Line-field confocal optical coherence tomography (LC-OCT) is an imaging technique based on a combination of confocal microscopy and OCT, allowing three-dimensional cellular-resolution imaging of the skin in vivo. We present the latest advances in LC-OCT to facilitate the use of the technique by dermatologists and improve the diagnosis and analysis of skin lesions. A video camera was incorporated into a handheld probe to acquire dermoscopic images in parallel with LCOCT images. A confocal Raman spectrometer was associated with a LC-OCT device to record morphological images of the skin in which points of interest can be subjected to molecular characterization.
KEYWORDS: Skin, Image segmentation, 3D modeling, 3D image processing, In vivo imaging, Optical coherence tomography, Artificial intelligence, Confocal microscopy, 3D acquisition
Line-field confocal optical coherence tomography (LC-OCT) is an imaging technique based on a combination of reflectance confocal microscopy and optical coherence tomography, allowing three-dimensional (3D) imaging of skin in vivo with an isotropic spatial resolution of about 1.3 micron and up to 400 microns in depth. Cellular-resolution 3D images obtained with LC-OCT offer a considerable amount of information for description and quantification of the upper layers of in vivo skin using morphological metrics, which can be critical for better understanding the skin changes leading to aging or some pathologies. This study introduces metrics for the quantification of the epidermis, and uses them to describe the variability of healthy epidermis between different body sites. These metrics include the stratum corneum thickness, the undulation of the dermal-epidermal junction (DEJ), and the quantification of the keratinocyte network. In order to generate relevant metrics over entire 3D images, an artificial intelligence approach was applied to automate the calculation of the metrics. We were able to quantify the epidermis of eight volunteers on seven body areas on the head, the upper limbs and the trunk. Epidermal thicknesses and DEJ undulation variations were observed between different body sites. The cheek presented the thinnest stratum corneum the least undulated DEJ, while the back of the hand presented the thickest stratum corneum and the back the most undulated DEJ. The process of keratinocyte maturation was evidenced in vivo. These 3D in vivo quantifications open the door in clinical practice to diagnose and monitor pathologies for which the epidermis is impaired.
The use of non-invasive imaging techniques in dermatology has been reported to improve the diagnostic accuracy and the practice of biopsies, and at the same time to reduce the need for tissue excision. However, the current clinically-available imaging techniques do not yet entirely meet the need for early and accurate, non-invasive detection of all skin cancers. A handheld line-field confocal optical coherence tomography (LC-OCT) device has been designed for high-resolution non-invasive imaging of human skin, in vivo. LC-OCT delivers tomographic images in real-time (10 frames/s) with a quasi isotropic spatial resolution of ~ 1 μm, revealing a comprehensive morphological mapping of skin tissues at a cellular level, down to a depth of ~500 μm. The device has been applied to the in vivo imaging of various skin lesions. Surgical excisions of the lesions have then been performed followed by tissue processing to realize H&E-stained histopathological images. The spatial resolution, orientation, and imaging contrast mechanism of the LC-OCT images have allowed for a good level of similarity with the conventional histopathological images. LC-OCT was able to show most of the histopathological elements that allow for medical diagnosis. Using handheld LC-OCT as an adjunct tool in dermatology could help improve clinical diagnostic accuracy, allowing for the early detection of malignant skin tumors and a reduction in the number of surgical excisions of benign lesions.
An improved optical coherence tomography (OCT) technique called line-field confocal OCT (LC-OCT) has been developed for high-resolution skin imaging. Combining the principles of time-domain OCT and confocal microscopy with line illumination and detection, LC-OCT acquires multiple A-scans in parallel with dynamic focusing. With a quasi isotropic resolution of ∼ 1 μm, the LC-OCT images reveal a comprehensive structural mapping of skin, in vivo, at the cellular level down to a depth of ∼ 500 μm. LC-OCT images of various skin lesions, including carcinomas and melanomas, are found to well correlate with histopathological images. LC-OCT could significantly improve clinical diagnostic accuracy, while reducing the number of biopsies of benign lesions.
An optical technique called line-field confocal optical coherence tomography (LC-OCT) is introduced for high-resolution, noninvasive imaging of human skin in vivo. LC-OCT combines the principles of time-domain optical coherence tomography and confocal microscopy with line illumination and detection using a broadband laser and a line-scan camera. LC-OCT measures the echo-time delay and amplitude of light backscattered from cutaneous microstructures through low-coherence interferometry associated with confocal spatial filtering. Multiple A-scans are acquired simultaneously while dynamically adjusting the focus. The resulting cross-sectional B-scan image is produced in real time at 10 frame / s. With an isotropic spatial resolution of ∼1 μm, the LC-OCT images reveal a comprehensive structural mapping of skin at the cellular level down to a depth of ∼500 μm. LC-OCT has been applied to the imaging of various skin lesions, in vivo, including carcinomas and melanomas. LC-OCT images are found to strongly correlate with conventional histopathological images. The use of LC-OCT as an adjunct tool in medical practice could significantly improve clinical diagnostic accuracy while reducing the number of biopsies of benign lesions.
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