Showing papers by "Xingde Li published in 2006"
TL;DR: This tutorial review highlights the surface plasmon resonance peaks of gold nanostructures by comparing four typical examples: nanospheres, nanorods, nanoshells, and nanocages.
Abstract: The surface plasmon resonance peaks of gold nanostructures can be tuned from the visible to the near infrared region by controlling the shape and structure (solid vs. hollow). In this tutorial review we highlight this concept by comparing four typical examples: nanospheres, nanorods, nanoshells, and nanocages. A combination of this optical tunability with the inertness of gold makes gold nanostructures well suited for various biomedical applications.
1,579 citations
TL;DR: The development of a miniature, flexible, fiber-optic scanning endoscope for two-photon fluorescence imaging using a tubular piezoelectric actuator for achieving two-dimensional beam scanning and a double-clad fiber for delivery of the excitation light and collection of two-Photon Fluorescence.
Abstract: We report on the development of a miniature, flexible, fiber-optic scanning endoscope for two-photon fluorescence imaging. The endoscope uses a tubular piezoelectric actuator for achieving two-dimensional beam scanning and a double-clad fiber for delivery of the excitation light and collection of two-photon fluorescence. Real-time imaging of fluorescent beads and cancer cells has been performed.
306 citations
TL;DR: The time scale for energy relaxation was found to increase with the size of the particles, with the relaxation time being independent of the laser intensity, and the period of the coherently excited vibrational mode is proportional to the dimensions of the nanocages.
Abstract: Au nanocages were synthesized via a galvanic replacement reaction. The extinction peak of these hollow structured particles is shifted into the near-IR compared with the Ag nanocube templates. Energy transfer from the Au nanocages into the surrounding environment (water) as well as the coherently excited vibrational modes of the nanocages were studied by femtosecond pump−probe spectroscopy. The time scale for energy relaxation was found to increase with the size of the particles, with the relaxation time being independent of the laser intensity. The time scales for relaxation are comparable to those for solid spherical gold particles and are consistent with energy relaxation being controlled by heat dissipation in the solvent. The period of the coherently excited vibrational mode is proportional to the dimensions of the nanocages. Intensity-dependent measurements show that in solution the nanocages maintain their integrity up to lattice temperatures of 1100 ± 100 K.
105 citations
TL;DR: Hallmarks of cutaneous wound healing such as wound size, epidermal migration, dermal-epidermal junction formation, and differences in wound composition were readily identified on the OCT images.
Abstract: Ultrahigh-resolution optical coherence tomography (OCT) was used for noninvasive in vivo evaluation of the wound healing process. Cutaneous wounds were induced by 2.5-mm diameter full-thickness punch biopsies on the dorsal surface of seven mice. OCT imaging was performed to assess the structural characteristics associated with the healing process. The OCT results were compared to corresponding histology. Two automated quantitative analysis routines were implemented to identify the dermal-epidermal junction and segment the OCT images. Hallmarks of cutaneous wound healing such as wound size, epidermal migration, dermal-epidermal junction formation, and differences in wound composition were readily identified on the OCT images. Blister formation was also observed. Preliminary findings suggest OCT is a viable tool to noninvasively monitor wound healing in vivo.
93 citations
TL;DR: Discrete dipole approximation calculations have been performed with and without surface scattering of electrons to compare with the experimental spectra, and confirm that both electron-surface scattering and radiation damping are important effects in this system.
Abstract: The optical properties of two Au−Ag nanobox samples with average edge lengths of 44 and 58 nm and wall thicknesses of 6 and 8 nm, respectively, have been studied by single particle spectroscopy. The measurements gave an average line width of Γ = 306 ± 7 meV with a standard deviation of σ = 30 meV for the 44-nm boxes, and Γ = 350 ± 9 meV with σ = 35 meV for the 58-nm boxes. These line widths are much broader than those of gold nanorods with comparable resonance energies. The increased broadening is attributed to a combination of surface scattering of electrons, as well as increased radiation damping for the nanoboxes. Discrete dipole approximation calculations have been performed with and without surface scattering of electrons to compare with the experimental spectra. The calculations confirm that both electron-surface scattering and radiation damping are important effects in this system.
86 citations
TL;DR: It is demonstrated that MSS-ODT is a useful technique for accurate determination of blood vessel size by imaging flow in a small capillary tube with a 75 microm inner diameter and provides improved sensitivity over the conventional phase-resolved method.
Abstract: We present a moving-scatterer-sensitive optical Doppler tomography (MSS-ODT) technique for in vivo blood flow imaging in real time by using a spectral-domain optical coherence tomography system. In MSS-ODT the influence of stationary scatterers is suppressed by subtracting adjacent complex axial scans before calculating the Doppler frequency shift. We demonstrate that MSS-ODT is a useful technique for accurate determination of blood vessel size by imaging flow in a small capillary tube with a 75μm inner diameter. The flow profile obtained with MSS-ODT yields a substantially more accurate tube diameter than that obtained with the conventional phase-resolved method, which underestimates the diameter by about 23%. We also demonstrate that MSS-ODT provides improved sensitivity over the conventional phase-resolved method for imaging in vivo blood flow in small vessels in a mouse ear.
61 citations
Patent•
13 Jan 2006TL;DR: In this article, a method for dynamic focus tracking during real-time optical coherence tomography (OCT) by simultaneously implementing geometric focus tracking (GFT) and coherence gate tracking (CGT) is presented.
