Zhinan Chen

© The Author 2017.The observation of replica bands in single-unit-cell FeSe on SrTiO3 by angle-resolved photoemission spectroscopy has led to the conjecture that the coupling between FeSe electrons and the STO phonons are responsible for the enhancement of T c over other FeSe-based superconductors. However the recent observation of a similar superconducting gap in single-unit-cell FeSe/STO raised the question of whether a similar mechanism applies. Here we report the ARPES study of the electronic structure of FeSe/STO. Similar to the results in FeSe/STO, clear replica bands are observed. We also present a comparative study of STO and STO bare surfaces, and observe similar replica bands separated by approximately the same energy, indicating this coupling is a generic feature of the STO surfaces and interfaces. Our findings suggest that the large superconducting gaps observed in FeSe films grown on different STO surface terminations are likely enhanced by a common mechanism.

Background: Optical Doppler tomography combines laser Doppler flowmetry with optical coherence tomography to obtain high-resolution images of blood flow in human skin in situ and in real time. Observations: We present a case in which ODT was used on a patient with a port-wine stain birth-mark to document the change of blood flow in response to laser therapy. It might be possible to use ODT blood flow measurements in situ to assist in assessing the efficacy of laser PWS therapy. If partial restoration of flow occurs immediately or shortly after laser exposure, indicative of reperfusion due to inadequate blood vessel injury, the PWS can be retreated using higher light dosages. Retreatment is continued until the measured Doppler shift is zero due to a permanent reduction in blood flow, indicative of irreversible microthrombus formation in the PWS vessels. Conclusions: We have demonstrated that ODT may be used for noninvasive imaging of blood vessels in PWS skin. Moreover, ODT will potentially allow laser therapy to be optimized on an individual patient basis by providing a fast, semiquantitative evaluation of the efficacy of PWS laser therapy in situ and in real time.

Background: In vivo, non-invasive optical coherence tomography permits high-resolution imaging of tissue surfaces and subsurfaces, with the potential capability for detection and mapping of epithelial pathologies. Purpose: To evaluate the clinical capability of non-invasive in vivo OCT for diagnosing oral dysplasia and malignancy. Experimental Design: In 50 patients with oral lesions, conventional clinical examination was followed by OCT imaging, then standard biopsy and histopathology. Two blinded, pre-standardized investigators separately diagnosed each lesion based on OCT and histopathology. Results: Intra- and inter-observer agreement between diagnoses based on histopathology and imaging data was excellent, with λ values between 0.844 and 0.896. Sensitivity and specificity were also very good. Conclusions: These data demonstrate the excellent capability of in vivo OCT for detecting and diagnosing oral premalignancy and malignancy in human subjects. © 2009 Wiley-Liss, Inc.

Hamster cheek pouches were exposed to 2-chloroethyl ethyl sulfide [CEES, half-mustard gas ] at a concentration of 0.4, 2.0, or 5.0 mg/ml for 1 or 5 min. Twenty-four hours post-HMG exposure, tissue damage was assessed by both stereomicrography and optical coherence tomography. Damage that was not visible on gross visual examination was apparent in the OCT images. Tissue changes were found to be dependent on both HMG concentration and exposure time. The submucosal and muscle layers of the cheek pouch tissue showed the greatest amount of structural alteration. Routine light microscope histology was performed to confirm the OCT observations. © 2010 Society of Photo-Optical Instrumentation Engineers.

Purpose: To assess noninvasive optical coherence tomography and optical Doppler tomography for early detection and evaluation of chemotherapy-induced oral mucositis. Experimental Design: Cheek pouches of 10 Syrian golden hamsters were imaged using OCT/ODT during development of chemotherapy-induced mucositis. I.p. injections of 5-fluorouracil and mechanical irritation induced oral lesions. At 2, 4, 7, and 11 days, one hamster was sacrificed and processed for histopathology. OCT images were visually examined; ODT results were semiquantified. Imaging data were compared with histologic findings. Results: During the development of mucositis, OCT/ODT identified the following events: change in epithelial thickness, loss of surface keratinized layer continuity, loss of epithelial and submucosal integrity, changes in axial blood flow velocity, and changes in blood vessel size. The semiquantitative imaging-based scoring system identified the severity of mucositis as defined by histopathology. The combination of imaging criteria used allowed for the detection of early, intermediate, and late mucositic changes. Imaging data gave higher scores compared with clinical scores early on, suggesting that the imaging-based diagnostic scoring was more sensitive to early mucositic change than the clinical scoring system. Once mucositis was established, imaging and clinical scores converged. Conclusion: OCT/ODT identified chemotherapy-induced oral changes before their clinical manifestation, and the proposed scoring system for oral mucositis was validated for the semiquantification of mucositic change. © 2007 American Association for Cancer Research.

Contrast in optical coherence tomography images can be enhanced by utilizing surface plasmon resonant gold nanoparticles. To improve the poor in vivo transport of gold nanoparticles through biological barriers, an efficient delivery strategy is needed. In this study, the improved penetration and distribution of gold nanoparticles were achieved by microneedle and ultrasound, respectively, and it was demonstrated that this multimodal delivery of antibody-conjugated PEGylated gold nanoparticles enhanced the contrast in in vivo OCT images of oral dysplasia in a hamster model. © 2009 Society of Photo-Optical Instrumentation Engineers.

