Noninvasive clinical assessment of port-wine stain birthmarks using current and future optical imaging technology: a review

Abstract

Port-wine stain (PWS) birthmarks are one class of benign congenital vascular malformation. Laser therapy is the most successful treatment modality of PWS. Unfortunately, this approach has limited efficacy, with only 10% of patients experiencing complete blanching of the PWS. To address this problem, several research groups have developed technologies and methods designed to study treatment outcome and improve treatment efficacy. This article reviews seven optical imaging techniques currently in use or under development to assess treatment efficacy, focusing on: reflectance spectrophotometers/tristimulus colorimeters; laser Doppler flowmetry and laser Doppler imaging; cross-polarized diffuse reflectance colour imaging system; reflectance confocal microscopy; optical coherence tomography; spatial frequency domain imaging; and laser speckle imaging.

Figure 1

Schematic diagram showing a basic spectrophotometer setup. The integrating sphere is used for both producing a diffuse light source, and for collection of light from the skin surface.

Figure 2

In LDF, a laser beam is directed at the tissue, with frequency of the reflected light, as altered by flowing red blood cells, indicating the concentration speed and volume of blood flow, termed collectively as “red blood cell flux”, through a region of interest. This flux value is assumed to be directly proportional to skin perfusion (28).

Figure 3

Color image of port wine stain (PWS) skin taken without use of crossed polarizers to illustrate the effect of glare (a). Cross-polarized diffuse reflectance color image taken (b) before and (c) next patient’s visitation, (4–8 weeks) after a single pulsed dye laser (PDL) treatment. Dashed black lines denote area used in subsequent erythema analysis. Although the contrast between normal and PWS skin appears to be more pronounced due to weaker lighting in image B, lighting artifacts can be discounted as the images were taken in dark environments, independent of background lighting. {Used with permission from Ref. (8)}

Figure 4

A schematic illustration of a confocal microscope.

Figure 5

(a) Clinical photograph of port wine stain (PWS) in trigeminal distribution on the face of a 46-year-old white man. Black arrow shows vascular nodule present within lesion. (b) Representative histology of a PWS with dilated postcapillary venules in the upper dermis. (c and d) Reflectance confocal microscopy (RCM) evaluation at the level of the upper dermis reveals medium-sized to large vessels as a distinct RCM feature of PWS (red arrowheads, dashed yellow line, blood vessel (BV)). In vivo RCM evaluation revealed medium flow velocity. {Used with permission from Ref. (20)}

Figure 6

Schematic of OCT imaging system. It uses a super luminescent laser and a spectral FWHM. After digital signal processing (DSP), structure OCT image is generated. {Used with permission from Ref. (23)}

Figure 7

Tomographic images taken in situ from human port-wine stained skin (PWS). Image A, Conventional optical coherence tomographic (OCT) image before laser exposure. Optical Doppler tomographic (ODT) blood flow images before (B) and immediately after (C) laser exposure. Images A, B, and C are the same skin site with a fixed probe beam. Images B and C, Color-coded tomographic images of blood flow velocity. PWS vessels not seen on the conventional OCT image (A) are detected in the dermis in the ODT image before laser exposure (B). Blood flow is absent in the ODT image immediately after laser exposure (C). Image D, Hematoxylin-eosin–stained histologic section from the imaged site. Comparable PWS blood vessels are noted in images B and D. {Used with permission from Ref. (22)}

Figure 8

Representative example of LSI during laser surgery of PWS skin. Images of a PWS subject are shown before treatment (top frames) and after laser treatment (bottom frames). False color images (left) depict SFI values. The speckle flow index scale, which is a metric of blood flow, is shown next to each speckle flow image (14). The white/red portion of pretreatment tissue in the speckle flow image corresponds to relatively high flow. After laser treatment, the speckle flow index has decreased (green region), indicating that at perfusion has been reduced. At this point, there is not enough data to show whether LSI provides quantitative information that alone serves as a sufficient prognostic tool. Clinical data are currently analyzing and a new study is designing that focuses specifically on the relationship between purpura and SFI values.

Figure 9

Sample PWS Data Collection. Collage of pre-operative (left) and immediately post PDL (right) (a) color images, (b) oxy-hemoglobin maps, (c) deoxy-hemoglobin maps (d) total hemoglobin maps, and (e) tissue oxygen saturation maps.