Angle-resolved low-coherence interferometry

Angle-resolved low-coherence interferometry (a/LCI) is an emerging biomedical imaging technology which uses the properties of scattered light to measure the average size of cell structures, including cell nuclei. The technology shows promise as a clinical tool for in situ detection of dysplastic, or precancerous tissue. Angle-resolved low-coherence interferometry (a/LCI) is an emerging biomedical imaging technology which uses the properties of scattered light to measure the average size of cell structures, including cell nuclei. The technology shows promise as a clinical tool for in situ detection of dysplastic, or precancerous tissue. A/LCI combines low-coherence interferometry with angle-resolved scattering to solve the inverse problem of determining scatterer geometry based on far field diffraction patterns. Similar to optical coherence domain reflectometry (OCDR) and optical coherence tomography (OCT), a/LCI uses a broadband light source in an interferometry scheme in order to achieve optical sectioning with a depth resolution set by the coherence length of the source. Angle-resolved scattering measurements capture light as a function of the scattering angle, and invert the angles to deduce the average size of the scattering objects via a computational light scattering model such as Mie theory, which predicts angles based on the size of the scattering sphere. Combining these techniques allows construction of a system that can measure average scatter size at various depths within a tissue sample. At present the most significant medical application of the technology is determining the state of tissue health based on measurements of average cell nuclei size. It has been found that as tissue changes from normal to cancerous, the average cell nuclei size increases. Several recent studies have shown that via cell nuclei measurements, a/LCI can detect the presence of low- and high-grade dysplasia with 91% sensitivity and distinguish between normal and dysplastic with 97% specificity. Since 2000, light scattering systems have been used for biomedical applications such as the study of cellular morphology as well as the diagnosis of dysplasia. Variations in scattering distributions as a function of angle or wavelength have been used to deduce information regarding the size of cells and subcellular objects such as nuclei and organelles. These size measurements can then be used diagnostically to detect tissue changes—including neoplastic changes (those leading to cancer). Light scattering spectroscopy has been used to detect dysplasia in the colon, bladder, cervix, and esophagus of human patients. Light scattering has also been used to detect Barrett’s esophagus, a metaplastic condition with a high probability of leading to dysplasia.