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Optical Coherence Tomography in Dermatology

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Optical coherence tomography (OCT), an emerging noninvasive imaging modality, recently received category III Current Procedural Terminology (CPT) codes from the American Medical Association, enabling tracking of its use in the medical community. In this article, we review OCT imaging and its variant systems, discussing its applications and limitations for clinical use. Future directions of OCT technology and goals for obtaining category I CPT codes and reimbursement also are discussed.

Practice Points

  • Optical coherence tomography (OCT) technology has considerable utility in research and clinical settings given its high resolution, wide field of view, moderate penetration depth, straightforward image acquisition, and accessibility to anatomically challenging areas.
  • Potential benefits of OCT include its ability to noninvasively diagnose and monitor nonmelanoma skin cancers as well as to delineate presurgical margins and elucidate the course and mechanism of action of skin conditions at the bedside.
  • Limitations of OCT include device cost, lack of reimbursement, and training, as well as restricted ability to image advanced deep tumors and differentiate melanocytic lesions.
  • Optical coherence tomography recently received 2 category III Current Procedural Terminology (CPT) codes to track its utilization in clinical practice and will hopefully receive category I CPT codes within the next 5 years.

 

References

Optical coherence tomography (OCT) is a noninvasive imaging technique that is cleared by the US Food and Drug Administration as a 510(k) class II regulatory device to visualize biological tissues in vivo and in real time.1-3 In July 2017, OCT received 2 category III Current Procedural Terminology (CPT) codes from the American Medical Association—0470T and 0471T—enabling physicians to report and track the usage of this emerging imaging method.4 Category III CPT codes remain investigational and therefore are not easily reimbursed by insurance.5 The goal of OCT manufacturers and providers within the next 5 years is to upgrade to category I coding before the present codes are archived. Although documented advantages of OCT include its unique ability to effectively differentiate and monitor skin lesions throughout nonsurgical treatment as well as to efficiently delineate presurgical margins, additional research reporting its efficacy may facilitate the coding conversion and encourage greater usage of OCT technology. We present a brief review of OCT imaging in dermatology, including its indications and limitations.

RELATED VIDEO: Imaging Overview: Report From the Mount Sinai Fall Symposium

Types of OCT

Optical coherence tomography, based on the principle of low-coherence interferometry, uses infrared light to extract fine details from within highly scattering turbid media to visualize the subsurface of the skin.2 Since its introduction for use in dermatology, OCT has been used to study skin in both the research and clinical settings.2,3 Current OCT devices on the market are mobile and easy to use in a busy dermatology practice. The Table reviews the most commonly used noninvasive imaging tools for the skin, depicting the inverse relationship between penetration depth and cellular resolution as well as field of view discrepancies.2,6-8 Optical coherence tomography technology collects cross-sectional (vertical) images similar to histology and en face (horizontal) images similar to reflective confocal microscopy (RCM) of skin areas with adequate cellular resolution and without compromising penetration depth as well as a field of view comparable to the probe aperture contacting the skin.

RELATED VIDEO: Noninvasive Imaging: Report From the Mount Sinai Fall Symposium

Conventional OCT
Due to multiple simultaneous beams, conventional frequency-domain OCT (FD-OCT) provides enhanced lateral resolution of 7.5 to 15 µm and axial resolution of 5 to 10 µm with a field of view of 6.0×6.0 mm2 and depth of 1.5 to 2.0 mm.2,6,8 Conventional FD-OCT detects architectural details within tissue with better cellular clarity than high-frequency ultrasound and better depth than RCM, yet FD-OCT is not sufficient to distinguish individual cells.

Dynamic OCT
The recent development of dynamic OCT (D-OCT) software based on speckle-variance has the added ability to visualize the skin microvasculature and therefore detect blood vessels and their distribution within specific lesions. This angiographic variant of FD-OCT detects motion corresponding to blood flow in the images and may enhance diagnostic accuracy, particularly in the differentiation of nevi and malignant melanomas.8-11

High-Definition OCT
High-definition OCT (HD-OCT), a hybrid of RCM and FD-OCT, provides improved optical resolution of 3 μm for both lateral and axial imaging approaching a resolution similar to RCM making it possible to visualize individual cells, though at the expense of lower penetration depth of 0.5 to 1.0 mm and reduced field of view of 1.8×1.5 mm2 to FD-OCT. High-definition OCT combines 2 different views to produce a 3-dimensional image for additional data interpretation (Table).7,8,12

Current CPT Guidelines

Two category III CPT codes—0470T and 0471T—allow the medical community to collect and track the usage of the emerging OCT technology. Code 0470T is used for microstructural and morphological skin imaging, specifically acquisition, interpretation, and reading of the images. Code 0471T is used for each additional skin lesion imaged.4

Current Procedural Terminology category III codes remain investigational in contrast to the permanent category I codes. Reimbursement for CPT III codes is difficult because it is not generally an accepted service covered by insurance.5 The goal within the next 5 years is to convert to category I CPT codes, meanwhile the CPT III codes should encourage increased utilization of OCT technology.

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