Non-invasive multimodal optical coherence and photoacoustic tomography for human skin imaging

Abstract

The cutaneous vasculature is involved in many diseases. Current clinical examination techniques, however, cannot resolve the human vasculature with all plexus in a non-invasive manner. By combining an optical coherence tomography system with angiography extension and an all optical photoacoustic tomography system, we can resolve in 3D the blood vessels in human skin for all plexus non-invasively. With a customized imaging unit that permits access to various parts of patients' bodies, we applied our multimodality imaging system to investigate several different types of skin conditions. Quantitative vascular analysis is given for each of the dermatological conditions to show the potential diagnostic value of our system in non-invasive examination of diseases and physiological processes. Improved performance of our system over its previous generation is also demonstrated with an updated characterization.

Figure 1

Schematic of the cart-based OCT/OCTA/PAT system. Blue, orange and purple dashed lines encircle the workstation with all the DAQ cards, the PAT and the OCT components, respectively.

Figure 2

(a) Design of the cart. (b) Photo of the back side of the cart during assembling. (c) Illustration of the system during imaging. (a) Dual monitors; (b) storage compartment; (c) excitation laser head; (d) power supply and control unit of the excitation laser; (e) chiller of the excitation laser; (f) breadboard for OCT optics; (g) swept source; (h) PAT interrogation laser; (i) workstation; (j) servo boards for scanning mirrors; (k) power supply for servo boards; (l) rollable rack with an articulated arm; m: OCT/OCTA/PAT probe; n: compartment for probe storage.

Figure 3

(a) Lateral resolution distribution at z = 0.5 mm. (b) Lateral resolution change over depth for three (x, y) coordinates.

Figure 4

(a) Surface topography of the skin given by OCT. (b) Absorption from skin surface given by PAT. Four colored circles in (a) and (b) indicate the same features seen in OCT and PAT. (c) Transition zone en face view showing the same vessels resolved by both OCTA (green) and PAT (red). (d) Skin vasculature in gray scale between the depth range [0 0.5 mm] in z direction imaged by OCTA. (e) 3D view in -z direction for the blood vessel network. PAT and OCTA resolved vessels are colored gold and red, respectively. (f) Depth color coded image of skin vasculature between [0.5 mm, 1 mm] in z direction using fused OCTA/PAT volume. (g) Depth color coded image of skin vasculature between [1 mm, 3 mm] in z direction using fused OCTA/PAT volume. Scale bar = 1 mm.

Figure 5

(a) OCT B scan of the skin over the dashed line in (b). (b) Photo of the surgical scar. (c) Depth color coded image of skin vasculature between [0.5 mm, 1 mm] in z direction using fused OCTA/PAT volume. (d) Depth color coded image of skin vasculature between [1 mm, 4 mm] in z direction using fused OCTA/PAT volume. (e) Skin vasculature in gray scale between [0 0.5 mm] in z direction imaged by OCTA. (f) Transition zone en face view showing the same vessels resolved by both OCTA (green) and PAT (red). (g) and (h) OCT/OCTA/PAT merged volume 3D rendering at two perspectives. Scale bar = 1 mm except in (a).

Figure 6

(a) Volumetric rendering of the fused OCT/OCTA/PAT volume. (b) Top view of the vasculature network. (c) Skin vasculature in gray scale between the depth range [0 0.5 mm] in z direction imaged by OCTA. (d) Transition zone between [0.94 mm, 1.2 mm] in z direction with OCTA in green and PAT in red. (e) Clinical image of a shiny pink macule on the thigh of a patient. (f) Dermatoscopy image of the same lesion. (g) Depth color coded image of skin vasculature between [0.5 mm, 1 mm] in z direction using fused OCTA/PAT volume. (h) Depth color coded image of skin vasculature between [1 mm, 5 mm] in z direction using fused OCTA/PAT volume. Scale bar = 1 mm.

Figure 7

The ROIs chosen for comparison between the healthy and diseased zones for nevus araneus (a), scar tissue (b), and basal cell carcinoma (c). Yellow dashed squares are the second healthy ROIs used in Table. 3.