Abstract: Method and apparatus for achieving dynamic focus tracking during real-time optical coherence tomography (OCT) by simultaneously implementing geometric focus tracking (GFT) and coherence gate tracking (CGT). GFT tracking involves changing a position of the focal point of the OCT probe in the sample during scanning. Preferably, the focal point is moved relative to the sample without disrupting the Gaussian beam profile of the scanner. CGT involves determining a change in the optical path length of the sample arm due to the GFT, and calculating the change in the optical path length in the reference arm required to maintain an equivalent optical path length in both the sample arm and the reference arm. The reference arm is then translated by the required amount, to maximize the OCT signal. A lateral priority scanning technique is employed, and this technique can be implemented using a single optical fiber suitable for endoscopic use.
57 citations
TL;DR: OCT is a viable tool for assessing the earliest stages of carcinogenesis and has potential for early detection of neoplasia in skin, as well as in epithelial linings of other organs.
Abstract: BACKGROUND AND OBJECTIVE Improved diagnostics capable of non-invasive detection of early stage carcinogenesis would benefit basic research, and potentially aid in clinical cancer diagnosis and management. The two-stage carcinogenesis protocol is widely used for studying the multi-stage nature of tumor development in mice and provides insight into tumor development in other animal models and humans. The objective of this study was to investigate the feasibility of non-invasive optical coherence tomography (OCT) for in vivo imaging of microanatomical changes in the epidermis and dermis during early carcinogenesis using a mouse skin model. MATERIALS AND METHODS 10 NIH mice were treated with DMBA and TPA following the well-established two-stage carcinogenesis protocol. OCT imaging of treated skin from live mice was performed at five time points (Week 4-8) after tumor initiation to reveal the structural changes in the epidermis and dermis associated with the earliest, premalignant stages of tumor development. OCT images were compared with histology findings. In addition, OCT signals were quantitatively analyzed to evaluate tissue optical property changes during early carcinogenesis. RESULTS Early structural changes in the epidermis, dermis and hair follicles during carcinogenesis were clearly delineated in vivo using OCT. OCT images correlated well with histological findings. Quantitative OCT signal analysis revealed a statistically significant change in the extinction coefficient for untreated (40.5 +/- 17.0 mm(-1)) and treated (9.6 +/- 3.6 mm(-1)) mouse epidermis (P 0.10). Furthermore, the papilloma extinction coefficient (2.9 +/- 0.3 mm(-1)) was significantly lower than the extinction coefficient for the treated epidermis (P < 0.005) and dermis (P < 0.01). CONCLUSION OCT is a viable tool for assessing the earliest stages of carcinogenesis and has potential for early detection of neoplasia in skin, as well as in epithelial linings of other organs.
13 citations
TL;DR: This PDF file contains the errata for “JBO Vol. 11 Issue 06 Paper 2430730” for JBO vol.
Abstract: This PDF file contains the errata for “JBO Vol. 11 Issue 06 Paper 2430730” for JBO Vol. 11 Issue 06
4 citations
TL;DR: It is demonstrated OCT can accurately distinguish subsquamous Barrett's epithelium (SBE) from surrounding tissue using freshly excised human esophagi with high-grade dysplasia.
Abstract: We demonstrate OCT can accurately distinguish subsquamous Barrett's epithelium (SBE) from surrounding tissue using freshly excised human esophagi. Detection sensitivity and specificity of SBE and high-grade dysplasia will also be discussed.
2 citations
TL;DR: A flexible fiber-optic scanning endoscope for two-photon fluorescence imaging is presented and demonstrated on live cells and two-dimensional beam scanning at kilohertz frequencies was achieved using a PZT tube to actuate a double-clad fiber.
Abstract: We present a flexible fiber-optic scanning endoscope for two-photon fluorescence imaging and demonstrate it on live cells. Two-dimensional beam scanning at kilohertz frequencies was achieved using a PZT tube to actuate a double-clad fiber.
01 Apr 2006
TL;DR: Hydrogel scaffolds releasing angiogenic and osteoinductive molecules were used to induce bone growth in a bone defect model and optical coherence tomography was utilized to characterize morphological changes during the temporal progression of bone regeneration.
Abstract: Hydrogel scaffolds releasing angiogenic and osteoinductive molecules were used to induce bone growth in a bone defect model. Optical coherence tomography was utilized to characterize morphological changes during the temporal progression of bone regeneration.
21 May 2006
TL;DR: In this paper, a method for improving the accuracy in determining blood flow rate and small vessel size by implementing a delay line filter when processing real-time spectral domain optical coherence tomography images of flow is presented.
Abstract: We report a method for improving the accuracy in determining blood flow rate and small vessel size by implementing a delay line filter when processing real-time spectral domain optical coherence tomography images of flow.
TL;DR: In this article, a phase-shifted delay line filter is implemented in a spectral domain optical Doppler tomography system to suppress the influence of stationary scatterers on blood flow rate estimation.
Abstract: A phase-shifted delay line filter is implemented in a spectral domain optical Doppler tomography system to suppress the influence of stationary scatterers on blood flow rate estimation.
TL;DR: In this article, gold nanocages with sizes of 35-65 nm and tunable optical properties were reported, which can be bioconjugated for target delivery and potentially function as contrast and photothermal therapeutic agents.
Abstract: We report on gold nanocages with sizes of 35-65 nm and tunable optical properties. The nanostructures can be bioconjugated for target delivery and potentially function as contrast and photo-thermal therapeutic agents.