Feature Of The Week 9/28/14: National Taiwan University Reports on Full-depth epidermis tomography using a Mirau-based full-field OCT
All living things are made of cells. Most living organisms are single cells; others, such as human bodies, are vast multicellular cities with an aggregation of more than 10 billion cells. Non-invasive and high speed imaging of cells and tissues with sub-micron resolution could help unveil functions of living organisms, and facilitate disease/cancer diagnosis, new drug development, etc. Such an imaging modality is one of the key technologies to detect disease and cancer in the early stage so that the ever-escalating medical cost could be controlled. At the same time, biomedical discovery often originated from technology advancement. Optical coherence tomography (OCT) can provide non-invasive tomographic images on living tissues without fluorescence markers. Recently, OCT has been applied for imaging a wide range of non-transparent tissues to perform in vivo imaging in human patients. The majority of studies have also suggested that OCT can be used to image both in vitro and in vivo tissues to identify regions that suggest abnormalities and should be biopsied for histopathological examination.
Full-field OCT (FF-OCT) utilizing two-dimensional CCD camera has the opportunity to observe the layer structure of skin for both cross section and en face monitoring. In this study, we have developed a near-isotropic sub-micron-resolution OCT system to image human skin and cancer cell for both morphological recognition as well as parametric analysis, which not only provide three-dimensional in vivo cellular-resolution image but also are able to delineate subcellular structure (i.e., the nucleus). The number of layers of stratum corneum and it thickness were quantitatively measured. This label free and non-invasive optical probe could be useful for evaluating the water barrier of skin tissue in clinics. In an in vivo experiment, the micro blood vessels in dermis were also observed, and the flowing of the red blood cells were traced. Image analysis algorithms have also been developed to automatically extract deterministic information from live tissue and single cells. The OCT light source was diode laser pumped crystalline fibers. To achieve high brightness and broadband emissions from 400 nm to 1.6 μm, glass-clad crystal fibers were drawn by the laser-heated pedestal growth and cladded by various glass capillaries. These light sources are eminently suitable for FF-OCT because of their cw operation and near-Gaussian spectra. With a Gaussian spectrum, the ghost image is minimized, and the pristine specimen image can be recorded.
To further facilitate the clinical realization of the imaging modality, flat field correction of the OCT en faces were compared with H&E stained histology sample with good agreement. With improved sensitivity/specificity, real-time data transmission and storage, and linking pathology to the treating physician, it is expected that the imaging advancement will eventually offer a see-and-treat paradigm, leading to improved patient care and medical expenditure reduction.
For more information see recent Article. Courtesy of Sheng-Lung Huang from National Taiwan University.