Showing papers by "Stephen A. Boppart published in 2002"
TL;DR: This work presents an inexpensive and easy-to-implement augmentation to a Ti:sapphire laser that widens the bandwidth from 20 to over 200 nm with commerically available ultrahigh-numerical-aperture fiber to provide a readily available broad-bandwidth source for researchers and a practical enhancement to a fiber-optic optical coherence tomography system.
Abstract: The axial resolution of optical coherence tomography images is primarily dependent on the bandwidth of the illumination source. Continuum generation is one way to generate the single-mode, high-bandwidth light needed for point illumination. We present an inexpensive and easy-to-implement augmentation to a Ti:sapphire laser that widens the bandwidth from 20 to over 200 nm with commerically available ultrahigh-numerical-aperture fiber. This technique can provide a readily available broad-bandwidth source for researchers and a practical enhancement to a fiber-optic optical coherence tomography system.
129 citations
TL;DR: In this article, the development and use of sonochemically generated microsphere contrast agents containing a suspension of iron-oxide particles is described. But the use of these microspheres represents a new class of magnetically-inducible optical contrast agents for diagnostic imaging techniques such as optical coherence tomography.
Abstract: We present the development and use of sonochemically-generated microsphere contrast agents containing a suspension of iron-oxide particles. These microspheres represent a new class of magnetically-inducible optical contrast agents for diagnostic imaging techniques such as optical coherence tomography.
8 citations
07 Aug 2002
TL;DR: The results suggest the feasibility of using molecular beacon hybridization in microfluidic devices for the detection of pathogenic bacteria in environmental and medical fluids.
Abstract: We present the use of molecular beacons as sensitive indicators in microfluidic bioMEM devices. A method has been developed to study mixing and hybridization of molecular beacons to target nucleic acids in real time in a microfluidic channel. This method allows quantification of DNA and RNA molecules in solution, i.e., without the prerequisite of an immobilization step necessary in most other hybridization formats. The detection limit for DNA was determined to be in the order of femtomoles. Our results suggest the feasibility of using molecular beacon hybridization in microfluidic devices for the detection of pathogenic bacteria in environmental and medical fluids.
4 citations
07 Nov 2002
TL;DR: A fast Fourier transform based algorithm that simultaneously corrects for the dispersion at all depths in a material, so that longer scan ranges are possible than can be compensated by optically correcting the disp immersion at a particular depth.
Abstract: We present and experimentally demonstrate a novel dispersion compensation algorithm for optical coherence tomography that can account for both material and delay-line induced dispersion. It is a fast Fourier transform based algorithm that simultaneously corrects for the dispersion at all depths in a material, so that longer scan ranges are possible than can be compensated by optically correcting the dispersion at a particular depth. Such an algorithm becomes necessary when large bandwidth illumination or a large scan range is employed. We validate the algorithm by correcting the OCT measurements of a multilayered transparent PDMS (polydimethyl siloxane) microfluidic device.
3 citations
24 May 2002
TL;DR: In this paper, a polygonal scanner based optical delay line was developed for OCT imaging, which allows for potentially higher axial scan speeds than traditional linear or resonant galvanometers while supporting higher bandwidths.
Abstract: Summary form only given. We have developed a polygonal scanner based optical delay line that allows for potentially higher axial scan speeds than traditional linear or resonant galvanometers while supporting higher bandwidths. This type of delay line is based on designs used for signal autocorrelation measurement and demonstrated for OCT. In this type of optical delay line, a grating dispersed spectrum is focused onto a planar mirror with a controllable tilt angle. Implementation will be demonstrated by the in vivo OCT imaging of Xenopus laevis (African frog) tadpole cardiac function. This optical delay line has broad applicability in the fields of medicine and biology where both high resolution and high speed OCT are required.
2 citations
07 Nov 2002
TL;DR: Spectroscopic OCT improves upon the conventional OCT system by processing the entire detected interference signal and extracting spectral information and proposes an algorithm based on the Morlet wavelet transform that can be approximated using the existing OCT system and hardware.
Abstract: Spectroscopic OCT improves upon the conventional OCT system by processing the entire detected interference signal and extracting spectral information. We implement it as a real-time process using FPGA/DSP based processing hardware. We propose an algorithm based on the Morlet wavelet transform that can be approximated using our existing OCT system and hardware. The spectral information that can be obtained by this system allows for better distinguishing of scattering properties when imaging biological tissue. We also present some of our experimental results to demonstrate the concept. The processing speed achieved by our system allows image generation at approximately the same rate as data acquisition.
2 citations
01 Jan 2002
2 citations
07 Aug 2002
TL;DR: In this article, a microfabricated blister-type device was proposed to examine the cellular response of isolated cells and multi-cellular aggregates to finite mechanical strains (1-5%).
Abstract: A methodology is presented for the design of a microfabricated blister-type device to examine the cellular response of isolated cells and multi-cellular aggregates to finite mechanical strains (1-5%):. The proposed device utilizes microfabrication technologies that incorporate the bonding, transfer, and assembly of thin (3 /spl mu/m < thickness < 100 /spl mu/m) elastic membranes onto rigid substrates with a circular hole or array of circular holes in the formation of diaphragm structures. An analysis of membrane deformations and strain fields of macro- and micro-scale polydimethylsiloxane (PDMS) diaphragm, blister-type devices demonstrates that microfabricated diaphragms can achieve finite strains corresponding to smaller axial displacements than those required for identical strains in macro-scale devices. Smaller axial displacements may decrease the confounding shear loading of the cell culture by the overlying nutrient medium. Additionally, it is shown that the uniform residual stress of a microfabricated diaphragm can be experimentally determined and utilized for more precise control of the incremental finite strains imposed on the diaphragm. Thus, microfabricated blister-type cell straining devices may potentially enhance future quantitative investigations of dynamic mechanically stimulated cell culture.
07 Apr 2002
TL;DR: In this paper, a femtosecond laser oscillator was used to control the topography of scaffolding for cell micropatterning in tissue engineering, which may be applicable to controlling the topology of scaffolds for cell microstructure fabrication.
Abstract: Micromachining of three-dimensional structures in biocompatible elastomers with a femtosecond laser oscillator is demonstrated. This technique may be applicable to controlling the topography of scaffolding for cell micropatterning in tissue engineering. 2001 Optical Society of America OCIS codes: (220.4000) Microstructure fabrication; (180.6900) 3D microscopy; (140.3440) Laser-induced breakdown
TL;DR: In this article, the authors presented a method for obtaining high-resolution images and 3D volumetric data sets from optical projection tomography (OPT) which is analogous to computed tomography.
Abstract: There are many approaches to obtaining high-resolution images and three dimensional volumetric data sets, but all have limitations. Many techniques involve reconstructing volumes of information from sections, either physical sections or optical sections. Recently, James Sharpe, Ulf Ahlgren, Paul Perry, Bill Hill, Allyson Ross, Jacob Hecksher-Sørensen, Richard Baldock, and Duncan Davidson have developed an optical technique that is analogous to computed tomography (CT). Whereas clinical CT involves an X-ray source and detector rotating around the patient, optical projection tomography (OPT) has the specimen rotating within an optical pathway.