Nate Kemp

Bio: Nate Kemp is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Optical tomography & Optical coherence tomography. The author has an hindex of 3, co-authored 5 publications receiving 50 citations.

Detection of macrophages in atherosclerotic tissue using magnetic nanoparticles and differential phase optical coherence tomography.

Abstract: We demonstrate the detection of iron oxide nanoparticles taken up by macrophages in atherosclerotic plaque with differential phase optical coherence tomogra- phy DP-OCT. Magneto mechanical detection of nano- particles is demonstrated in hyperlipidemic Watanabe and balloon-injured fat-fed New Zealand white rabbits in- jected with monocrystalline iron oxide nanoparticles MI- ONs of 40 nm diam. MIONs taken up by macrophages was excited by an oscillating magnetic flux density and resulting nanometer tissue surface displacement was de- tected by DP-OCT. Frequency response of tissue surface displacement in response to an externally applied mag- netic flux density was twice the stimulus frequency as ex- pected from the equations of motion for the nanoparticle cluster. © 2008 Society of Photo-Optical Instrumentation Engineers.

Gas-Cell Referenced Swept Source Phase Sensitive Optical Coherence Tomography

Abstract: Distinct reference and signal interferometers in combination with a gas-cell spectral reference are employed to increase sensitivity and environmental stability of a swept source phase-sensitive optical coherence tomography. A displacement sensitivity (DS) of 65 pm at 280-μm depth and DS degradation with depth of 0.0015 rad/mm is achieved. Differential DS of 234 pm in a 127-μm -thick scattering phantom is six-fold superior to previously reported values. DS degradation with a depth of 0.026 rad/mm is reported for tissue-like scattering phantoms. Measured depth-dependent DS suggests that digitization time jitter noise contributes to degradation of phase sensitivity with depth.

Safety and efficacy of frequency domain optical coherence tomography in pigs

Abstract: AIMS To determine the safety and efficacy of frequency domain OCT, which can scan at much higher rates and make it possible to avoid an occlusion balloon and image during an angiographic injection through guide catheter. The catheters have diameters ranging from 2.7 to 3.5 Fr. The presence of the imaging catheter increases fluid resistance to the injection of viscous solutions necessary for clearing the blood. METHODS AND RESULTS The Volcano 3.5 Fr frequency domain OCT catheter system was investigated for safety in (a) n=10 porcine studies using acute and 30-day histology, and (b) for efficacy in n=9 in vivo porcine coronary arteries. We found: (a) frequency domain imaging is safe in the porcine model using histology as an endpoint; (b) the addition of a viscous contrast (iodixonal) to saline is superior for lumen clearance compared to saline alone; (c) hand injection, 4 ml/sec, and 6 ml/sec power injection all provided similar vessel wall clearance; (d) the anticipated loss of vessel wall visualisation with left main injection (due to half the injectate in the non-imaged vessel) was not evident in proximal and middle coronary artery OCT catheter positions. CONCLUSIONS Frequency domain OCT is safe and efficacious in the porcine model.

Forward-Imaging Swept Source Optical Coherence Tomography using Silicon MEMS Scanner for High-Speed 3-D Volumetric Imaging

Abstract: We demonstrate a fiber-based forward-imaging swept source OCT (SS-OCT) system using a two-axis silicon micromachined vertical comb-drive microscanner for high-speed, 3-D imaging of biological specimens. Higher signal-to-noise ratio of SS-OCT over traditional time-domain techniques, combined with low beam-steering loss of silver-coated scanning micromirrors with over 90% reflectivity, provide good imaging performance. Fast wavelength scanning of the laser source (scan rate: 20 kHz) over 110 nm spectral bandwidth enabled image acquisition at 8 million voxels/sec (3-D imaging) or 40 fps (2-D imaging, 500 transverse pixels per image). We successfully acquired en face and tomographic in vitro images of rigid structures (microscanner), soft materials (onion and pickle slices), and in vivo images of epidermis. Lateral resolution of 12.5 mum and axial resolution of 10 mum over a 2x1times4 mm3 imaging volume has been demonstrated. The compact forward-imaging OCT probe may be suitable for image-guided minimal-invasive examination of various diseased tissues.

In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomography

Abstract: Current medical imaging technologies allow visualization of tissue anatomy in the human body at resolutions ranging from 100 micrometers to 1 millimeter. These technologies are generally not sensitive enough to detect early-stage tissue abnormalities associated with diseases such as cancer and atherosclerosis, which require micrometer-scale resolution. Here, optical coherence tomography was adapted to allow high-speed visualization of tissue in a living animal with a catheter-endoscope 1 millimeter in diameter. This method, referred to as "optical biopsy," was used to obtain cross-sectional images of the rabbit gastrointestinal and respiratory tracts at 10-micrometer resolution.

Akinetic all-semiconductor programmable swept-source at 1550 nm and 1310 nm with centimeters coherence length

Abstract: We demonstrate, for the first time, OCT imaging capabilities of a novel, akinetic (without any form of movement in the tuning mechanism), all-semiconductor, all-electronic tunable, compact and flexible swept source laser technology at 1550 nm and 1310 nm. To investigate its OCT performance, 2D and 3D ex vivo and in vivo OCT imaging was performed at different sweep rates, from 20 kHz up to 200 kHz, with different axial resolutions, about 10 µm to 20 µm, and at different coherence gate displacements, from zero delay to >17 cm. Laser source phase linearity and phase repeatability standard deviation of <2 mrad (<160 pm) were observed without external phase referencing, indicating that the laser operated close to the shot noise limit (~2 × factor); constant percentile wavelengths variations of sliding RIN and ortho RIN <0.2% could be demonstrated, ~5 times better as compared to other swept laser technologies.

Stable Citrate-Coated Iron Oxide Superparamagnetic Nanoclusters at High Salinity

Abstract: Superparamagnetic nanoclusters may be used in imaging in biomedicine and in mapping of petroleum reservoirs, by generating either ultrasonic or acoustic signals with oscillating magnetic motion. For a given magnetization per weight of iron oxide, nanoclusters with diameters from 20 to 100 nm experience a much larger magnetic force than that of the primary sub-10-nm primary particles. Aqueous dispersions of 0.1 wt % superparamagnetic iron oxide nanoclusters were stabilized with citric acid on the particle surface, with a high loading of 90% iron oxide. The dispersions were stable for months even with high salt concentrations up to 4 wt % at a pH of 6 and 8 based on the hydrodynamic diameter from dynamic light scattering. The citrate ligands provide electrostatic repulsion, as characterized by the ζ potential. The small size of the clusters, superparamagnetic properties, and high salt tolerance are highly beneficial in various applications including the mapping of petroleum reservoirs with magnetomotive tec...

Determination of oil saturation in reservoir rock using paramagnetic nanoparticles and magnetic field

Abstract: Methods for detection of the presence and distribution of oil in subsurface formation are described herein. The present invention involves injection of an aqueous dispersion of the nanoparticles into the potentially oil containing subsurface formation, followed by a remote detection of the oscillation responses of the nanoparticles in the oil/water interfaces in the reservoir rock by applying magnetic field.