Biomedical Engineering and Bioengineering Commons^™

Image Reconstruction In Photoacoustic Computed Tomography With Acoustically Heterogeneous Media, Chao Huang

All Theses and Dissertations (ETDs)

Photoacoustic computed tomography (PACT), also known as optoacoustic or thermoacoustic tomography, is a rapidly emerging hybrid imaging modality that combines optical image contrast with ultrasound detection. The majority of currently available PACT image reconstruction algorithms are based on idealized imaging models that assume a lossless and acoustically homogeneous medium. However, in many applications of PACT these assumptions are violated and the induced photoacoustic (PA) wavefields are scattered and absorbed as they propagate to the receiving transducers. In those applications of PACT, the reconstructed images can contain significant distortions and artifacts if the inhomogeneous acoustic properties of the object are not …

Modeling And Development Of Iterative Reconstruction Algorithms In Emerging X-Ray Imaging Technologies, Jiaofeng Xu

All Theses and Dissertations (ETDs)

Many new promising X-ray-based biomedical imaging technologies have emerged over the last two decades. Five different novel X-ray based imaging technologies are discussed in this dissertation: differential phase-contrast tomography (DPCT), grating-based phase-contrast tomography (GB-PCT), spectral-CT (K-edge imaging), cone-beam computed tomography (CBCT), and in-line X-ray phase contrast (XPC) tomosynthesis. For each imaging modality, one or more specific problems prevent them being effectively or efficiently employed in clinical applications have been discussed. Firstly, to mitigate the long data-acquisition times and large radiation doses associated with use of analytic reconstruction methods in DPCT, we analyze the numerical and statistical properties of two classes …

Submicron-Resolution Photoacoustic Microscopy Of Endogenous Light-Absorbing Biomolecules, Chi Zhang

All Theses and Dissertations (ETDs)

Photoacoustic imaging in biomedicine has the unique advantage of probing endogenous light absorbers at various length scales with a 100% relative sensitivity. Among the several modalities of photoacoustic imaging, optical-resolution photoacoustic microscopy (OR-PAM) can achieve high spatial resolution, on the order of optical wavelength, at <1 mm depth in biological tissue (the optical ballistic regime). OR-PAM has been applied successfully to structural and functional imaging of blood vasculature and red blood cells in vivo. Any molecules which absorb sufficient light at certain wavelengths can potentially be imaged by PAM. Compared with pure optical imaging, which typically targets fluorescent markers, label-free PAM avoids the major concerns that the fluorescent labeling probes may disturb the function of biomolecules and may have an insufficient density. This dissertation aims to advance label-free OR-PAM to the subcellular scale.

The first part of this dissertation describes the technological advancement of PAM yielding high spatial resolution in 3D. The lateral resolution was improved by using optical objectives with high numerical apertures for optical focusing. The axial resolution was improved by using broadband ultrasonic transducers for ultrasound detection. We achieved 220 nm lateral resolution in transmission …

Thrombin-Inhibiting Perfluorocarbon Nanoparticles: A New Class Of Therapeutic For Acute Thrombosis Treatment And Diagnosis, Jacob Wheatley Myerson

All Theses and Dissertations (ETDs)

Optimization of the mediation of acute thrombi remains a significant research challenge in the treatment of emergency conditions including heart attack and ischemic stroke. We have demonstrated that a nanoparticle carrying potent direct thrombin inhibitors can advance the treatment of acute thrombosis arising from various cardiovascular pathologies. The thrombin-inhibiting nanoparticles presented herein are designed to focus the antithrombotic impact of direct thrombin inhibitors at the site of thrombus formation and to provide imaging contrast to highlight the formation or the abatement and eventual disintegration of the thrombus.

Perfluorocarbon nanoparticles were functionalized by covalent addition of PPACK or bivalirudin to carboxy-PEG …

Elucidation Of Emergent Regional Mechanisms Of Heart Muscle Dysfunction In The Mouse Model Of Duchenne Muscular Dystrophy, Ya-Jian Cheng

All Theses and Dissertations (ETDs)

Cardiac dysfunction is a primary cause of mortality in Duchenne Muscular Dystrophy (DMD), potentially related to elevated cytosolic calcium. However, the regional versus global functional consequences of cellular calcium mishandling have not been defined in the whole heart. Here, we elucidate, for the first time, loci- and age-dependencies between calcium mishandling and myocardial sheet function as a manifestation of dystrophin-deficient cardiomyopathy. We also map calcium transients to illustrate the regional dependence of ion flux disturbances in the dystrophin-deficient (mdx) mouse heart. Furthermore, we elucidate abnormalities in autophagic processes that can be corrected with nanoparticle therapeutics delivering rapamycin to heart tissues …

Ecog Correlates Of Visuomotor Transformation, Neural Plasticity, And Application To A Force-Based Brain Computer Interface, Jordan John Williams

All Theses and Dissertations (ETDs)

Electrocorticography: ECoG) has gained increased notoriety over the past decade as a possible recording modality for Brain-Computer Interface: BCI) applications that offers a balance of minimal invasiveness to the patient in addition to robust spectral information over time. More recently, the scale of ECoG devices has begun to shrink to the order of micrometer diameter contacts and millimeter spacings with the intent of extracting more independent signals for BCI control within less cortical real-estate. However, most control signals to date, whether within the field of ECoG or any of the more seasoned recording techniques, have translated their control signals to …