Optical coherence tomography angiography of normal skin and inflammatory dermatologic conditions

Abstract

Background: In clinical dermatology, the identification of subsurface vascular and structural features known to be associated with numerous cutaneous pathologies remains challenging without the use of invasive diagnostic tools.

Objective: To present an advanced optical coherence tomography angiography (OCTA) method to directly visualize capillary-level vascular and structural features within skin in vivo.

Methods: An advanced OCTA system with a 1310 nm wavelength was used to image the microvascular and structural features of various skin conditions. Subjects were enrolled and OCTA imaging was performed with a field of view of approximately 10 × 10 mm. Skin blood flow was identified using an optical microangiography (OMAG) algorithm. Depth-resolved microvascular networks and structural features were derived from segmented volume scans, representing tissue slabs of 0-132, 132-330, and 330-924 μm, measured from the surface of the skin.

Results: Subjects with both healthy and pathological conditions, such as benign skin lesions, psoriasis, chronic graft-versus-host-disease (cGvHD), and scleroderma, were OCTA scanned. Our OCTA results detailed variations in vascularization and local anatomical characteristics, for example, depth-dependent vascular, and structural alterations in psoriatic skin, alongside their resolve over time; vascular density changes and distribution irregularities, together with corresponding structural depositions in the skin of cGvHD patients; and vascular abnormalities in the nail folds of a patient with scleroderma.

Conclusion: OCTA can image capillary blood flow and structural features within skin in vivo, which has the potential to provide new insights into the pathophysiology, as well as dynamic changes of skin diseases, valuable for diagnoses, and non-invasive monitoring of disease progression and treatment. Lasers Surg. Med. 50:183-193, 2018. © 2018 Wiley Periodicals, Inc.

Keywords: OCT angiography; graft-versus-hostdisease; optical coherence tomography; psoriasis; scleroderma; skin conditions.

Figure 1. Healthy skin (upper arm, male, Asian, 53 year old)

A schematic diagram of 3D OCT, OMAG, and volume segmentation. A) The component scans that produce a 3D OCT image. B) A typical 2D B-scan representing a cross-section of static tissue (structure). C) The same 2D B-scan from (B) overlaid with vascular information, showing the locations of functional blood vessels in relation to tissue structure. D) A 3D OCT volume scan highlighting how segmented slabs might be positioned. E) An enface projection of the 3D OCTA vasculature. F – H) The different vessel networks of the skin’s dermis layer, derived from the slabs highlighted in (D). The three slabs represent depths of 0 – 132 µm, 132 – 330 µm, and 330 – 924 µm, as measured from the skin’s surface, respectively. Shown are different vascular traits, i.e. size, density, and tortuosity, at each depth. I – K) Corresponding with the vascular slabs, shown is how tissue structure also differs with depth. The insert between (A) and (D) shows the color bars used to code OCT structural intensity, and depth information of blood vessels. These same color bars apply to all OCTA images in the study. Scale bars = 1 mm.

Figure 2. Normal and benign skin lesions

Enface OCTA images showing the vasculatures of normal skin and benign skin lesions taken from different anatomic sites on numerous individuals. A) Normal skin, right shoulder. B) Normal skin, palm of the right hand. C) Normal nail unit. D) Photograph of a common blue nevus. E) An enface vascular image of (D). F and G) Two typical B-scans corresponding to the central and lower regions of (E), respectively; their locations highlighted by the corresponding perforated lines in (E). H) Photograph of an achrocordon. I) An enface vascular image of (H). J and K) Two B-scans corresponding to the central and lower regions of (I), respectively; their locations highlighted by the corresponding perforated lines in (I). Each B-scan shows the static tissue structure overlaid with the vasculature of their respective regions. On each of the B-scans, red lines highlight avascular epidermal boundaries. Shown is the normally homogenous distribution of vessels being altered by topographical and structural features, demonstrating the link between tissue structure and vasculature. Scale bars = 1 mm.

