This paper reports on line-field confocal optical coherence tomography (LC-OCT), a recently invented imaging technology now capable of generating either a horizontal (en face) section image at an adjustable depth, or a vertical section image (B-scan) at an adjustable lateral position. For both operating modes, images are acquired in real-time (10 frames/second), with real-time control of the depth and lateral positions. Using a supercontinuum laser as a broadband light source and a high numerical microscope objective, an isotropic spatial resolution of ∼ 1 μm is achieved. The imaging fields of view are 1.2×0.5 mm² (x×y, horizontal) and 1.2×0.5 mm² (x×z, vertical). LC-OCT has been used in dermatology for skin imaging.
Line-field confocal optical coherence tomography (LC-OCT) is an imaging method based on dynamically-focused line-field time-domain OCT to generate vertical section images of biological tissues with cellular spatial resolution. We demonstrate here an improvement in the LC-OCT technology that makes it possible to also generate horizontal (en face) section images, as in conventional optical coherence microscopy (OCM) or reflectance confocal microscopy (RCM). This improvement is based on the implementation of a lateral scanning device using a mirror galvanometer to scan the laser beam laterally at a given depth. The reference mirror of the interferometer is mounted on a piezoelectric transducer to generate a sinusoidal phase modulation during lateral scanning in order to extract the tomographic signal. The LC-OCT device is capable of generating either a horizontal section image at an adjustable depth in the sample, or a vertical section image at an adjustable lateral position in the sample. For both operating modes, images are acquired in real-time (8 frames per second), with real-time control of the depth/lateral position. The user can switch between the two operating modes by clicking on a button. Using a supercontinuum laser as a light source and 0.5 NA microscope objectives, the image resolution is 0.9 × 0.9 × 1.1 μm3 (x × y × z), with fields of view of 1.2 × 0.5 mm2 (x × y, horizontal) and 1.2 × 0.4 mm2 (x × z, vertical). In vivo cellular-level imaging of human skin is demonstrated for both modes of operation.
An imaging device based on line-field confocal optical coherence tomography (LC-OCT) operating in two distinct spectral bands centered at 770 nm and 1250 nm is presented. A single supercontinuum light source and two different line-scan cameras are used. B-scans are acquired simultaneously in the two bands at 4 frames per second. In the 770-nm band, high resolution (1.3 μm x 1.2 μm, lateral x axial) imaging is achieved, while extended penetration (~ 700 μm) is obtained in the 1250-nm band. Greyscale fusion of the two images is performed to produce a single image with both high resolution in the superficial part of the image and deep penetration. A color representation is also used to highlight spectroscopic properties of the sample and to enhance contrast.
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.
We present an improved time-domain optical coherence tomography technique designed for ultrahigh-resolution B-scan imaging in real-time. The technique, called line-field confocal optical coherence tomography, is based on a Linnik-type interference microscope with line illumination using a supercontinuum laser and line detection using a line-scan camera. Bscan imaging with dynamic focusing is achieved by acquiring multiple A-scans in parallel. In vivo cellular level resolution imaging of skin is demonstrated at 10 frame/s with a penetration depth of ∼ 500 μm, with a spatial resolution of 1.3 μm × 1.1 μm (transverse × axial).
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.
This paper reports on advances in optical coherence tomography (OCT) for application in dermatology. Full-field OCT is a particular approach of OCT based on white-light interference microscopy. FF-OCT produces en face tomographic images by arithmetic combination of interferometric images acquired with an area camera and by illuminating the whole field of view with low-coherence light. The major interest of FF-OCT lies in its high imaging spatial resolution (∼ 1.0 μm) in both lateral and axial directions, using a simple and robust experimental arrangement. Line-field OCT (LFOCT) is a recent evolution of FF-OCT with line illumination and line detection using a broadband spatially coherent light source and a line-scan camera in an interference microscope. LF-OCT and FF-OCT are similar in terms of spatial resolution. LF-OCT has a significant advantage over FF-OCT in terms of imaging penetration depth due to the confocal gate achieved by line illumination and detection. B-scan imaging using FF-OCT requires the acquisition of a stack of en face images, which usually prevents in vivo applications. B-scan imaging using LF-OCT can be considerably faster due to the possibility of using a spatially coherent light source with much higher brightness along with a high-speed line camera. Applied in the field of dermatology, the LF-OCT images reveal a comprehensive morphological mapping of skin tissues in vivo at a cellular level similar to histological images.
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