In vivo photoacoustic microscopy of human cutaneous microvasculature and a nevus

Abstract

In several human volunteers, photoacoustic microscopy (PAM) has been utilized for noninvasive cutaneous imaging of the skin microvasculature and a melanocytic nevus. Microvascular networks in both acral and nonacral skin were imaged, and multiple features within the skin have been identified, including the stratum corneum, epidermal-dermal junction, and subpapillary vascular plexus. Several vascular and structural differences between acral and nonacral skin were also observed in the photoacoustic images. In addition, a nevus was photoacoustically imaged, excised, and histologically analyzed. The photoacoustic images allowed for in vivo measurement of tumor thickness, depth, and microvasculature-values confirmed by histologic examination. The presented images demonstrate the potential of PAM to aid in the study and evaluation of cutaneous microcirculation and analysis of pigmented lesions. Through its ability to three-dimensionally image the structure and function of the microvasculature and pigmented lesions, PAM can have a clinical impact in diagnosis and assessment of systemic diseases that affect the microvasculature such as diabetes and cardiovascular disease, cutaneous malignancies such as melanoma, and potentially other skin disorders.

Figure 1

Schematic of the photoacoustic microscope used in the described experiments.

Figure 2

(a) Photo of the palm of the volunteer. The red box indicates the imaged area 8 mm × 8 mm. (b) B-scan PA image taken along the dashed line in (c). Notable features including the stratum corneum, epidermal–dermal junction, and subpapillary blood vessels, are all labeled. Selected vessels have been labeled with color arrows for reference with the image in (c). (c) Maximum amplitude projection PA image taken from the palm using a 584 nm laser excitation wavelength. The green dashed line indicates the cross-section shown in (b). (Color online only.)

Figure 3

(a) Photo of the forearm of the volunteer. The red box indicates the imaged area 8 mm × 8 mm. (b) B-scan PA image taken along the dashed line in (c). Notable features, including the epidermal–dermal junction and subpapillary blood vessels, are labeled. Selected vessels have been labeled with color arrows and for reference the image in (c). (c) Maximum amplitude projection PA image taken from the forearm using a 584 nm laser excitation wavelength. The green dashed line indicates the cross-section shown in (b). (Color online only.)

Figure 4

(a) Photo of a nevus located on the forearm of the volunteer. (b) B-scan PA image taken along the blue dashed line in (c). Notable features including the nevus, epidermal–dermal junction, and subpapillary blood vessels, are all labeled. (c) MAP image of a nevus acquired using 570 nm laser illumination. The nevus is clearly shown in “green scale,” and blood vessels are shown in red. The blue dashed line indicates the cross-section shown in (b) and the yellow dashed line indicates the cross-section depicted in Fig. 5c. (d) MAP image of a nevus acquired with a 700 nm laser excitation wavelength. The yellow line indicates the cross-section shown in Fig. 5d. (Color online only.)

Figure 5

(a) Maximum amplitude projection of a nevus generated from serial histology sections (top view, i.e., en face view, of the nevus) used to match histology with PA data. The nevus is shown in red, and a large hair follicle near the top was used to orient the image with the PA MAP image. (b) Histology section along the dashed line in (a), in which the location of the nevus thickness is indicated by the dashed line and two hash marks. A blood vessel used for orientation is circled in green. [(c) and (d)] Cross-sectional PA images of the nevus in the approximate region as (b) and are marked in Figs. 4b, 4c. (c) Image acquired with 570 nm laser illumination. The blood vessel circled in green matches with the vessels outlined in (b). (d) Image acquired using 700 nm laser illumination. The red dashed lines in both images (c) and (d) indicate the depth profiles shown in (e) and (f). Depth profile plots of the nevus are indicated by the dashed line in the cross-sectional images in (c) and (d). (e) Profile plot from the image acquired with a 570 nm laser excitation wavelength shows the nevus thickness to be 270 μm. (f) Profile plot from the image acquired with a 700 nm laser excitation wavelength shows the nevus thickness to be 262 μm. (Color online only.)

Video 1

In this video, there are two figures. The upper figure is the MAP image of the nevus and surrounding vasculature taken from the forearm of the volunteer. The lower figure shows the consecutively acquired B-scan images. The position of each B-scan image or cross-section in relation to the MAP image is indicated by the red bar on the MAP image. (QuickTime, 1 MB)