Catheter for intravascular ultrasound and photoacoustic imaging

A design and a fabrication method for an intravascular imaging and therapeutic catheters for combined ultrasound, photoacoustic, and elasticity imaging and for optical and/or acoustic therapy of hollow organs and diseased blood vessels and tissues are disclosed in the present invention. The invention comprises both a device—optical fiber-based intravascular catheter designs for combined IVUS/IVPA, and elasticity imaging and for acoustic and/or optical therapy—and a method of combined ultrasound, photoacoustic, and elasticity imaging and optical and/or acoustic therapy. The designs of the catheters are based on single-element catheter-based ultrasound transducers or on ultrasound array-based units coupled with optical fiber, fiber bundles or a combination thereof with specially designed light delivery systems. One approach uses the side fire fiber, similar to the one utilized for biomedical optical spectroscopy. The second catheter design uses the micro-optics in the manner of a probe for optical coherent tomography.Board of Regents, University of Texas Syste

Combined ultrasound and photoacoustic imaging of metal objects

Methods of combined ultrasound and photoacoustic imaging are provided. In some embodiments, the methods may be used to determine the location or positioning of a metal object in a sample. In other embodiments, the methods may be used to determine the composition of a sample surrounding a metal object. Other methods are also provided.Board of Regents, University of Texas Syste

Multimodal characterization of compositional, structural and functional features of human atherosclerotic plaques

Detection of atherosclerotic plaque vulnerability has critical clinical implications for avoiding sudden death in patients with high risk of plaque rupture. We report on multimodality imaging of ex-vivo human carotid plaque samples using a system that integrates fluorescence lifetime imaging (FLIM), ultrasonic backscatter microscopy (UBM), and photoacoustic imaging (PAI). Biochemical composition is differentiated with a high temporal resolution and sensitivity at the surface of the plaque by the FLIM subsystem. 3D microanatomy of the whole plaque is reconstructed by the UBM. Functional imaging associated with optical absorption contrast is evaluated from the PAI component. Simultaneous recordings of the optical, ultrasonic, and photoacoustic data present a wealth of complementary information concerning the plaque composition, structure, and function that are related to plaque vulnerability. This approach is expected to improve our ability to study atherosclerotic plaques. The multimodal system presented here can be translated into a catheter based intraluminal system for future clinical studies

Feasibility of optical coherence elastography measurements of shear wave propagation in homogeneous tissue equivalent phantoms

In this work, we explored the potential of measuring shear wave propagation using optical coherence elastography (OCE) based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a 20 MHz piezoelectric transducer (circular element 8.5 mm diameter) transmitting sine-wave bursts of 400 μs, synchronized with the OCT swept source wavelength sweep. The acoustic radiation force (ARF) was applied to two gelatin phantoms (differing in gelatin concentration by weight, 8% vs. 14%). Differential OCT phase maps, measured with and without the ARF, demonstrate microscopic displacement generated by shear wave propagation in these phantoms of different stiffness. We present preliminary results of OCT derived shear wave propagation velocity and modulus, and compare these results to rheometer measurements. The results demonstrate the feasibility of shear wave OCE (SW-OCE) for high-resolution microscopic homogeneous tissue mechanical property characterization

Model validation for a noninvasive arterial stenosis detection problem

Copyright @ 2013 American Institute of Mathematical SciencesA current thrust in medical research is the development of a non-invasive method for detection, localization, and characterization of an arterial stenosis (a blockage or partial blockage in an artery). A method has been proposed to detect shear waves in the chest cavity which have been generated by disturbances in the blood flow resulting from a stenosis. In order to develop this methodology further, we use both one-dimensional pressure and shear wave experimental data from novel acoustic phantoms to validate corresponding viscoelastic mathematical models, which were developed in a concept paper [8] and refined herein. We estimate model parameters which give a good fit (in a sense to be precisely defined) to the experimental data, and use asymptotic error theory to provide confidence intervals for parameter estimates. Finally, since a robust error model is necessary for accurate parameter estimates and confidence analysis, we include a comparison of absolute and relative models for measurement error.The National Institute of Allergy and Infectious Diseases, the Air Force Office of Scientific Research, the Deopartment of Education and the Engineering and Physical Sciences Research Council (EPSRC)

Combining optical coherence tomography with acoustic radiation force for depth-dependent biomechanics of crystalline lens

Noninvasively probing the biomechanical properties of crystalline lens has been challenging due to its unique features such as location inside the eye and being optically and ultrasonically transparent. Here we introduce a method of relying on the spectral analysis of the lens surface response to a mechanical stimulation for the depthdependent assessment of lens biomechanical properties. In this method, acoustic radiation force (ARF) is used to remotely induce the deformation on the surface of the crystalline lens, and a phase-sensitive optical coherence tomography (PhS-OCT) system, co-focused with ARF, utilized to monitor the localized temporal response of ARFinduced deformations on the lens surface. The dominant frequency from the amplitude spectra of the surface response is obtained as the indicator of the depthwise elasticity distribution. Pilot experiments were performed on tissue-mimicking layered phantoms and ex vivo porcine crystalline lens. Results indicate that the frequency response of the sample surface is contributed by the mechanical properties of layers located at different depths and the depthdependent elastic properties can be revealed from the amplitude spectrum. Further study will be focused on combining the experimental measurements with theoretical model and inverse numerical method for depth-resolved elastography of the crystalline lens

Controlling aqueous sorption of humic substances on silica gel by directed alkoxysilyl-derivatization of their functionalities.

In this study we explored a possibility for enhancing aqueous sorption of humic substances (HS) onto hydroxylated surfaces (e.g., silica gel) by increasing modification rate of their most abundant functional groups - carboxyls with mineral-adhesive alkoxysilyl moieties. The synthesis included treatment of dried humic material with 3-aminopropyl trimethoxy silane (APTS) capable of forming amide bonds with carboxyl groups of HS under anhydrous conditions. The reaction was run at six different HS to APTS ratio for achieving different modification degrees of the carboxyl groups in the humic backbone. The obtained derivatives were characterized using elemental analysis, 13C NMR Spectroscopy, Fourier transform infrared spectroscopy, and size exclusion chromatography that confirmed quantitative incorporation of alkoxysilyl-moieties into HS structure. Aqueous adsorption was investigated in 0.028 M phosphate buffer using silica gel as a surrogate for mineral surface. Both distribution coefficients as well adsorption capacities paralleled the amount of alkoxysilyl-moieties incorporated into backbone of the parental HS. The adsorption capacity reached its maximum value of 210 mg of HS per g of SiO2 for the APTS derivative synthesized at the equimolar reagent ratio. This value was comparable to the amount of the same HS immobilized onto the APTS-treated silica gel (265 mg of HS per g of SiO2). Adsorption of alkoxysilyl-derivatives was found to be irreversible under conditions studied. Conclusively, we believe that the directed modification of HS by incorporating alkoxysilyl-moieties is well suited for producing humic derivatives with controllable affinity for aqueous sorption onto hydroxylated surfaces