Spelling suggestions: "subject:"electroacoustic microscopy""
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In vivo blood oxygenation level measurements using photoacoustic microscopySivaramakrishnan, Mathangi 17 September 2007 (has links)
We investigate the possibility of extracting accurate functional information such
as local blood oxygenation level using multi-wavelength photoacoustic measurements.
Photoacoustic microscope is utilized to acquire images of microvasculature in smallanimal
skin. Owing to endogenous optical contrast, optical spectral information obtained
from spectral photoacoustic measurements are successfully inverted to yield oxygenation
level in blood. Analysis of error propagation from photoacoustic measurements to
inverted quantities showed minimum inversion error in the optical wavelength region of
570-600 nm. To obtain accurate and vessel size independent blood oxygenation
measurements, transducers with central frequency of more than 25 MHz are needed for
the optical region of 570-600 nm used in this study. The effect of transducer focal
position on accuracy of blood oxygenation level quantification was found to be
negligible. To obtain accurate measurements in vivo, one needs to compensate for
factors such as spectral dependent optical attenuation.
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Optical Coherence Photoacoustic Microscopy (OC-PAM) for Multimodal ImagingLiu, Xiaojing 23 November 2016 (has links)
Optical coherence tomography (OCT) and Photoacoustic microscopy (PAM) are two noninvasive, high-resolution, three-dimensional, biomedical imaging modalities based on different contrast mechanisms. OCT detects the light backscattered from a biological sample either in the time or spectral domain using an interferometer to form an image. PAM is sensitive to optical absorption by detecting the light-induced acoustic waves to form an image. Due to their complementary contrast mechanisms, OCT and PAM are suitable for being combined to achieve multimodal imaging.
In this dissertation, an optical coherence photoacoustic microscopy (OC-PAM) system was developed for in vivo multimodal retinal imaging with a pulsed broadband NIR light source. To test the capabilities of the system on multimodal ophthalmic imaging, the retina of pigmented rats was imaged. The OCT images showed the retinal structures with quality similar to conventional OCT, while the PAM images revealed the distribution of melanin in the retina since the NIR PAM signals are generated mainly from melanin in the posterior segment of the eye.
By using the pulsed broadband light source, the OCT image quality highly depends on the pulse-to-pulse stability of the light source without averaging. In addition, laser safety is always a concern for in vivo applications, especially for eye imaging with a pulsed light source. Therefore, a continuous wave (CW) light source is desired for OC-PAM applications. An OC-PAM system using an intensity-modulated CW superluminescent diode was then developed. The system was tested for multimodal imaging the vasculature of a mouse ear in vivo by using Gold Nanorods (GNRs) as contrast agent for PAM, as well as excised porcine eyes ex vivo.
Since the quantitative information of the optical properties extracted from the proposed NIR OC-PAM system is potentially able to provide a unique technique to evaluate the existence of melanin and lipofuscin specifically, a phantom study has been conducted and the relationship between image intensity of OCT and PAM was interpreted to represent the relationship between the optical scattering property and optical absorption property. It will be strong evidence for practical application of the proposed NIR OC-PAM system.
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Inverse opal scaffolds and photoacoustic microscopy for regenerative medicineZhang, Yu 13 January 2014 (has links)
This research centers on the fabrication, characterization, and engineering of inverse
opal scaffolds, a novel class of three-dimensional (3D) porous scaffolds made of
biocompatible and biodegradable polymers, for applications in tissue engineering and
regenerative medicine. The unique features of an inverse opal scaffold include a highly
ordered array of pores, uniform and finely tunable pore sizes, high interconnectivity, and
great reproducibility.
The first part of this work focuses on the fabrication and functionalization of inverse
opal scaffolds based on poly(D,L-lactic-co-glycolic acid) (PLGA), a biodegradable
material approved by the U.S. Food and Drug Administration (FDA). The advantages of
the PLGA inverse opal scaffolds are also demonstrated by comparing with their
counterparts with spherical but non-uniform pores and poor interconnectivity.
The second part of this work shows two examples where the PLGA inverse opal
scaffolds were successfully used as a well-defined system to investigate the effect of pore
size of a 3D porous scaffold on the behavior of cell and tissue growth. Specifically, I
have demonstrated that i) the differentiation of progenitor cells in vitro was dependent on
the pore size of PLGA-based scaffolds and the behavior of the cells was determined by
the size of individual pores where the cells resided in, and ii) the neovascularization
process in vivo could be directly manipulated by controlling a combination of pore and
window sizes when they were applied to a mouse model.
The last part of this work deals with the novel application of photoacoustic
microscopy (PAM), a volumetric imaging modality recently developed, to tissue
engineering and regenerative medicine, in the context of non-invasive imaging and
quantification of cells and tissues grown in PLGA inverse opal scaffolds, both in vitro
and in vivo. Furthermore, the capability of PAM to monitor and quantitatively analyze
the degradation of the scaffolds themselves was also demonstrated.
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