Figure 3. Psoriasis

Enface vascular images and corresponding structural images of a psoriatic plaque over two time points. A) An enface vascular image of an active psoriatic plaque. B – D) The vasculature of (A) segmented into three slabs of 0 – 132 µm, 132 – 330 µm, and 330 – 924 µm, approximately, respectively. Shown is the most severe vascular response to the plaque being located in the papillary dermis. E and F) Two B-scans corresponding to the upper and lower regions of (A), respectively; their locations highlighted by the corresponding perforated lines in (A). On both B-scans, red lines highlight avascular epidermal boundaries. G – I) The structure of (A) segmented into three slabs of 0 – 132 µm, 132 – 330 µm, and 330 – 924 µm, approximately, respectively. Alterations in tissue structure correlate with vascular changes and are most severe in the papillary dermis. J) An enface image of the same psoriatic plaque identified in (A), taken after two months when the plaque had resolved. K – M) The vasculature of (J) segmented into three slabs of 0 – 132 µm, 132 – 330 µm, and 330 – 924 µm, approximately, respectively. Normalization of the vasculature is clear. N and O) Two B-scans corresponding to the upper and lower regions of (J), respectively; their locations highlighted by the corresponding perforated lines in (J). On both B-scans, red lines highlight avascular epidermal boundaries. Little or no difference can be seen between either of the two regions. P – R) The structure of (J) segmented into three slabs of 0 – 132 µm, 132 – 330 µm, and 330 – 924 µm, approximately, respectively. Normalization of tissue structure correlates with vascular normalization and plaque resolution. Scale bars = 1 mm.

Figure 4. cGvHD

Photographs and corresponding enface vascular images and B-scans of a cutaneous cGvHD patient’s hands. The first photograph highlights two areas on the left hand, marked [1] and [2], identified for imaging. A and B) Enface vascular images corresponding to areas marked [1] and [2] on the left hand, respectively. C and E) Two B-scans corresponding to the upper and lower regions of (A); their locations highlighted by the corresponding perforated lines in (A). D and F) Two B-scans corresponding to the upper and lower regions of (B), respectively; their locations highlighted by the corresponding perforated lines in (B). The second photograph highlights two areas on the right hand, marked [1] and [2], identified for imaging. G and H) Enface vascular images corresponding to areas marked [1] and [2] on the right hand, respectively. I and K) Two B-scans corresponding to the upper and lower regions of (G), respectively; their locations highlighted by the corresponding perforated lines in (G). J and L) Two B-scans corresponding to the upper and lower regions of (H), respectively; their locations highlighted by the corresponding perforated lines in (H). On all B-scans, red lines highlight avascular epidermal boundaries, perforated green lines highlight enhanced structural brightness, and light blue lines highlight enhanced dermal reflectivity. In all cases, vasculatures correlated with strong structural features, such as enhanced brightness thought to be caused by collagen deposition, and enhanced dermal reflectivity thought to be associated with increased epidermal activity. Scale bars = 1 mm.

Figure 5. cGvHD

A photograph and corresponding enface vascular, B-scan and enface structure images of a cutaneous cGvHD patient’s foot. The photograph identifies the region chosen for imaging. A) An enface vascular image corresponding to the site identified in the photograph. B and C) Two B-scans corresponding to the upper and lower regions of (A), respectively; their locations highlighted by the corresponding perforated lines in (A). On both B-scans, red lines highlight avascular epidermal boundaries, perforated green lines highlight enhanced structural brightness, and light blue lines highlight enhanced dermal reflectivity. Numerous structural features, such as fluctuating epidermal thickness, enhanced structural brightness and enhanced dermal reflectivity, are seen here to correlate with vasculature. D – F) Enface structure images corresponding to (A), segmented into three slabs representing depths of 0 – 132 µm, 132 – 330 µm, and 330 – 924 µm, approximately, respectively. Structural alterations correlating with vasculature appear most prominent in the papillary dermis region, (E). Scale bars = 1 mm.

Figure 6. cGvHD

Enface vascular images displaying microaneurysms in the skin of a cutaneous cGvHD patient. A – C) Enface vascular images showing the presence of microaneurysms on the left thigh, the left calf, and the right forearm, respectively. D – F) Enface vascular images of the skin of healthy individuals taken at sites corresponding to those mentioned in (A) – (C), respectively. The microaneurysms noted with the cGvHD patient were not seen with healthy subjects. Scale bars = 1 mm.

Figure 7. Scleroderma

Photograph and corresponding enface vascular images and B-scans of sclerodermatous nail folds. The photograph shows the fingers of a scleroderma patient. Typical sclerodermatous features, such as tightening of the fingertips and joints, can be seen. A) An enface vascular image of a healthy nail fold. B) The middle finger of a scleroderma patient. C) The ring finger of a scleroderma patient. Vascular traits commonly associated with scleroderma, such as enlarged and/or angiogenic capillaries, and capillary voids, are identified. D) B-scan corresponding to the central region identified in (A); its location highlighted by the corresponding perforated line in (A). E) B-scan corresponding to the central region identified in (B); its location highlighted by the corresponding perforated line in (B). F) B-scan corresponding to the central region identified in (C); its location highlighted by the corresponding perforated line in (C). Highlighted in (F) are abnormal nail unit features, i.e. the acute nail/proximal nail fold angle, a ridge in the nail plate, and a brighter-than-normal nail matrix. Scale bars = 1 mm.