A, C) immediately before, and (B, D) 40 minutes after, treatment. Areas enclosed in dashed lines in (C) and (D) were selected to calculate the change in perfusion and DoH. B perfusion was decreased by 50% after treatment, with a post-treatment DoH of 0.38 (i.e., moderate level).

Fig. 5

Example of low DoH achieved after laser therapy. Top: Photograph of user-specified region of interest (ROI) identified on a female Caucasian patient with a facial PWS birthmark. A, B: Grayscale and (C, D) corresponding SFI maps of ROI treated with a pulsed dye laser. Images were acquired (A, C) immediately before, and (B, D) 40 minutes after, treatment. Areas enclosed in dashed lines in (C) and (D) were selected to calculate the change in perfusion and DoH. Blood perfusion decreased by 71% after treatment, with a post-treatment DoH of 0.27 (i.e., low level).

Fig. 6

Summary of DoH outcomes for the 54 treatment sessions in which a mean perfusion of reduction of at least 20% was obtained.

Fig. 7

Over the initial 30 minutes after laser therapy, the perfusion of the treated PWS region is dynamic. Top: Photograph from male Caucasian patient with PWS on the left side of the face. Bottom: SFI images taken from ROI enclosed in the solid black line (A) immediately before; and (B) 5 minutes, (C) 10 minutes, (D) 20 minutes, and (E) 30 minutes post-treatment. Compared to the baseline image (A), the mean SFI value of the region enclosed by the dashed line was 29%, 12%, and 11% greater than baseline values at 5, 10, and 20 minutes after treatment, respectively. At 30 minutes after treatment, the mean SFI value was 4% below the baseline value.