Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Oceanography." Includes bibliographical references (p. 22-27).

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 29, 2007) Vita. Includes bibliographical references.

A photoacoustic spectrometer was developed and built for measuring absorption of light by collected particles. Major advantages of the photoacoustic method are that it measures absorption directly, it is insensitive to scattered light, and it is readily used at different wavelengths. To evaluate the performance of the spectrometer, comparisons were made between photoacoustic absorption spectra and spectra calculated with Mie thoery. Pure powders with varied optical properties were used in the comparison, including carbon, hematite, and others. Results were reasonable in both absolute magnitude and spectral shape. Aerosol particles were collected in different environments in southern Arizona under background conditions in the mid-troposphere, and in a moderately polluted city. Results for the two locations, and two size ranges, are compared and contrasted in this thesis. Absolute magnitudes of absorption coefficients, measured at green wavelengths, are used to summarize many important results. Absorption by fine urban aerosol was 6 ± 4 x 10⁻⁷ m⁻¹, and four times larger than absorption by coarse urban aerosol. Normalized photoacoustic absorption spectra for urban aerosol are uniform with wavelength; background aerosol spectra have a relative increase in absorption at near UV wavelengths compared to near IR wavelengths. Urban aerosol absorption can be attributed to carbon particles larger than approximately 0.1 micron. Absorption by hematite (alpha iron oxide) particles in more strongly wavelength dependent than absorption by carbon particles, of the same size. This wavelength dependence is still not great enough to be attributed to hematite alone--although submicron hematite particles may be the dominant absorber in coarse background aerosol. (Abstract shortened with permission of author.)

University of Macau / Faculty of Health Sciences

Thesis (doctoral)--Universität der Bundeswehr, München, 2000. / Includes bibliographical references (p. 165-172).

By integrating three complementary imaging techniques - ultrasound, elasticity and photoacoustic imaging, a hybrid imaging system utilizing an array transducer is proposed for various biomedical imaging applications including cancer detection, diagnosis and therapy monitoring. Simultaneous imaging of the anatomy (ultrasound imaging), changes in biomechanical properties (elasticity imaging) and cancer-induced angiogenesis (photoacoustic imaging) of tissue is based on many synergistic features of these modalities and may result in a unique and important imaging tool. In this study, numerical analysis and experimental studies are presented to demonstrate the feasibility, to evaluate the performance, and also to improve the quality of the combined array-based ultrasound, elasticity and photoacoustic imaging system. To estimate spatial resolution, a point source was imaged using ultrasound and photoacoustic imaging modes. Then, several tissue mimicking phantoms were examined using ultrasound, photoacoustic and elasticity imaging. In elasticity imaging, ultrasound frames were acquired during deformation of the tissue. To reduce the data acquisition time of the system, high frame rate imaging was used. High frame rate imaging is possible by transmitting a broader and less focused ultrasound beam but the image quality is sacrificed. Thus, we compared the quality of the high frame rate and conventional ultrasound images. In photoacoustic imaging, acoustic transients are generated simultaneously in the entire volume of the laser irradiated tissue. Hence, image formation (beamforming) algorithms were developed based on the characteristics of the photoacoustic signals. Then, adaptive beamforming method is suggested to improve the image quality of the photoacoustic imaging. The results of the numerical analyses and experimental studies clearly indicate that ultrasound, elasticity and photoacoustic imaging techniques complement each other and together provide critical information needed for the reliable detection and diagnosis of diseases. / text

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Research in biology and medicine depends heavily on what we can measure. Photoacoustic imaging techniques allow for imaging both structural and functional information simultaneously. Current photoacoustic imaging technology is limited by either the speed at which the images are formed or resolution of the images. By increasing the resonant frequency at which the transducers receive photoacoustic signals, the resolution of a photoacoustic tomography setup can be improved without compromising on imaging speed. Due to their size, the resulting transducers must be placed directly onto a complementary metal-oxide-semiconductor (CMOS) integrated circuit (IC). This thesis describes a fabrication flow and electronics design that opens the door to high speed, high resolution photoacoustic imaging. A microfabrication flow is developed to place high frequency polyvinylidene fluoride transducers onto an integrated circuit. A 1-D array of transducers are fabricated and characterized on a CMOS IC. The custom IC (TSMC 90 nm) is designed to amplify the signals coming from the small transducers using a proposed two-stage LNA. The circuit is electrically characterized before and after transducer fabrication showcasing the CMOS-compatible nature of the fabrication flow. The transducers and integrated circuit are characterized in a photoacoustic setup using two phantoms to verify the functionality of the system. Compared to similar systems, this system displays monolthically integrated transducers that receive broadband responses centered at 35 MHz with 140 bandwidth.

Optoacoustic spectroscopy is a relatively old technique first described by Alexander Graham Bell in 1881. However, over the intervening years, little use was made of the technique due to its low sensitivity. This was due to low source intensities of available infrared light sources which limited the optoacoustic signal strength. With the advent of laser infrared light sources in the 1960's, there has been a resurgence of interest in optoacoustics. No longer is low source intensity a major limitation to successful optoacoustic spectroscopy. Although adequate infrared light sources are available, the large window background signal observed in all optoacoustic systems has been the major limitation in extending trace gas detection limits to the ppb or sub-ppb level. Similarly, there has been little demonstration of the use of the optoacoustic technique in environments where mixtures of gases are present which have severe spectral overlap. This work will discuss a new windowless cell design that largely eliminates the signal background problem ubiquitous to all presently available optoacoustic cells. New methodologies will be discussed that allow analyses of mixtures to be performed even in cases where spectral overlap is severe. Limitations to both the windowless cell and the various multicomponent analysis strategies are discussed.