Biomedical Commons^™

Scatter Estimation And Correction For Experimental And Simulated Data In Multi-Slice Computed Tomography Using Machine Learning And Minimum Least Squares Methods, Cornelia Wang

McKelvey School of Engineering Theses & Dissertations

Current research aims to reduce the stopping power ratio prediction error in the inputs to the proton therapy planning process to less than 1%, which allows for improved radiation therapy planning. Our present study on reducing SPR error neglects the effect of scattering, which can increase SPR error by as much as 1-1.5%. The idea is that for each source-to-detector pair, 24 mm collimation data is close to 3 mm collimation data but with increased signal due to scattering. The goal is to estimate 3 mm collimation data from 24 mm collimation data. Pairs of sinograms, both experimental data and …

Optimization Of Gpu-Accelerated Iterative Ct Reconstruction Algorithm For Clinical Use, Tao Ge

McKelvey School of Engineering Theses & Dissertations

In order to transition the GPU-accelerated CT reconstruction algorithm to a more clinical environment, a graphical user interface is implemented. Some optimization methods on the implementation are presented. We describe the alternating minimization (AM) algorithm as the updating algorithm, and the branchless distance-driven method for the system forward operator. We introduce a version of the Feldkamp-Davis-Kress algorithm to generate the initial image for our alternating minimization algorithm and compare it to a choice of a constant initial image. For the sake of better rate of convergence, we introduce the ordered-subsets method, find the optimal number of ordered subsets, and discuss …

Development And Applications Of Novel Fluorescent Molecular Probe Strategies, Dolonchampa Maji

McKelvey School of Engineering Theses & Dissertations

Optical imaging and spectroscopy technologies offer the ability to provide structural and functional information in a fast, low-cost, ionizing radiation free, highly sensitive and high throughput fashion. The diverse contrast mechanisms and complementary imaging platforms form the foundation for the application of optical imaging in pre-clinical studies of pathophysiological development as well as direct clinical application as a tool for diagnosis and therapy. Fluorescence imaging techniques have been one of the most rapidly adopted methods in biology and biomedicine. Visualization of biological processes and pathologic conditions at the cellular and tissue levels largely relies on the use of exogenous fluorophores …

Pet/Mr Imaging Of Hypoxic Atherosclerotic Plaque Using 64cu-Atsm, Xingyu Nie

McKelvey School of Engineering Theses & Dissertations

ABSTRACT OF THE DISSERTATION

PET/MR Imaging of Hypoxic Atherosclerotic Plaque Using 64Cu-ATSM

by

Xingyu Nie

Doctor of Philosophy in Biomedical Engineering

Washington University in St. Louis, 2017

Professor Pamela K. Woodard, Chair

Professor Suzanne Lapi, Co-Chair

It is important to accurately identify the factors involved in the progression of atherosclerosis because advanced atherosclerotic lesions are prone to rupture, leading to disability or death. Hypoxic areas have been known to be present in human atherosclerotic lesions, and lesion progression is associated with the formation of lipid-loaded macrophages and increased local inflammation which are potential major factors in the formation of vulnerable …

Using Pet/Mri To Assess Hepatic Radioembolization Of Yttrium-90 Microspheres, Nichole Millward Maughan

McKelvey School of Engineering Theses & Dissertations

Radioembolization of yttrium-90 (Y-90) microspheres is used to treat primary and secondary cancers in the liver. Though this therapy has existed for decades, the treatment is not well optimized from treatment planning to post-procedural assessment. Recently, there has been a surge to utilize the small positron yield from the radioactive decay of Y-90 for post-radioembolization positron emission tomography (PET) imaging of the microsphere activity distribution. These images provide promise for dosimetry assessment, identifying extrahepatic uptake and possible under-dosed lesions that may benefit from subsequent therapy. However, due to the low positron statistics and high flux of Bremsstrahlung radiation, PET imaging …

The Electrophysiology Of Resting State Fmri Networks, Carl David Hacker

McKelvey School of Engineering Theses & Dissertations

Traditional research in neuroscience has studied the topography of specific brain functions largely by presenting stimuli or imposing tasks and measuring evoked brain activity. This paradigm has dominated neuroscience for 50 years. Recently, investigations of brain activity in the resting state, most frequently using functional magnetic resonance imaging (fMRI), have revealed spontaneous correlations within widely distributed brain regions known as resting state networks (RSNs). Variability in RSNs across individuals has found to systematically relate to numerous diseases as well as differences in cognitive performance within specific domains. However, the relationship between spontaneous fMRI activity and the underlying neurophysiology is not …

New Tools For Viscoelastic Spectral Analysis, With Application To The Mechanics Of Cells And Collagen Across Hierarchies, Behzad Babaei

McKelvey School of Engineering Theses & Dissertations

Viscoelastic relaxation spectra are essential for predicting and interpreting the mechanical responses of materials and structures. For biological tissues, these spectra must usually be estimated from viscoelastic relaxation tests. Interpreting viscoelastic relaxation tests is challenging because the inverse problem is expensive computationally. We present here (1) an efficient algorithm and (2) a quasi-linear model that enable rapid identification of the viscoelastic relaxation spectra of both linear and nonlinear materials. We then apply these methods to develop fundamental insight into the mechanics of collagenous and fibrotic tissues.