The Mueller matrix describes all the polarizing properties of a sample and, therefore, the optical differences between noncancerous and precancerous tissue that may be present within the matrix elements. A high-speed polarimetry system that generates 16 full Mueller matrices to characterize tissues is presented. Feature extraction is done on the Mueller matrix elements resulting in depolarization and retardance images by polar decomposition. These are used to detect and classify early oral cancers and precancerous changes in epithelium such as dysplasia. These images are compared with orthogonal polarization images and analyzed in an attempt to identity useful factors for the differentiation between cancerous lesions and their benign counterparts. Our results indicate that polarimetry has potential as a method for the in vivo early detection and diagnosis of oral premalignancy. © 2007 Optical Society of America.

Early detection of cancer and its precursors remains the best way to ensure patient survival and quality of life. Our specific aim is to test a multimodality approach to noninvasive diagnostics of oral premalignancy and malignancy. In the hamster cheek pouch model, in vivo optical coherence tomography and optical Doppler tomography map epithelial, subepithelial, and vascular change throughout carcinogenesis. In vivo multiwavelength multiphoton and second-harmonic generated fluorescence techniques provided parallel data on surface and subsurface tissue structure, specifically collagen presence and structure, cellular presence, and vasculature. Images are diagnosed by two blinded, prestandardized investigators using a scale from 0 to 6 for all modalities. After sacrifice, histopathology is evaluated on a scale of 0 to 6. Imaging data are reproducibly obtained with good accuracy. Carcinogenesis-related structural and vascular changes are clearly visible to tissue depths of 2 mm. Sensitivity and specificity compare well with conventional techniques. Our conclusions are that OCT/ODT and MPM/SHG are promising noninvasive in vivo diagnostic modalities for oral dysplasia and malignancy. © 2005 Society of Photo-Optical Instrumentation Engineers.

Optical coherence tomography is a catheter-based imaging technology with powerful resolution capable of identifying vulnerable plaques and guiding coronary intervention. However, a significant limitation of intravascular OCT imaging is its attenuation by blood. We propose that the use of an oxygen-carrying blood substitute could potentially optimize OCT image quality. Surgical isolation of the descending thoracic aorta of six rabbits is performed, followed by intravascular OCT imaging of the abdominal aorta. Perfluorodecalin is oxygenated using a bubble-through technique with 100% oxygen. OCT imaging is performed and compared using three different flushing modalities: PFD; saline; and blood. OCT imaging of the rabbit abdominal aorta is successful in all of the subjects. In each of the six studied subjects, flushing with PFD consistently provides dramatically better imaging of the vessel wall tissue structures. OCT image quality is highly dependent on the ability of the flushing modality to remove blood from the imaging field. From this proof-of-concept study, we demonstrate that endovascular flushing with an oxygen-carrying blood substitute is optically superior to saline flushing for intravascular imaging. © 2009 Society of Photo-Optical Instrumentation Engineers.

We describe an algorithm based on shrinkage in the curvelet domain to attenuate speckles in optical coherence tomography images. The algorithm exploits the curvelet transform's sparse representation of edge discontinuities that are common in OCT images and its ability to map signals and noise into different areas in the curvelet domain. The speckle attenuation is controlled by a single parameter that determines the threshold in the curvelet domain. Applying the algorithm to OCT images shows significant improvement of image quality. © 2009 Optical Society of America.

The structural origin of scattering contrast from single cells is examined by using a combined optical coherence and multiphoton microscope based on a 12 fs Ti:sapphire source and a 0.95 NA objective. High-resolution coherence-gated scattering images from single cells are coregistered and compared with two-photon-excited fluorescence images. Scattering contrast is observed from mitochondria, plasma membrane, actin filaments, and the boundary between cytoplasm and nucleus. There is little contribution to scattering from regions inside the nuclear core. These results confirm that light scattering signals from specific subcellular structures can be visualized by using coherent reflectance geometry. © 2007 Optical Society of America.

Early detection of cancer remains the best way to ensure patient survival and quality of life. Squamous cell carcinoma is usually preceded by dysplasia presenting as white, red, or mixed red and white epithelial lesions on the oral mucosa. Dysplastic lesions in the form of erythroplakia can carry a risk for malignant conversion of 90%. A noninvasive diagnostic modality would enable monitoring of these lesions at regular intervals and detection of treatment needs at a very early, relatively harmless stage. The specific aim of this work was to test a multimodality approach [three-dimensional optical coherence tomography and polarimetry] to noninvasive diagnosis of oral premalignancy and malignancy using the hamster cheek pouch model. The results were compared to tissue histopathology. During carcinogenesis, epithelial down grow, eventual loss of basement membrane integrity, and subepithelial invasion were clearly visible with OCT. Polarimetry techniques identified a four to five times increased retardance in sites with squamous cell carcinoma, and two to three times greater retardance in dysplastic sites than in normal tissues. These techniques were particularly useful for mapping areas of field cancerization with multiple lesions, as well as lesion margins. © 2011 Society of Photo-Optical Instrumentation Engineers.