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You searched for subject:(dynamic speckle). Showing records 1 – 3 of 3 total matches.

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University of Texas – Austin

1. Davis, Mitchell Alan. Three dimensional simulation of functional neuro-vascular imaging.

Degree: PhD, Electrical and Computer Engineering, 2014, University of Texas – Austin

Functional optical imaging has become a powerful tool for measuring physiological parameters in the brain without disrupting normal physiology. Fluorescence lifetime imaging (FLIM) has been shown to allow near real time mapping of oxygen tension in plasma (pO2), and Laser Speckle Contrast Imaging (LSCI) has been demonstrated to provide qualitative assessments of blood flow in the cortex. However, as both of these methods provide physiological parameters based on the spatial sampling of photons arriving at a detector, it is crucially important to understand either where the photons originated, in the case of FLIM, or which moving particles the photons have sampled, in the case of LSCI. Traditionally, these questions have been difficult to solve because of the heterogeneity of the distribution of particles which contribute to the measured signal. In both FLIM and LSCI, for example, only the light which samples the intravascular space will contribute to the signal. While analytical methods have proven to be successful at predicting the imaging depth of homogeneous materials, they are not able to predict imaging depth when measuring a fluorophore or a moving particle that is only present inside blood vessels. Unlike analytical methods, numerical methods can be used to approximate light propagation in an arbitrary geometry. While both deterministic and stochastic models of light propagation can, and have been, successfully employed to determine light fluence in an arbitrary geometry, deterministic methods are not well suited to the task of simulating light propagation in large volumes of turbid media. For this reason, three dimensional Monte Carlo simulations of light propagation combined with high resolution vascular anatomy were used to directly simulate FLIM and LSCI in the brain. Using these simulations, the imaging depth, degree of multiple scattering, and sensitivity of LSCI and FLIM to physiological changes were determined. Advisors/Committee Members: Dunn, Andrew Kenneth, 1970- (advisor), Pearce, John (committee member), Thomas, Robert (committee member), Tunnell, James (committee member), Ling, Hao (committee member).

Subjects/Keywords: Laser-tissue interactions; Vascular fluorescence imaging; Speckle contrast imaging; Dynamic light scattering; Blood flow imaging

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APA (6th Edition):

Davis, M. A. (2014). Three dimensional simulation of functional neuro-vascular imaging. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/38225

Chicago Manual of Style (16th Edition):

Davis, Mitchell Alan. “Three dimensional simulation of functional neuro-vascular imaging.” 2014. Doctoral Dissertation, University of Texas – Austin. Accessed January 27, 2021. http://hdl.handle.net/2152/38225.

MLA Handbook (7th Edition):

Davis, Mitchell Alan. “Three dimensional simulation of functional neuro-vascular imaging.” 2014. Web. 27 Jan 2021.

Vancouver:

Davis MA. Three dimensional simulation of functional neuro-vascular imaging. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2014. [cited 2021 Jan 27]. Available from: http://hdl.handle.net/2152/38225.

Council of Science Editors:

Davis MA. Three dimensional simulation of functional neuro-vascular imaging. [Doctoral Dissertation]. University of Texas – Austin; 2014. Available from: http://hdl.handle.net/2152/38225


University of Texas – Austin

2. Parthasarathy, Ashwin Bharadwaj. Quantitative cerebral blood flow measurement with Multi Exposure Speckle Imaging.

Degree: PhD, Biomedical Engineering, 2010, University of Texas – Austin

Cerebral blood flow (CBF) measures are central to the investigation of ischemic strokes, spreading depressions, functional and neuronal activation. Laser Speckle Contrast Imaging (LSCI) is an optical imaging technique that has been used to obtain CBF measures in vivo at high spatial and temporal resolutions, by quantifying the localized spatial blurring of backscattered coherent light induced by blood flow. Despite being widely used for biomedical applications, LSCI's critical limitations such as its tendency to underestimate large flow changes and its inability to accurately estimate CBF through a thinned skull have not been overcome. This dissertation presents a new Multi Exposure Speckle Imaging (MESI) technique that combines a new instrument and mathematical model to overcome these limitations. Additionally, in a pilot clinical study, an adapted neurosurgical microscope was used to obtain intra-operative LSCI images of CBF in humans. The MESI instrument accurately estimates experimental constants by imaging backscattered speckles over a wide range of the camera's exposure durations. The MESI mathematical model helps account for light that has scattered from both static and moving particles. In controlled flow experiments using tissue simulating phantoms, the MESI technique was found to estimate large changes in flow accurately and the estimates of flow changes were found to be unaffected by the presence of static particles in these phantoms. In an in vivo experiment in which the middle cerebral artery in mice was occluded to induce ~100% reduction in CBF, not only was the reduction in CBF accurately estimated by the MESI technique but these estimates of CBF changes were found to be unaffected by the presence of a thinned skull. The validity of statistical models used to derive the MESI mathematical model was confirmed using in vivo dynamic light scattering (DLS) measurements of CBF in mice. The MESI technique's potential to estimate absolute values of CBF in vivo was demonstrated by comparing CBF estimates obtained using the MESI technique to DLS measurements. The MESI technique's ability to measure CBF changes quantitatively through a thinned skull makes it particularly useful in chronic and long term studies leading to the development of better, more accurate stroke models. Advisors/Committee Members: Dunn, Andrew Kenneth, 1970- (advisor), Milner, Thomas (committee member), Tunnell, James (committee member), Emelianov, Stanislav (committee member), Fox, Douglas (committee member).

