Application of Sparse Modeling to Ultrasound and Photoacoustic Microscopy

Diagnostic ultrasound imaging is a mainstay of modern clinical medicine. While ultrasound is relatively inexpensive, portable, does not use ionizing radiation and is versatile as a diagnostic tool, its contrast is limited by artifacts, thus limiting its effectiveness. Photoacoustic microscopy leverages the specificity of endogenous optical absorption to obtain high resolution and contrast images of the microvasculature. Additionally, the utility of photoacoustic microscopy has been extended to functional imaging by imaging blood flow speed in the microvasculature. However, photoacoustic microscopy is associated with similar artifacts as in diagnostic ultrasound imaging, and dense spatial sampling is necessary to estimate blood flow, which may lead to safety considerations regarding laser fluence in tissue. Sparse modeling leverages redundancy in data to obtain parsimonious representations. Sparse modeling has been employed in other imaging modalities, such as magnetic resonance imaging (MRI), and its applications in ultrasound and photoacoustic microscopy are an emerging area of interest. In this dissertation, the utility of sparse modeling in suppressing quasi-static artifacts in echocardiography is demonstrated. Additionally, the suppression of reverberant artifacts in photoacoustic microscopy using sparse modeling is demonstrated. Finally, photoacoustic data are sparsely modeled, and blood flow speed measurements are recovered from undersampled observations using sparse modeling.

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