The first algorithm, which we term the discrete spectral approach, is fast enough to …

Neural Representation Of Vocalizations In Noise In The Primary Auditory Cortex Of Marmoset Monkeys, Ruiye Ni

McKelvey School of Engineering Theses & Dissertations

Robust auditory perception plays a pivotal function in processing behaviorally relevant sounds, particularly when there are auditory distractions from the environment. The neuronal coding enabling this ability, however, is still not well understood. In this study we recorded single-unit activity from the primary auditory cortex of alert common marmoset monkeys (Callithrix jacchus) while delivering conspecific vocalizations degraded by two different background noises: broadband white noise (WGN) and vocalization babble (Babble).

Noise effects on single-unit neural representation of target vocalizations were quantified by measuring the response similarity elicited by natural vocalizations as a function of signal-to-noise ratio (SNR). Four consistent response …

Translational Photoacoustic Tomography, Yong Zhou

McKelvey School of Engineering Theses & Dissertations

Combining optical excitation and ultrasonic detection, photoacoustic tomography (PAT) offers deep imaging with high resolution. With optical excitation, PAT maintains the high contrast of optical imaging. Because of the low scattering of ultrasonic waves in tissue, PAT achieves high spatial resolution at depths. Several advantages make PAT suitable for clinical application, including its scalable penetration and resolution, high optical absorption contrast, fast imaging speed, and ability to perform spectral decomposition. Based on different image reconstruction mechanisms, PAT can be further divided into two embodiments: raster-scanning-based photoacoustic microscopy (PAM) and reconstruction-algorism-based photoacoustic computed tomography (PACT). This dissertation aims to advance the …

Improving Radiation Therapy Through Motion Tracking, Hanlin Wan

McKelvey School of Engineering Theses & Dissertations

Radiation therapy is a widely-used cancer treatment method in which lethal doses of ionizing radiation are delivered to cancerous cells. Given the high dose requirements and the risk of associated complications, it is essential that radiation be targeted to cancerous cells while minimizing the dose to surrounding tissue. While current technology allows for accurate targeting of radiation dose, there is one major hurdle: Respiratory motion causes movement of up to a few centimeters of tumors in the abdomen and thorax, rendering even the most accurate radiation delivery machine highly inaccurate. Imaging devices integrated with the treatment machines allow us to …

Goggle Augmented Imaging And Navigation System For Fluorescence-Guided Surgery, Suman Bikash Mondal

McKelvey School of Engineering Theses & Dissertations

Surgery remains the only curative option for most solid tumors. The standard-of-care usually involves tumor resection and sentinel lymph node biopsy for cancer staging. Surgeons rely on their vision and touch to distinguish healthy from cancer tissue during surgery, often leading to incomplete tumor resection that necessitates repeat surgery. Sentinel lymph node biopsy by conventional radioactive tracking exposes patients and caregivers to ionizing radiation, while blue dye tracking stains the tissue highlighting only superficial lymph nodes. Improper identification of sentinel lymph nodes may misdiagnose the stage of the cancer. Therefore there is a clinical need for accurate intraoperative tumor and …

Mechanics Of Early Retina And Lens Development In The Embryo, Alina Oltean

McKelvey School of Engineering Theses & Dissertations

Mechanical forces play an essential role in morphogenesis, the shaping of embryonic structures. This research focuses mainly on eye development, a problem that has been studied for decades using a variety of approaches. However, the mechanics of the early stages of eye formation remain incompletely understood.

The embryonic eyes begin as bilateral protrusions called optic vesicles (OVs) that grow outward from the anterior end of the brain tube. The optic vesicles contact and adhere to the overlying surface ectoderm (SE) via extracellular matrix (ECM). Then, both layers thicken in the region of contact to form the retinal and lens placodes, …

Development And Investigation Of Sparse Co-Adaptive Algorithms In Ecog Based Closed-Loop Brain Computer Interface, Piyush Karande

McKelvey School of Engineering Theses & Dissertations

Electrocorticography (ECoG) has gained a lot of momentum and has become a serious contender as a recording modality for the implementation of Brain-Computer Interface (BCI) systems in the last few years. ECoG signals provide the right balance between minimal invasiveness and robust spectral information to accomplish a BCI task. However, all the BCI studies until now have used signals recorded from a large number of implanted electrodes and a larger number of spectral features. The recording and processing of these signals uses a lot of electrical power and thus hinders its use outside the research setting. To translate this research …

Feed-Forward Inhibitory Circuits In Hippocampus And Their Computational Role In Fragile X Syndrome, Sarah Lauren Wahlstrom Helgren

McKelvey School of Engineering Theses & Dissertations

Feed-forward inhibitory (FFI) circuits are canonical neural microcircuits. They are unique in that they are comprised of excitation rapidly followed by a time-locked inhibition. This sequence provides for a powerful computational tool, but also a challenge in the analysis and study of these circuits. In this work, mechanisms and computations of two hippocampal FFI circuits have been examined. Specifically, the modulation of synaptic strength of the excitation and the inhibition is studied during constant-frequency and naturalistic stimulus patterns to reveal how FFI circuit properties and operations are dynamically modulated during ongoing activity. In the first part, the FFI circuit dysfunction …

Detection Of Parkinson Disease Rest Tremor, Matthew J. Johnson

McKelvey School of Engineering Theses & Dissertations

Parkinson Disease (PD) is a debilitating and progressive movement disorder that is estimated to affect over six million worldwide. One of the most characteristic symptoms of PD is resting tremor, which involves unintentional and rhythmic muscle oscillations of an afflicted extremity while the muscles of said extremity are relaxed. This study involved measuring the rest tremor of 10 PD subjects, 10 Essential Tremor subjects, and 10 healthy control subjects using two devices. One device was an FDA approved accelerometry system to measure human tremor known as the Tremorometer^TM and the other was a consumer three-dimensional camera known as the …