Subjects/Keywords: Laser Speckle Contrast Imaging; Multi Exposure Speckle Imaging; Optical blood flow measurements; LSCI; MESI; Cerebral blood flow; Ischemic stroke; Speckle spectroscopy; Dynamic Light Scattering; Intra-operative imaging

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Parthasarathy, A. B. (2010). Quantitative cerebral blood flow measurement with Multi Exposure Speckle Imaging. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2010-05-996

Chicago Manual of Style (16th Edition):

Parthasarathy, Ashwin Bharadwaj. “Quantitative cerebral blood flow measurement with Multi Exposure Speckle Imaging.” 2010. Doctoral Dissertation, University of Texas – Austin. Accessed January 27, 2021. http://hdl.handle.net/2152/ETD-UT-2010-05-996.

MLA Handbook (7th Edition):

Parthasarathy, Ashwin Bharadwaj. “Quantitative cerebral blood flow measurement with Multi Exposure Speckle Imaging.” 2010. Web. 27 Jan 2021.

Vancouver:

Parthasarathy AB. Quantitative cerebral blood flow measurement with Multi Exposure Speckle Imaging. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2010. [cited 2021 Jan 27]. Available from: http://hdl.handle.net/2152/ETD-UT-2010-05-996.

Council of Science Editors:

Parthasarathy AB. Quantitative cerebral blood flow measurement with Multi Exposure Speckle Imaging. [Doctoral Dissertation]. University of Texas – Austin; 2010. Available from: http://hdl.handle.net/2152/ETD-UT-2010-05-996

3. Young, Anthony M. Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow.

Degree: MS, Physics, 2018, Miami University

This thesis presents data from a series of experiments that investigate the ability of laser speckle contrast imaging (LSCI) to sense changes in flow in turbid media. I first provide a theoretical overview and a description of the experimental approach used in this flow imaging technique. Experimental validation of the technique’s ability to sense induced changes in blood flow in the human forearm is demonstrated. Then, the technique’s sensitivity to buried flow in controlled optical phantoms is examined. It is shown that the buried depth and optical properties of the media surrounding flow impact the measured flow indices. Lastly, a study shows how the polarization state of the imaged light impacts the flow measurements as a function of the buried depth and rate of the flow. The results demonstrate that the measurements are dependent on the flow rates and optical properties of the sample as well as the imaging setup used to capture the speckle. Advisors/Committee Members: Vishwanath, Karthik (Advisor).

Subjects/Keywords: Biomedical Research; Biophysics; Optics; Medical Imaging; Physics; laser speckle; laser speckle contrast imaging; flow imaging; dynamic light scattering; coherence imaging; biomedical imaging; blood flow measurement; flow phantom

…of speckle patterns and that which relates dynamic speckle to the velocity of scatterers. A… …21 Figure 10. Schematic of the imaging system used to collect speckle images. Flip mirrors… …22 Figure 11. The raw speckle image (Fig. 11a) and the LSCI flow map of 𝜏c-1… …16b used to collect speckle images. D: Ground diffuser; BE: Beam expander; P1: Illumination… …29 Figure 17. An image of the flow phantom (Fig. 17a) and captured raw speckle… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Young, A. M. (2018). Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow. (Masters Thesis). Miami University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362

Chicago Manual of Style (16th Edition):

Young, Anthony M. “Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow.” 2018. Masters Thesis, Miami University. Accessed January 27, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362.

MLA Handbook (7th Edition):

Young, Anthony M. “Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow.” 2018. Web. 27 Jan 2021.

Vancouver:

Young AM. Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow. [Internet] [Masters thesis]. Miami University; 2018. [cited 2021 Jan 27]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362.

Council of Science Editors:

Young AM. Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow. [Masters Thesis]. Miami University; 2018. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362

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