Contrast of nuclei in stratified squamous epithelium in optical coherence tomography images at 800 nm

Abstract

Imaging nuclei of keratinocytes in the stratified squamous epithelium has been a subject of intense research since nucleus associated cellular atypia is the key criteria for the screening and diagnosis of epithelial cancers and their precursors. However, keratinocyte nuclei have been reported to be either low scattering or high scattering, so that these inconsistent reports might have led to misinterpretations of optical images, and more importantly, hindered the establishment of optical diagnostic criteria. We disclose that they are generally low scattering in the core using Micro‐optical coherence tomography (μOCT) of 1.28‐μm axial resolution in vivo; those previously reported “high scattering” or “bright” signals from nuclei are likely from the nucleocytoplasmic boundary, and the low‐scattering nuclear cores were missed possibly due to insufficient axial resolutions (~4μm). It is further demonstrated that the high scattering signals may be associated with flattening of nuclei and cytoplasmic glycogen accumulation, which are valuable cytologic hallmarks of cell maturation.

Understanding optical reflectance contrast for real‐time characterization of epithelial precursor lesions

“…The corresponding experimental realizations were carried out using μOCT on intact mammalian epithelia including simple columnar epithelia from swine stomach, colon and small intestine, and stratified squamous epithelia (SSE) from swine skin (orthokeratinized), esophagus (parakeratinized), and floor of month (nonkeratinized), respectively. 23 On one hand, we validated our theoretical predictions by correlating the cytoplasmic reflectance contrasts with the micro-or ultra-structural features of the above mentioned cytoplasmic inclusions pertaining to the physiological states of specialized epithelial cells; on the other, our theoretical analysis provide meaningful explanations of the mechanisms underlying the observed back-scattering phenomena. Thereafter, we conducted a preliminary study to evaluate the feasibility of the new understandings on the image contrast for the interpretation of back-scattering features in precancerous lesions using specimens from the mice esophageal and human gastrointestinal tracts.…”

“…The results show that these clustered or packed nanometer‐scale scatterers may contribute significantly or even dominantly to cell back‐scattering, depending on their clustering or packing states. The corresponding experimental realizations were carried out using μOCT on intact mammalian epithelia including simple columnar epithelia from swine stomach, colon and small intestine, and stratified squamous epithelia (SSE) from swine skin (orthokeratinized), esophagus (parakeratinized), and floor of month (nonkeratinized), respectively . On one hand, we validated our theoretical predictions by correlating the cytoplasmic reflectance contrasts with the micro‐ or ultra‐structural features of the above mentioned cytoplasmic inclusions pertaining to the physiological states of specialized epithelial cells; on the other, our theoretical analysis provide meaningful explanations of the mechanisms underlying the observed back‐scattering phenomena.…”

“…We used a μOCT system described in one of our previous works . The system provides a transverse resolution of 1.8 μm and an axial resolution of 1.28 μm in tissue (refractive index = 1.33).…”

“…While cell nuclei have a quasi‐uniform distribution of its compositions and consistently present low back‐scattering in the core, the cytoplasm is the predominant site reflecting the specialization‐mediated intracellular variations and corresponding alterations in their back‐scattered intensity. Chen et al measured the back‐scattered intensity of the nuclear cores and cytoplasm in the stratified squamous epithelium to be in the order of 10 −7 and 10 −6 , respectively, when they are normalized to a perfect reflector . Saidi et al used Mie theory to approximate skin tissue scattering but by assuming cells are homogeneous spheres of a single size .…”

“…Chen et al measured the back-scattered intensity of the nuclear cores and cytoplasm in the stratified squamous epithelium to be in the order of 10 −7 and 10 −6 , respectively, when they are normalized to a perfect reflector. 23 Saidi et al used Mie theory to approximate skin tissue scattering but by assuming cells are homogeneous spheres of a single size. 25 Dunn and Drezek et al used the finite-difference time-domain (FDTD) method to model light scattering from cells containing multiple organelles of arbitrary shape.…”