
Optical Coherence Tomography
Overview
Optical coherence tomography (OCT) uses near-infrared low-power laser light to create images of live tissues through reflection interference, meaning it utilizes back-scattered light reflected by tissue to generate images. This technique produces images similar to ultrasound scans but uses light waves instead of sound waves.
Studies have demonstrated that OCT improves diagnostic efficacy in various fields, including cervical neoplasia, gastrointestinal diseases, and oral malignancies. Developed in the late 1980s, OCT was initially employed in ophthalmology for non-invasive microscopic imaging of the cornea.
OCT offers higher resolution and contrast than ultrasound and greater detection depth than confocal microscopy, with a resolution in the 3–15 µm range and a penetration depth of 1-2 mm. OCT can visualize the skin in both horizontal and vertical planes and generates cross-sectional two and three-dimensional images. OCT provides high-resolution images of deeper skin layers, including the epidermis, dermis, and subcutaneous tissue. OCT is useful for assessing tissue architecture, measuring skin thickness, and evaluating the depth and extent of lesions. The entire lesion can be visualized, reducing the risk of misdiagnosis due to sampling errors. However, the resolution is insufficient for analyzing single-cell morphology making it unsuitable for identifying cellular subtypes or cellular atypia. An important advantage of OCT is its ease of use; it requires no skin preparation and is safe due to the low-power laser beam. Diagnosis can be made on the spot, as images are generated instantly, with rapid image capture (<1 min).
OCT in skin cancer detection
Basal cell carcinoma (BCC)
The most significant applications of OCT in dermatology so far have been in diagnosing, classifying, and monitoring the treatment of basal cell carcinoma (BCC). Despite its limitations in analyzing single-cell morphology, OCT allows for the live analysis of cell clusters within the dermis, making it particularly effective for diagnosing BCC.
Because vascular morphology correlates with BCC subtypes, OCT can be used to determine the subtype of BCC using techniques such as angiographic and dynamic OCT. It is also valuable for evaluating therapeutic responses to various treatments, including photodynamic therapy (PDT), topical treatments, and systemic therapies. Additionally, OCT can be used to assess tumor depth and margins.
A multicenter prospective study (1) found that the sensitivity and specificity of OCT for diagnosing BCC were 95.7% and 75.3%, respectively.
However, pigmented lesions continue to present significant challenges in OCT imaging.
Squamous cell carcinoma (SCC)
Invasive SCC, in situ SCC, and actinic keratosis (AK) with thick hyperkeratotic scales can be difficult to evaluate with structural OCT images (Figure 2). This difficulty arises mainly because the hyperkeratotic epidermis of these lesions hinders OCT from penetrating deeper skin layers and observing the dermal–epidermal junction (3). Consequently, it is often impossible to determine whether the keratinocytes have invaded the deep dermis. Additionally, diagnosing moderately or poorly differentiated SCC is challenging due to the lack of detailed information on cellular morphology.
However, the development and introduction of High-Definition OCT (HD-OCT) and angiographic OCT have proven highly effective in distinguishing between AK and SCC, providing increased accuracy in diagnosis. (4)

Figure 2: Upper image: Hypertrophic AK; lower image: Invasive SCC (moderately differentiated). "ApolloVue OCT Imaging System," Apollo Medical Optics, Ltd. Manu Jain, MD; Rozina Zeidan, BA-CRSp; Chin-Shan Chen, MD.
Melanoma
The lack of diagnostic parameters for differentiating between dysplastic nevi and melanomas, are the main factors that have limited the use of OCT. While OCT can reveal characteristics of melanomas, such as architectural disarray (Figure 3) and an indistinct dermal-epidermal junction, it has lower sensitivity for detecting early melanomas. However, some studies (5) have reported that OCT has high overall sensitivity compared to other techniques such as reflectance confocal microscopy, ultrasonography, and multispectral imaging. Additionally, the fact that vessel patterns may be associated with melanoma tumor stages has prompted researchers to explore the potential of angiographic OCT for melanoma diagnosis.

Figure 3: Superficial spreading melanoma."ApolloVue OCT Imaging System," Apollo Medical Optics, Ltd. Manu Jain, MD; Rozina Zeidan, BA-CRSp; Chin-Shan Chen, MD.
The Cochrane study in 2018 (2) summarized that there is insufficient data on the use of OCT for the detection of melanoma or cutaneous SCC. Initial data suggest that conventional OCT may be useful for diagnosing BCC in clinically challenging lesions.
Combined RCM-OCT
A combined Reflectance Confocal Microscopy-Optical Coherence Tomography (RCM-OCT) device integrates these two advanced imaging technologies into a single system. This integration offers a comprehensive approach to skin imaging by combining RCM’s detailed cellular-level imaging with the deeper tissue imaging provided by OCT.
The combined RCM-OCT device has higher sensitivity for diagnosing BCC and predicting depth, making it helpful in selecting tailored treatments.
References:
(1). https://academic.oup.com/bjd/article/173/2/428/6616476?login=true
(2). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6516952/
(3)https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9866322/
(4). https://pubmed.ncbi.nlm.nih.gov/27311752/
(5). https://pubmed.ncbi.nlm.nih.gov/26963113/
(6). https://www.ncbi.nlm.nih.gov/pmc/articles/mid/NIHMS979808/pdf/nihms979808.pdf
Relevant Links
Recent Developments
micro-registered OCT
n recent work by Winetraub et al., a micron-accuracy coregistration method called micro-registered optical coherence tomography (OCT) was developed. his method can match two-dimensional (2D) H&E slides with the exact corresponding sections in three-dimensional (3D) OCT images from fresh tissue. This could help physicians integrate OCT imaging into clinical practice, potentially reducing the number of unnecessary biopsies.
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