Showing papers by "Xingde Li published in 2013"

Dynamic focus-tracking MEMS scanning micromirror with low actuation voltages for endoscopic imaging.

Abstract: We demonstrate a 3-D scanning micromirror device that combines 2-D beam scanning with focus control in the same device using micro-electro-mechanical-systems (MEMS) technology. 2-D beam scanning is achieved with a biaxial gimbal structure and focus control is obtained with a deformable mirror membrane surface. The micromirror with 800 micrometer diameter is designed to be sufficiently compact and efficient so that it can be incorporated into an endoscopic imaging probe in the future. The design, fabrication and characterization of the device are described in this paper. Using the focus-tracking MEMS scanning mirror, we achieved an optical scanning range of >16 degrees with <40 V actuation voltage at resonance and a tunable focal length between infinity and 25 mm with <100V applied bias.

Characterizing optical properties of nano contrast agents by using cross-referencing OCT imaging.

Abstract: We report a cross-referencing method to quickly and accurately characterize the optical properties of nanoparticles including the extinction, scattering, absorption and backscattering cross sections by using an OCT system alone. Among other applications, such a method is particularly useful for developing nanoparticle-based OCT imaging contrast agents. The method involves comparing two depth-dependent OCT intensity signals collected from two samples (with one having and the other not having the nanoparticles), to extract the extinction and backscattering coefficient, from which the absorption coefficient can be further deduced (with the help of the established scattering theories for predicting the ratio of the backscattering to total scattering cross section). The method has been experimentally validated using test nanoparticles and was then applied to characterizing gold nanocages. With the aid of this method, we were able to successfully synthesize scattering dominant gold nanocages for the first time and demonstrated the highest contrast enhancement ever achieved by the gold nanocages (and by any nanoparticles of a similar size and concentration) in an in vivo mouse tumor model. This method also enables quantitative analysis of contrast enhancement and provides a general guideline on choosing the optimal concentration and optical properties for the nanoparticle-based OCT contrast agents.

Epithelium percentage estimation facilitates epithelial quantitative protein measurement in tissue specimens.

Abstract: Background The rapid advancement of high-throughput tools for quantitative measurement of proteins has demonstrated the potential for the identification of proteins associated with cancer. However, the quantitative results on cancer tissue specimens are usually confounded by tissue heterogeneity, e.g. regions with cancer usually have significantly higher epithelium content yet lower stromal content.

An electrothermal/electrostatic dual driven MEMS scanner with large in-plane and out-of-plane displacement

Abstract: This paper reports the design, fabrication and characterization of an MEMS scanner with combined electrothermal and electrostatic actuation. The scanner can generate large out-of-plane and in-plane displacement. The out-of-plane displacement is achieved by a pair of electro-thermal bimorph actuators, which is as much as 370 μm at only 2.5 V. The in-plane displacement is obtained by employing electrostatic comb drives, which can achieve fast scan up to 10 kHz. A special process has been developed to fabricate microstructures with both thin-film bimorphs and single-crystal-silicon comb drives.

Mass spectrometry imaging of glycans from tissue sections and improved analyte detection methods

Abstract: The presently disclosed subject matter provides methods using mass spectrometry for direct profiling of N-linked glycans from a biological sample. In addition, the embodiments of the present invention also disclose novel methods, known as targeted analyte detection (TAD), for improving the detection limit of MALDI-MS. These methods take advantage of the carrier effect of the added standard analytes, which occurs due to the generic sigmoidal shape of the calibration curve. The functionality of TAD depends on the relative enhancement of sensitivity over the increase of the standard deviation at the analysis of target analytes with spiking in exogenous concentration. At certain ranges of exogenous concentration, the increment in the sensitivity overcomes the standard deviation, resulting in an improved LOD. Theoretically, exogenous concentrations approximately at 1 LODorig would generate the optimum LOD improvement. TAD is a cost-effective LOD improvement method, which is not limited to a certain group of analytes, or detection methods or instruments. It can be applied to enhance the detection of any analyte with different detection methods, provided that the analyte of interest can be extracted or is available in synthetic form.

Monocytes loaded with indocyanine green as active homing contrast agents permit optical differentiation of infectious and non-infectious inflammation

Abstract: Distinguishing cutaneous infection from sterile inflammation is a diagnostic challenge and currently relies upon subjective interpretation of clinical parameters, microbiological data, and nonspecific imaging. Assessing characteristic variations in leukocytic infiltration may provide more specific information. In this study, we demonstrate that homing of systemically administered monocytes tagged using indocyanine green (ICG), an FDA-approved near infrared dye, may be assessed non-invasively using clinically-applicable laser angiography systems to investigate cutaneous inflammatory processes. RAW 264.7 mouse monocytes co-incubated with ICG fluoresce brightly in the near infrared range. In vitro, the loaded cells retained the ability to chemotax toward monocyte chemotactic protein-1. Following intravascular injection of loaded cells into BALB/c mice with induced sterile inflammation (Complete Freund's Adjuvant inoculation) or infection (Group A Streptococcus inoculation) of the hind limb, non-invasive whole animal imaging revealed local fluorescence at the inoculation site. There was significantly higher fluorescence of the inoculation site in the infection model than in the inflammation model as early as 2 hours after injection (p<0.05). Microscopic examination of bacterial inoculation site tissue revealed points of near infrared fluorescence, suggesting the presence of ICG-loaded cells. Development of a non-invasive technique to rapidly image inflammatory states without radiation may lead to new tools to distinguish infectious conditions from sterile inflammatory conditions at the bedside.

Abstract 7: IMAGING WITH INDOCYANINE GREEN-LOADED MONOCYTES FOR DIFFERENTIATION OF CUTANEOUS INFLAMMATORY STATES IN A MOUSE MODEL

Abstract: Introduction: Distinguishing normal postoperative in ammation from infectious processes can be challenging, and relies largely upon interpretation of clinical parameters and microbiologic data. An imaging modality that assesses variations in leukocytic in ltration could provide more speci c information without the delays inherent in culture. Autologous monocytes loaded with the only FDA-approved near infrared  uorophore, indocyanine green (ICG), may be injected intravenously and homing assessed non-invasively using a clinically-applicable near infrared laser to investigate cutaneous in ammatory processes.

Fiber-optic Multiphoton Endomicroscopy

Abstract: We report recent progresses in the fiber-optic multiphoton endomicroscopy technology. High-quality two-photon images of unstained biological tissues along with potential clinical applications are presented.